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Analytical Methods (v.4, #1)
Front cover (pp. 1-1).
Although spectrophotometric methods seem to be outdated as analytical tools for the analysis of trace metals in waters, there is no doubt that they still present a series of advantages over other advanced techniques (simplicity, speed, low cost and maintenance, portable instrumentation, etc. ). Even more, if experimental conditions are strictly controlled, it is possible to develop highly competitive methods. In this sense, method validation turns into a key feature to improve and demonstrate its applicability. Bearing this in mind, a simple and very sensitive spectrophotometric method for the direct determination of μg L−1 levels of zinc in natural waters has been developed and in-house validated. It is based on the reaction of Zn(ii ) with di-2-pyridyl ketone benzoylhydrazone (dPKBH) under slightly acidic conditions (pH 6.4) and 15% (v/v) ethanol to produce a 1 : 2 (Zn : dPKBH) complex (λ max 370 nm). Beer's law is obeyed in the range 6.3–3000 μg L−1 Zn(ii ) with a detection limit of 0.7 μg L−1. Different parameters such as selectivity, recovery, linearity, limits of detection and quantification, precision, and uncertainty of the measurements were evaluated in order to validate the proposed method. Then, the new method was applied to the analysis of different water samples (e.g. , tap and river water), demonstrating its applicability to the determination of Zn at environmental levels.
Inside front cover (pp. 2-2).
Purinergic receptor signaling events in platelets are a major determinant in platelet function. However, investigating the ATP-sensitive P2X1 platelet receptor is difficult due to its rapid desensitization in the washed platelet sample matrix. To minimize desensitization, most studies involving P2X1 activity in washed platelets require apyrase in the sample to reduce matrix ATP levels. Unfortunately, the apyrase will also rapidly degrade any ATP added exogenously during the studies. Here, we describe a method that employs the reported P2X1 inhibitor NF449 to sensitize washed platelets in the absence of any added apyrase. Sensitization is verified by spectrofluorometric determination of Ca2+ entry into the platelets after stimulation with concentrations of ATP ranging from 0.625 μM to 5 μM. Results suggest that sensitization of the P2X1 receptor by NF449 is not necessarily dependent upon the inhibitor concentration, but rather the ratio of the inhibitor to exogenously-added ATP concentrations. With a ratio of ATP agonist to NF440 concentration of ∼5 : 1, the resulting percent change in fluorescence due to Ca2+ entry into the platelet is 39.3 ± 0.8%; however, at a ratio of 1 : 8 ATP to NF449 the percent change is reduced to 13.1 ± 2.2%. The sensitizing effect is also investigated as a function of time. The results obtained verify that NF449 can behave as a concentration-dependent inhibitor and sensitizer of the platelet P2X1 receptor in washed platelet samples, depending on the ATP concentration in the matrix.
Contents list (pp. 3-18).
Arsenic is highly toxic in all of its forms found in natural groundwater. An improved method for the estimation of inorganic arsenic at low levels (μg L−1) in water has been proposed. The method involves the generation of arsine in a specially designed cell by borohydride reduction of arsenite (AsO2 1−). The resulting arsine is passed through a filter paper pre-dipped in mercuric bromide solution giving a yellowish brown complex. The color intensity of the spots is calculated by scanning the spotted paper and analyzing the image using specially designed software. The method was found to be effective at trace levels having a linear response at the concentration range 2–20μg L−1 (8–80ng). The detection limit of the proposed method is 1 μg L−1 (4 ng) which can be reduced further by making some modifications to the apparatus. The method was successfully applied to the analysis of synthetic samples and field samples of water.
Analytical science – a complex and diverse union (pp. 19-20).
Although spectrophotometric methods seem to be outdated as analytical tools for the analysis of trace metals in waters, there is no doubt that they still present a series of advantages over other advanced techniques (simplicity, speed, low cost and maintenance, portable instrumentation, etc. ). Even more, if experimental conditions are strictly controlled, it is possible to develop highly competitive methods. In this sense, method validation turns into a key feature to improve and demonstrate its applicability. Bearing this in mind, a simple and very sensitive spectrophotometric method for the direct determination of μg L−1 levels of zinc in natural waters has been developed and in-house validated. It is based on the reaction of Zn(ii ) with di-2-pyridyl ketone benzoylhydrazone (dPKBH) under slightly acidic conditions (pH 6.4) and 15% (v/v) ethanol to produce a 1 : 2 (Zn : dPKBH) complex (λ max 370 nm). Beer's law is obeyed in the range 6.3–3000 μg L−1 Zn(ii ) with a detection limit of 0.7 μg L−1. Different parameters such as selectivity, recovery, linearity, limits of detection and quantification, precision, and uncertainty of the measurements were evaluated in order to validate the proposed method. Then, the new method was applied to the analysis of different water samples (e.g. , tap and river water), demonstrating its applicability to the determination of Zn at environmental levels.
Editorial Board profiles (pp. 21-24).
The magnetic multiwalled carbon nanotube (MWCNT-MNP) was successfully synthesized. MWCNT-MNP and gas chromatography-tandem mass spectrometry (GC-MS/MS) were used for rapid, simple and reliable determination of bisphenol A (BPA), bisphenol F (BPF), bisphenol F diglycidyl ether (BFDGE) and bisphenol A diglycidyl ether (BADGE) at trace levels in water. The major factors affecting the recovery efficiency, such as amount of MWCNT-MNP, pH of water sample and sample volume, were carefully investigated. The recovery of these compounds was in the range of 88.5–115.1% with relative standard deviation less than 10%. Good linearities (r 2 > 0.995) were obtained. The limits of detection for BPA, BPF, BFDGE and BADGE were 0.001, 0.002, 0.06, and 0.05 μg L−1, respectively. Finally, the method was applied to tap water, river water and snow water, the results show that the developed method is suitable for monitoring trace BPA, BPF, and their diglycidyl ethers in environmental water samples.
Capacitively coupled contactless conductivity detection on microfluidic systems—ten years of development by Wendell Karlos Tomazelli Coltro; Renato Sousa Lima; Thiago Pinotti Segato; Emanuel Carrilho; Dosil Pereira de Jesus; Claudimir Lucio do Lago; José Alberto Fracassi da Silva (pp. 25-33).
The use of capacitively coupled contactless conductivity detection (C4D) on miniaturized systems has increased considerably over the last few years. Since the first report, 10 years ago, several advances on the detection cell geometry, strategies for increasing the sensitivity and a wide range of applications have been reported. This review intends to cover the main features related to the instrumental setup of this detection method for analytical and bioanalytical assays on microfluidic chips.
Thermoresponsive polymers in liquid chromatography by Irene Tan; Farnoosh Roohi; Maria-Magdalena Titirici (pp. 34-43).
In liquid chromatography, ‘reversed’ phase (RP) HPLC accounts for the vast majority of analyses concerning the separation of biomolecules. However, the typical usage of organic mobile phases as eluents associated with this technique has drawbacks in certain applications due to the possible denaturation of biocompounds, including other concerns related to the high cost of separations along with environment pollution. This disadvantage prompted the development of novel analytical methods in HPLC related to ‘greener’ stationary phases and process conditions. In this mini review, some advances in thermoresponsive liquid chromatography allowing separation processes on biomolecule mixtures using purely aqueous eluents under isocratic conditions are described.
A facile transport assay for H+ coupled membrane transport using fluorescence probes by Wanjun Lan; Hongliu Ren; Yu Pang; Chuseng Huang; Yufang Xu; Robert J. Brooker; Jingyan Zhang (pp. 44-46).
A facile activity assay for an H+-coupled transporter using florescent probes was developed with an H+-coupled manganese transporter (MntH) as a model. Making use of coupled-proton transport, the transport activity (H+/Mn2+ cotransport) can be directly determined via fluorescence intensity changes of the probe, 5-(and-6)-carboxyfluorescein (5(6)-FAM). The approach of using highly sensitive fluorescence probes provides a more simple and convenient assay method for the determination of proton-coupled metal-ion uptake by transporters.
Determination of critical concentrations by synchronous fluorescence spectrometry by Daoyong Yu; Fang Huang; Hai Xu (pp. 47-49).
We demonstrate that by using constant wavelength synchronous fluorescence spectrometry (CW-SFS) critical concentrations of some types of aggregation can be quantified. Detection of aggregation associated with hydrogen bonding in Chlorin e6 and Triton X-100 suggest that CW-SFS may be a technique that can explore aggregation at much lower levels (dimer, trimer, oligomer, etc. )
Identification of fluid and substrate chemistry based on automatic pattern recognition of stains by Namwon Kim; Zhenguo Li; Cedric Hurth; Frederic Zenhausern; Shih-Fu Chang; Daniel Attinger (pp. 50-57).
This study proposes that images of stains from 100-nanolitre drops can be automatically identified as signatures of fluid composition and substrate chemistry, for e.g. rapid biological testing. Two datasets of stain images are produced and made available online, one with consumable fluids, and the other with biological fluids. Classification algorithms are used to identify an unknown stain by measuring its similarity to representative examples of predefined categories. The accuracy ranges from 80 to 94%, compared to an accuracy by random assignment of 3 to 4%. Clustering algorithms are also applied to group unknown stain images into a number of clusters each likely to correspond to similar combinations of fluids and substrates. The clustering accuracy ranges from 62 to 80%, compared to an accuracy by random assignment of 3 or 4%. The algorithms were also remarkably accurate at determining the presence or absence of biotin and streptavidin respectively in the liquid and on the glass, the salt composition, or the pH of the solution.
EndoV/DNA ligase mutation scanning assay using microchip capillary electrophoresis and dual-color laser-induced fluorescence detection by Akira Kotani; Małgorzata A. Witek; John K. Osiri; Hong Wang; Rondedrick Sinville; Hanna Pincas; Francis Barany; Steven A. Soper (pp. 58-64).
We report the ability to detect with high sensitivity sporadic mutations using a mutation scanning assay, which employs thermostable endonuclease V (EndoV) and DNA ligase. The products of the mutation scanning assay were separated using microchip capillary electrophoresis (μCE) and detected with a dual-color laser-induced fluorescence (LIF) detector. PCR products from mutant and wild-type DNA of p53 exon 8 were generated using Cy3-labeled forward and Cy5-labeled reverse primers to allow LIF detection with μCE. EndoV recognizes and primarily cleaves heteroduplexed DNA one base 3′ to a mismatch and can nick matched sites at low levels as well. DNA ligase is used to reseal nicks generated at matched sites, which creates a highly sensitive and specific assay for analyzing sporadic mutations in genomic DNA. Heteroduplexed DNA samples were treated with EndoV alone and with both EndoV and DNA ligase and separated using a 4% (w/v) linear polyacrylamide gel constituted in 1x TTE buffer, 7 M urea, and 0.05% (w/v) methyl hydroxyethyl cellulose, which was used to suppress the EOF in the microchip. Sizing of the bands appearing in the electropherogram revealed the approximate position of the mutation. In this study, mutations present in p53 exon 8 generated Cy3-labeled cleavage products of 158 nt and Cy5-labeled cleavage products of 195 nt. The DNA fragments were simultaneously monitored at their respective color using a dual-color LIF system with the 158 and 195 nt fragments detected along with heteroduplexed fragments of 350 nt. The microchip separation was completed within 7 min, almost ten-fold shorter time compared to conventional capillary gel electrophoresis.
Quantitative UPLC-MS/MS analysis of the gut microbial co-metabolites phenylacetylglutamine, 4-cresyl sulphate and hippurate in human urine: INTERMAP Study by Anisha Wijeyesekera; Philip A. Clarke; Magda Bictash; Ian J. Brown; Mark Fidock; Thomas Ryckmans; Ivan K. S. Yap; Queenie Chan; Jeremiah Stamler; Paul Elliott; Elaine Holmes; Jeremy K. Nicholson (pp. 65-72).
The role of the gut microbiome in human health, and non-invasive measurement of gut dysbiosis are of increasing clinical interest. New high-throughput methods are required for the rapid measurement of gut microbial metabolites and to establish reference ranges in human populations. We used ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) -- positive and negative electrospray ionization modes, multiple reaction monitoring transitions -- to simultaneously measure three urinary metabolites (phenylacetylglutamine, 4-cresyl sulphate and hippurate) that are potential biomarkers of gut function, among multi-ethnic US men and women aged 40–59 from the INTERMAP epidemiologic study (n = 2000, two timed 24-hr urine collections/person). Metabolite concentrations were quantified via stable isotope labeled internal standards. The assay was linear in the ranges 1ng mL−1 (lower limit of quantification) to 1000ng mL−1 (phenylacetylglutamine and 4-cresyl sulfate) and 3ng mL−1 to 3000ng mL−1 (hippurate). These quantitative data provide new urinary reference ranges for population-based human samples: mean (standard deviation) 24-hr urinary excretion for phenylacetylglutamine was: 1283.0 (751.7) μmol/24-hr (men), 1145.9 (635.5) μmol/24-hr (women); for 4-cresyl sulphate, 1002.5 (737.1) μmol/24-hr (men), 1031.8 (687.9) μmol/24-hr (women); for hippurate, 6284.6 (4008.1) μmol/24-hr (men), 4793.0 (3293.3) μmol/24-hr (women). Metabolic profiling by UPLC-MS/MS in a large sample of free-living individuals has provided new data on urinary reference ranges for three urinary microbial co-metabolites, and demonstrates the applicability of this approach to epidemiological investigations.
We report the application of multi-wavelength resonance Raman (rR) spectroscopy for the characterisation of vinyl-bridged polysexithiophene films formed by electropolymerisation on gold electrodes. Resonance Raman spectroscopy of the neutral, polaronic and bipolaronic states of the polymer were determined by in situ
Characterizing the dual-wavelength dye indo-1 for calcium-ion sensing under pressure by Jordan Ryan; Paul Urayama (pp. 80-84).
Indo-1 is a dual-wavelength fluorophore widely used for calcium-ion sensing at ambient pressure. Because understanding the physico-chemical nature of high-pressure effects on probe dyes extends the range over which quantitative sensing is possible and informs the development of more robust probes, we report the high-pressure characterization of indo-1 for potential use in calcium-ion sensing under pressure. We find that indo-1 emission remains consistent with a two-state binding model when pressurized to 510 atm, accompanied by a decrease in calcium-binding affinity and an observation of piezochromic behavior. An estimate of the thermodynamic volume change of the indo-1 calcium dissociation reaction is consistent with values for other metal-ion chelators, and piezochromic shifts appear to be due to a pressure-induced change in solvent polarity versus a change in solvent viscosity. The two-state behavior and the linear response of parameters needed for dye calibration makes indo-1 amenable for use under pressure.
Preconcentration and determination of As, Cd, Pb and Bi using different sample introduction systems, cloud point extraction and inductively coupled plasma optical emission spectrometry by Fernanda dos Santos Depoi; Tiago Charão de Oliveira; Diogo Pompéu de Moraes; Dirce Pozebon (pp. 89-95).
This study deals with the development of a method for As, Bi, Cd and Pb preconcentration and determination using cloud point extraction (CPE) and inductively coupled plasma optical emission spectrometry (ICP OES). Hydride generation, pneumatic nebulization and micronebulization/aerosol desolvation were investigated for introducing the surfactant rich phase into the ICP. O ,O -Diethyldithiophosphate (DDTP) was used as complexant and octylphenoxypolyethoxyethanol (Triton X-114) as surfactant. The influence of concentration of HNO3 , HCl, DDTP, Triton X-114, surfactant rich phase in methanol, reductant of As, and NaBH4 was evaluated. The enrichment factors obtained were 10, 18, 12 and 14 for As, Bi, Cd and Pb, respectively. The limits of detection (LODs) of As, Bi, Cd and Pb were 0.055, 0.063, 0.047 and 0.28 μg L−1, respectively. Precision and accuracy were assessed by analysis of certified enriched water (NIST 1643e), oyster tissue (NIST 1566b), tobacco leaves (CTA-OTL-1), bush branches and leaves (GBW 07602) and analyte spiking. Microwave-induced combustion (MIC), sonication, and acid digestion were used for sample preparation. The developed method was applied for extraction and determination of As, Bi, Cd and Pb in river water, wine, fertilizer and urine. Analyte recovery close to 100% and relative standard deviation (RSD) lower than 5% were observed.
Integrated DNA extraction and amplification using electrokinetic pumping in a microfluidic device by Joseph Parton; Christopher Birch; Cordula Kemp; Stephen J. Haswell; Nicole Pamme; Kirsty J. Shaw (pp. 96-100).
An integrated system employing anion exchange for the extraction of DNA from biological samples prior to polymerase chain reaction DNA amplification has been developed, based on microfluidic methodology utilising electrokinetic pumping. In this system, the biological samples were added directly to chitosan-coated silica beads to facilitate DNA immobilisation. The purified, pre-concentrated DNA was then eluted using a combination of electro-osmotic flow enhanced with electrophoretic mobility, which enable DNA to be transported by both mechanisms into the DNA amplification chamber. Through optimisation of the DNA elution conditions, average DNA extraction efficiencies of 69.1% were achievable. Subsequent DNA amplification performed on the microfluidic system demonstrated not only the ability to use electrokinetic movement to integrate the two processes on a single device, but also that the quality and quantity of DNA eluted was suitable for downstream analysis. This work offers an attractive real-world to chip interface and a route to simpler Lab-on-a-Chip technology which eliminates the need for moving parts.
Measuring P2X1 receptor activity in washed platelets in the absence of exogenous apyrase by Kari B. Anderson; Welivitiya Karunarathne; Dana M. Spence (pp. 101-105).
Purinergic receptor signaling events in platelets are a major determinant in platelet function. However, investigating the ATP-sensitive P2X1 platelet receptor is difficult due to its rapid desensitization in the washed platelet sample matrix. To minimize desensitization, most studies involving P2X1 activity in washed platelets require apyrase in the sample to reduce matrix ATP levels. Unfortunately, the apyrase will also rapidly degrade any ATP added exogenously during the studies. Here, we describe a method that employs the reported P2X1 inhibitor NF449 to sensitize washed platelets in the absence of any added apyrase. Sensitization is verified by spectrofluorometric determination of Ca2+ entry into the platelets after stimulation with concentrations of ATP ranging from 0.625 μM to 5 μM. Results suggest that sensitization of the P2X1 receptor by NF449 is not necessarily dependent upon the inhibitor concentration, but rather the ratio of the inhibitor to exogenously-added ATP concentrations. With a ratio of ATP agonist to NF440 concentration of ∼5 : 1, the resulting percent change in fluorescence due to Ca2+ entry into the platelet is 39.3 ± 0.8%; however, at a ratio of 1 : 8 ATP to NF449 the percent change is reduced to 13.1 ± 2.2%. The sensitizing effect is also investigated as a function of time. The results obtained verify that NF449 can behave as a concentration-dependent inhibitor and sensitizer of the platelet P2X1 receptor in washed platelet samples, depending on the ATP concentration in the matrix.
Quantitative characterization of silicon solar cells in the electro-analytical approach: Combined measurements of temperature and voltage dependent electrical parameters by D. J. Crain; J. E. Garland; S. E. Rock; D. Roy (pp. 106-117).
Electrochemical and photo-electrochemical systems, often involving solid-liquid interfaces, have traditionally dominated the field of material/device characterization using electro-analytical tools such as linear sweep voltammetry (LSV) and impedance spectroscopy (IS). Recent developments in these measurement techniques have broadened their applications to various studies of non-electrochemical solid state systems. The present work provides further experimental illustration of these latter utilities of LSV and IS through a detailed study of the temperature and voltage sensitive features of the minority carrier lifetime, series resistance and back surface field (BSF) parameters of a mono-crystalline Si solar cell. Apart from displaying their characteristic temperature dependencies, the measured parameters respond to variations in the cell voltage, and exhibit certain mutually interacting features of the observed effects. The results also demonstrate how the characteristic features of charge recombination in the quasi-neutral and space charge regions of the solar cell can be resolved with D.C. voltage dependent A.C. impedance measurements.
Polyaniline/polyacrylic acid/multi-walled carbon nanotube modified electrodes for sensing ascorbic acid by Ida Tiwari; Karan Pratap Singh; Manorama Singh; Craig E. Banks (pp. 118-124).
A multi-walled carbon nanotube composite electrode incorporating Polyaniline (PANI) and Polyacrylic acid (PAA) is presented by diffusing aniline and PAA into Nafion- MWCNTs membranes supported upon a platinum macrodisc electrode. Nafion is found to be an ideal medium for dispersion of MWCNTs and for the formation of a homogeneous composite. The composite has been characterized utilizing SEM, TEM, FT-IR and electrochemical techniques. Electrochemical characterization reveals that the redox activity of the composite is improved with the cumulative effect of MWCNTs and PAA as additives. The electroanalytical behavior of the composite is evaluated towards the sensing of ascorbic acid in the presence of dopamine and uric acid exhibiting a detection limit of 2.5 × 10−7 M.
Solid phase extraction and sequential elution for pre-concentration of traces of Mn and Zn in analysis of honey by flame atomic absorption spectrometry by Pawel Pohl; Helena Stecka; Piotr Jamroz (pp. 125-131).
A pre-concentration procedure based on solid phase extraction and two-step elution was developed for the determination of the total concentrations of traces of food safety relevant elements (Mn and Zn) in ripened honeys. Accordingly, 10% (m/v) solutions of analyzed honeys (100 ml) were passed at 20 ml min−1 through resin beds of Dowex 50W × 8–400 to retain Mn and Zn ions and separate them from the glucose and fructose matrix. Afterwards, 20 ml of a 0.5 mol l−1 HNO3 solution was used to elute K and Na, easily ionized interfering metals. Finally, Mn and Zn were recovered prior to measurements by flame atomic absorption spectrometry (FAAS) using 5 ml of a 2 mol l−1 HCl solution. This procedure was applied in the analysis of six honeys and resulted in the determination of 0.2–13.6 μg g−1 of Mn and 0.2–1.2 μg g−1 of Zn with the precision (n = 3) within 3–10% and an accuracy better than 5%. Detection limits of Mn and Zn with this pre-concentration/separation procedure and the FAAS detection were 4 and 3 ng g−1, respectively.
Novel electrode reactions of diazepam, flunitrazepam and lorazepam and their exploitation in a new redox mode LC-DED assay for serum by Kevin C. Honeychurch; Ai Teng Chong; Khalil Elamin; John P. Hart (pp. 132-140).
Previously unreported voltammetric redox behaviour was identified for flunitrazepam, lorazepam and diazepam at a glassy carbon electrode. This was successfully exploited for their determination in serum by high performance liquid chromatography dual electrode detection in the redox mode (LC-DED). Initial studies were performed to optimise the chromatographic conditions and these were found to be 50% acetone, 50% 100 mM pH 2 phosphate buffer at a flow rate of 0.8 ml min−1, employing a Hypersil C18 , 5 μm, 250 mm × 4.6 mm column held at 40 °C. Cyclic voltammetric studies were made to ascertain the redox behaviour of these benzodiazepines over the pH range 2–10. Hydrodynamic voltammetry was used to optimise the applied potential at the amperometric generator and detector cells; these were identified to be −2.45 V (vs. stainless steel) and +1.0 V. (vs. Ag/AgCl).
A novel enzymatic technique for determination of sarcosine in urine samples by Casey Burton; Sanjeewa Gamagedara; Yinfa Ma (pp. 141-146).
Metabolites impart a significant importance to the understanding of biological reactions and consequently to the development of diagnostic and therapeutic techniques for specific diseases. Furthermore, there has been recent interest in metabolite concentrations present in urine for potential noninvasive disease diagnosis. The detection of specific metabolites, however, presents certain analytical difficulties such as low or ambiguous specificity of the techniques. This study developed a new technique, utilizing oxidative, enzymatic production of formaldehyde from the metabolite to produce a pH-induced change observed by fluorescein in acetone. This probe displays high sensitivity towards pH imbalances and, coupled with high enzymatic specificity, forms an accurate method to measure metabolite concentrations. Sarcosine was used as a model analyte in this study due to its potential for serving as a prostate cancer biomarker. Sarcosine was treated with sarcosine oxidase to generate formaldehyde, which was further oxidized to formic acid, and subsequently measured by the corresponding change in fluorescein. A good linearity was revealed with a correlation coefficient of 0.9961 and a detection limit of 20 nmol L−1. This method was applied to sarcosine analysis in nine urine samples. The results suggest that this is a viable, cost-effective technique for determination of sarcosine in urine samples without interferences such as alanine.
Enhanced spectrophotometric methods for trace metal determination in waters: zinc as an example by Juan J. Pinto; Manuel García-Vargas; Carlos Moreno (pp. 147-152).
Although spectrophotometric methods seem to be outdated as analytical tools for the analysis of trace metals in waters, there is no doubt that they still present a series of advantages over other advanced techniques (simplicity, speed, low cost and maintenance, portable instrumentation, etc. ). Even more, if experimental conditions are strictly controlled, it is possible to develop highly competitive methods. In this sense, method validation turns into a key feature to improve and demonstrate its applicability. Bearing this in mind, a simple and very sensitive spectrophotometric method for the direct determination of μg L−1 levels of zinc in natural waters has been developed and in-house validated. It is based on the reaction of Zn(ii ) with di-2-pyridyl ketone benzoylhydrazone (dPKBH) under slightly acidic conditions (pH 6.4) and 15% (v/v) ethanol to produce a 1 : 2 (Zn : dPKBH) complex (λ max 370 nm). Beer's law is obeyed in the range 6.3–3000 μg L−1 Zn(ii ) with a detection limit of 0.7 μg L−1. Different parameters such as selectivity, recovery, linearity, limits of detection and quantification, precision, and uncertainty of the measurements were evaluated in order to validate the proposed method. Then, the new method was applied to the analysis of different water samples (e.g. , tap and river water), demonstrating its applicability to the determination of Zn at environmental levels.
Monitoring of decolorization of a two dyes mixture using spectrophotometric data and multivariate curve resolution: modeling the removal process using an experimental design method by Abdolhossein Naseri; Hasan Ayadi-Anzabi (pp. 153-161).
Developing a simple analytical method to determine azo dyes in environmental samples is important. Spectrophotometric techniques remain largely used in this field because of the easy interpretation and handling of the spectral data. But, this method suffers a main problem, spectral overlapping. In this paper, in spite of spectral overlapping, multivariate curve-alternating least squares was used to determine Acid Red 27 and Methyl Red dyes in a mixture of them. Resolution of binary mixtures of analytes with minimum sample pre-treatment and without analyte separation was successfully achieved by analyzing the UV-Vis spectral data. Also, central composite design was applied for modeling of the decolorization of a dye solution that contains two dyes using the Fenton reaction. The investigated factors (variables) were the initial concentration of Fe(ii ), the initial concentration of the two dyes and the initial H2 O2 concentration.
Employment of multivariate curve resolution to liquid chromatography coupled with NMR by Mohsen Kompany-Zareh; Somayeh Gholami; Babak Kaboudin (pp. 162-170).
NMR spectral data from aliquots at different retention times of an ordinary liquid chromatographic column were resolved into individual concentration and spectral profiles using multivariate curve resolution based on alternative least squares (MCR-ALS) and canonical correlation analysis (CCA). Samples were a number of the reaction product mixtures obtained at different experimental conditions, based on a simple experimental design, and for synthesis of α-amido phosphonate. NMR data from different experiments were augmented and aligned using correlation optimized warping (COW) procedure. Orthogonal projection approach (OPA) was applied to make initial estimates for MCR-ALS. CCA was implemented in three steps; the first step was determining the regions of NMR peak clusters, the second was the rank analysis of each peak cluster, and the third was assignment of peak clusters to different compounds using CCA. Employing both resolution methods, the NMR data from liquid chromatographic column was successfully resolved to spectral and concentration profiles of pure components. From the resolved concentration profiles the optimum experimental conditions with maximum yield of reaction were obtained as air atmosphere and at 25 °C. Due to the fact that there is rotational ambiguity in the obtained results of MCR-ALS, the resolved concentration profiles from the two methods were different. However, both methods resulted in the same optimal experimental conditions.
Analysis of HPLC fingerprints: discrimination of raw and processed
Chromatographic fingerprints of raw, wine-treated and braised rhubarb samples were obtained by liquid chromatography with a diode array detector (LC-DAD). Eight LC peaks were selected for fingerprint analysis, and six compounds were identified as gallic acid, emodin, chrysophanol, palmidin, rhein glucoside and desoxyrhaponticin. A data matrix of the chromatographic fingerprints from the three types of sample was submitted to principal component analysis (PCA) and this indicated that the three types of rhubarb were distinguished in the PC1 versus PC2 space. Training, verification and prediction data sets of the three types of HPLC fingerprint were processed successfully by chemometrics data classification methods, K -nearest neighbor (KNN), linear discriminant analysis (LDA) and least squares support vector machines (LS-SVM), and these types of rhubarb sample were classified satisfactorily.
A novel high selectivity sensor for tetradifon residues based on double-side hollow molecularly imprinted materials by Jixian Yan; Jinghua Yu; Peini Zhao; Lei Ge; Mei Yan; Shiquan Liu (pp. 177-182).
A sensitive and rapid technique for high selectivity detection of tetradifon has been developed. This method is based on a new kind of hollow shell molecularly imprinted (MI) polymer. In this method, the new hollow shell MI polymer has bigger specific surface areas compared with the traditional one based on the double-sides hollow microspheres structure. The proposed method has the advantage of wider linear range and lower limit of detection compared with the traditional one. The change in chemiluminescence (CL) intensity is linearly proportional with the concentration of tetradifon in the range 0.1∼12 μg mL−1 and the detection limit has reached 0.0483 μg mL−1. The new MI-CL sensor has been successfully applied to the determination of residual tetradifon in food and the results obtained compare well with those by other methods.
Electrophoretic mobility measurement by laser Doppler velocimetry and capillary electrophoresis of micrometric fluorescent polystyrene beads by Bo Xiong; Antoine Pallandre; Isabelle le Potier; Pierre Audebert; Elias Fattal; Nicolas Tsapis; Gillian Barratt; Myriam Taverna (pp. 183-189).
Many studies have been made and techniques developed to measure the mobility of particles and molecules by laser Doppler velocimetry and capillary electrophoresis. We propose here to evaluate and compare these two measurement techniques for their ability to characterize various fluorescent polystyrene beads as a function of the buffer pH. The repeatability of electrophoretic mobility determination by the two techniques in buffer at different pHs (neutral to alkaline) was first examined and compared. The accuracy of the determination was then evaluated. A wide range of beads which varied in their size (diameters ranging from 270 to 1000 nm), surface functional groups (NH2 , COOH, and neutral), and the presence or absence of surfactants or incorporated dye molecules were investigated in order to perform a comprehensive study. The results indicated that apart from large amino beads (with a diameter over 800 nm), capillary electrophoresis generally gave better or similar relative standard deviations for most polystyrene beads, which could be attributed to a stronger adsorption of these beads onto the silica capillary surface in CE. Beads with neutral pH were more difficult to measure accurately with both methods. We also concluded that capillary electrophoresis measurements are not accurate for amino beads in the pH range of this study. However, both methods were capable of distinguishing polystyrene beads with different sizes or surface groups. We found that dye molecules introduced in beads did not alter their electrophoretic mobility values. Taken together, the data and discussion provide a guide to choose the right technique to characterize any given set of functional particles precisely and with the highest accuracy.
Optimized conditions for liquid-phase microextraction based on solidification of floating organic droplet for extraction of nitrotoluene compounds by using response surface methodology by Laleh Adlnasab; Homeira Ebrahimzadeh; Yadollah Yamini (pp. 190-195).
Solidification of floating organic droplet microextraction (SFODME) method followed by gas chromatography-flame ionization detector (GC-FID) was applied for ultra-preconcentration and determination of nitrotoluene compounds in water samples. The effects of several factors such as volume of organic solvent, sample solution temperature, extraction time, stirring rate and ionic strength were simultaneously investigated on the extraction efficiency using an experimental design. For the first time, quarter fraction factorial design was applied to screening in order to determine the significant factors in the extraction efficiency. Then, central composite design (CCD) was used for the optimization of important factors and the response surface equations were obtained. The optimized conditions were established to be 600 rpm for stirring rate, 30 min for extraction time, 60 °C for extraction temperature, 5 μL for organic solvent volume, and 3% (w/v) of NaCl for ionic strength. Limit of detections (LODs) for the extraction method were in the range of 0.3–0.5 μg L−1. Linear dynamic ranges were in the range of 0.5–200 μg L−1 for three nitrotoluene compounds and the obtained preconcentration factor was in the range of 535–640. The relative standard deviations of the proposed method were 4–10%. Finally, performance of the proposed method was tested for the extraction and determination of the nitrotoluene compounds at microgram per litre levels in samples and satisfactory results were achieved.
Target and non-target screening strategies for organic contaminants, residues and illicit substances in food, environmental and human biological samples by UHPLC-QTOF-MS by Ramon Díaz; María Ibáñez; Juan V. Sancho; Félix Hernández (pp. 196-209).
In this paper, we illustrate the potential of ultra-high performance liquid chromatography (UHPLC) coupled with hybrid quadrupole time-of-flight mass spectrometry (QTOF MS) for large scale screening of organic contaminants in different types of samples. Thanks to the full-spectrum acquisition at satisfactory sensitivity, it is feasible to apply both (post)-target and non-target approaches for the rapid qualitative screening of organic pollutants in food, biological and environmental samples. Different strategies have been applied and compared in this work. The first approach consists of target screening based on automatically extracting the exact analyte masses with a narrow mass window (±10 mDa). The selection of analytes can be made after MS acquisition as non-specific analyte information is required when injecting the samples. The second, non-targeted approach, consists of a first component detection step followed by the search of the detected components in home-made spectral libraries. In this work, two types of libraries have been evaluated: a theoretical database, including the molecular formula of a large number of pollutants (∼1000), and an empirical mass spectra library which includes a lower number of compounds for which reference standards were available. In all cases the confidence of the identification process was excellent, thanks to the value of information given in QTOF MSE acquisition mode (i.e. simultaneous acquisition of low and high energy TOF MS spectra in a unique run). Both, target and non-target approaches, are complementary and both have advantages and drawbacks. Their application to different types of samples has allowed the detection of diverse organic compounds, for example the mycotoxin fumonisin B1 in food samples, cocaine and several metabolites in human urine, as well as several pesticides, antibiotics and drugs of abuse in urban wastewater.
A simple in-house dry ashing chamber for the rapid determination of total mercury in organic-rich solid materials by oxidative pyrolysis followed by CVAAS and FI-ICPMS detection by M. V. Balarama Krishna; A. C. Sahayam; D. Karunasagar (pp. 210-216).
A simple in-house pyrolysis chamber made of quartz material is described for the determination of total mercury content in a wide variety of organic-rich solid materials (plant, fish tissues and polymer based) by oxidative pyrolysis and cold vapour atomic absorption spectrometry (CVAAS). Oxidative pyrolysis was carried out by means of a Bunsen burner in the presence of an oxygen stream. Mercury liberated from the sample was collected in 0.1% KMnO4 trapping solution. Determination of mercury was achieved by CVAAS. Under optimal conditions, the limit of detection (LOD), calculated as the concentration of mercury yielding a signal equivalent to three times of the standard deviation of the blank value (3σ ), obtained for CVAAS in conjunction with the oxidative pyrolysis method was found to be 0.08 ng g−1. Flow injection inductively coupled plasma mass spectrometry (FI-ICPMS) was used to validate the developed method. The results obtained for several reference materials, such as mussel tissue (CE-278), tuna fish (CE-463), tuna fish (464), polyethylene (EC-681), plankton (CRM-414), lichen (CRM-482) and human hair (CRM-397), by the developed method agreed well with the certified values. These studies clearly demonstrate the capabilities of the pyrolysis set-up that can potentially be used for the rapid determination of total mercury in a wide variety of organic-rich matrices.
A specific UPLC-ESI-MS/MS method for analysis of cyadox and its three main metabolites in fish samples by Linli Cheng; Zhanhui Wang; Jianzhong Shen; Linxia Li; Haixia Wu; Suxia Zhang (pp. 217-221).
A rapid and sensitive ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was developed for the determination of cyadox (CYX) and its three major metabolites, quinoxaline-2-carboxylic acid (QCA), 1-desoxycyadox (1-DCYX) and 1,4-bisdesoxycyadox (BDCYX) in fish. Samples were extracted with acetonitrile–0.5 M hydrochloric acid (9 + 1) and cleaned up using Oasis MAX cartridges. The total time taken for separation by UPLC was less than 5 min. The four target compounds were then determined by ESI-MS/MS. At the fortified levels of 2–50 μg kg−1 in fish, recoveries of all the compounds ranged from 80.2% to 88.2%, with a relative standard deviation of 6.8 to 14.6%. Limits of detection for CYX, QCA, 1–DCYX and BDCYX were 0.52, 1.07, 0.69 and 0.38 μg kg−1, respectively.
Measuring estriol and estrone simultaneously in liquid cosmetic samples using second-order calibration coupled with excitation–emission matrix fluorescence based on region selection by De-Zhu Tu; Hai-Long Wu; Yuan-Na Li; Juan Zhang; Yong Li; Chong-Chong Nie; Xiao-Hua Zhang; Ru-Qin Yu (pp. 222-229).
This paper describes a sensitive excitation–emission matrix fluorescence (EEM) method for simultaneously measuring contents of two estrogens, estriol (E3) and estrone (E1), in liquid cosmetic samples with the aid of a second-order calibration method based on a parallel factor analysis (PARAFAC) algorithm. Before processing the obtained three-way data, a better region of the excitation and emission spectra was purposely selected. Then PARAFAC was recommended to acquire the clean spectra and predict the individual concentrations of the analytes of interest even in the presence of uncalibrated interferences. The standard curves of the two analytes are linear within a linear concentration range of 0–0.736 μg mL−1 of E3 and 0–18.000 μg mL−1 of E1 with correlation coefficients typically greater than 0.99. In the analysis of watermelon frost anti-acne toner sold on the internet web site, the limit of detection (LOD) of E3 is 4.7 ng mL−1 with an accuracy of 102.3–113.7%, and for E1, the LOD is 96.1 ng mL−1 with an accuracy of 92.3–111.0%. In the analysis of pagoda flower relaxing lotion from the commercial market in Changsha, the LOD of E3 is 8.9 ng mL−1 with an accuracy of 95.0–107.1%, and for E1, the LOD is 76.9 ng mL−1 with an accuracy of 98.6–119.3%. Generally, a new avenue has been opened up to determine estrogens quantitatively in cosmetic samples. This methodology will achieve greater development and gradually become a more routine approach in cosmetic quality control due to its advantages of high sensitivity, simple pretreatment procedure and non-destructive nature.
Screening for aromatase ligands in the extract of
Aromatase (CYP19), which can catalyze the conversion of androgens to estrogens, has been one of the main inducers of hormone-related cancers. As a result, it is very important and necessary to find an aromatase inhibitor quickly and effectively. In this article, we screened for compounds that can bind to aromatase in the extract of Broussonetia papyrifera . The screening method HPLC/ESI-MS was employed in this presentation. Structures of twelve compounds were studied on the basis of LC-MS data. Six compounds were characterized as aromatase ligands through HPLC. Three of the ligands were identified as the glucosides of scopoletin, kaempferol and apigenin, whilst the others were vitexin, luteolin-7-O -β-D-glucopyranosid and dihydrochalcone. The bioassay indicated these compounds had aromatase inhibitory activity. We concluded that HPLC/ESI-MS was an effective means to reveal aromatase ligands. Moreover, five of the ligands found in this study were flavonoids. The C2, C3 double bond and the 7-OH were essential for the binding activity, which may be the binding sites for flavonoids.
Ligandless-ultrasound-assisted emulsification-microextraction combined with inductively coupled plasma-optical emission spectrometry for simultaneous determination of heavy metals in water samples by Hassan Sereshti; Vahid Khojeh; Maryam Karimi; Soheila Samadi (pp. 236-241).
In the present study, the simple and efficient method of ligandless-ultrasound-assisted emulsification-microextraction (LL-USAEME) has been developed for the simultaneous preconcentration and determination of chromium and zinc in water samples by inductively coupled plasma-optical emission spectrometry (ICP-OES). Tetrachloroethylene was selected as the extraction solvent. A fractional factorial design (25−1) and a Box–Behnken design (BBD) were used to identify and optimize the most important parameters that influence the ultrasound microextraction process. The optimum levels of the effective parameters were: 190 μL for volume of extraction solvent, 11.4 for pH, 15% (w/v) for the salt concentration and 5 min for sonication time. Under the optimum conditions, the relative standard deviations (RSDs, C = 100 μg L−1, n = 7) were 2.5% and 3.1% for Cr and Zn respectively. The calibration graphs were linear in the range of 0.5–1500 μg L−1 for both the metal ions with determination coefficients (R 2) of 0.997. The limits of detection (LODs) for Cr and Zn were 0.20 and 0.28 μg L−1, respectively. The proposed method was successfully applied to the analysis of three real environmental water samples and satisfactory recoveries (90–109%) were achieved.
Micro-determination of arsenic in aqueous samples by image scanning and computational quantification by Muhammad Salman; Makshoof Athar; Waheed-uz-Zaman; Umer Shafique; Jamil Anwar; Rabia Rehman; Sadia Ameer; Muhammad Azeem (pp. 242-246).
Arsenic is highly toxic in all of its forms found in natural groundwater. An improved method for the estimation of inorganic arsenic at low levels (μg L−1) in water has been proposed. The method involves the generation of arsine in a specially designed cell by borohydride reduction of arsenite (AsO2 1−). The resulting arsine is passed through a filter paper pre-dipped in mercuric bromide solution giving a yellowish brown complex. The color intensity of the spots is calculated by scanning the spotted paper and analyzing the image using specially designed software. The method was found to be effective at trace levels having a linear response at the concentration range 2–20μg L−1 (8–80ng). The detection limit of the proposed method is 1 μg L−1 (4 ng) which can be reduced further by making some modifications to the apparatus. The method was successfully applied to the analysis of synthetic samples and field samples of water.
The preparation of a novel organic–inorganic hybrid monolithic column with sonication-assist and its application by Junjie Ma; Gengliang Yang; Cuihong Yan; Yanzhao Gu; Ligai Bai; Yanhui Duan; Jia Li (pp. 247-253).
A novel hydroxyl functionalized organic–inorganic hybrid monolithic column for high performance liquid chromatography (HPLC) was synthesized via free radical copolymerization with sonocation-assist, which could shorten the time of the sol–gel process. Vinyltrimethoxysilane (VTMS) was used as the monomer and vinyl ester resin was used as both the monomer and crosslinker. The conditions of preparation were investigated and the characteristics of the hybrid column were studied by SEM and Fourier transform infrared spectroscopy. The obtained column showed high permeability and low backpressure. The column was used to separate lysozyme from egg white in a short time (6 min) by HPLC, and benzene and its homologs were separated by the hybrid column. In addition, influences on the elution of lysozyme, such as the pH value and the buffer concentration, were studied. Additionally, the lysozyme separated by the hybrid column showed high biological activity, which was assayed by the method of turbidimetry.
Determination of diesel cetane number by consensus modeling based on uninformative variable elimination by Li Yan-kun (pp. 254-258).
Consensus modeling based on improved Boosting algorithm (Boosting-PLS, BPLS) combined with wavelength (variable) selection by MC-UVE (Monte Carlo-Uninformative Variable Elimination) method is applied to determination of cetane number (CN) of diesel. MC-UVE is firstly used to select characteristic variables from Near-infrared (NIR) spectra of diesel based on principles of MC simulation and UVE, and then the selected variables instead of the full spectra are used for BPLS modeling to predict results. From predicted results, the proposed MC-UVE-BPLS algorithm improves the performance of conventional linear PLS modeling in terms of accuracy and robustness, so it is more efficient and parsimonious with few numbers of useful variables when applied to the relationship between CN and diesel NIR spectra. Simultaneously, the prediction results of MC-UVE-BPLS compared with those of MC-UVE-PLS, BPLS and CPLS (Consensus modeling based on Bagging) show that MC-UVE-BPLS is superior to other models, and also verifies the efficiency of MC-UVE and improved BPLS. So the proposed MC-UVE-BPLS method provides a new approach for determination of diesel CN by NIR spectra.
Fabrication of a sensor for simultaneous determination of norepinephrine, acetaminophen and tryptophan using a modified carbon nanotube paste electrode by Mohammad Reza Akhgar; Hadi Beitollahi; Mohammad Salari; Hassan Karimi-Maleh; Hassan Zamani (pp. 259-264).
A carbon paste electrode (CPE) was modified by incorporation of carbon nanotubes and ferrocene (FC) and studied in pH 7.0 phosphate buffer solution (PBS) by cyclic voltammetry (CV). The modified electrode showed an excellent electrocatalytic effect on the oxidation of norepinephrine (NE). In PBS of pH 7.0, the oxidation current increased linearly with concentration of NE from 0.47 to 500.0 μmol L−1. The detection limit (3σ) obtained by differential pulse voltammetry (DPV) was 0.21 μmol L−1. Then the modified electrode was used to determine NE in an excess of acetaminophen (AC) and tryptophan (TRP) by DPV. Finally, this method was used for the determination of NE, AC and TRP in some real samples.
Study on the separation mechanism of 1-phenyl-3-methyl-5-pyrazolone derivatives of aldoses in acid buffer by capillary zone electrophoresis by Huaizhong Guo; Wenyue Jiang; Xiaomin Pang; Fang Wu; Fangli Liu (pp. 265-269).
Baseline separation was achieved for 1-phenyl-3-methyl-5-pyrazolone (PMP) derivatives of six usual aldoses by capillary zone electrophoresis (CZE) using acid buffer (pH 2.5). The result showed that the migration times of mannose and rhamnose were much longer than those of the other four aldoses, though the molecular weights of the two monosaccharides were parallel to the others. This phenomenon is due to the intramolecular ring formation in PMP-aldoses, which impairs the conjugate in the pyrazolone ring, and further increases the alkalinity and positive charge of PMP-aldoses in acidic ambience. The aldose having 2,3-trans disposition will be favorable for ring formation and has more positive charge than that of the aldose having 2,3-cis disposition.
A novel method for picoxystrobin determination by flow injection chemiluminescence assistance with ultrasonic treatment by Wang-bing Zhang; Xin-an Yang; Hai-xia Zhu; Yong-ping Dong (pp. 270-276).
A simple and sensitive flow injection chemiluminescence (FI-CL) method for determination of the fungicide picoxystrobin was described for the first time. Picoxystrobin was injected into the mixed stream of luminol with KMnO4 , and the CL signal of picoxystrobin could be greatly improved when an ultrasonic treatment was adopted. Meanwhile, the signal intensity increases with the analyte concentration proportionally. The effects of the ultrasonic conditions including ultrasonic frequency, time, power and temperature on the CL signal have been studied in detail. It was found that the higher the ultrasonic frequency used, the stronger the CL intensity increased. Since the variety of ultrasonic parameters can lead to the fluctuation of signal intensity, the CL mechanism was discussed. Under the optimized conditions, the CL intensity was linear for picoxystrobin concentration over the range of 2–150 ng mL−1 with a 3σ detection limit of 0.27 ng mL−1. The relative standard deviation was 3.9% for 11 consecutive measurements of 20 ng mL−1 picoxystrobin. The method was demonstrated by application to spiked water samples from different origins including river, ground and tap water.
Optimization of solid-phase microextraction (SPME) to determine airborne biogenic volatile organic compounds (BVOCs): An application for measurement of household cleaning products by Yu Huang; Steven Sai Hang Ho; Kin Fai Ho; Shun Cheng Lee; Yuan Gao; Natale Sin Yau Feng (pp. 277-283).
Biogenic volatile organic compounds (BVOCs) in household cleaning products play key roles in indoor air quality (IAQ) because they are precursors for secondary pollutants formation. An accurate and rapid analytical technique for their measurement is of importance. This paper describes an optimization of a method for solid-phase microextraction (SPME) coupled with gas chromatography/mass spectrometry (GC-MS) for the determination of BVOCs. SPME fibers coated with Carboxen-PDMS are used to collect 12 individual BVOCs under standard conditions with a short exposure time of 5 min. Parameters influencing the extraction processes including sampling time, temperature and relative humidity are also investigated. All of the targeted BVOCs are shown to have limits of detection (LODs) in mixing ratios ranging from 0.31–0.50 ppbv, which are two magnitudes better than the LODs reported. The method precisions are between 1.1% and 6.7%. Comparison studies were carried out on a set of four floor cleaner extracts using the SPME method and traditional liquid injection method. Good agreement of the targeted BVOCs by the two methods was demonstrated. Our results indicated that SPME can serve as a simple and rapid sample collection approach to quantify BVOCs accurately and precisely in the indoor environment.
Development of a novel analytical approach combining the quantification of amino acids, organic acids and glucose using HPLC-UV-Vis and HPLC-MS with screening
A simple, rapid, sensitive and selective procedure based on the combination of HPLC-UV-Vis and HPLC-MS has been developed and single laboratory partially validated for the determination of a set of 13 analytes present in a commercially available IVF medium utilising small sample volumes (20–30 μL). The composition fingerprint of the complex sample obtained by NMR spectroscopy in 11 minutes provided identification based on a screening of the metabolomic profile. HPLC-MS allowed the glucose–sodium adduct to be measured accurately and the working and linear ranges achieved were 0.028–0.389 mmol L−1 with a detection limit of 13 μM. HPLC-UV-Vis allowed accurate concentrations of pyruvic and lactic acids with linear ranges over 0.005–0.1 mmol L−1 with a limit of detection of 28 μM for pyruvic acid to be determined in 8 minutes, while lactic acid presented a linear range over 0.1–2 mmol L−1 with a limit of detection of 1.2 mM possible. The use of HPLC-UV-Vis allowed the chromatographic separation of 8 amino acids (aspartate, glutamate, serine, glycine, asparagine, glutamine, alanine, and proline), the dipeptide alanyl-glutamine and taurine previous to a chemical derivatization, providing a total run time of 40 minutes. The method was partially validated to show a linear range of 0.028–0.280 mmol L−1 with detection limits ranging between 1 and 30 μM. Development of the analytical approach provided determination and quantification of a set of 13 analytes from a very complex sample. Although well established analytical techniques were used here, combinatory methodologies were partially validated for the first time to this purpose. The novelty of the combination of techniques relies on a screening tool and a strategy to the future evaluation and an improved assessment of human embryo viability.
Determination of bisphenol A, bisphenol F and their diglycidyl ethers in environmental water by solid phase extraction using magnetic multiwalled carbon nanotubes followed by GC-MS/MS by Yanna Jiao; Li Ding; Shanliang Fu; Shaohua Zhu; Hui Li; Libing Wang (pp. 291-298).
The magnetic multiwalled carbon nanotube (MWCNT-MNP) was successfully synthesized. MWCNT-MNP and gas chromatography-tandem mass spectrometry (GC-MS/MS) were used for rapid, simple and reliable determination of bisphenol A (BPA), bisphenol F (BPF), bisphenol F diglycidyl ether (BFDGE) and bisphenol A diglycidyl ether (BADGE) at trace levels in water. The major factors affecting the recovery efficiency, such as amount of MWCNT-MNP, pH of water sample and sample volume, were carefully investigated. The recovery of these compounds was in the range of 88.5–115.1% with relative standard deviation less than 10%. Good linearities (r 2 > 0.995) were obtained. The limits of detection for BPA, BPF, BFDGE and BADGE were 0.001, 0.002, 0.06, and 0.05 μg L−1, respectively. Finally, the method was applied to tap water, river water and snow water, the results show that the developed method is suitable for monitoring trace BPA, BPF, and their diglycidyl ethers in environmental water samples.
Chromatographic fingerprint of
Thirteen real Semen Armeniacae Amarae (SAA) samples and 28 commercial SAA samples were obtained from four typical sources of China. The high-performance liquid chromatographic (HPLC) fingerprints of them were firstly recorded. Chromatographic fingerprint was estimated by adding all the UV spectra recorded at each wavelength in the range between 210 and 360 nm. The chromatographic fingerprint obtained in this way provided more information than the chromatograms recorded at single wavelengths. Principal component analysis (PCA) based on the chromatographic fingerprint obtained as referred in previous paragraphs was performed to visualize and classify the studied samples in principal spaces. Similarity analysis (SA) and absolute peak areas (APA) were applied to estimate the concentrations of their components. Hierarchical clustering analysis (HCA) was also carried out to validate the clustering results. Furthermore, amygdalin and another four components were checked out by loadings plots of PCA and could be used as potential chemical markers for discrimination among different sources of samples. The results indicate that herbal medicines from different geographical conditions lead to different constituent contents. The total chromatographic fingerprint adding UV spectra recorded at each wavelength between 210 and 360 nm was reliable for the chemical fingerprint analysis of herbal medicine and would provide a useful reference for quality control of herbal medicines.
Strong size-dependent photoacoustic effect on gold nanoparticles: a sensitive tool for aggregation-based colorimetric protein detection by Xiangjiang Liu; Martín G. González; Reinhard Niessner; Christoph Haisch (pp. 309-311).
Based on measuring the change of the photoacoustic (PA) signal generated by laser-induced nanobubbles, a new way to detect gold nanoparticles (GNPs) aggregation is demonstrated and applied to selective protein detection.
Back matter (pp. 312-312).
We report the application of multi-wavelength resonance Raman (rR) spectroscopy for the characterisation of vinyl-bridged polysexithiophene films formed by electropolymerisation on gold electrodes. Resonance Raman spectroscopy of the neutral, polaronic and bipolaronic states of the polymer were determined by in situ
Back cover (pp. 313-314).
Based on measuring the change of the photoacoustic (PA) signal generated by laser-induced nanobubbles, a new way to detect gold nanoparticles (GNPs) aggregation is demonstrated and applied to selective protein detection.