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Analytica Chimica Acta (v.587, #2)
Application of inductively coupled plasma sector field mass spectrometry for low-level environmental americium-241 analysis by Zsolt Varga (pp. 165-169).
An improved and novel sample preparation method for241Am analysis by inductively coupled plasma sector field mass spectrometry has been developed. The procedure involves a selective CaF2 pre-concentration followed by an extraction chromatographic separation using TRU™ resin. The achieved absolute detection limit of 0.86fg (0.11mBq) is comparable to that of alpha spectrometry (0.1mBq) and suitable for low-level environmental measurements. Analysis of different kinds of environmental standard reference materials (IAEA-384 – Fangataufa lagoon sediment, IAEA-385 – Irish Sea sediment and IAEA-308 – Mixed seaweed from the Mediterranean Sea) and alpha spectrometry were used to validate the procedure. The chemical recovery of sample preparation ranged between 72 and 94%. The results obtained are in good agreement with reference values and those measured by alpha spectrometry. The proposed method offers a rapid and less labor-intensive possibility for environmental241Am analysis than the conventionally applied radioanalytical techniques.
Keywords: Americium; Inductively coupled plasma mass spectrometry; Extraction chromatography; Environmental analysis
Application of inductively coupled plasma sector field mass spectrometry for low-level environmental americium-241 analysis by Zsolt Varga (pp. 165-169).
An improved and novel sample preparation method for241Am analysis by inductively coupled plasma sector field mass spectrometry has been developed. The procedure involves a selective CaF2 pre-concentration followed by an extraction chromatographic separation using TRU™ resin. The achieved absolute detection limit of 0.86fg (0.11mBq) is comparable to that of alpha spectrometry (0.1mBq) and suitable for low-level environmental measurements. Analysis of different kinds of environmental standard reference materials (IAEA-384 – Fangataufa lagoon sediment, IAEA-385 – Irish Sea sediment and IAEA-308 – Mixed seaweed from the Mediterranean Sea) and alpha spectrometry were used to validate the procedure. The chemical recovery of sample preparation ranged between 72 and 94%. The results obtained are in good agreement with reference values and those measured by alpha spectrometry. The proposed method offers a rapid and less labor-intensive possibility for environmental241Am analysis than the conventionally applied radioanalytical techniques.
Keywords: Americium; Inductively coupled plasma mass spectrometry; Extraction chromatography; Environmental analysis
Multi-isotopic determination of plutonium (239Pu,240Pu,241Pu and242Pu) in marine sediments using sector-field inductively coupled plasma mass spectrometry by O.F.X. Donard; F. Bruneau; M. Moldovan; H. Garraud; V.N. Epov; D. Boust (pp. 170-179).
Among the transuranic elements present in the environment, plutonium isotopes are mainly attached to particles, and therefore they present a great interest for the study and modelling of particle transport in the marine environment. Except in the close vicinity of industrial sources, plutonium concentration in marine sediments is very low (from 10−4ngkg−1 for241Pu to 10ngkg−1 for239Pu), and therefore the measurement of238Pu,239Pu,240Pu,241Pu and242Pu in sediments at such concentration level requires the use of very sensitive techniques. Moreover, sediment matrix contains huge amounts of mineral species, uranium and organic substances that must be removed before the determination of plutonium isotopes. Hence, an efficient sample preparation step is necessary prior to analysis. Within this work, a chemical procedure for the extraction, purification and pre-concentration of plutonium from marine sediments prior to sector-field inductively coupled plasma mass spectrometry (SF-ICP-MS) analysis has been optimized. The analytical method developed yields a pre-concentrated solution of plutonium from which238U and241Am have been removed, and which is suitable for the direct and simultaneous measurement of239Pu,240Pu,241Pu and242Pu by SF-ICP-MS.
Keywords: SF-ICP-MS; Plutonium; Liquid–liquid extraction; Ion-exchange separation; High-grade purification; Marine sediments
Multi-isotopic determination of plutonium (239Pu,240Pu,241Pu and242Pu) in marine sediments using sector-field inductively coupled plasma mass spectrometry by O.F.X. Donard; F. Bruneau; M. Moldovan; H. Garraud; V.N. Epov; D. Boust (pp. 170-179).
Among the transuranic elements present in the environment, plutonium isotopes are mainly attached to particles, and therefore they present a great interest for the study and modelling of particle transport in the marine environment. Except in the close vicinity of industrial sources, plutonium concentration in marine sediments is very low (from 10−4ngkg−1 for241Pu to 10ngkg−1 for239Pu), and therefore the measurement of238Pu,239Pu,240Pu,241Pu and242Pu in sediments at such concentration level requires the use of very sensitive techniques. Moreover, sediment matrix contains huge amounts of mineral species, uranium and organic substances that must be removed before the determination of plutonium isotopes. Hence, an efficient sample preparation step is necessary prior to analysis. Within this work, a chemical procedure for the extraction, purification and pre-concentration of plutonium from marine sediments prior to sector-field inductively coupled plasma mass spectrometry (SF-ICP-MS) analysis has been optimized. The analytical method developed yields a pre-concentrated solution of plutonium from which238U and241Am have been removed, and which is suitable for the direct and simultaneous measurement of239Pu,240Pu,241Pu and242Pu by SF-ICP-MS.
Keywords: SF-ICP-MS; Plutonium; Liquid–liquid extraction; Ion-exchange separation; High-grade purification; Marine sediments
Dye sensitized luminescent europium nanoparticles and its time-resolved fluorometric assay for DNA by Yang Chen; Zuhong Lu (pp. 180-186).
The preparation and detection of highly luminescent aqueous europium nanoparticle labels for the time-resolved fluorometric assays has been demonstrated. The luminescent complexes included in the nanoparticle were composed of a dye sensitizer and a polyaminocarboxylate-based chelator with excellent water-solubility and a high binding constant for lanthanides. The luminescence of europium is greatly enhanced by the sensitization of the dye. The structure design of two functional entities in the single molecule made the lanthanide complex to have both strong luminescence and good aqueous solubility. SiO2 nanoparticles containing europium complexes were prepared by the reverse microemulsion method. One particle of ∼55nm in diameter has a luminescent intensity corresponding ∼1300 free europium complexes and 0.61ms fluorescence lifetime. The DNA time-resolved fluorometric assay with this nanoparticle label was carried out by magnetic microbeads as solid phase carrier. The detection sensitivity with the nanoparticles is improved more than 50-fold compared with the conventional dye FITC molecules. This luminescent nanoparticle label based on dye sensitization can be applied in ultrasensitive time-resolved fluorometric assays and imaging.
Keywords: Europium nanoparticle labels; Sensitized luminescence; Time-resolved fluorometric assay
Dye sensitized luminescent europium nanoparticles and its time-resolved fluorometric assay for DNA by Yang Chen; Zuhong Lu (pp. 180-186).
The preparation and detection of highly luminescent aqueous europium nanoparticle labels for the time-resolved fluorometric assays has been demonstrated. The luminescent complexes included in the nanoparticle were composed of a dye sensitizer and a polyaminocarboxylate-based chelator with excellent water-solubility and a high binding constant for lanthanides. The luminescence of europium is greatly enhanced by the sensitization of the dye. The structure design of two functional entities in the single molecule made the lanthanide complex to have both strong luminescence and good aqueous solubility. SiO2 nanoparticles containing europium complexes were prepared by the reverse microemulsion method. One particle of ∼55nm in diameter has a luminescent intensity corresponding ∼1300 free europium complexes and 0.61ms fluorescence lifetime. The DNA time-resolved fluorometric assay with this nanoparticle label was carried out by magnetic microbeads as solid phase carrier. The detection sensitivity with the nanoparticles is improved more than 50-fold compared with the conventional dye FITC molecules. This luminescent nanoparticle label based on dye sensitization can be applied in ultrasensitive time-resolved fluorometric assays and imaging.
Keywords: Europium nanoparticle labels; Sensitized luminescence; Time-resolved fluorometric assay
Synchronous fluorescence determination of DNA based on the interaction between methylene blue and DNA by Zhou Hu; Changlun Tong (pp. 187-193).
The fluorescence intensity of methylene blue (MB) quenched by DNA in the pH range of 6.5–8.0 was studied with synchronous fluorescence technology. A novel method for detecting single-stranded and double-stranded DNA was developed. The decreased fluorescence intensity at 664nm is in proportion to the concentration of DNA in the range of 0.28–11.0μmolL−1 for ctDNA, 0.14–8.25μmolL−1 for thermally denatured ctDNA and 0.28–8.25μmolL−1 for hsDNA. The detection limits ( S/ N=3) are 0.11, 0.04 and 0.04μmolL−1, respectively. The method is rapid, selective, and the reagents are lower toxic. It has been used for the determination of DNA in synthetic samples with good satisfaction. In addition, the interaction modes between MB and ctDNA and the mechanism of the fluorescence quenching were also discussed in detail. The experimental results from absorption spectra and fluorescence polarization indicate that the possible interaction modes between MB and DNA are the electrostatic binding and the intercalation binding.
Keywords: Deoxyribonucleic acid (DNA); Methylene blue (MB); Synchronous fluorescence; Determination; Interaction
Synchronous fluorescence determination of DNA based on the interaction between methylene blue and DNA by Zhou Hu; Changlun Tong (pp. 187-193).
The fluorescence intensity of methylene blue (MB) quenched by DNA in the pH range of 6.5–8.0 was studied with synchronous fluorescence technology. A novel method for detecting single-stranded and double-stranded DNA was developed. The decreased fluorescence intensity at 664nm is in proportion to the concentration of DNA in the range of 0.28–11.0μmolL−1 for ctDNA, 0.14–8.25μmolL−1 for thermally denatured ctDNA and 0.28–8.25μmolL−1 for hsDNA. The detection limits ( S/ N=3) are 0.11, 0.04 and 0.04μmolL−1, respectively. The method is rapid, selective, and the reagents are lower toxic. It has been used for the determination of DNA in synthetic samples with good satisfaction. In addition, the interaction modes between MB and ctDNA and the mechanism of the fluorescence quenching were also discussed in detail. The experimental results from absorption spectra and fluorescence polarization indicate that the possible interaction modes between MB and DNA are the electrostatic binding and the intercalation binding.
Keywords: Deoxyribonucleic acid (DNA); Methylene blue (MB); Synchronous fluorescence; Determination; Interaction
Adulteration of diesel/biodiesel blends by vegetable oil as determined by Fourier transform (FT) near infrared spectrometry and FT-Raman spectroscopy by Flavia C.C. Oliveira; Christian R.R. Brandão; Hugo F. Ramalho; Leonardo A.F. da Costa; Paulo A.Z. Suarez; Joel C. Rubim (pp. 194-199).
In this work it has been shown that the routine ASTM methods (ASTM 4052, ASTM D 445, ASTM D 4737, ASTM D 93, and ASTM D 86) recommended by the ANP (the Brazilian National Agency for Petroleum, Natural Gas and Biofuels) to determine the quality of diesel/biodiesel blends are not suitable to prevent the adulteration of B2 or B5 blends with vegetable oils. Considering the previous and actual problems with fuel adulterations in Brazil, we have investigated the application of vibrational spectroscopy (Fourier transform (FT) near infrared spectrometry and FT-Raman) to identify adulterations of B2 and B5 blends with vegetable oils. Partial least square regression (PLS), principal component regression (PCR), and artificial neural network (ANN) calibration models were designed and their relative performances were evaluated by external validation using the F-test. The PCR, PLS, and ANN calibration models based on the Fourier transform (FT) near infrared spectrometry and FT-Raman spectroscopy were designed using 120 samples. Other 62 samples were used in the validation and external validation, for a total of 182 samples. The results have shown that among the designed calibration models, the ANN/FT-Raman presented the best accuracy (0.028%, w/w) for samples used in the external validation.
Keywords: Fourier transform Raman spectrometry; Fourier transform (FT) near infrared spectrometry; Partial least squares regression; Principal component regression; Artificial neural network; Diesel/biodiesel blends
Adulteration of diesel/biodiesel blends by vegetable oil as determined by Fourier transform (FT) near infrared spectrometry and FT-Raman spectroscopy by Flavia C.C. Oliveira; Christian R.R. Brandão; Hugo F. Ramalho; Leonardo A.F. da Costa; Paulo A.Z. Suarez; Joel C. Rubim (pp. 194-199).
In this work it has been shown that the routine ASTM methods (ASTM 4052, ASTM D 445, ASTM D 4737, ASTM D 93, and ASTM D 86) recommended by the ANP (the Brazilian National Agency for Petroleum, Natural Gas and Biofuels) to determine the quality of diesel/biodiesel blends are not suitable to prevent the adulteration of B2 or B5 blends with vegetable oils. Considering the previous and actual problems with fuel adulterations in Brazil, we have investigated the application of vibrational spectroscopy (Fourier transform (FT) near infrared spectrometry and FT-Raman) to identify adulterations of B2 and B5 blends with vegetable oils. Partial least square regression (PLS), principal component regression (PCR), and artificial neural network (ANN) calibration models were designed and their relative performances were evaluated by external validation using the F-test. The PCR, PLS, and ANN calibration models based on the Fourier transform (FT) near infrared spectrometry and FT-Raman spectroscopy were designed using 120 samples. Other 62 samples were used in the validation and external validation, for a total of 182 samples. The results have shown that among the designed calibration models, the ANN/FT-Raman presented the best accuracy (0.028%, w/w) for samples used in the external validation.
Keywords: Fourier transform Raman spectrometry; Fourier transform (FT) near infrared spectrometry; Partial least squares regression; Principal component regression; Artificial neural network; Diesel/biodiesel blends
A new non-invasive, quantitative Raman technique for the determination of an active ingredient in pharmaceutical liquids by direct measurement through a plastic bottle by Minjung Kim; Hoeil Chung; Youngah Woo; Mark S. Kemper (pp. 200-207).
The concentration of an active pharmaceutical ingredient (povidone) in a commercial eyewash solution has been measured directly through a plastic (low-density polyethylene: LDPE) container using a wide area illumination (WAI) Raman scheme. The WAI scheme allows excitation using a 6mm laser spot (focal length: 248mm) that is designed to cover a wide sample area. As a result, it has the potential to improve the reliability Raman measurements by significantly enhancing representative sample interrogation, thus improving the reproducibility of sampling. It also decreases the sensitivity of sample placement with regard to the excitation focal plane. Simultaneously, isobutyric anhydride was placed in front of the bottles to use for a synchronous external standard configuration. This helps to correct the problematic variation of Raman intensity from the inherent fluctuation in laser power. Using the WAI Raman scheme combined with the synchronous standard method, the povidone concentration was successfully measured with spectral collection that was performed through a plastic barrier. The conventional Raman scheme was difficult to employ for the same purpose because of the degraded spectral reproducibility resulting from the smaller laser illumination area and the sensitivity of such an approach to the position of the sample bottle. The result from this study suggests that the WAI scheme exhibits a strong potential for the non-destructive quantitative analysis of pharmaceuticals measured directly in plastic containers. Preliminary work also shows that similar measurements can also be made in glass bottles. If implemented, this technique could be utilized as a simple and rugged method for quality assurance of final products in a manner consistent with Process analytical technology (PAT) requirements.
Keywords: Pharmaceutical liquids; Raman spectroscopy; Process analytical technology; Non-destructive analysis
A new non-invasive, quantitative Raman technique for the determination of an active ingredient in pharmaceutical liquids by direct measurement through a plastic bottle by Minjung Kim; Hoeil Chung; Youngah Woo; Mark S. Kemper (pp. 200-207).
The concentration of an active pharmaceutical ingredient (povidone) in a commercial eyewash solution has been measured directly through a plastic (low-density polyethylene: LDPE) container using a wide area illumination (WAI) Raman scheme. The WAI scheme allows excitation using a 6mm laser spot (focal length: 248mm) that is designed to cover a wide sample area. As a result, it has the potential to improve the reliability Raman measurements by significantly enhancing representative sample interrogation, thus improving the reproducibility of sampling. It also decreases the sensitivity of sample placement with regard to the excitation focal plane. Simultaneously, isobutyric anhydride was placed in front of the bottles to use for a synchronous external standard configuration. This helps to correct the problematic variation of Raman intensity from the inherent fluctuation in laser power. Using the WAI Raman scheme combined with the synchronous standard method, the povidone concentration was successfully measured with spectral collection that was performed through a plastic barrier. The conventional Raman scheme was difficult to employ for the same purpose because of the degraded spectral reproducibility resulting from the smaller laser illumination area and the sensitivity of such an approach to the position of the sample bottle. The result from this study suggests that the WAI scheme exhibits a strong potential for the non-destructive quantitative analysis of pharmaceuticals measured directly in plastic containers. Preliminary work also shows that similar measurements can also be made in glass bottles. If implemented, this technique could be utilized as a simple and rugged method for quality assurance of final products in a manner consistent with Process analytical technology (PAT) requirements.
Keywords: Pharmaceutical liquids; Raman spectroscopy; Process analytical technology; Non-destructive analysis
Improving the sensitivity of the determination of ceftiofur by capillary electrophoresis in environmental water samples: In-line solid phase extraction and sample stacking techniques by Patricia Puig; Francesc Borrull; Marta Calull; Fernando Benavente; Victoria Sanz-Nebot; José Barbosa; Carme Aguilar (pp. 208-215).
This paper describes two different approaches for increasing the sensitivity for the analysis of ceftiofur by capillary electrophoresis (CE). Two different techniques based on the introduction of an enlarged volume of sample, namely large volume sample stacking (LVSS) and in-line solid phase extraction (SPE) were studied and compared. LVSS allowed the on-column electrophoretic preconcentration of ceftiofur without modification of the separation capillary. In-line SPE-CE was developed by using a home-made microcartridge that was filled with a reversed-phase sorbent (C18). The microcartridge was coupled in-line near the inlet of the separation capillary. LVSS and in-line SPE-CE allowed automated operation and improved sensitivity for the analysis of ceftiofur with respect to conventional CE. When environmental water samples were analyzed, an additional pretreatment step based on off-line SPE was necessary in both cases to further decrease the detection limits. In terms of sensitivity for the determination of ceftiofur in river water samples, the combination of off-line SPE with in-line SPE-CE was found the most sensitive with a detection limit of 10ngL−1, whereas the method based on the use of off-line SPE with LVSS presented a detection limit of 100ngL−1.
Keywords: Abbreviations; SPE; solid phase extraction; LVSS; large volume sample stacking; REPSM; reversed electrode polarity stacking mode; SRMP; reverse migrating pseudostationary phaseCeftiofur; Capillary electrophoresis; In-line preconcentration; Large volume sample stacking; Solid phase extraction
Improving the sensitivity of the determination of ceftiofur by capillary electrophoresis in environmental water samples: In-line solid phase extraction and sample stacking techniques by Patricia Puig; Francesc Borrull; Marta Calull; Fernando Benavente; Victoria Sanz-Nebot; José Barbosa; Carme Aguilar (pp. 208-215).
This paper describes two different approaches for increasing the sensitivity for the analysis of ceftiofur by capillary electrophoresis (CE). Two different techniques based on the introduction of an enlarged volume of sample, namely large volume sample stacking (LVSS) and in-line solid phase extraction (SPE) were studied and compared. LVSS allowed the on-column electrophoretic preconcentration of ceftiofur without modification of the separation capillary. In-line SPE-CE was developed by using a home-made microcartridge that was filled with a reversed-phase sorbent (C18). The microcartridge was coupled in-line near the inlet of the separation capillary. LVSS and in-line SPE-CE allowed automated operation and improved sensitivity for the analysis of ceftiofur with respect to conventional CE. When environmental water samples were analyzed, an additional pretreatment step based on off-line SPE was necessary in both cases to further decrease the detection limits. In terms of sensitivity for the determination of ceftiofur in river water samples, the combination of off-line SPE with in-line SPE-CE was found the most sensitive with a detection limit of 10ngL−1, whereas the method based on the use of off-line SPE with LVSS presented a detection limit of 100ngL−1.
Keywords: Abbreviations; SPE; solid phase extraction; LVSS; large volume sample stacking; REPSM; reversed electrode polarity stacking mode; SRMP; reverse migrating pseudostationary phaseCeftiofur; Capillary electrophoresis; In-line preconcentration; Large volume sample stacking; Solid phase extraction
Determination of tocopherols and tocotrienols in cereals by pressurized liquid extraction–liquid chromatography–mass spectrometry by M. Bustamante-Rangel; M.M. Delgado-Zamarreño; A. Sánchez-Pérez; R. Carabias-Martínez (pp. 216-221).
A rapid analytical method including pressurized liquid extraction (PLE) and liquid chromatography–electrospray ionisation-mass spectrometry (LC–ESI-MS) has been developed for the determination of tocopherols and tocotrienols in cereals. The pressurized liquid extraction parameters were optimized in order to maximize the extraction efficiency. The use of methanol as extraction solvent at a temperature of 50°C and a pressure of 110bar, using one cycle of extraction with a static time of 5min, provided the best results. A good LC separation was achieved using a C18 column and a solution of 6.0mM ammonia in methanol/water (97:3, v/v) as the mobile phase at a flow rate of 0.2mLmin−1. MS coupling with an ESI interface in the negative ion mode was used as the detection technique. In the present work, it is shown that the addition of a base to the mobile phase is required to enhance the ionization of tocopherols and tocotrienols in negative ion mode electrospray ionization. The applicability of the method to cereal samples was confirmed. The reproducibility of the procedure was good, with relative standard deviations in the 6–10% range. The recoveries of added tocopherols from cereal samples ranged from 91 to 109%.
Keywords: Tocopherols; Tocotrienols; Liquid chromatography; Mass spectrometry; Pressurized liquid extraction
Determination of tocopherols and tocotrienols in cereals by pressurized liquid extraction–liquid chromatography–mass spectrometry by M. Bustamante-Rangel; M.M. Delgado-Zamarreño; A. Sánchez-Pérez; R. Carabias-Martínez (pp. 216-221).
A rapid analytical method including pressurized liquid extraction (PLE) and liquid chromatography–electrospray ionisation-mass spectrometry (LC–ESI-MS) has been developed for the determination of tocopherols and tocotrienols in cereals. The pressurized liquid extraction parameters were optimized in order to maximize the extraction efficiency. The use of methanol as extraction solvent at a temperature of 50°C and a pressure of 110bar, using one cycle of extraction with a static time of 5min, provided the best results. A good LC separation was achieved using a C18 column and a solution of 6.0mM ammonia in methanol/water (97:3, v/v) as the mobile phase at a flow rate of 0.2mLmin−1. MS coupling with an ESI interface in the negative ion mode was used as the detection technique. In the present work, it is shown that the addition of a base to the mobile phase is required to enhance the ionization of tocopherols and tocotrienols in negative ion mode electrospray ionization. The applicability of the method to cereal samples was confirmed. The reproducibility of the procedure was good, with relative standard deviations in the 6–10% range. The recoveries of added tocopherols from cereal samples ranged from 91 to 109%.
Keywords: Tocopherols; Tocotrienols; Liquid chromatography; Mass spectrometry; Pressurized liquid extraction
Validation of an analytical method to determine sulfamides in kidney by HPLC-DAD and PARAFAC2 with first-order derivative chromatograms by I. García; M.C. Ortiz; L. Sarabia; J.M. Aldama (pp. 222-234).
Six sulfamides were extracted from kidney and analysed by high-performance liquid chromatography with diode array detection (HPLC-DAD): sulfadiazine, sulfamethazine, sulfamethoxypyridazine, sulfamethoxazole, sulfadimethoxine and sulfaquinoxaline.Two main difficulties arose in identifying and quantifying the analytes. Firstly, the chromatographic peaks of the matrix interferences overlapped with those of the analytes. The uniqueness property of PARAFAC2 solved this problem. Secondly, the gradient elution caused a baseline drift. The first-order derivative of the chromatograms minimized its effect.The analytical method was validated. As the performance criteria detailed in the European Decision 2002/657/EC are based on specific signals, this paper generalizes those criteria for higher-order and non-specific signals. In this sense the proposed methodology is general and can be applied to any chromatographic method (HPLC or GC) with a detector that provide a multivariate signal (MS, DAD, EC, etc.).
Keywords: PARAFAC2; Sulfonamides; First-order derivative; Three-way models; Baseline drift; Decision limit CCα; Capability of detection CCβ; Decision 2002/657/EC
Validation of an analytical method to determine sulfamides in kidney by HPLC-DAD and PARAFAC2 with first-order derivative chromatograms by I. García; M.C. Ortiz; L. Sarabia; J.M. Aldama (pp. 222-234).
Six sulfamides were extracted from kidney and analysed by high-performance liquid chromatography with diode array detection (HPLC-DAD): sulfadiazine, sulfamethazine, sulfamethoxypyridazine, sulfamethoxazole, sulfadimethoxine and sulfaquinoxaline.Two main difficulties arose in identifying and quantifying the analytes. Firstly, the chromatographic peaks of the matrix interferences overlapped with those of the analytes. The uniqueness property of PARAFAC2 solved this problem. Secondly, the gradient elution caused a baseline drift. The first-order derivative of the chromatograms minimized its effect.The analytical method was validated. As the performance criteria detailed in the European Decision 2002/657/EC are based on specific signals, this paper generalizes those criteria for higher-order and non-specific signals. In this sense the proposed methodology is general and can be applied to any chromatographic method (HPLC or GC) with a detector that provide a multivariate signal (MS, DAD, EC, etc.).
Keywords: PARAFAC2; Sulfonamides; First-order derivative; Three-way models; Baseline drift; Decision limit CCα; Capability of detection CCβ; Decision 2002/657/EC
Fitting Lorentzian peaks with evolutionary genetic algorithm based on stochastic search procedure by Mustafa Karakaplan (pp. 235-239).
A global search technique for curve fitting based on evolutionary random search was modified and applied for quantifying a combination of Gaussian and Lorentzian peaks. This stochastic search procedures based on randomized operators is a modified Monte Carlo method. The proposed method tested on self obtained several overlapped Lorentzian peaks with random noise, Lennard particles in three dimensions and discrete mathematical functions previously used for optimization in literature. It was found to be the proposed method is suitable for complex and large scale optimization. The results of the new method have been compared with those obtained by two peak fitting programs. Developed method was found to be very fast and thus it is time saving.
Keywords: Genetic algorithms; Optimization; Peak resolution
Fitting Lorentzian peaks with evolutionary genetic algorithm based on stochastic search procedure by Mustafa Karakaplan (pp. 235-239).
A global search technique for curve fitting based on evolutionary random search was modified and applied for quantifying a combination of Gaussian and Lorentzian peaks. This stochastic search procedures based on randomized operators is a modified Monte Carlo method. The proposed method tested on self obtained several overlapped Lorentzian peaks with random noise, Lennard particles in three dimensions and discrete mathematical functions previously used for optimization in literature. It was found to be the proposed method is suitable for complex and large scale optimization. The results of the new method have been compared with those obtained by two peak fitting programs. Developed method was found to be very fast and thus it is time saving.
Keywords: Genetic algorithms; Optimization; Peak resolution
Lead(IV) oxide–graphite composite electrodes: Application to sensing of ammonia, nitrite and phenols by Biljana Šljukić; Craig E. Banks; Alison Crossley; Richard G. Compton (pp. 240-246).
Carbon powder modified with lead(IV) oxide was synthesised by a wet impregnation procedure from concentrated lead(II) nitrate solution. The impregnated powder was subsequently thermally treated at 823K. Electrochemical and spectroscopic characterisation of the modified powder showed that lead(IV) oxide has been formed during the procedure. A novel composite lead(IV) oxide modified carbon powder epoxy electrode was developed for electrocatalytic sensing of gaseous, inorganic and organic analytes. The behaviour and analytical advantages of the composite electrode are evaluated with respect to determination of ammonia, nitrite ions and several different phenols. It has been demonstrated that the composite electrode can be used to analyze these analytes in standard aqueous solutions with competitively low limits of detection.
Keywords: Lead oxide–graphite composite electrode; Graphite powder; Ammonia; Nitrite ions; Phenols
Lead(IV) oxide–graphite composite electrodes: Application to sensing of ammonia, nitrite and phenols by Biljana Šljukić; Craig E. Banks; Alison Crossley; Richard G. Compton (pp. 240-246).
Carbon powder modified with lead(IV) oxide was synthesised by a wet impregnation procedure from concentrated lead(II) nitrate solution. The impregnated powder was subsequently thermally treated at 823K. Electrochemical and spectroscopic characterisation of the modified powder showed that lead(IV) oxide has been formed during the procedure. A novel composite lead(IV) oxide modified carbon powder epoxy electrode was developed for electrocatalytic sensing of gaseous, inorganic and organic analytes. The behaviour and analytical advantages of the composite electrode are evaluated with respect to determination of ammonia, nitrite ions and several different phenols. It has been demonstrated that the composite electrode can be used to analyze these analytes in standard aqueous solutions with competitively low limits of detection.
Keywords: Lead oxide–graphite composite electrode; Graphite powder; Ammonia; Nitrite ions; Phenols
Potentiometric response and mechanism of anionic recognition of heterocalixarene-based ion selective electrodes by T.V. Shishkanova; D. Sýkora; J.L. Sessler; V. Král (pp. 247-253).
The ion selective electrode (ISE)-based potentiometric approach is shown to be an effective means of characterizing the anion recognition sites in the molecular receptor calix[2]pyridino[2]pyrrole (CPP). In particular, potentiometric pH-measurements involving the use of experimental PVC-membranes based on CPP revealed the existence of both mono- and diprotonated forms of the receptor under readily accessible conditions. Based on these analyses, apparent surface protonation constants for this heterocalixarene were found to lie between 8.5–8.9 (p KB1) and 3.3–3.8 (p KB2). CPP was found to interact with targeted anionic analytes based on both coulombic and hydrogen bond interactions, as inferred from varying the kinds of ionic sites present within the membrane phase. Potentiometric selectivity studies revealed that CPP preferred “Y-shaped” anions ( e.g. acetate, lactate, benzoate) over spherical anions ( e.g. fluoride and chloride), fluoride over chloride within the set of spherical anions, and the ortho-isomer over the corresponding meta- and para-isomers in the case of hydroxybenzoate (salicylate and congeners). In the context of this study, the advantages of potentiometric determinations of acetylsalicylic acid using optimized PVC-membranes based on CPP relative to more conventional PVC-membrane ISEs based on traditional anion exchanger were also demonstrated.
Keywords: Potentiometry; Ion-selective electrodes; Hydroxybenzoate; Heterocalixarene; Anion recognition
Potentiometric response and mechanism of anionic recognition of heterocalixarene-based ion selective electrodes by T.V. Shishkanova; D. Sýkora; J.L. Sessler; V. Král (pp. 247-253).
The ion selective electrode (ISE)-based potentiometric approach is shown to be an effective means of characterizing the anion recognition sites in the molecular receptor calix[2]pyridino[2]pyrrole (CPP). In particular, potentiometric pH-measurements involving the use of experimental PVC-membranes based on CPP revealed the existence of both mono- and diprotonated forms of the receptor under readily accessible conditions. Based on these analyses, apparent surface protonation constants for this heterocalixarene were found to lie between 8.5–8.9 (p KB1) and 3.3–3.8 (p KB2). CPP was found to interact with targeted anionic analytes based on both coulombic and hydrogen bond interactions, as inferred from varying the kinds of ionic sites present within the membrane phase. Potentiometric selectivity studies revealed that CPP preferred “Y-shaped” anions ( e.g. acetate, lactate, benzoate) over spherical anions ( e.g. fluoride and chloride), fluoride over chloride within the set of spherical anions, and the ortho-isomer over the corresponding meta- and para-isomers in the case of hydroxybenzoate (salicylate and congeners). In the context of this study, the advantages of potentiometric determinations of acetylsalicylic acid using optimized PVC-membranes based on CPP relative to more conventional PVC-membrane ISEs based on traditional anion exchanger were also demonstrated.
Keywords: Potentiometry; Ion-selective electrodes; Hydroxybenzoate; Heterocalixarene; Anion recognition
Functionalization of gold cysteamine self-assembled monolayer with ethylenediaminetetraacetic acid as a novel nanosensor by Reza Karimi Shervedani; Anahita Farahbakhsh; Mojtaba Bagherzadeh (pp. 254-262).
Electrochemical characterization of gold cysteamine self-assembled monolayer, in situ functionalized with ethylenediaminetetraacetic acid (Au–CA–EDTA SAM), is described by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and Osteryoung square wave voltammetry (OSWV). The results obtained by EIS and CV, in the presence of [Fe(CN)6]3−/4− redox probe, show that EDTA is successfully grafted to the surface of Au–CA electrode. Reproducible and reversible variation of the Rct and ΔEp as a function of solution pH show that Au–CA–EDTA SAM is stable in a wide range of pH and potentials. Accumulation of the Pb2+ and Cu2+ ions on the Au–CA–EDTA SAM electrode is investigated using faradaic currents or impedimetric effects measured by OSWV and EIS, respectively. These results reveal the presence of active complexing functional groups of EDTA on the surface, and thus, the formation of Au–CA–EDTA SAM electrode. The new sensor responds to the Pb2+ and Cu2+ separately and simultaneously in a wide linear range of concentrations.
Keywords: Self-assembled monolayer; EDTA; Cysteamine; Electrochemical impedance spectroscopy; Modified gold electrode; In situ functionalization
Functionalization of gold cysteamine self-assembled monolayer with ethylenediaminetetraacetic acid as a novel nanosensor by Reza Karimi Shervedani; Anahita Farahbakhsh; Mojtaba Bagherzadeh (pp. 254-262).
Electrochemical characterization of gold cysteamine self-assembled monolayer, in situ functionalized with ethylenediaminetetraacetic acid (Au–CA–EDTA SAM), is described by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and Osteryoung square wave voltammetry (OSWV). The results obtained by EIS and CV, in the presence of [Fe(CN)6]3−/4− redox probe, show that EDTA is successfully grafted to the surface of Au–CA electrode. Reproducible and reversible variation of the Rct and ΔEp as a function of solution pH show that Au–CA–EDTA SAM is stable in a wide range of pH and potentials. Accumulation of the Pb2+ and Cu2+ ions on the Au–CA–EDTA SAM electrode is investigated using faradaic currents or impedimetric effects measured by OSWV and EIS, respectively. These results reveal the presence of active complexing functional groups of EDTA on the surface, and thus, the formation of Au–CA–EDTA SAM electrode. The new sensor responds to the Pb2+ and Cu2+ separately and simultaneously in a wide linear range of concentrations.
Keywords: Self-assembled monolayer; EDTA; Cysteamine; Electrochemical impedance spectroscopy; Modified gold electrode; In situ functionalization
Investigation of the role of chelating ligand in the synthesis of ion-imprinted polymeric resins on the selective enrichment of uranium(VI) by P. Metilda; J. Mary Gladis; G. Venkateswaran; T. Prasada Rao (pp. 263-271).
Uranyl ion-imprinted polymeric (IIP) resins were prepared by dissolving stoichiometric amounts of uranyl nitrate and selected chelating ligands, viz. salicylaldoxime, catechol, succinicacid, 5,7-dichloroquinoline-8-ol and 4-vinyl pyridine in 2-methoxy ethanol (porogen) and copolymerizing thermally in the presence of 2-hydroxyethylmethacrylate (HEMA) and ethyleneglycol-dimethacrylate (EGDMA), using 2,2′-azobisisobutyronitrile (initiator). Again, IIP resins were also prepared on similar lines by utilizing ternary [uranium-non-vinylated ligand–vinylated ligand (4-vinyl pyridine)] complexes. Non-imprinted polymeric resins were identically prepared in both cases without the use of uranyl imprint ion. The percent enrichment and retention capacity studies showed significant imprinting effect in all cases. However, ion-imprinted polymeric resins formed with succinic acid (SA) or 5,7-dichloroquinoline-8-ol (DCQ) and 4-vinylpyridine (VP) alone gave quantitative enrichment and various parameters that influence the enrichment and elution were then optimized. The percent enrichment of uranium from synthetic seawater solutions was found to be 25.0±0.5 and 83.0±0.8 for SA–VP and DCQ–VP systems, respectively. The DCQ–VP-based IIP resins were successfully tested for the recovery of uranium from real seawater samples.
Keywords: Ion-imprinted polymers; Preconcentration; Chelating ligand; Uranium recovery; Analysis; Seawater
Investigation of the role of chelating ligand in the synthesis of ion-imprinted polymeric resins on the selective enrichment of uranium(VI) by P. Metilda; J. Mary Gladis; G. Venkateswaran; T. Prasada Rao (pp. 263-271).
Uranyl ion-imprinted polymeric (IIP) resins were prepared by dissolving stoichiometric amounts of uranyl nitrate and selected chelating ligands, viz. salicylaldoxime, catechol, succinicacid, 5,7-dichloroquinoline-8-ol and 4-vinyl pyridine in 2-methoxy ethanol (porogen) and copolymerizing thermally in the presence of 2-hydroxyethylmethacrylate (HEMA) and ethyleneglycol-dimethacrylate (EGDMA), using 2,2′-azobisisobutyronitrile (initiator). Again, IIP resins were also prepared on similar lines by utilizing ternary [uranium-non-vinylated ligand–vinylated ligand (4-vinyl pyridine)] complexes. Non-imprinted polymeric resins were identically prepared in both cases without the use of uranyl imprint ion. The percent enrichment and retention capacity studies showed significant imprinting effect in all cases. However, ion-imprinted polymeric resins formed with succinic acid (SA) or 5,7-dichloroquinoline-8-ol (DCQ) and 4-vinylpyridine (VP) alone gave quantitative enrichment and various parameters that influence the enrichment and elution were then optimized. The percent enrichment of uranium from synthetic seawater solutions was found to be 25.0±0.5 and 83.0±0.8 for SA–VP and DCQ–VP systems, respectively. The DCQ–VP-based IIP resins were successfully tested for the recovery of uranium from real seawater samples.
Keywords: Ion-imprinted polymers; Preconcentration; Chelating ligand; Uranium recovery; Analysis; Seawater
Matrix elimination method for the determination of precious metals in ores using electrothermal atomic absorption spectrometry by Bekir Salih; Ömür Çelikbıçak; Serhat Döker; Mehmet Doğan (pp. 272-280).
Poly( N-(hydroxymethyl)methacrylamide)-1-allyl-2-thiourea) hydrogels, poly(NHMMA-ATU), were synthesized by gamma radiation using60Co γ source in the ternary mixture of NHMMA-ATU-H2O. These hydrogels were used for the specific gold, silver, platinum and palladium recovery, pre-concentration and matrix elimination from the solutions containing trace amounts of precious metal ions. Elimination of inorganic matrices such as different transition and heavy metal ions, and anions was performed by adjusting the solution pH to 0.5 that was the selective adsorption pH of the precious metal ions. Desorption of the precious metal ions was performed by using 0.8M thiourea in 3M HCl as the most efficient desorbing agent with recovery values more than 95%. In the desorption medium, thiourea effect on the atomic signal was eliminated by selecting proper pyrolysis and atomization temperatures for all precious metal ions. Precision and the accuracy of the results were improved in the graphite furnace-atomic absorption spectrometer (GFAAS) measurements by applying the developed matrix elimination method performing the adsorption at pH 0.5. Pre-concentration factors of the studied precious metal ions were found to be at least 1000-fold. Detection limits of the precious metal ions were found to be less than 10ngL−1 of the all studied precious metal ions by using the proposed pre-concentration method. Determination of trace levels of the precious metals in the sea-water, anode slime, geological samples and photographic fixer solutions were performed using GFAAS clearly after applying the adsorption–desorption cycle onto the poly(NHMMA-UTU) hydrogels.
Keywords: Hydrogels; Recovery; Pre-concentration; Matrix elimination; Precious metal; Graphite furnace atomic absorption spectrometer
Matrix elimination method for the determination of precious metals in ores using electrothermal atomic absorption spectrometry by Bekir Salih; Ömür Çelikbıçak; Serhat Döker; Mehmet Doğan (pp. 272-280).
Poly( N-(hydroxymethyl)methacrylamide)-1-allyl-2-thiourea) hydrogels, poly(NHMMA-ATU), were synthesized by gamma radiation using60Co γ source in the ternary mixture of NHMMA-ATU-H2O. These hydrogels were used for the specific gold, silver, platinum and palladium recovery, pre-concentration and matrix elimination from the solutions containing trace amounts of precious metal ions. Elimination of inorganic matrices such as different transition and heavy metal ions, and anions was performed by adjusting the solution pH to 0.5 that was the selective adsorption pH of the precious metal ions. Desorption of the precious metal ions was performed by using 0.8M thiourea in 3M HCl as the most efficient desorbing agent with recovery values more than 95%. In the desorption medium, thiourea effect on the atomic signal was eliminated by selecting proper pyrolysis and atomization temperatures for all precious metal ions. Precision and the accuracy of the results were improved in the graphite furnace-atomic absorption spectrometer (GFAAS) measurements by applying the developed matrix elimination method performing the adsorption at pH 0.5. Pre-concentration factors of the studied precious metal ions were found to be at least 1000-fold. Detection limits of the precious metal ions were found to be less than 10ngL−1 of the all studied precious metal ions by using the proposed pre-concentration method. Determination of trace levels of the precious metals in the sea-water, anode slime, geological samples and photographic fixer solutions were performed using GFAAS clearly after applying the adsorption–desorption cycle onto the poly(NHMMA-UTU) hydrogels.
Keywords: Hydrogels; Recovery; Pre-concentration; Matrix elimination; Precious metal; Graphite furnace atomic absorption spectrometer
A new method for nanomolar determination of silicic acid in seawater by Peggy Rimmelin-Maury; Thierry Moutin; Bernard Quéguiner (pp. 281-286).
A novel method is proposed to determine concentrations of silicic acid in seawater in the nanomolar range of 3–500nM. It preconcentrates silicic acid through a “Magnesium Induced Co-precipitation” (MAGIC) step before a classical spectrophotometric measurement. The detection limit (3±2nM) is improved by a factor 10 in comparison to the conventional colorimetric methods. The best precision obtained to date is ±2nM for a natural sample of 69nM Si. No interference of phosphate was observed by contrast to previous methods. This simple method offers a simple, sensitive and accurate tool for silicic acid determination in depleted seawater, where its availability remains unknown.
Keywords: Magnesium Induced Co-precipitation; Spectrophotochemical analysis; Silicic acid; Seawater; Mediterranean sea
A new method for nanomolar determination of silicic acid in seawater by Peggy Rimmelin-Maury; Thierry Moutin; Bernard Quéguiner (pp. 281-286).
A novel method is proposed to determine concentrations of silicic acid in seawater in the nanomolar range of 3–500nM. It preconcentrates silicic acid through a “Magnesium Induced Co-precipitation” (MAGIC) step before a classical spectrophotometric measurement. The detection limit (3±2nM) is improved by a factor 10 in comparison to the conventional colorimetric methods. The best precision obtained to date is ±2nM for a natural sample of 69nM Si. No interference of phosphate was observed by contrast to previous methods. This simple method offers a simple, sensitive and accurate tool for silicic acid determination in depleted seawater, where its availability remains unknown.
Keywords: Magnesium Induced Co-precipitation; Spectrophotochemical analysis; Silicic acid; Seawater; Mediterranean sea
Preparation of a multi-hapten antigen and broad specificity polyclonal antibodies for a multiple pesticide immunoassay by Shu Ting Wang; Wen Jun Gui; Yi Rong Guo; Guo Nian Zhu (pp. 287-292).
A multi-determinant artificial antigen was prepared by haptens of four pesticides (chlorpyrifos, triazophos, carbofuran and parathion methyl) conjugating to the carrier protein BSA in turn. Male New Zealand white rabbits were immunized with this multi-determinant immunogen to produce the polyclonal antibodies (PAbs), which can recognize the four pesticides. The PAbs displayed high level for each relative hapten-OVA conjugate, with the favorable titers of 4.49×104, 8.98×104, 2.24×104 and 1.86×104, for CHBu-OVA, THHe-OVA, BFNB-OVA and MP5-OVA, respectively. Characterization studies of the PcAbs showed that it has high affinity and specificity to the four relative pesticides. An indirect competitive ELISA was developed for multi-residue determination. The I50 value for the four pesticides was 0.290, 0.065, 0.582 and 2.824μgmL−1, with the detection limit ( I10) of 0.022, 0.005, 0.015 and 0.115μgmL−1 for carbofuran, triazophos, chlorpyrifos and parathion methyl, respectively. The linear rang was 0.016–2.000, 0.005–0.500, 0.010–2.000 and 0.063–5.000μgmL−1, respectively, for carbofuran, triazophos, chlorpyrifos and parathion methyl. Results indicated that, this study provided a new strategy to develop immunoassays through artificial antigen design for pesticides multi-residue determination.
Keywords: Multi-hapten antigen; Broad specificity; Antibody; Enzyme-linked immunosorbence assay; Multi-residue
Preparation of a multi-hapten antigen and broad specificity polyclonal antibodies for a multiple pesticide immunoassay by Shu Ting Wang; Wen Jun Gui; Yi Rong Guo; Guo Nian Zhu (pp. 287-292).
A multi-determinant artificial antigen was prepared by haptens of four pesticides (chlorpyrifos, triazophos, carbofuran and parathion methyl) conjugating to the carrier protein BSA in turn. Male New Zealand white rabbits were immunized with this multi-determinant immunogen to produce the polyclonal antibodies (PAbs), which can recognize the four pesticides. The PAbs displayed high level for each relative hapten-OVA conjugate, with the favorable titers of 4.49×104, 8.98×104, 2.24×104 and 1.86×104, for CHBu-OVA, THHe-OVA, BFNB-OVA and MP5-OVA, respectively. Characterization studies of the PcAbs showed that it has high affinity and specificity to the four relative pesticides. An indirect competitive ELISA was developed for multi-residue determination. The I50 value for the four pesticides was 0.290, 0.065, 0.582 and 2.824μgmL−1, with the detection limit ( I10) of 0.022, 0.005, 0.015 and 0.115μgmL−1 for carbofuran, triazophos, chlorpyrifos and parathion methyl, respectively. The linear rang was 0.016–2.000, 0.005–0.500, 0.010–2.000 and 0.063–5.000μgmL−1, respectively, for carbofuran, triazophos, chlorpyrifos and parathion methyl. Results indicated that, this study provided a new strategy to develop immunoassays through artificial antigen design for pesticides multi-residue determination.
Keywords: Multi-hapten antigen; Broad specificity; Antibody; Enzyme-linked immunosorbence assay; Multi-residue