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Analytica Chimica Acta (v.567, #1)
Environmental perchlorate: Why it matters by Andrea B. Kirk (pp. 4-12).
The only known mechanism of toxicity for perchlorate is interference with iodide uptake at the sodium-iodide symporter (NIS). The NIS translocates iodide across basolateral membranes to the thyroid gland so it can be used to form thyroid hormones (TH). NIS is also expressed in the mammary gland during lactation, so that iodide can be transferred from a mother to her child. Without adequate iodide, an infant cannot produce sufficient TH to meet its developmental needs. Effects expected from perchlorate are those that would be seen in conditions of hypothyroidism or hypothyroxinemia. The probability of a permanent adverse effect is greatest during early life, as successful neurodevelopment is TH-dependent. Study of perchlorate risk is complicated by a number of factors including thyroid status of the mother during gestation, thyroid status of the fetus, maternal and infant iodine intake, and exposure of each to other TH-disrupting chemicals. Perhaps the greatest standing issue, and the issue most relevant to the field of analytical chemistry, is the simple fact that human exposure has not been quantified. This review will summarize perchlorate's potential to adversely affect neurodevelopment. Whether current environmental exposures to perchlorate contribute to neuro-impairment is unknown. Risks posed by perchlorate must be considered in conjunction with iodine intake.
Keywords: Perchlorate; Thyroid hormone disruption; Neurodevelopment; Hypothyroidism
Environmental perchlorate: Why it matters by Andrea B. Kirk (pp. 4-12).
The only known mechanism of toxicity for perchlorate is interference with iodide uptake at the sodium-iodide symporter (NIS). The NIS translocates iodide across basolateral membranes to the thyroid gland so it can be used to form thyroid hormones (TH). NIS is also expressed in the mammary gland during lactation, so that iodide can be transferred from a mother to her child. Without adequate iodide, an infant cannot produce sufficient TH to meet its developmental needs. Effects expected from perchlorate are those that would be seen in conditions of hypothyroidism or hypothyroxinemia. The probability of a permanent adverse effect is greatest during early life, as successful neurodevelopment is TH-dependent. Study of perchlorate risk is complicated by a number of factors including thyroid status of the mother during gestation, thyroid status of the fetus, maternal and infant iodine intake, and exposure of each to other TH-disrupting chemicals. Perhaps the greatest standing issue, and the issue most relevant to the field of analytical chemistry, is the simple fact that human exposure has not been quantified. This review will summarize perchlorate's potential to adversely affect neurodevelopment. Whether current environmental exposures to perchlorate contribute to neuro-impairment is unknown. Risks posed by perchlorate must be considered in conjunction with iodine intake.
Keywords: Perchlorate; Thyroid hormone disruption; Neurodevelopment; Hypothyroidism
Risk assessment, remedial decisions and the challenge to protect public health: The perchlorate case study by Cal Baier-Anderson (pp. 13-19).
While scientists have a responsibility to defer judgment in the absence of conclusive data, public health and ecological protection require that government regulators make decisions based on available information. The risk assessment paradigm has evolved to help risk managers balance risks to public health with the cost of pollution control and remediation. Risk assessments are designed to be reasonably protective of public health, however the time and money required to develop and evaluate a robust scientific database can significantly delay regulatory action while exposures continue. The federal assessment of perchlorate, a component of rocket fuel and a thyroid toxicant, is presented here as a case study that demonstrates some of the limitations of risk assessment in protecting public health. Perchlorate was detected in a city well field that lies beneath a military training range at Aberdeen Proving Ground, a U.S. Army garrison in Maryland. Cleanup was put on hold, pending promulgation of a national drinking water standard for perchlorate. This case study (1) illustrates the challenge of preventing chemical exposures in the absence of promulgated standards, and (2) makes recommendations for approaches to preventing exposures to chemicals of unknown, or uncertain toxicity before they occur.
Keywords: Perchlorate; Risk assessment; Public health protection
Risk assessment, remedial decisions and the challenge to protect public health: The perchlorate case study by Cal Baier-Anderson (pp. 13-19).
While scientists have a responsibility to defer judgment in the absence of conclusive data, public health and ecological protection require that government regulators make decisions based on available information. The risk assessment paradigm has evolved to help risk managers balance risks to public health with the cost of pollution control and remediation. Risk assessments are designed to be reasonably protective of public health, however the time and money required to develop and evaluate a robust scientific database can significantly delay regulatory action while exposures continue. The federal assessment of perchlorate, a component of rocket fuel and a thyroid toxicant, is presented here as a case study that demonstrates some of the limitations of risk assessment in protecting public health. Perchlorate was detected in a city well field that lies beneath a military training range at Aberdeen Proving Ground, a U.S. Army garrison in Maryland. Cleanup was put on hold, pending promulgation of a national drinking water standard for perchlorate. This case study (1) illustrates the challenge of preventing chemical exposures in the absence of promulgated standards, and (2) makes recommendations for approaches to preventing exposures to chemicals of unknown, or uncertain toxicity before they occur.
Keywords: Perchlorate; Risk assessment; Public health protection
Development of a drinking water regulation for perchlorate in California by Maria W. Tikkanen (pp. 20-25).
Perchlorate is an environmental contaminant often associated with military installations and rocket propellant manufacture and testing facilities across the U.S. Highly water soluble, perchlorate has been found by federal and state agencies at almost 400 sites within the U.S. in groundwater, surface water, soil or public drinking water. There is no federal drinking water standard for perchlorate, but it is on the drinking water Contaminant Candidate List, and falls under the Unregulated Contaminant Monitoring Rule (UCMR) for which monitoring is required. The recent National Academy of Science (NAS) report on the potential health effects of perchlorate recommended a perchlorate reference dose of 0.0007mg/kg of body weight which would be equivalent to a drinking water concentration of 24.5μg/L.In California, approximately 395 wells in 96 water systems have been shown to contain perchlorate, and about 90% of these are located in Southern California. Water taken from the Colorado River, a major surface water supply to Southern California, has had reported detections of perchlorate ranging from non-detect to 9μg/L. California has established a Public Health Goal (PHG) of 6μg/L for perchlorate, and a proposed drinking water regulation is imminent. This review details the regulatory process involved with particular attention given to the occurrence of perchlorate in California drinking water sources and analytical methodology utilized.
Keywords: Perchlorate; Drinking water; Regulation; California
Development of a drinking water regulation for perchlorate in California by Maria W. Tikkanen (pp. 20-25).
Perchlorate is an environmental contaminant often associated with military installations and rocket propellant manufacture and testing facilities across the U.S. Highly water soluble, perchlorate has been found by federal and state agencies at almost 400 sites within the U.S. in groundwater, surface water, soil or public drinking water. There is no federal drinking water standard for perchlorate, but it is on the drinking water Contaminant Candidate List, and falls under the Unregulated Contaminant Monitoring Rule (UCMR) for which monitoring is required. The recent National Academy of Science (NAS) report on the potential health effects of perchlorate recommended a perchlorate reference dose of 0.0007mg/kg of body weight which would be equivalent to a drinking water concentration of 24.5μg/L.In California, approximately 395 wells in 96 water systems have been shown to contain perchlorate, and about 90% of these are located in Southern California. Water taken from the Colorado River, a major surface water supply to Southern California, has had reported detections of perchlorate ranging from non-detect to 9μg/L. California has established a Public Health Goal (PHG) of 6μg/L for perchlorate, and a proposed drinking water regulation is imminent. This review details the regulatory process involved with particular attention given to the occurrence of perchlorate in California drinking water sources and analytical methodology utilized.
Keywords: Perchlorate; Drinking water; Regulation; California
Perchlorate and chlorate in dietary supplements and flavor enhancing ingredients by Shane A. Snyder; Richard C. Pleus; Brett J. Vanderford; Janie C. Holady (pp. 26-32).
The oxyhalide anions perchlorate and chlorate were measured in a series of dietary (vitamin and mineral) supplements and flavor enhancing ingredients collected from various commercial vendors in two large US cities. Analyses were conducted using liquid chromatography with tandem mass spectrometry (LC–MS/MS). The limit of detection was based on the mass of supplements and ingredients extracted and ranged from 2 to 15ng/g for perchlorate and 4 to 30ng/g for chlorate. Perchlorate and chlorate were detected in 20 and 26, respectively, of the 31 dietary supplements tested, with concentrations ranging from non-detectable to as high as 2400 and 10,300ng/g, respectively. Based upon the recommended dose provided by each manufacturer for different supplements, the daily oral dose of perchlorate and chlorate could be as high as 18 and 20μg/day, respectively. The highest level of perchlorate was found in a supplement recommended for pregnant women as a prenatal nutritional supplement. Of the 31 dietary supplements investigated, 12 were specifically marketed for pregnant women and children. Perchlorate and chlorate were also detectable in four products marketed for the enhancement of food flavor. Perchlorate is found naturally in some parts of the world, is present in some natural fertilizers, is used as an oxidizer in solid fuel engines, and has been used at therapeutic doses in humans to treat overactive thyroid glands. Perchlorate has been detected in drinking water, dairy products, some produce and grains, and human breast milk. This is the first report of perchlorate measured in over-the-counter dietary supplements and flavor enhancing ingredients.
Keywords: Perchlorate; Chlorate; Kelp; Vitamin; Liquid chromatography tandem mass spectrometry
Perchlorate and chlorate in dietary supplements and flavor enhancing ingredients by Shane A. Snyder; Richard C. Pleus; Brett J. Vanderford; Janie C. Holady (pp. 26-32).
The oxyhalide anions perchlorate and chlorate were measured in a series of dietary (vitamin and mineral) supplements and flavor enhancing ingredients collected from various commercial vendors in two large US cities. Analyses were conducted using liquid chromatography with tandem mass spectrometry (LC–MS/MS). The limit of detection was based on the mass of supplements and ingredients extracted and ranged from 2 to 15ng/g for perchlorate and 4 to 30ng/g for chlorate. Perchlorate and chlorate were detected in 20 and 26, respectively, of the 31 dietary supplements tested, with concentrations ranging from non-detectable to as high as 2400 and 10,300ng/g, respectively. Based upon the recommended dose provided by each manufacturer for different supplements, the daily oral dose of perchlorate and chlorate could be as high as 18 and 20μg/day, respectively. The highest level of perchlorate was found in a supplement recommended for pregnant women as a prenatal nutritional supplement. Of the 31 dietary supplements investigated, 12 were specifically marketed for pregnant women and children. Perchlorate and chlorate were also detectable in four products marketed for the enhancement of food flavor. Perchlorate is found naturally in some parts of the world, is present in some natural fertilizers, is used as an oxidizer in solid fuel engines, and has been used at therapeutic doses in humans to treat overactive thyroid glands. Perchlorate has been detected in drinking water, dairy products, some produce and grains, and human breast milk. This is the first report of perchlorate measured in over-the-counter dietary supplements and flavor enhancing ingredients.
Keywords: Perchlorate; Chlorate; Kelp; Vitamin; Liquid chromatography tandem mass spectrometry
Potential perchlorate exposure from Citrus sp. irrigated with contaminated water by C.A. Sanchez; R.I. Krieger; N.R. Khandaker; L. Valentin-Blasini; B.C. Blount (pp. 33-38).
Citrus produced in the southwestern United States is often irrigated with perchlorate-contaminated water. This irrigation water includes Colorado River water which is contaminated with perchlorate from a manufacturing plant previously located near the Las Vegas Wash, and ground water from wells in Riverside and San Bernardino counties of California which are affected by a perchlorate plume associated with an aerospace facility once located near Redlands, California. Studies were conducted to evaluate the uptake and distribution of perchlorate in citrus irrigated with contaminated water, and estimate potential human exposure to perchlorate from the various citrus types including lemon ( Citrus limon), grapefruit ( Citrus paradise), and orange ( Citrus sinensis) produced in the region. Perchlorate concentrations ranged from less than 2–9μg/L for Colorado River water and from below detection to approximately 18μg/L for water samples from wells used to irrigate citrus. Destructive sampling of lemon trees produced with Colorado River water show perchlorate concentrations larger in the leaves (1835μg/kg dry weight (dw)) followed by the fruit (128μg/kg dw). Mean perchlorate concentrations in roots, trunk, and branches were all less than 30μg/kg dw. Fruit pulp analyzed in the survey show perchlorate concentrations ranged from below detection limit to 38μg/kg fresh weight (fw), and were related to the perchlorate concentration of irrigation water. Mean hypothetical exposures (μg/person/day) of children and adults from lemons (0.005 and 0.009), grapefruit (0.03 and 0.24), and oranges (0.51 and 1.20) were estimated. These data show that potential perchlorate exposures from citrus in the southwestern United States are negligible relative to the reference dose recommended by the National Academy of Sciences.
Keywords: Lemon (; Citrus limon; ); Grapefruit (; Citrus paradise; ); Orange (; Citrus sinensis; ); Colorado River; Perchlorate
Potential perchlorate exposure from Citrus sp. irrigated with contaminated water by C.A. Sanchez; R.I. Krieger; N.R. Khandaker; L. Valentin-Blasini; B.C. Blount (pp. 33-38).
Citrus produced in the southwestern United States is often irrigated with perchlorate-contaminated water. This irrigation water includes Colorado River water which is contaminated with perchlorate from a manufacturing plant previously located near the Las Vegas Wash, and ground water from wells in Riverside and San Bernardino counties of California which are affected by a perchlorate plume associated with an aerospace facility once located near Redlands, California. Studies were conducted to evaluate the uptake and distribution of perchlorate in citrus irrigated with contaminated water, and estimate potential human exposure to perchlorate from the various citrus types including lemon ( Citrus limon), grapefruit ( Citrus paradise), and orange ( Citrus sinensis) produced in the region. Perchlorate concentrations ranged from less than 2–9μg/L for Colorado River water and from below detection to approximately 18μg/L for water samples from wells used to irrigate citrus. Destructive sampling of lemon trees produced with Colorado River water show perchlorate concentrations larger in the leaves (1835μg/kg dry weight (dw)) followed by the fruit (128μg/kg dw). Mean perchlorate concentrations in roots, trunk, and branches were all less than 30μg/kg dw. Fruit pulp analyzed in the survey show perchlorate concentrations ranged from below detection limit to 38μg/kg fresh weight (fw), and were related to the perchlorate concentration of irrigation water. Mean hypothetical exposures (μg/person/day) of children and adults from lemons (0.005 and 0.009), grapefruit (0.03 and 0.24), and oranges (0.51 and 1.20) were estimated. These data show that potential perchlorate exposures from citrus in the southwestern United States are negligible relative to the reference dose recommended by the National Academy of Sciences.
Keywords: Lemon (; Citrus limon; ); Grapefruit (; Citrus paradise; ); Orange (; Citrus sinensis; ); Colorado River; Perchlorate
Analysis of perchlorate in foods and beverages by ion chromatography coupled with tandem mass spectrometry (IC-ESI-MS/MS) by Houssain El Aribi; Yves J.C. Le Blanc; Stephen Antonsen; Takeo Sakuma (pp. 39-47).
A new IC-ESI-MS/MS method, with simple sample preparation procedure, has been developed for quantification and confirmation of perchlorate (ClO4−) anions in water, fresh and canned food, wine and beer samples at low part-per-trillion (ngl−1) levels. To the best of our knowledge, this is the first time an analytical method is used for determination of perchlorate in wine and beer samples. The IC-ESI-MS/MS instrumentation consisted of an ICS-2500 ion chromatography (IC) system coupled to either an API 2000™ or an API 3200™ mass spectrometer. The IC-ESI-MS/MS system was optimized to monitor two pairs of precursor and fragment ion transitions, i.e., multiple reaction monitoring (MRM). All samples had oxygen-18 isotope labeled perchlorate internal standard (ISTD) added prior to extraction. Chlorine isotope ratio (35Cl/37Cl) was used as a confirmation tool. The transition of35Cl16O4− ( m/ z 98.9) into35Cl16O3− ( m/ z 82.9) was monitored for quantifying the main analyte; the transition of37Cl16O4− ( m/ z 100.9) into37Cl16O3− ( m/ z 84.9) was monitored for examining a proper isotopic abundance ratio of35Cl/37Cl; and the transition of35Cl18O4− ( m/ z 107.0) into35Cl18O3− ( m/ z 89.0) was monitored for quantifying the internal standard. The minimum detection limit (MDL) for this method in de-ionized water is 5ngl−1 (ppt) using the API 2000™ mass spectrometer and 0.5ngl−1 using the API 3200™ mass spectrometer. Over 350 food and beverage samples were analyzed mostly in triplicate. Except for four, all samples were found to contain measurable amounts of perchlorate. The levels found ranged from 5ngl−1 to 463.5±6.36μgkg−1 using MRM 98.9→82.9 and 100μl injection.
Keywords: Perchlorate; Produce; Wine; Beer; IC; ESI-MS/MS
Analysis of perchlorate in foods and beverages by ion chromatography coupled with tandem mass spectrometry (IC-ESI-MS/MS) by Houssain El Aribi; Yves J.C. Le Blanc; Stephen Antonsen; Takeo Sakuma (pp. 39-47).
A new IC-ESI-MS/MS method, with simple sample preparation procedure, has been developed for quantification and confirmation of perchlorate (ClO4−) anions in water, fresh and canned food, wine and beer samples at low part-per-trillion (ngl−1) levels. To the best of our knowledge, this is the first time an analytical method is used for determination of perchlorate in wine and beer samples. The IC-ESI-MS/MS instrumentation consisted of an ICS-2500 ion chromatography (IC) system coupled to either an API 2000™ or an API 3200™ mass spectrometer. The IC-ESI-MS/MS system was optimized to monitor two pairs of precursor and fragment ion transitions, i.e., multiple reaction monitoring (MRM). All samples had oxygen-18 isotope labeled perchlorate internal standard (ISTD) added prior to extraction. Chlorine isotope ratio (35Cl/37Cl) was used as a confirmation tool. The transition of35Cl16O4− ( m/ z 98.9) into35Cl16O3− ( m/ z 82.9) was monitored for quantifying the main analyte; the transition of37Cl16O4− ( m/ z 100.9) into37Cl16O3− ( m/ z 84.9) was monitored for examining a proper isotopic abundance ratio of35Cl/37Cl; and the transition of35Cl18O4− ( m/ z 107.0) into35Cl18O3− ( m/ z 89.0) was monitored for quantifying the internal standard. The minimum detection limit (MDL) for this method in de-ionized water is 5ngl−1 (ppt) using the API 2000™ mass spectrometer and 0.5ngl−1 using the API 3200™ mass spectrometer. Over 350 food and beverage samples were analyzed mostly in triplicate. Except for four, all samples were found to contain measurable amounts of perchlorate. The levels found ranged from 5ngl−1 to 463.5±6.36μgkg−1 using MRM 98.9→82.9 and 100μl injection.
Keywords: Perchlorate; Produce; Wine; Beer; IC; ESI-MS/MS
Photochemical formation of perchlorate from aqueous oxychlorine anions by Namgoo Kang; Todd A. Anderson; W. Andrew Jackson (pp. 48-56).
Evidence of atmospherically produced perchlorate is being accumulated, yet information regarding its formation process is largely unknown. For the first time, the present study demonstrates that perchlorate can be generated as an end-product of photochemical transformation reactions of chlorine precursors such as aqueous salt solutions of hypochlorite, chlorite, and chlorate upon exposure to ultraviolet (UV) radiation. For example, under exposure to UV light from photochemical reactor lamps at a peak wavelength of 253.7nm for 7 days, the observed perchlorate concentrations were 5, 25, and 626μg/L at initial chlorite concentrations of 100, 1000, and 10,000mg/L, respectively. In addition, perchlorate was generated within 7 days from aqueous chlorite solutions at mid-latitude (33°59′N, 101°89′W) spring and summer solar radiation. Via UV radiation from the artificial lamps and sunlight, chlorite was converted to chloride (68%) and chlorate (32%) as end-products on the basis of molar percentage. However, perchlorate was not detected from aqueous chloride solutions at initial concentrations up to 10,000mg/L under the experimental conditions. Relevant mechanistic pathways were proposed based on the fact that chlorine dioxide (as a primary intermediate) may play a significant role in phototransformation of the precursors leading to perchlorate.
Keywords: Photodecomposition; Precursor; UV; Sunlight; Radiation; Photochemistry
Photochemical formation of perchlorate from aqueous oxychlorine anions by Namgoo Kang; Todd A. Anderson; W. Andrew Jackson (pp. 48-56).
Evidence of atmospherically produced perchlorate is being accumulated, yet information regarding its formation process is largely unknown. For the first time, the present study demonstrates that perchlorate can be generated as an end-product of photochemical transformation reactions of chlorine precursors such as aqueous salt solutions of hypochlorite, chlorite, and chlorate upon exposure to ultraviolet (UV) radiation. For example, under exposure to UV light from photochemical reactor lamps at a peak wavelength of 253.7nm for 7 days, the observed perchlorate concentrations were 5, 25, and 626μg/L at initial chlorite concentrations of 100, 1000, and 10,000mg/L, respectively. In addition, perchlorate was generated within 7 days from aqueous chlorite solutions at mid-latitude (33°59′N, 101°89′W) spring and summer solar radiation. Via UV radiation from the artificial lamps and sunlight, chlorite was converted to chloride (68%) and chlorate (32%) as end-products on the basis of molar percentage. However, perchlorate was not detected from aqueous chloride solutions at initial concentrations up to 10,000mg/L under the experimental conditions. Relevant mechanistic pathways were proposed based on the fact that chlorine dioxide (as a primary intermediate) may play a significant role in phototransformation of the precursors leading to perchlorate.
Keywords: Photodecomposition; Precursor; UV; Sunlight; Radiation; Photochemistry
Approaches to sample pretreatment in the determination of perchlorate in real world samples by R. Slingsby; C. Pohl; C. Saini (pp. 57-65).
Perchlorate can be determined by the tandem technique of ion chromatography (IC) coupled to electrospray ionization mass spectrometry (ESI–MS). However, detection by ESI–MS can be compromised by the coelution of matrix components that can suppress the analyte signal. In addition, the presence of surface-active and other types of matrix components can cause fouling of the electrospray inlet, reducing overall signal and requiring frequent maintenance. The influences of matrix components can be minimized by using analytical columns with different selectivities, in-line diversion of separated matrix components, and off-line selective removal of matrix components via ion exchange or adsorption. This paper will discuss these sample preparation approaches for samples containing anionic species including surfactants and inorganic ions that elute in the vicinity of perchlorate.
Keywords: Perchlorate; Ion chromatography; Electrospray ionization mass spectrometry; IC–MS
Approaches to sample pretreatment in the determination of perchlorate in real world samples by R. Slingsby; C. Pohl; C. Saini (pp. 57-65).
Perchlorate can be determined by the tandem technique of ion chromatography (IC) coupled to electrospray ionization mass spectrometry (ESI–MS). However, detection by ESI–MS can be compromised by the coelution of matrix components that can suppress the analyte signal. In addition, the presence of surface-active and other types of matrix components can cause fouling of the electrospray inlet, reducing overall signal and requiring frequent maintenance. The influences of matrix components can be minimized by using analytical columns with different selectivities, in-line diversion of separated matrix components, and off-line selective removal of matrix components via ion exchange or adsorption. This paper will discuss these sample preparation approaches for samples containing anionic species including surfactants and inorganic ions that elute in the vicinity of perchlorate.
Keywords: Perchlorate; Ion chromatography; Electrospray ionization mass spectrometry; IC–MS
Challenges in determining perchlorate in biological tissues and fluids: Implications for characterizing perchlorate exposure by Lu Yu; Qiuqiong Cheng; Jaclyn Cañas; Liza Valentin-Blasini; Benjamin C. Blount; Todd Anderson (pp. 66-72).
The ability to measure environmental contaminants in biological tissues and fluids is important in the characterization of exposure. However, the analysis of certain contaminants in these matrices presents significant challenges. Perchlorate (ClO4−) has emerged as a potential contaminant of concern primarily in drinking water and also in contaminated food. Significant advances have been made in the analysis of perchlorate in environmental matrices (water, soil) by ion chromatography (IC). In contrast, the analysis of perchlorate in extracts of biological tissues and fluids (vegetation, organs, milk, blood, urine, etc.) presents several challenges including small sample sizes, extracts with high matrix conductivity, and co-elution of other ions during IC analysis. To be able to detect low concentrations of perchlorate in biological samples, interferences must be removed or minimized, such as through the use of preparative chromatography cleanup techniques and/or alternative analytical methods less susceptible to common interferences (preconcentration or mass spectrometric detection). We present discussion and examples of the challenges encountered in the analysis of tissue extracts and fluids for perchlorate by IC and how some of those analytical challenges have been overcome.
Keywords: Perchlorate; Biological tissues; Cleanup methods; Ion chromatography
Challenges in determining perchlorate in biological tissues and fluids: Implications for characterizing perchlorate exposure by Lu Yu; Qiuqiong Cheng; Jaclyn Cañas; Liza Valentin-Blasini; Benjamin C. Blount; Todd Anderson (pp. 66-72).
The ability to measure environmental contaminants in biological tissues and fluids is important in the characterization of exposure. However, the analysis of certain contaminants in these matrices presents significant challenges. Perchlorate (ClO4−) has emerged as a potential contaminant of concern primarily in drinking water and also in contaminated food. Significant advances have been made in the analysis of perchlorate in environmental matrices (water, soil) by ion chromatography (IC). In contrast, the analysis of perchlorate in extracts of biological tissues and fluids (vegetation, organs, milk, blood, urine, etc.) presents several challenges including small sample sizes, extracts with high matrix conductivity, and co-elution of other ions during IC analysis. To be able to detect low concentrations of perchlorate in biological samples, interferences must be removed or minimized, such as through the use of preparative chromatography cleanup techniques and/or alternative analytical methods less susceptible to common interferences (preconcentration or mass spectrometric detection). We present discussion and examples of the challenges encountered in the analysis of tissue extracts and fluids for perchlorate by IC and how some of those analytical challenges have been overcome.
Keywords: Perchlorate; Biological tissues; Cleanup methods; Ion chromatography
Sample processing method for the determination of perchlorate in milk by Jason V. Dyke; Andrea B. Kirk; P. Kalyani Martinelango; Purnendu K. Dasgupta (pp. 73-78).
In recent years, many different water sources and foods have been reported to contain perchlorate. Studies indicate that significant levels of perchlorate are present in both human and dairy milk. The determination of perchlorate in milk is particularly important due to its potential health impact on infants and children. As for many other biological samples, sample preparation is more time consuming than the analysis itself. The concurrent presence of large amounts of fats, proteins, carbohydrates, etc., demands some initial cleanup; otherwise the separation column lifetime and the limit of detection are both greatly compromised. Reported milk processing methods require the addition of chemicals such as ethanol, acetic acid or acetonitrile. Reagent addition is undesirable in trace analysis. We report here an essentially reagent-free sample preparation method for the determination of perchlorate in milk. Milk samples are spiked with isotopically labeled perchlorate and centrifuged to remove lipids. The resulting liquid is placed in a disposable centrifugal ultrafilter device with a molecular weight cutoff of 10kDa, and centrifuged. Approximately 5–10ml of clear liquid, ready for analysis, is obtained from a 20ml milk sample. Both bovine and human milk samples have been successfully processed and analyzed by ion chromatography–mass spectrometry (IC–MS). Standard addition experiments show good recoveries. The repeatability of the analytical result for the same sample in multiple sample cleanup runs ranged from 3 to 6% R.S.D. This processing technique has also been successfully applied for the determination of iodide and thiocyanate in milk.
Keywords: Sample preparation; Milk; Perchlorate; Ultrafiltration; Centrifugal filter
Sample processing method for the determination of perchlorate in milk by Jason V. Dyke; Andrea B. Kirk; P. Kalyani Martinelango; Purnendu K. Dasgupta (pp. 73-78).
In recent years, many different water sources and foods have been reported to contain perchlorate. Studies indicate that significant levels of perchlorate are present in both human and dairy milk. The determination of perchlorate in milk is particularly important due to its potential health impact on infants and children. As for many other biological samples, sample preparation is more time consuming than the analysis itself. The concurrent presence of large amounts of fats, proteins, carbohydrates, etc., demands some initial cleanup; otherwise the separation column lifetime and the limit of detection are both greatly compromised. Reported milk processing methods require the addition of chemicals such as ethanol, acetic acid or acetonitrile. Reagent addition is undesirable in trace analysis. We report here an essentially reagent-free sample preparation method for the determination of perchlorate in milk. Milk samples are spiked with isotopically labeled perchlorate and centrifuged to remove lipids. The resulting liquid is placed in a disposable centrifugal ultrafilter device with a molecular weight cutoff of 10kDa, and centrifuged. Approximately 5–10ml of clear liquid, ready for analysis, is obtained from a 20ml milk sample. Both bovine and human milk samples have been successfully processed and analyzed by ion chromatography–mass spectrometry (IC–MS). Standard addition experiments show good recoveries. The repeatability of the analytical result for the same sample in multiple sample cleanup runs ranged from 3 to 6% R.S.D. This processing technique has also been successfully applied for the determination of iodide and thiocyanate in milk.
Keywords: Sample preparation; Milk; Perchlorate; Ultrafiltration; Centrifugal filter
Matrix interference free determination of perchlorate in urine by ion association–ion chromatography–mass spectrometry by P. Kalyani Martinelango; Gülçin Gümüş; Purnendu K. Dasgupta (pp. 79-86).
Quantitative measurement of perchlorate in biological fluids is of importance to assess its toxicity and to study its effects on the thyroid gland. Whenever possible, urine samples are preferred in toxicologic/epidemiologic studies because sample collection is non-invasive. We present here a pretreatment method for the determination of perchlorate in urine samples that lead to a clean matrix. Urine samples, spiked with isotopically labeled perchlorate, are exposed to UV to destroy/decompose organic molecules and then sequentially treated with an H+-form cation exchange resin to remove protolyzable compounds, with ammonia to raise the pH to 10–11 and finally passed through a mini-column of basic alumina to remove the color and other organic matter. After filtration through a 0.45μm syringe filter, the sample thus prepared can be directly injected into an ion chromatograph (IC). We use ion association–electrospray ionization–mass spectrometry (ESI-MS) to detect and quantify perchlorate. The proposed sample preparation method leads to excellent limits of detection (LOD's) for perchlorate since there is essentially no dilution of sample and the matrix effects are eliminated. Results of urine samples from both men and women volunteers are reported for perchlorate, as well as for iodide and thiocyanate, which are generally present at much higher concentrations and for which a “dilute and shoot? approach is adequate. The limit of detection ( S/ N=3) for iodide, thiocyanate and perchlorate by the present method was 0.40, 0.10 and 0.080μgl−1, respectively.
Keywords: Urine; Perchlorate; Ion chromatography; Mass spectrometry; Sample preparation
Matrix interference free determination of perchlorate in urine by ion association–ion chromatography–mass spectrometry by P. Kalyani Martinelango; Gülçin Gümüş; Purnendu K. Dasgupta (pp. 79-86).
Quantitative measurement of perchlorate in biological fluids is of importance to assess its toxicity and to study its effects on the thyroid gland. Whenever possible, urine samples are preferred in toxicologic/epidemiologic studies because sample collection is non-invasive. We present here a pretreatment method for the determination of perchlorate in urine samples that lead to a clean matrix. Urine samples, spiked with isotopically labeled perchlorate, are exposed to UV to destroy/decompose organic molecules and then sequentially treated with an H+-form cation exchange resin to remove protolyzable compounds, with ammonia to raise the pH to 10–11 and finally passed through a mini-column of basic alumina to remove the color and other organic matter. After filtration through a 0.45μm syringe filter, the sample thus prepared can be directly injected into an ion chromatograph (IC). We use ion association–electrospray ionization–mass spectrometry (ESI-MS) to detect and quantify perchlorate. The proposed sample preparation method leads to excellent limits of detection (LOD's) for perchlorate since there is essentially no dilution of sample and the matrix effects are eliminated. Results of urine samples from both men and women volunteers are reported for perchlorate, as well as for iodide and thiocyanate, which are generally present at much higher concentrations and for which a “dilute and shoot” approach is adequate. The limit of detection ( S/ N=3) for iodide, thiocyanate and perchlorate by the present method was 0.40, 0.10 and 0.080μgl−1, respectively.
Keywords: Urine; Perchlorate; Ion chromatography; Mass spectrometry; Sample preparation
Analysis of perchlorate, thiocyanate, nitrate and iodide in human amniotic fluid using ion chromatography and electrospray tandem mass spectrometry by Benjamin C. Blount; Liza Valentin-Blasini (pp. 87-93).
Because of health concerns surrounding in utero exposure to perchlorate, we developed a sensitive and selective method for quantifying iodide, as well as perchlorate and other sodium-iodide symporter (NIS) inhibitors in human amniotic fluid using ion chromatography coupled with electrospray ionization tandem mass spectrometry. Iodide and NIS inhibitors were quantified using a stable isotope-labeled internal standards (Cl18O4−, S13CN− and15NO3− with excellent assay accuracy of 100%, 98%, 99%, 95% for perchlorate, thiocyanate, nitrate and iodide, respectively, in triplicate analysis of spiked amniotic fluid sample). Excellent analytical precision (<5.2% RSD for all analytes) was found when amniotic fluid quality control pools were repetitively analyzed for iodide and NIS-inhibitors. Selective chromatography and tandem mass spectrometry reduced the need for sample cleanup, resulting in a rugged and rapid method capable of routinely analyzing 75 samples/day. Analytical response was linear across the physiologically relevant concentration range for the analytes. Analysis of a set of 48 amniotic fluid samples identified the range and median levels for perchlorate (0.057–0.71, 0.18μg/L), thiocyanate (<10–5860, 89μg/L), nitrate (650–8900, 1620μg/L) and iodide (1.7–170, 8.1μg/L). This selective, sensitive, and rapid method will help assess exposure of the developing fetus to low levels of NIS-inhibitors and their potential to inhibit thyroid function.
Keywords: Perchlorate; Thiocyanate; Nitrate; Iodide; Amniotic fluid; IC; MS
Analysis of perchlorate, thiocyanate, nitrate and iodide in human amniotic fluid using ion chromatography and electrospray tandem mass spectrometry by Benjamin C. Blount; Liza Valentin-Blasini (pp. 87-93).
Because of health concerns surrounding in utero exposure to perchlorate, we developed a sensitive and selective method for quantifying iodide, as well as perchlorate and other sodium-iodide symporter (NIS) inhibitors in human amniotic fluid using ion chromatography coupled with electrospray ionization tandem mass spectrometry. Iodide and NIS inhibitors were quantified using a stable isotope-labeled internal standards (Cl18O4−, S13CN− and15NO3− with excellent assay accuracy of 100%, 98%, 99%, 95% for perchlorate, thiocyanate, nitrate and iodide, respectively, in triplicate analysis of spiked amniotic fluid sample). Excellent analytical precision (<5.2% RSD for all analytes) was found when amniotic fluid quality control pools were repetitively analyzed for iodide and NIS-inhibitors. Selective chromatography and tandem mass spectrometry reduced the need for sample cleanup, resulting in a rugged and rapid method capable of routinely analyzing 75 samples/day. Analytical response was linear across the physiologically relevant concentration range for the analytes. Analysis of a set of 48 amniotic fluid samples identified the range and median levels for perchlorate (0.057–0.71, 0.18μg/L), thiocyanate (<10–5860, 89μg/L), nitrate (650–8900, 1620μg/L) and iodide (1.7–170, 8.1μg/L). This selective, sensitive, and rapid method will help assess exposure of the developing fetus to low levels of NIS-inhibitors and their potential to inhibit thyroid function.
Keywords: Perchlorate; Thiocyanate; Nitrate; Iodide; Amniotic fluid; IC; MS
Streamlined sample preparation procedure for determination of perchlorate anion in foods by ion chromatography–tandem mass spectrometry by Alexander J. Krynitsky; Richard A. Niemann; Anthony D. Williams; Marvin L. Hopper (pp. 94-99).
A rapid, sensitive, and specific method was developed for the determination of perchlorate anion in foods. The foods included high moisture fruits and vegetables, low moisture foods (e.g. wheat flour and corn meal), and infant foods. Improvements to existing procedures were made in sample preparation that reduced sample test portion size from 100 to 5 or 10g, extraction solvent volume from 150 to 20–40ml, and replaced blending extraction–vacuum filtration and their associated large glassware with a simple shakeout-centrifugation in a small conical tube. Procedures common to all matrices involved: extraction, centrifugation, graphitized carbon solid phase extraction (SPE) cleanup, and ion chromatography–tandem mass spectrometry (IC–MS/MS) analysis. A Waters IC-Pak Anion HR column (4.6mm×75mm) was eluted with 100mM ammonium acetate in 50:50 (v/v) acetonitrile/water mobile phase at a rate of 0.35ml/min. A triple stage quadrupole mass spectrometer, equipped with electrospray ionization (ESI) in the negative ion mode, was used to detect perchlorate anion. An18O4-labeled perchlorate anion internal standard was used to correct for any matrix effects. The method limit of quantitation (LOQ) was: 1.0μg/kg in fruits, vegetables, and infant foods; 3.0μg/kg in dry products. Fortified test portions gave 80–120% recoveries. Determination of incurred perchlorate anion residues agreed well with results for comparable commodities or products analyzed by published methods.
Keywords: Perchlorate anion; Foods; SPE; IC–MS/MS
Streamlined sample preparation procedure for determination of perchlorate anion in foods by ion chromatography–tandem mass spectrometry by Alexander J. Krynitsky; Richard A. Niemann; Anthony D. Williams; Marvin L. Hopper (pp. 94-99).
A rapid, sensitive, and specific method was developed for the determination of perchlorate anion in foods. The foods included high moisture fruits and vegetables, low moisture foods (e.g. wheat flour and corn meal), and infant foods. Improvements to existing procedures were made in sample preparation that reduced sample test portion size from 100 to 5 or 10g, extraction solvent volume from 150 to 20–40ml, and replaced blending extraction–vacuum filtration and their associated large glassware with a simple shakeout-centrifugation in a small conical tube. Procedures common to all matrices involved: extraction, centrifugation, graphitized carbon solid phase extraction (SPE) cleanup, and ion chromatography–tandem mass spectrometry (IC–MS/MS) analysis. A Waters IC-Pak Anion HR column (4.6mm×75mm) was eluted with 100mM ammonium acetate in 50:50 (v/v) acetonitrile/water mobile phase at a rate of 0.35ml/min. A triple stage quadrupole mass spectrometer, equipped with electrospray ionization (ESI) in the negative ion mode, was used to detect perchlorate anion. An18O4-labeled perchlorate anion internal standard was used to correct for any matrix effects. The method limit of quantitation (LOQ) was: 1.0μg/kg in fruits, vegetables, and infant foods; 3.0μg/kg in dry products. Fortified test portions gave 80–120% recoveries. Determination of incurred perchlorate anion residues agreed well with results for comparable commodities or products analyzed by published methods.
Keywords: Perchlorate anion; Foods; SPE; IC–MS/MS
Perchlorate in seawater by P. Kalyani Martinelango; Kang Tian; Purnendu K. Dasgupta (pp. 100-107).
There has been no reliable published data on the presence of perchlorate in seawater. Seaweeds are among the most important plant life in the ocean and are good sources of iodine and have been widely used as food and nutritional supplement. Perchlorate is known to inhibit the transport of iodide by the sodium iodide symporter (NIS), present e.g., in the thyroid and mammary glands. With perchlorate being increasingly detected in drinking water, milk and various other foods, increasing the iodide intake through inexpensive natural supplements may be an attractive solution for maintaining iodine assimilation. We report here measurable concentrations of perchlorate in several samples of seawater (detectable in about half the samples analyzed). We also report the iodide and perchlorate concentrations of 11 different species of seaweed and the corresponding bioconcentration factors (BCF) for perchlorate and iodide, relative to the seawater from which they were harvested. All seaweed samples came from the same region, off the coast of Northeastern Maine. Concentrations of iodide and perchlorate in four seawater samples collected from the region near harvest time were 30±11 and 0.16±0.084μgl−1, respectively. Concentrations of both iodide and perchlorate varied over a wide range for different seaweed species; iodide ranging from 16 to 3134mgkg−1 and perchlorate from 0.077 to 3.2mgkg−1. The Laminaria species had the highest iodide concentration; Laminaria digitata is the seaweed species most commonly used in the kelp tablets sold in health food stores. Our sample of L. digitata contained 3134±15mg iodide/kg dry weight. The BCF varied widely for different species, with Laminaria species concentrating iodide preferentially over perchlorate. The iodide BCF (BCFi) to perchlorate BCF (BCFp) quotient ranged from 0.66 to 53; L. digitata and L. saccarina having a BCFi/BCFp value of 45 and 53, respectively, far greater than a simple anion exchange process will allow. Although most seaweed samples contain some amount of perchlorate, the great majority contains iodide in so much higher amount that at least for the commonly used Laminaria species, the iodide/perchlorate ratio is greater than the square of the perchlorate to iodide selectivity factor reported for the mammalian NIS and should thus lead to net beneficial iodine nutrition even in a two-stage mother-infant scenario.
Keywords: Perchlorate; Iodide; Bioconcentration; Seaweed; Kelp; NIS
Perchlorate in seawater by P. Kalyani Martinelango; Kang Tian; Purnendu K. Dasgupta (pp. 100-107).
There has been no reliable published data on the presence of perchlorate in seawater. Seaweeds are among the most important plant life in the ocean and are good sources of iodine and have been widely used as food and nutritional supplement. Perchlorate is known to inhibit the transport of iodide by the sodium iodide symporter (NIS), present e.g., in the thyroid and mammary glands. With perchlorate being increasingly detected in drinking water, milk and various other foods, increasing the iodide intake through inexpensive natural supplements may be an attractive solution for maintaining iodine assimilation. We report here measurable concentrations of perchlorate in several samples of seawater (detectable in about half the samples analyzed). We also report the iodide and perchlorate concentrations of 11 different species of seaweed and the corresponding bioconcentration factors (BCF) for perchlorate and iodide, relative to the seawater from which they were harvested. All seaweed samples came from the same region, off the coast of Northeastern Maine. Concentrations of iodide and perchlorate in four seawater samples collected from the region near harvest time were 30±11 and 0.16±0.084μgl−1, respectively. Concentrations of both iodide and perchlorate varied over a wide range for different seaweed species; iodide ranging from 16 to 3134mgkg−1 and perchlorate from 0.077 to 3.2mgkg−1. The Laminaria species had the highest iodide concentration; Laminaria digitata is the seaweed species most commonly used in the kelp tablets sold in health food stores. Our sample of L. digitata contained 3134±15mg iodide/kg dry weight. The BCF varied widely for different species, with Laminaria species concentrating iodide preferentially over perchlorate. The iodide BCF (BCFi) to perchlorate BCF (BCFp) quotient ranged from 0.66 to 53; L. digitata and L. saccarina having a BCFi/BCFp value of 45 and 53, respectively, far greater than a simple anion exchange process will allow. Although most seaweed samples contain some amount of perchlorate, the great majority contains iodide in so much higher amount that at least for the commonly used Laminaria species, the iodide/perchlorate ratio is greater than the square of the perchlorate to iodide selectivity factor reported for the mammalian NIS and should thus lead to net beneficial iodine nutrition even in a two-stage mother-infant scenario.
Keywords: Perchlorate; Iodide; Bioconcentration; Seaweed; Kelp; NIS
Stability of low levels of perchlorate in drinking water and natural water samples by Sarah J. Stetson; Richard B. Wanty; Dennis R. Helsel; Stephen J. Kalkhoff; Donald L. Macalady (pp. 108-113).
Perchlorate ion (ClO4−) is an environmental contaminant of growing concern due to its potential human health effects, impact on aquatic and land animals, and widespread occurrence throughout the United States. The determination of perchlorate cannot normally be carried out in the field. As such, water samples for perchlorate analysis are often shipped to a central laboratory, where they may be stored for a significant period before analysis. The stability of perchlorate ion in various types of commonly encountered water samples has not been generally examined—the effect of such storage is thus not known. In the present study, the long-term stability of perchlorate ion in deionized water, tap water, ground water, and surface water was examined. Sample sets containing approximately 1000, 100, 1.0, and 0.5μgl−1 perchlorate ion in deionized water and also in local tap water were formulated. These samples were analyzed by ion chromatography for perchlorate ion concentration against freshly prepared standards every 24h for the first 7 days, biweekly for the next 4 weeks, and periodically after that for a total of 400 or 610 days for the two lowest concentrations and a total of 428 or 638 days for the high concentrations. Ground and surface water samples containing perchlorate were collected, held and analyzed for perchlorate concentration periodically over at least 360 days. All samples except for the surface water samples were found to be stable for the duration of the study, allowing for holding times of at least 300 days for ground water samples and at least 90 days for surface water samples.
Keywords: Perchlorate; Sample storage; Ion chromatography; Ground water; Surface water; Holding time
Stability of low levels of perchlorate in drinking water and natural water samples by Sarah J. Stetson; Richard B. Wanty; Dennis R. Helsel; Stephen J. Kalkhoff; Donald L. Macalady (pp. 108-113).
Perchlorate ion (ClO4−) is an environmental contaminant of growing concern due to its potential human health effects, impact on aquatic and land animals, and widespread occurrence throughout the United States. The determination of perchlorate cannot normally be carried out in the field. As such, water samples for perchlorate analysis are often shipped to a central laboratory, where they may be stored for a significant period before analysis. The stability of perchlorate ion in various types of commonly encountered water samples has not been generally examined—the effect of such storage is thus not known. In the present study, the long-term stability of perchlorate ion in deionized water, tap water, ground water, and surface water was examined. Sample sets containing approximately 1000, 100, 1.0, and 0.5μgl−1 perchlorate ion in deionized water and also in local tap water were formulated. These samples were analyzed by ion chromatography for perchlorate ion concentration against freshly prepared standards every 24h for the first 7 days, biweekly for the next 4 weeks, and periodically after that for a total of 400 or 610 days for the two lowest concentrations and a total of 428 or 638 days for the high concentrations. Ground and surface water samples containing perchlorate were collected, held and analyzed for perchlorate concentration periodically over at least 360 days. All samples except for the surface water samples were found to be stable for the duration of the study, allowing for holding times of at least 300 days for ground water samples and at least 90 days for surface water samples.
Keywords: Perchlorate; Sample storage; Ion chromatography; Ground water; Surface water; Holding time
Surface-enhanced Raman scattering for perchlorate detection using cystamine-modified gold nanoparticles by Chuanmin Ruan; Wei Wang; Baohua Gu (pp. 114-120).
Perchlorate (ClO4−) has recently emerged as a widespread environmental contaminant found in groundwater and surface water, and there is a great need for rapid detection and monitoring of this contaminant. This study presents a new technique using cystamine-modified gold nanoparticles as a substrate for surface-enhanced Raman scattering (SERS) detection of perchlorate at low concentrations. A detection limit of 5×10−6M (0.5mg/L) has been achieved using this method without sample preconcentration. This result was attributed to a strong plasmon enhancement by gold metal surfaces and the electrostatic attraction of ClO4− onto positively charged, cystamine-modified gold nanoparticles at a low pH. The methodology also was found to be reproducible, quantitative, and not susceptible to significant interference from the presence of anions such as sulfate, phosphate, nitrate and chloride at concentrations <1mM, making it potentially suitable for rapid screening and routine analysis of perchlorate in environmental samples.
Keywords: Surface-enhanced Raman scattering (SERS); Perchlorate detection; Cystamine; Gold nanoparticles
Surface-enhanced Raman scattering for perchlorate detection using cystamine-modified gold nanoparticles by Chuanmin Ruan; Wei Wang; Baohua Gu (pp. 114-120).
Perchlorate (ClO4−) has recently emerged as a widespread environmental contaminant found in groundwater and surface water, and there is a great need for rapid detection and monitoring of this contaminant. This study presents a new technique using cystamine-modified gold nanoparticles as a substrate for surface-enhanced Raman scattering (SERS) detection of perchlorate at low concentrations. A detection limit of 5×10−6M (0.5mg/L) has been achieved using this method without sample preconcentration. This result was attributed to a strong plasmon enhancement by gold metal surfaces and the electrostatic attraction of ClO4− onto positively charged, cystamine-modified gold nanoparticles at a low pH. The methodology also was found to be reproducible, quantitative, and not susceptible to significant interference from the presence of anions such as sulfate, phosphate, nitrate and chloride at concentrations <1mM, making it potentially suitable for rapid screening and routine analysis of perchlorate in environmental samples.
Keywords: Surface-enhanced Raman scattering (SERS); Perchlorate detection; Cystamine; Gold nanoparticles
Development of gold–silica composite nanoparticle substrates for perchlorate detection by surface-enhanced Raman spectroscopy by Wei Wang; Chuanmin Ruan; Baohua Gu (pp. 121-126).
Surface-enhanced Raman spectroscopy (SERS) holds promise for rapid, in situ detection of perchlorate (ClO4−) in the environment if sensitive and reproducible SERS substrates can be developed. In this study, new, functionalized gold–silica (Au–SiO2) composite nanoparticles were synthesized and used as SERS substrates for ClO4− detection. These nanoparticles were composed of a silica core with Au nanoparticles grafted onto the SiO2 spheres by in situ chemical reduction of AuCl4− or physisorption of Au colloids. Chemical coupling agents with such functional groups as –N+(CH3)3 and –NH3+/–NH2 were used to enhance perchlorate sorption onto the substrate and therefore the detection of ClO4−. These new substrates were found to be optically stable and provide a greatly enhanced surface plasmon or SERS, resulting in a detection limit as low as 10−6M ClO4− (0.1mg/L) in water.
Keywords: Raman spectroscopy; Perchlorate detection; SERS; Gold; Silica; Nanoparticles
Development of gold–silica composite nanoparticle substrates for perchlorate detection by surface-enhanced Raman spectroscopy by Wei Wang; Chuanmin Ruan; Baohua Gu (pp. 121-126).
Surface-enhanced Raman spectroscopy (SERS) holds promise for rapid, in situ detection of perchlorate (ClO4−) in the environment if sensitive and reproducible SERS substrates can be developed. In this study, new, functionalized gold–silica (Au–SiO2) composite nanoparticles were synthesized and used as SERS substrates for ClO4− detection. These nanoparticles were composed of a silica core with Au nanoparticles grafted onto the SiO2 spheres by in situ chemical reduction of AuCl4− or physisorption of Au colloids. Chemical coupling agents with such functional groups as –N+(CH3)3 and –NH3+/–NH2 were used to enhance perchlorate sorption onto the substrate and therefore the detection of ClO4−. These new substrates were found to be optically stable and provide a greatly enhanced surface plasmon or SERS, resulting in a detection limit as low as 10−6M ClO4− (0.1mg/L) in water.
Keywords: Raman spectroscopy; Perchlorate detection; SERS; Gold; Silica; Nanoparticles
Rapid on-line preconcentration and suppressed micro-bore ion chromatography of part per trillion levels of perchlorate in rainwater samples by Leon Barron; Pavel N. Nesterenko; Brett Paull (pp. 127-134).
The development of a rapid method for the determination of perchlorate in rain and drinking waters is presented. In the optimised method, an on-line preconcentration technique was employed utilising a 10mm×4.6mm Phenomenex Onyx monolithic guard cartridge coated with ( N-dodecyl- N, N-dimethylammonio)undecanoate for selective preconcentration, with subsequent elution into a fixed volume injection loop (‘heart-cut’ of the concentrator column eluate) and separation using an IonPac AS16 (250mm×2mm) anion exchange column and a potassium hydroxide concentration gradient. Off-line optimisation studies showed that the coated monolith displayed near quantitative recovery up to 50μg/L perchlorate level from standards prepared in reagent water. On-line preconcentration of perchlorate obtained detection limits down to 56ng/L in reagent water, between 70 and 80ng/L in rainwater samples and 2.5μg/L in non-pretreated drinking water. After an additional sample sulphate/carbonate removal step, low ng/L perchlorate concentrations could also be observed in drinking water. The complete on-line method exhibited reproducibility for n=10 replicate runs of R.S.D.≤3% for peak height/area and R.S.D.=0.08% for retention time. The optimised method, of 20min total duration, was applied to the determination of perchlorate by standard addition in 10 rainwater samples and one drinking water sample. Concentrations of perchlorate present ranged from below the detection limit for four rainwater samples, with another three samples showing perchlorate present at between 70 and 100ng/L, and one sample showing perchlorate present at 2.8μg/L. Levels of 1.1μg/L in the drinking water sample were also recorded.
Keywords: Perchlorate; Ion chromatography; On-line preconcentration; Monolithic concentrator column; Rainwater
Rapid on-line preconcentration and suppressed micro-bore ion chromatography of part per trillion levels of perchlorate in rainwater samples by Leon Barron; Pavel N. Nesterenko; Brett Paull (pp. 127-134).
The development of a rapid method for the determination of perchlorate in rain and drinking waters is presented. In the optimised method, an on-line preconcentration technique was employed utilising a 10mm×4.6mm Phenomenex Onyx monolithic guard cartridge coated with ( N-dodecyl- N, N-dimethylammonio)undecanoate for selective preconcentration, with subsequent elution into a fixed volume injection loop (‘heart-cut’ of the concentrator column eluate) and separation using an IonPac AS16 (250mm×2mm) anion exchange column and a potassium hydroxide concentration gradient. Off-line optimisation studies showed that the coated monolith displayed near quantitative recovery up to 50μg/L perchlorate level from standards prepared in reagent water. On-line preconcentration of perchlorate obtained detection limits down to 56ng/L in reagent water, between 70 and 80ng/L in rainwater samples and 2.5μg/L in non-pretreated drinking water. After an additional sample sulphate/carbonate removal step, low ng/L perchlorate concentrations could also be observed in drinking water. The complete on-line method exhibited reproducibility for n=10 replicate runs of R.S.D.≤3% for peak height/area and R.S.D.=0.08% for retention time. The optimised method, of 20min total duration, was applied to the determination of perchlorate by standard addition in 10 rainwater samples and one drinking water sample. Concentrations of perchlorate present ranged from below the detection limit for four rainwater samples, with another three samples showing perchlorate present at between 70 and 100ng/L, and one sample showing perchlorate present at 2.8μg/L. Levels of 1.1μg/L in the drinking water sample were also recorded.
Keywords: Perchlorate; Ion chromatography; On-line preconcentration; Monolithic concentrator column; Rainwater
Matrix diversion methods for improved analysis of perchlorate by suppressed ion chromatography and conductivity detection by Rong Lin; Brian De Borba; Kannan Srinivasan; Andy Woodruff; Chris Pohl (pp. 135-142).
Two inline matrix diversion methods were developed for the sensitive analysis of perchlorate in a matrix comprising up to 1000mgl−1 of chloride, sulfate and bicarbonate ions using suppressed ion chromatography and conductivity detection. The first method used a cryptand C1 concentrator column, which exhibited a high selectivity for perchlorate ion over the other matrix anions. After retaining the sample anions in a concentrator column derivatized with a crytpand phase, a rinse step was implemented with a weak base to divert the matrix ions to waste while selectively retaining perchlorate in the concentrator column for subsequent analysis. The analysis was done using a 2mm IonPac® AS16 or 2mm IonPac® AS20 separator column. The second method was a two-dimensional matrix diversion method with a focus on improving the detection sensitivity. The first dimension was used to achieve some resolution of the matrix ions from perchlorate. The perchlorate ion was then diverted into a concentrator column for subsequent analysis in the second dimension. By pursuing analysis using a 4mm IonPac® AS16 or IonPac® AS20 column in the first dimension and subsequently pursuing analysis using a 2mm IonPac® AS16 or IonPac® AS20 column format, excellent sensitivities were achieved when the first and second dimensions were operated at the same linear flow velocity (cmmin−1). While sensitive detection of perchlorate in the low μgl−1 regime was achieved by the above methods in the presence of matrix ions, superior recovery for perchlorate was demonstrated under a variety of matrix concentrations by the second method.
Keywords: Perchlorate; Two-dimensional; Cryptand; Cryptand C1
Matrix diversion methods for improved analysis of perchlorate by suppressed ion chromatography and conductivity detection by Rong Lin; Brian De Borba; Kannan Srinivasan; Andy Woodruff; Chris Pohl (pp. 135-142).
Two inline matrix diversion methods were developed for the sensitive analysis of perchlorate in a matrix comprising up to 1000mgl−1 of chloride, sulfate and bicarbonate ions using suppressed ion chromatography and conductivity detection. The first method used a cryptand C1 concentrator column, which exhibited a high selectivity for perchlorate ion over the other matrix anions. After retaining the sample anions in a concentrator column derivatized with a crytpand phase, a rinse step was implemented with a weak base to divert the matrix ions to waste while selectively retaining perchlorate in the concentrator column for subsequent analysis. The analysis was done using a 2mm IonPac® AS16 or 2mm IonPac® AS20 separator column. The second method was a two-dimensional matrix diversion method with a focus on improving the detection sensitivity. The first dimension was used to achieve some resolution of the matrix ions from perchlorate. The perchlorate ion was then diverted into a concentrator column for subsequent analysis in the second dimension. By pursuing analysis using a 4mm IonPac® AS16 or IonPac® AS20 column in the first dimension and subsequently pursuing analysis using a 2mm IonPac® AS16 or IonPac® AS20 column format, excellent sensitivities were achieved when the first and second dimensions were operated at the same linear flow velocity (cmmin−1). While sensitive detection of perchlorate in the low μgl−1 regime was achieved by the above methods in the presence of matrix ions, superior recovery for perchlorate was demonstrated under a variety of matrix concentrations by the second method.
Keywords: Perchlorate; Two-dimensional; Cryptand; Cryptand C1