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Analytical and Bioanalytical Chemistry (v.379, #3)
Double-focusing ICP-MS for the analysis of biological materials
by Juan Manuel Marchante-Gayón (pp. 335-337).
Analytical applications of planar bilayer lipid membranes
by Marek Trojanowicz; Ashok Mulchandani (pp. 347-350).
Challenges and progress in the analysis of polycyclic aromatic compounds
by Digambara Patra (pp. 355-357).
Bead-based immunoassays with microelectrode detection by Svetlana Farrell; Niina J. Ronkainen-Matsuno; H. Brian Halsall; William R. Heineman (pp. 358-367).
The suitability of a microelectrode as the detector for a small-volume, bead-based enzyme-labeled immunoassay for later use in a microfluidic device was investigated. The microelectrode helps to overcome consumption of the electroactive species by the electrode (depletion) that is encountered with macroelectrodes such as the rotating disk electrode (RDE) and allows the volume of the detection cell to be reduced. Microelectrodes also allow the chemical reactions to be monitored in real time due to the electrodes’ close proximity to the assay site. A bead-based sandwich immunoassay for mouse IgG was developed with alkaline phosphatase (AP) as the enzyme label, p-aminophenyl phosphate (PAPP) as the enzyme substrate, and microelectrode detection. The diffusion coefficient of the product of enzymatic hydrolysis, p-aminophenol (PAP), was determined to be 7.2±0.9×10−6 cm2 s−1. The detection limits were determined for free (0.52 ng mL−1) and bead-bound AP (10 ng mL−1). The number of binding sites for AP per bead was calculated to be 9.6×104 molecules/bead, and under saturation conditions the minimum detectable number of beads was 2500. Lower detection limits could be achieved with the microelectrode than the RDE while maintaining similar reproducibility. The microelectrode also made it possible to work with lower sample volumes (down to 10 μL) than with the RDE (minimum volume of 40 μL). Depletion of PAP was not observed with the microelectrode. The results obtained here with a microelectrode showed great promise for later use of microelectrodes in microfluidic devices with limited sample volumes. RDE detection cannot be used in a microfluidic system due to its complex set-up that includes a motor for rotation.
Keywords: Microelectrode; Detection; Voltammetry; Immunobeads; Sandwich immunoassay
Development of a sensitivity enhanced multiplexed fluorescence covalent microbead immunosorbent assay (FCMIA) for the measurement of glyphosate, atrazine and metolachlor mercapturate in water and urine by R. E. Biagini; J. P. Smith; D. L. Sammons; B. A. MacKenzie; C. A. F. Striley; S. K. Robertson; J. E. Snawder (pp. 368-374).
Body burdens from exposures to pesticides may be estimated from urinary analyses of pesticide parent/metabolite concentrations. Pesticide applicators and others are often exposed to numerous unrelated pesticides, either sequentially or simultaneously. Classically, body burdens of pesticides are analyzed using chemical/instrumental analysis (CIM) or enzyme immunoassays (EIAs). Both of these technologies can usually be used to quantitate one analyte (or closely related groups of analytes) per analysis. Alternatively, multiple analytes can be measured simultaneously using a multiplexed fluorescence covalent microbead immunoassay (FCMIA). We developed a multiplexed FCMIA to simultaneously measure glyphosate (Gly), atrazine (Atz), and metolachlor mercapturate (MM) in water and urine. The assay had least detectable doses (LDDs) in water/diluted urine of 0.11/0.09 ng/ml (Gly, water/urine LDD), 0.10/0.07 ng/ml (Atz), and 0.09/0.03 ng/ml (MM). The sensitivity for the measurement of Gly was enhanced by derivatization. All assays gave linear responses from the LDDs for each respective pesticide to 300 ng/ml. There was no cross-reactivity between the three analytes. Using a 96-well microplate and an autosampler, as many as 288 separate analyses can be completed in ~120 min with precision, sensitivity, and specificity equivalent to, if not better, than that found when these same analytes are measured by CIM or EIA.
Keywords: Biomonitoring; Luminex; Glyphosate; Atrazine; Metolachlor mercapturate
Detection method for microchip separations by Katsumi Uchiyama; Hizuru Nakajima; Toshiyuki Hobo (pp. 375-382).
The features of analytical systems utilizing microfluidic devices, especially detection methods, are described. Electrochemical detection (EC), laser-induced fluorescence (LIF), mass spectrometry (MS), and chemical luminescence (CL) methods are covered. EC enables detection without labeling and has been used in recent years because of its low cost and sensitivity. LIF is the most generally used detection method in microchip separations. Use of LED as an excitation source for fluorescence measurement was also developed for the purpose of miniaturization of the entire system, including detection and separation. Although MS enables highly sensitive analysis, the interface between MS and micro channels is still under examination. This review with fifty-two references introduces interesting detection methods for microchip separations. Related separation methods using microfluidic devices are also discussed.
Keywords: Microchannel; Electrophoresis; Detection method
Exploring bioanalytical applications of assisted protein reassembly by Sapna K. Deo (pp. 383-390).
Reassembly of protein from its peptide fragments is a technique that can have many applications in the bioanalytical field. Typically, a reporter protein fragmented into its two peptides is employed as a label in this study. This fragments of peptide can reassemble yielding an active functional reporter. This reassembly of the protein can be assisted by non-covalently interacting peptides or proteins, which are attached to the fragmented reporter. This technique has been employed in several applications including study of protein–protein interactions, antibody screening, immunoassays, and high-throughput screening. This review focuses on different reporters employed in the study of reassembly of proteins and applications of this strategy in bioanalysis.
Keywords: Assisted protein reassembly; Protein-protein interactions; Immunoassasy; Reporter protein; Molecular rulers
Single nucleotide polymorphism analysis by chip-based hybridization and direct current electrical detection of gold-labeled DNA by Jens Burmeister; Viktoria Bazilyanska; Klaus Grothe; Burkhard Koehler; Ingmar Dorn; Brian D. Warner; Edgar Diessel (pp. 391-398).
Single nucleotide polymorphism (SNP) analysis at the point of care requires a low cost detection technology that is capable of miniaturization, multiplexing, and high sensitivity. Direct current electrical detection (DCED) of DNA following nanoparticle labeling and silver enhancement is a promising candidate technology for point-of-care diagnostics. In this work we present, for the first time, SNP analysis in PCR products from patient samples using DCED, taking this platform technology a step closer to practical application. We developed a silane functionalized polymer for coating of biochip surfaces. This polymeric coating is stable under harsh conditions and has exceptionally high binding capacity. Allele-specific oligonucleotide probes were immobilized on chips coated with this polymer. Biotinylated PCR products of the human cholesteryl ester transfer protein gene from different patients were hybridized to the chips, labeled with gold nanoparticles, and autometallographically enhanced. The chips were scanned for DC electrical resistance by applying movable electrodes to the surface. Eighteen of nineteen patient samples were assigned the correct genotype. Our results demonstrate that SNP analysis of patient samples is feasible with DCED.
Keywords: SNP; Point-of care DNA analysis; PCR; Direct current electrical detection; Gold labeling; DNA chips
Study of titanocene–DNA and molybdenocene–DNA interactions by inductively coupled plasma–atomic emission spectroscopy by José L. Vera; Félix R. Román; Enrique Meléndez (pp. 399-403).
Titanocene and molybdenocene dichlorides belong to a new class of organometallic antitumor agent. Although these complexes are isostructural, they behave differently under physiological conditions and hence have different mechanisms of action. It was initially proposed that these species interact with DNA, inhibiting the cell cycle. Recent studies using nucleotides and oligonucleotides suggest that molybdenocene does not bind DNA constituents at physiological pH whereas titanocene apparently interacts weakly with nucleotides through the phosphoesters. The evidence for this was, however, obtained under non-physiological conditions. Herein we report an analytical method that enables determination of the amount of metal bound to DNA under physiological conditions (pH 7.4 and buffer solution) and with sample preparation (dialysis) that resembles the cell environment. It was found that more than 90% titanium was bound to DNA after 46 h whereas binding of molybdenum was no more than 5%.
Keywords: Titanocene dichloride; Molybdenocene dichloride; Antitumor agents; ICP–AES; Metal–DNA interaction
Fast and sensitive diagnosis of thalassemia by capillary electrophoresis by Po-Ling Chang; I-Ting Kuo; Tai-Chia Chiu; Huan-Tsung Chang (pp. 404-410).
This paper demonstrates the diagnosis of β-thalassemia by capillary electrophoresis in conjunction with laser-induced fluorescence using poly(ethylene oxide) (PEO) solutions in the presence of electroosmotic flow (EOF). During the electrophoretic separation, PEO solution entered a capillary from the anodic vial by EOF. The separation of a mixture of the polymerase chain reaction (PCR) products (330 and 334 base pairs) from a healthy person and a β-thalassemia patient was accomplished within 15 min at 15 kV using 1.5% PEO containing 2 M urea at 30 °C. The electropherogram patterns instead of migration times were used to diagnose β-thalassemia, with an accuracy of 100% for the analyses of 11 blood samples from suspected patients. After injecting a large volume of the mixture to the capillary filled with 800 mM Tris-borate buffer (pH 10.0), the DNA fragments stacked due to increases in viscosity and sieving when migrating into 1.5% PEO solution. As a result of improved sensitivity, only 15 PCR cycles were required when using 500 ng of DNA templates. The results shown in this study indicate the potential of this simple, rapid, and cost-effective method for the diagnosis of β-thalassemia.
Keywords: Capillary electrophoresis; DNA; Laser-induced fluorescence; Polymer solutions; Thalassemia
Evaluation of a polyclonal antiserum to pentachlorothiophenol-acetic acid-KLH immunogen: binding properties and use with heterologous PCP derivatives in ELISA for pentachlorophenol by Ramadan A. Abuknesha; Hannah M. T. Griffith (pp. 411-418).
A polyclonal antiserum to pentachlorothiophenol-acetic acid-KLH was generated in sheep and assessed by solid phase ELISA. The assessment procedure included use of double checkerboard analysis in the absence and in the presence of analyte loads, estimation of cross reactivities of chlorophenol pesticides, assessment of the effect of pH, Tween 20, and Thames water matrix. The antiserum was highly specific for pentachlorophenol and enabled minimum detection limits of less than 0.2 ng mL−1 in river water matrix. Particularly important was the significant improvement of assay performance in the absence of Tween 20 and at pH 4 and the very low cross reactivity (less than 0.01%) for other commonly used chlorophenols—2,4,5-trichlorophenol and 2,4,6-trichlorophenol, 2-methyl-4-chlorophenoxyacetic acid, and 2,4-dichlorophenoxy acetic acid. The study re-affirms the importance of the judicious choice of hapten derivatives in the synthesis of immunogens and assay reagents for pentachlorophenol analysis by competitive immunoassays.
Keywords: ELISA; Pentachlorophenol; Polyclonal antiserum; Pentachlorothiophenol-acetic acid-KLH immunogen; Double checkerboard analysis; Chlorophenol cross reactivity
Biomagnetic separation of Escherichia coli by use of anion-exchange beads: measurement and modeling of the kinetics of cell–bead interactions by S. Deponte; J. Steingroewer; C. Löser; E. Boschke; T. Bley (pp. 419-426).
Analyses of food-borne pathogens are of great importance in order to minimize the risk of infection for customers. These analyses should be as fast as possible. Any detection method requires enrichment and quantitative analysis of the enriched microbes. Conventional enrichment methods, which take several days, need to be replaced by faster techniques such as biomagnetic separation (BMS). This technique involves the use of paramagnetic microspheres coated with ligands that have special affinity to the microbes that have to be detected. In the studies reported here, enrichment experiments by BMS were carried out using the non-pathogenic E. coli DSM 498 as a model strain and beads coated with a polyethylenimine (PEI) anion-exchange material. The results show that the number of cells separated, as a proportion of the total, was positively correlated with the bead concentration and the length of the period they were mixed together. In addition, a mathematical model, based on the rate of impact between two different sorts of particles, was developed to describe the proportion of separated cells as a function of incubation time and the concentration, size and density of the beads and cells. This is the first mathematical description of cell–bead interactions to be based on well-understood physicochemical principles. The model was confirmed by separation experiments in which the concentration of beads and the incubation period were varied. The developed model enables optimization of the amount of beads added and the reaction period necessary for complete cell separation and thus minimization of costs in BMS.
Keywords: BMS; Escherichia coli ; Anion exchange; PEI beads; Separation kinetics; Modeling
Investigation of metal-binding metallothioneins in the tissues of rats after oral intake of cinnabar by Zhi-Yong Huang; Jin-Can Shen; Zhi-Xia Zhuang; Xiao-Ru Wang; Frank S. C. Lee (pp. 427-432).
The multi-metal-binding MT fractions in rat tissues after oral intake of cinnabar were characterized by hyphenated size-exclusion chromatography (SEC) and inductively coupled plasma mass spectrometry (ICP–MS). With the increase of both the feeding time and dosage of cinnabar the amounts of Hg-binding MT fractions in rat kidney of groups fed cinnabar increased significantly compared with the control group. Meanwhile, more Cu-binding MT were synthesized in the rat kidney, which confirmed the manipulating effect of MT in the homeostasis of Cu for detoxification of nephritic mercury. Although the Hg-binding MT fractions in rat liver of all cinnabar groups were almost independent of cinnabar dosage (2.5–5.0 g kg−1 bw) and feeding time (2–4 weeks), the amount was much higher than that of the control group. The amounts of Hg-MT in other rat tissues of the cinnabar groups and the control group were compared and their significance is discussed.
Keywords: Cinnabar; Metallothioneins (MT); Size-exclusion chromatography (SEC); Inductively coupled plasma mass spectrometry (ICP–MS)
The effects of chronic hypoperfusion on rat cranial bone mineral and organic matrix by Handan Boyar; Faruk Zorlu; Melike Mut; Feride Severcan (pp. 433-438).
Arteriovenous malformations (AVM) of the brain, errors in the development of the vasculature, produce high flow arteriovenous shunts. They steal blood from surrounding brain tissue, which is chronically hypoperfused. Hypoperfusion is a condition of inadequate tissue perfusion and oxygenation resulting in abnormal tissue metabolism. In the present study Fourier transform infrared (FTIR) spectroscopy was used to investigate the effects of hypoperfusion on rat cranial bone mineral and organic matrix at the molecular level. FTIR spectroscopic analysis revealed that in cranial bones of an experimental group the relative amount of carbonate and phosphate groups increased whereas that of protein (amide I) decreased. Curve-fitting analysis of the v 2 carbonate band showed that amounts of type A and type B carbonates increased slightly (p=0.423 for both) whereas, type L carbonate decreased slightly (p=0.522) in hypoperfused cranial bones. Analysis of the C–H region revealed a significant increase (p=0.037) in the lipid to protein ratio. Because the lipid content is high, hypoperfused cranial bone tissue is more prone to lipid peroxidation. Dialdehydes derived from lipid peroxidation can make cross-links with collagen and might lead to disturbances in the collagen cross-link profile. The 1660 cm−1/1690 cm−1 partial area ratio derived from curve-fitting analysis of the Amide I band is sensitive to the relative amount of collagen non-reducible cross-link hydroxylysyl/lysylpyridinolines (Pyr) and reducible cross-link dihydroxylysinonorleucine (DHLNL) and this ratio reflects collagen maturity. In chronic hypoperfusion a significant decrease (p=0.004) was observed in this ratio. This means there were less mature collagen cross-links. Disturbances in the collagen maturation can affect mineralization process and lead to formation of pathologic structures in cranial bones. These findings clearly demonstrate that FTIR spectroscopy can be used to extract valuable information at molecular level, leading to better understanding of the effect of hypoperfusion on rat cranial bones.
Keywords: Hypoperfusion; AVM; Cranial bone; FTIR; Spectroscopy; Mineral
Simultaneous micellar liquid chromatographic analysis of seven water-soluble vitamins: optimization using super-modified simplex by Ali R. Ghorbani; Fariborz Momenbeik; Jafar H. Khorasani; Mohammad K. Amini (pp. 439-444).
A super-modified simplex (SMS) method has been used to optimize the mobile phase used for separation of seven water-soluble vitamins in multivitamin tablets by gradient micellar liquid chromatography (MLC) with ultraviolet (UV) detection at 254, 295, and 361 nm. Effect of column temperature and addition of organic modifier to the mobile phase on separation efficiency were investigated: the appropriate conditions used were a temperature of 35°C and 1-butanol modifier. The sodium dodecyl sulfate (SDS) concentration, pH, and 1-butanol% in the mobile phase were chosen for simultaneous optimization using the SMS method. The optimum mobile phase was found to be 16 mmol L−1 (mM) SDS, 0.02 M phosphate buffer, pH 3.6, and a gradient of 3.5–10% (v/v) butanol. The total analysis time for vitamins was 75 min. The analytical parameters including linearity (r>0.9970), limit of detection (0.12–50 µg mL−1), precision of method (relative standard deviation (RSD) <8.90%), and accuracy obtained by the recovery assay (88–103%) support the usefulness of the proposed method for the determination of the water-soluble vitamins.
Keywords: Micellar liquid chromatography; Water-soluble vitamins; Sodium dodecyl sulfate; Super-modified simplex
Determination of ginkgolide A, B, and bilobalide in biloba L. extracts by microdialysis-HPLC by Houn-Lin Chiu; Hui-Ya Lin; Thomas Ching-Cherng Yang (pp. 445-448).
A method has been developed for measuring ginkgolide A, B, and bilobalide in ginkgo biloba L. extracts by using a self-assembled microdialysis device coupled on-line to high-performance liquid chromatography. The optimal conditions for dialysis efficiency and chromatographic analysis were investigated. The results show that the dialysis efficiencies for ginkgolide A, B, and bilobalide are 97.8–100.4%. For the spike concentration of 45 mg L−1, the recoveries of ginkgolide A, B, and bilobalide in ginkgo biloba L. extracts were at 97–100.7% with 3.1–4.7% RSD. The proposed method has therefore been shown to be applicable to the analysis of ginkgolide A, B, and bilobalide in ginkgo biloba L. extracts.
Keywords: High-performance liquid chromatography; Microdialysis; Ginkgolide A; Ginkgolide B; Bilobalide
Evaluation of the results from an inter-laboratory comparison study of the determination of acrylamide in crispbread and butter cookies by Thomas Wenzl; Beatriz de la Calle; R. Gatermann; K. Hoenicke; F. Ulberth; Elke Anklam (pp. 449-457).
Analytical methods currently employed for determination of acrylamide (AA) in two carbohydrate-rich food samples, crispbread and butter cookies, obtained commercially, and native and spiked bread extract samples have been evaluated in a collaborative study. The objective of the study was to obtain information about the performance of the participating laboratories when analysing samples with an AA content close to the limit of quantification (LOQ) and at a higher AA level, and to investigate the influence of sample-preparation procedures on the results of the analysis. For this purpose an aqueous native extract of white bread crumb, a fortified extract, and AA standard solutions, the analyte content of which were not disclosed to the participants, were included in the study. A total of 62 laboratories, applying seven different measurement techniques and a broad spectrum of analyte extraction and sample-preparation procedures reported their analytical results. Because the measurement data were not normally distributed, they were evaluated by application of robust statistics. The relative performance of the laboratories was highlighted by calculation of z-scores. For the crispbread sample, especially, a large percentage of the calculated z-scores were outside the satisfactory range. From their distribution it became obvious that one of the analytical techniques might be biased, if not applied correctly. Consequently, the impact of the applied methods was examined in more detail. Information about the analytical technique, extraction solvent, quantity weighed, calibration method, clean-up, and the experience of the participating laboratories were extracted from the analytical protocols and transcribed into a data matrix which was evaluated by multifactor analysis of variance. The applied measurement technique seems to have a statistically significant influence on the analytical results.
Keywords: Acrylamide; Crispbread; Butter cookies; Bread extract; Inter-laboratory comparison; Robust statistical analysis
Determination of carbendazim, thiabendazole, and o-phenylphenol residues in lemons by HPLC following sample clean-up by ion-pairing by Konstantinos P. Prousalis; Dimitris A. Polygenis; Alexandra Syrokou; Fotini N. Lamari; Theodore Tsegenidis (pp. 458-463).
An efficient analytical method is presented involving effective sample clean-up with solid-phase extraction and HPLC-UV analysis for the simultaneous determination of carbendazim, thiabendazole, and o-phenylphenol residues in lemons. Sample preparation involves extraction with acetonitrile acidified with trifluoroacetic acid and an ethyl acetate/petroleum ether mixture. Purification of the crude extract was carried out with liquid–liquid partitioning after addition of an aqueous ammonia solution. Final clean-up was performed on polymeric reversed-phase cartridges pretreated with sodium dodecyl sulfate. Chromatographic analysis was performed on a reversed-phase HPLC column isocratically eluted with an acetonitrile/water/ammonia mixture and UV detection at 254 nm. The chromatographic method is repeatable, reproducible, and sensitive. Fungicide recoveries from lemon samples fortified at levels of 5 and 1 mg kg−1 were 81–85% for carbendazim, 96–98% for thiabendazole, and 81–106% for o-phenylphenol with coefficients of variation of 2.5–7.4%. Detection limits for carbendazim, thiabendazole, and o-phenylphenol in lemons were 0.21, 0.27, and 0.51 mg kg−1, respectively.
Keywords: High-performance liquid chromatography (HPLC); Solid-phase extraction (SPE); Carbendazim; Thiabendazole; o-Phenylphenol; Pesticides
Chemometric characterisation of Basque and French ciders according to their polyphenolic profiles by R. M. Alonso-Salces; S. Guyot; C. Herrero; L. A. Berrueta; J. F. Drilleau; B. Gallo; F. Vicente (pp. 464-475).
Polyphenolic compositions of Basque and French ciders were determined by HPLC-DAD following thiolysis, in order to characterise and differentiate these beverages and then develop a classification system capable of confirming the authenticities of both kinds of cider. A data set consisting of 165 cider samples and 27 measured features was evaluated using multivariate chemometric techniques, such as cluster analysis and principal component analysis, in order to perform a preliminary study of data structure. Supervised pattern recognition techniques such as linear discriminant analysis (LDA), K-nearest neighbours (KNN), soft independent modelling of class analogy (SIMCA), and multilayer feed-forward artificial neural networks (MLF-ANN) attained classification rules for the two categories using the chemical data, which produced satisfactory results. Authentication systems obtained by combining two of these techniques were proposed. We found that SIMCA and LDA or KNN models achieved 100% hit-rates, since LDA and KNN permit the detection of every Basque cider and SIMCA provides a model for Basque cider that excludes all French ciders. Polyphenolic profiles of the ciders provided enough information to be able to develop classification rules for identifying ciders according to their geographical origin (Basque or French regions). Chemical and organoleptic differences between these two types of cider are probably due to the original and distinctive cidermaking technologies used for their elaboration. Using polyphenic profiles, about 80% of French ciders could be distinguished according to their region of origin (Brittany or Normandy). Although their polyphenolic profiles did not provide enough information to achieve an authentication system for Breton and Norman ciders.
Keywords: Polyphenol; Cider; HPLC; Thiolysis; Chemometrics; Pattern recognition
Multiresidue method using SPME for the determination of various pesticides with different volatility in confined atmospheres by Federico Ferrari; Astrid Sanusi; Maurice Millet; Michel Montury (pp. 476-483).
An analytical method is described for assessing the vapour concentration of 11 pesticides (bioallethrin, chlorpyriphos methyl, folpet, malathion, procymidone, quintozene, chlorothalonil, fonofos, penconazole and trimethacarb) in confined atmospheres (e.g. a greenhouse after pesticide application). This study is a successful extension of a method previously developed by the authors for dichlorvos to much less volatile pesticides. Sampling was performed by using polydimethylsiloxane–solid phase micro-extraction (PDMS–SPME) fibres immersed in a 250-mL sampling flask through which air samples were dynamically pumped from the analysed atmosphere. After a 40-min sampling duration, samples were analysed by GC/MS.Calibration was performed from a vapour-saturated air sample. The linearity of the observed signal versus pesticide concentration in the vapour phase was proved from spiked liquid samples whose headspace concentrations were measured by using the proposed method. This procedure gave calibration curves with regression coefficients (R 2) greater than 0.98, and the repeatability of these measurements was found with RSDs of 1.9–7.6%. As a field application test, this analysis procedure was used for the determination of gaseous procymidone concentrations as a function of time in the atmosphere of an experimental 8-m2 and 20-m3 greenhouse. The pesticide was sprayed according to real cultivation conditions, and measurements were made for 80 h after application (8 measurements). The observed concentrations found ranged from 200 to 500 µg m−3, thus indicating the level of contamination of the air breathed by people in such working conditions.
Keywords: Pesticide vapours; SPME/GC/MS analysis; Air sampling; Greenhouse atmospheres
Study of the carbonyl products of terpene/OH radical reactions: detection of the 2,4-DNPH derivatives by HPLC-MS by Viviane Van den Bergh; Hans Coeckelberghs; Hans Vankerckhoven; Frans Compernolle; Chris Vinckier (pp. 484-494).
The oxidation of the terpenes α- and β-pinene, limonene and Δ3-carene by hydroxyl radicals has been investigated in a fast-flow reactor coupled to a liquid nitrogen trap for collecting the carbonyl compounds. Identification of the products was performed via 2,4-dinitrophenylhydrazone (DNPH) derivatization of the carbonyls to form the mono- and di-DNPH derivatives, which were analysed by high-performance liquid chromatographic (HPLC)-DAD (diode array detector) and HPLC-mass spectrometry (HPLC-MS). Both electrospray ionization [ESI(−)] and atmospheric pressure chemical ionization [APCI(−)] were suitable for the detection of the DNPH derivatives of formaldehyde, acetaldehyde, myrtanal, campholene aldehyde, perillaldehyde, acetone, nopinone, trans-4-hydroxynopinone and 4-acetyl-1-methylcyclohexene. Also the mono-DNPH derivatives of the dicarbonyl compounds pinonaldehyde, endolim and caronaldehyde could be identified. The MS2 spectra generated in the ion trap of the mass spectrometer allowed us to distinguish between aldehydes and ketones on the basis of the characteristic fragment ion m/z 163 for the aldehydes. For the quantitative analysis of the mono-DNPH derivatives, ESI(−) in combination with single ion monitoring (SIM) detection showed the lowest detection limits. For the quantification of the dicarbonyl compounds, the acid-sensitive di-DNPH derivatives had to be formed by keeping the acidity in the acid-catalysed derivatization reaction at about 1.7 mM H2SO4. Detection of these dicarbonyl compounds can only be performed by APCI(−) with somewhat lesser sensitivity than by HPLC-DAD.
Keywords: Terpenes; HPLC-MS; DNPH derivatives; ESI; APCI
Speciation of nickel, copper, zinc, and manganese in different edible nuts: a comparative study of molecular size distribution by SEC–UV–ICP–MS by Rodolfo G. Wuilloud; Sasi S. Kannamkumarath; Joseph A. Caruso (pp. 495-503).
Molecular size distribution patterns of Cu, Mn, Ni, and Zn were determined in several nut species by size-exclusion liquid chromatography (SEC) coupled on-line to UV and inductively coupled plasma mass spectrometry (ICP–MS) for detection. The molecular weight (MW) fractionation of the different metals was performed with a Superdex Peptide column, injecting 100 μL of the extracted solutions. The association of the elements with different MW fractions was observed with sequential detection by UV and ICP–MS. Various separation conditions were evaluated to obtain proper resolution and reproducible results with the size-exclusion column. Complete MW information of the elemental fractions in the nut samples was obtained within a retention time of 30 min. Fractionation of the above mentioned elements was done in nine different nut species commonly found in commercial markets. Variability of the fractionation patterns for two different extraction media, 0.05 mol L−1 NaOH and 0.05 mol L−1 HCl, was evaluated for every nut sample. Differences in the elemental fractionation patterns were found depending on the extraction procedure, nut species, and the type of element studied. It was also observed that the elements studied showed predominant association with high MW fractions when extracted with basic solution whereas with acidic extraction media only low MW fractions were obtained.
Keywords: Multielemental speciation; Nuts; Fractionation; Metalloproteins; SEC–ICP–MS
Hyphenated techniques for speciation of Se in in vitro gastrointestinal digests of Saccharomyces cerevisiae by Emmie Dumont; Frank Vanhaecke; Rita Cornelis (pp. 504-511).
A method was developed allowing the separation, detection and identification of Se species extracted from yeast supplements during simulated digestion processes. The in vitro gastric and intestinal digests were studied for their Se compounds by successive high-performance liquid chromatography–inductively coupled plasma mass spectrometry (HPLC-ICP-MS) and high-performance liquid chromatography–electrospray tandem mass spectrometry (HPLC-ES-MS-MS) analyses. The conditions for the separation were chosen as to be compatible with both ICP-MS and ES-MS-MS detection. HPLC-ICP-MS was used to screen the extracts for their Se content. By means of HPLC-ES-MS-MS, the compounds extracted were identified on-line according to their retention time, m/z of the molecular ion and the presence of typical product ions. From these results, it was clear that the main compound extracted by both gastric and intestinal fluid was Se-methionine, which was also the main Se compound extracted by proteolytic digestion from the yeast supplements. Two other minor compounds could be identified as Se-cystine and Se(O)-methionine, a degradation product of Se-methionine.
Keywords: Speciation; Se; HPLC; ICP-MS; ES-MS-MS
Rapid multi-element analysis of groundwater by high-resolution inductively coupled plasma mass spectrometry by Z. Cheng; Y. Zheng; R. Mortlock; A. van Geen (pp. 512-518).
A rapid and sensitive method was developed to determine, with a single dilution, the concentration of 33 major and trace elements (Na, Mg, Si, K, Ca, Li, Al, P, S, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Mo, Cd, In, Sn, Sb, Cs, Ba, Re, Hg, Pb, Bi, U) in groundwater. The method relies on high-resolution inductively coupled plasma mass spectrometry (HR ICP-MS) and works across nine orders of magnitude of concentrations. For most elements, detection limits for this method are considerably lower than methods based on quadrupole ICP-MS. Precision was within or close to ±3% (1σ) for all elements analyzed, with the exception of Se (±10%) and Al (±6%). The usefulness of the method is demonstrated with a set of 629 groundwater samples collected from tube wells in Bangladesh (Northeast Araiharzar). The results show that a majority of tube well samples in this area exceed the WHO guideline for As of 10 μg L−1, and that those As-safe wells frequently do not meet the guideline for Mn of 500 µg L−1 and U of 2 µg L−1.
Keywords: HR ICP-MS; Groundwater; Multi-element analyses; Bangladesh
Selective extraction of U(VI), Th(IV), and La(III) from acidic matrix solutions and environmental samples using chemically modified Amberlite XAD-16 resin by D. Prabhakaran; M. S. Subramanian (pp. 519-525).
A new grafted polymer has been developed by the chemical modification of Amberlite XAD-16 (AXAD-16) polymeric matrix with [(2-dihydroxyarsinoylphenylamino)methyl]phosphonic acid (AXAD-16-AsP). The modified polymer was characterized by a combination of 13C CPMAS and 31P solid-state NMR, Fourier transform-NIR-FIR-Raman spectroscopy, CHNPS elemental analysis, and thermogravimetric analysis (TGA). The distribution studies for the extraction of U(VI), Th(IV), and La(III) from acidic solutions were performed using an AXAD-16-AsP-packed chromatographic column. The influences of various physiochemical parameters on analyte recovery were optimized by both static and dynamic methods. Accordingly, even under high acidities (>4 M), good distribution ratio (D) values (102–104) were achieved for all the analytes. Metal ion desorption was effective using 1 mol L−1 (NH4)2CO3. From kinetic studies, a time duration of <15 min was sufficient for complete metal ion saturation of the resin phase. The maximum metal sorption capacities were found to be 0.25, 0.13, and 1.49 mmol g−1 for U(VI); 0.47, 0.39, and 1.40 mmol g−1 for Th(IV); and 1.44, 1.48, and 1.12 mmol g−1 for La(III), in the presence of 2 mol L−1 HNO3, 2 mol L−1 HCl, and under pH conditions, respectively. The analyte selectivity of the grafted polymer was tested in terms of interfering species tolerance studies. The system showed an enrichment factor of 365, 300, and 270 for U(VI), Th(IV), and La(III), and the limit of analyte detection was in the range of 18–23 ng mL−1. The practical applicability of the polymer was tested with synthetic nuclear spent fuel and seawater mixtures, natural water, and geological samples. The RSD of the total analytical procedure was within 4.9%, thus confirming the reliability of the developed method.
Keywords: AXAD-16; Polymeric matrix; Acidic streams; Metal extraction and preconcentration
Freon (CHF3)-assisted atomization for the determination of titanium using ultrasonic slurry sampling–graphite furnace atomic absorption spectrometry (USS–GFAAS): a simple and advantageous method for solid samples by Alemayehu Asfaw; Grethe Wibetoe (pp. 526-531).
A simple and advantageous method for the determination of titanium using graphite furnace atomic absorption spectrometry with slurry sampling has been developed. Titanium is one of the refractory elements that form thermally stable carbides in the graphite tube, which leads to severe memory effects. Trifluoromethane (Freon-23) was applied in the purge gas during the atomization step or alternatively just prior to the atomization to successfully eliminate the problems of carbide formation and increase the lifetime of the furnace tube which could be used for more than 600 heating cycles. A flow rate of 40 mL min−1 (5% of Freon in argon) was used to obtain symmetrical peaks with no tailing. However, when the gas flow rate was too high (250 mL min−1) the peak-tailing and memory effects reappeared. Ti was determined in various materials covering a wide range of concentrations, from 2.8 μg g−1 to 12% (m/m) Ti. The accuracy of the method was confirmed by analyzing certified reference materials (CRMs) or by comparing the results with those obtained using inductively coupled plasma–atomic emission spectrometry (ICP–AES) after decomposition of the samples. The materials analyzed were soil, plant, human hair, coal, urban particulate matters, toothpaste, and powdered paint.
Keywords: GFAAS; Titanium; Carbide formation; Memory effect; Slurry sampling; Freon-23
Determination of plutonium and its isotopic ratio in marine sediment samples using quadrupole ICP-MS with the shield torch system under normal plasma conditions by Jian Zheng; Masatoshi Yamada; Zhongliang Wang; Tatsuo Aono; Masashi Kusakabe (pp. 532-539).
An analytical method for determining 239Pu and 240Pu in marine sediment samples, which uses quadrupole ICP-MS, was developed in this work. A simple anion-exchange chromatography system was employed for the separation and purification of Pu from the sample matrix. A sufficient decontamination factor of 1.4×104 for U, which interferes with the determination of 239Pu, was achieved. High sensitivity Pu determination was obtained, which led to an extremely low concentration detection limit of ~8 fg/ml (0.019 mBq/ml for 239Pu; 0.071 mBq/ml for 240Pu) in a sample solution, or an absolute detection limit of 42 fg in a 5 ml sample solution, by using the shield torch technique. Analytical results for the determination of the 239+240Pu and the 240Pu/239Pu ratio in IAEA 368 (ocean sediment) reference material indicated that the accuracy of the method was satisfactory. The method developed was successfully applied to a study of Pu behavior in the sediments from Sagami Bay, Japan. The observed high 240Pu/239Pu ratio in the sediment core indicated that there was additional Pu input derived from close-in fallout in addition to the global fallout.
Keywords: Plutonium; Marine sediment; ICP-MS; Shield torch; Sagami Bay
Rapid quantification of juvenile hormones and their metabolites in insect haemolymph by liquid chromatography–mass spectrometry (LC-MS) by Stephanie A. Westerlund; Klaus H. Hoffmann (pp. 540-543).
A simple, fast and sensitive method was developed for routine determination of juvenile hormone (JH), JH diols and JH acids in insect haemolymph, by liquid chromatography–mass spectrometry (LC-MS). Sample clean-up involves the precipitation of proteins by methanol/isooctane (1:1, v/v), centrifugation and partial evaporation of the organic solvents. Since JH is bound to a carrier protein in the haemolymph, a binding protein (BP) assay was performed to ensure JH is removed during precipitation. The JH compounds were separated on a C18 column (ReproSil-Pur ODS-3) by gradient elution with water and methanol in less than 22 min and analysed by electrospray mass spectrometry. Due to the high abundance of Na+ in insect haemolymph, [M+Na]+ is primarily formed. The limit of detection and quantification was 6 and 20 pg for JHs, and 8 and 25 pg for JH diols, respectively. To demonstrate the applicability of the method to different insect orders, haemolymph samples from the Mediterranean field cricket (Gryllus bimaculatus), the fall armyworm (Spodoptera frugiperda), the pea aphid (Acyrthosiphon pisum) and an ant species (Myrmicaria eumenoides) were analysed.
Keywords: LC-MS; Juvenile hormone titer; Acyrthosiphon pisum ; Gryllus bimaculatus ; Spodoptera frugiperda ; Myrmicaria eumenoides