High-performance Liquid Chromatography-inductively Coupled Plasma-mass Spectrometry Research Articles

Simultaneous determination of organotin pesticides by HPLC-ICP-MS and their sorption, desorption, and transformation in freshwater sediments

In order to better assess their environmental risks, the sorption and degradation of triphenyltin hydroxide, azocyclotin and fenbutatin oxide were studied in two sediments under varying laboratory conditions in this study. An analytical method for simultaneous determination of the three organotins in environmental samples was firstly developed using high performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS). The limit of detection and limit of quantification for standards ranged from 0.13 to 1.46 μg/L. Fortification study showed that when spiked at 2–250 μg/kg the mass recoveries were 73.7–119.6%. Sorption isotherm experiments indicated that the organotins could be strongly adsorbed by the sediments, and organotin sorption kinetics obeyed the pseudo second-order kinetic model. The sorption affinity was inversely related to their water solubility. All isotherms fitted with the Henry mode fairly well (r2 > 0.96) with distribution coefficients (Kd) ranging from 746.1 to 2465.2 mL/g. The three organotins could rapidly move from the upper water layer to the lower sediment layer, and they were all of moderate degradation compounds with the degradation half lives varying from 38.3 to 84.5d in anaerobic and aerobic water-sediment systems. The degradation rate seemed to be positively related to organic matter content of sediment. Result inferred that the three organotins had the low risks to pollute groundwater when applied on dry land and could moderately degrade in water-sediment system. However, more attention should still be paid to these organotins due to the wide application on agricultural field.

In situ rapid magnetic solid-phase extraction coupled with HPLC-ICP-MS for mercury speciation in environmental water

SiO2 was coated on the surface of Fe3O4 nanoparticles through hydrolyzation of Na2SiO3, and then thiol groups were modified on SiO2 by silanization reaction to form Fe3O4@SiO2–SH sorbents. Due to high affinity between thiol group and mercury, the Fe3O4@SiO2–SH was applied as magnetic sorbent for in situ extraction and stabilization of trace mercury species from natural water. Trace Hg2+ and methylmercury in 500mL of water sample could be almost recovered with only 60mg sorbents. Magnetic separation and rapid adsorption equilibrium greatly simplified extraction procedure and shortened analysis time. Solution pH had no obvious effect on mercury recoveries in the range of 3–9. The loaded Hg2+ and methylmercury were readily desorbed with 2.5mL of 0.5molL−1 HCl containing 1% thiourea. The mercury speciation in eluate was acquired by using high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS). The detection limits of the present method for Hg2+ and methylmercury were 1.0 and 0.3ngL−1, respectively. The recoveries of spiked water samples were in the range of 96%–104% with relative standard deviations varying from 0.2% to 4.2%, showing good accuracy of the method.

Arsenic, antimony and chromium speciation using HPLC-ICP-MS in selected river ecosystems of Upper Silesia, Poland – a preliminary study and validation of methodology

Upper Silesia is the most transformed by humans of the Polish territories. As a result of mining, urbanization and other industrial activities, irreversible changes have taken place in the environment. In this paper, the method of collecting, preserving, storing and preparing samples from four Silesian rivers was optimized. Silesian sediment and river water samples are a challenge for the analyst, because they have complex matrices and high content of chlorides coming from the discharges of saline water. This study concerned determination of Sb(III), Sb(V), As(III), As(V), MMA, DMA, AB, Cr(III) and Cr(VI) with high-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS). The following columns were used: Dionex Ion Pack AG7 to determine chromium forms, Hamilton PRP-X100 to separate antimony species and Dionex Ion Pack AS7 to determine five chemical arsenic forms. The methodology used allowed for elimination of interferences during analysis of highly saline and complex samples and ions separation directly without adding any complexing compounds. Depending on the analytes, full separation was obtained within 3–9.5 min. The sediment sample extraction and determination were validated (recovery, limit of detection, repeatability and uncertainty) with the certified reference materials (CRMs). The optimized methodology allowed for study of mobility and seasonality changes of As, Sb and Cr species in the river environment.

Arsenic(+3) and DNA methyltransferases, and arsenic speciation in tadpole and frog life stages of western clawed frogs (Silurana tropicalis) exposed to arsenate.

Western clawed frog (Silurana tropicalis) embryos were exposed to control, low (nominally 0.5 mg L(-1)) and high (nominally 1 mg L(-1)) arsenate (As(V)) culture water concentrations to investigate the effects of arsenic (As) on different life stages, namely tadpole (Nieuwkoop and Faber stage 56, NF56) and frog stages (NF66). The effects were assessed by measuring arsenic(+3) and DNA methyltransferases (AS3MT and DNMT1), as well as As speciation in the tissues. The As content in frog tissues increased with water As concentration. The As species observed by high performance liquid chromatography - inductively coupled plasma mass spectrometry (HPLC-ICPMS) were mostly inorganic, dimethylarsinic acid (DMA) and trimethylarsine oxide (TMAO). With solid state X-ray absorption near edge structure (XANES) analysis, arsenobetaine/tetramethylarsonium ion were also seen. AS3MT levels decreased upon low As exposure in NF56, rising again to control levels at the high As exposure. In NF66 tissues, on the other hand, AS3MT decreased only with NF66 high As exposure. DNMT1 increased with exposure, and this was statistically significant only for the high As exposure at both life stages. Thus these enzymes seem to be affected by the As exposure. Methylation of As to form monomethylarsonate (MMA), DMA and TMAO in the frogs appeared to be inversely related to AS3MT levels. A possible interpretation of this finding is that when AS3MT is higher, excretion of MMA + DMA + TMAO is more efficient, leaving lower concentrations in the tissues, with the opposite effect (less excretion) when AS3MT is lower; alternatively, other enzymes or linked genes may affect the methylation of As.

Excretion patterns of arsenic and its metabolites in human saliva and urine after ingestion of Chinese seaweed

There are no reports in scientific literature on arsenic species in human saliva after seaweed exposure. The present article reports for the first time the regular excretion patterns of arsenic in the saliva of volunteers with one-time ingestion of Chinese seaweed. Total arsenic and speciation analyses were carried out by high-performance liquid chromatography–inductively coupled plasma–mass spectrometry (HPLC-ICP-MS). Results show that the excretion time of total arsenic in saliva is a trifle earlier than that in urine, total arsenic in human saliva also shows a regular excretion pattern like that in urine within 72 h after exposure to seaweed. For speciation analysis, four species, including the major dimethylarsinic acid (DMA) species, were detected in urine prior to seaweed intake. Six species were detected in urine after seaweed ingestion, including DMA, methylarsonic acid (MMA), oxo-dimethylarsinoylethanol (oxo-DMAE), thio-dimethlyarsenoacetate (thio-DMAA), arsenite (AsIII) and arsenate (AsV). In saliva samples, three species were found before seaweed ingestion, with the major peak identified as AsIII. After consumption, the kinds of arsenic metabolites in saliva were less than those in urine. The major species was inorganic arsenic (iAs AsIII+AsV), followed by DMA, MMA and a trace amount of oxo-DMAE. Taken together, the present study suggests that saliva assay can be used as a potential tool for understanding the regular excretion pattern of total arsenic after seaweed ingestion. Whether or not it’s an efficient tool for assessing arsenic metabolites in humans exposed to seaweed requires further investigation.

Arsenic in rice and diets of children

Levels of arsenic in Australian and imported rice (n = 36) were evaluated using inductively coupled plasma mass spectrometry (ICP-MS) for total arsenic and a hyphenated high-performance liquid chromatography ICP-MS system for arsenic species. The study also assessed the daily intake of total As from diets of healthy children (n = 15), collected over three consecutive days. A wide variation of total As levels (range: <0.05–0.42 mg/kg) in Australian and imported rice was found. The mean level of total As (0.24 ± 0.09 mg/kg, n = 10) in the Australian rice was relatively higher than imported rice from other countries (0.09 ± 0.04 mg/kg, n = 26). The mean level (0.25 ± 0.08 mg/kg, n = 7) of dimethylarsenic acid was considerably higher than that of inorganic As (III) (0.07 ± 0.03 mg/kg, n = 7) in the Australian rice. Children’s daily intakes of total As varied widely, ranging from 1.7 to 31.2 (11.5 ± 8.9 µg/day), which was comparable to other countries.

Levels and assessment of organotin contamination at Futian Mangrove Wetland in Shenzhen, China

The concentrations of organotins (OTs) were measured in the surface sediments, mollusks and mudskippers at Futian Mangrove Wetland in Shenzhen, China, an ecologically important wetland that serves as a wintering ground and a stop-over point for migrating birds. The average concentrations of tributyltin (TBT), dibutyltin (DBT), triphenyltin (TPhT) and diphenyltin (DPhT) were 2.42, 9.11, 1.10 and 13.99 ng Sn⋅g−1 (dry weight, dw) in sediments respectively, 1.19, 5.19, 14.41 and 6.11 ng Sn⋅g−1 dw in organisms respectively. Contamination by OTs in the wetland was considered low and concentrations appeared to be declining; this decline presumably comes on the heels of China adopting in 2011, the International Convention on the Control of Harmful Anti-fouling Systems on Ships (AFS convention). However, the biota-sediment accumulation factor of TPhT was relatively high in mollusks and mudskippers. The potential ecotoxicological risk of OTs contamination to the benthic biota and those organisms at higher trophic levels, especially endangered waterfowl inhabiting wetlands, should be of concern. Further, the present study confirmed the accuracy, high stability and time-saving procedure in determination of TBT, DBT, TPhT and DPhT in sediment and organisms through the use of a high-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS), which may potentially be useful to a wider application in environmental monitoring with limitations of the analytical method for analysis of monobutyltin (MBT) and monophenyltin (MPhT).

Preparation of selenium-enriched Bifidobacterium longum and its effect on tumor growth and immune function of tumor-bearing mice.

In this study, we demonstrated selenium (Se) accumulation in Bifidobacterium longum strain (B. longum) and evaluated the effect of Se-enriched B. longum (Se-B. longum) on tumor growth and immune function in tumor-bearing mice. Analysis using high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) revealed that more than 99% of Se in Se-B. longum was organic, the main component of which was selenomethionine (SeMet). In the in vivo experiments, tumor-bearing mice (n=8) were orally administrated with different doses of Se-B. longum alone or combined with cyclophosphamide (CTX). The results showed that the middle and high dose of Se-B. longum significantly inhibited tumor growth. When Se-B. longum and CTX were combined, the antitumor effect was significantly enhanced and the survival time of tumor-bearing mice (n=12) was prolonged. Furthermore, compared with CTX alone, the combination of Se-B. longum and CTX stimulated the activity of natural killer (NK) cells and T lymphocytes, increasing the levels of interleukin-2 (IL-2) and tumor necrosis factor-α (TNF-α), and the leukocyte count of H22 tumor-bearing mice (n=12).

Maternal Arsenic Exposure and DNA Damage Biomarkers, and the Associations with Birth Outcomes in a General Population from Taiwan

Inorganic arsenic (iAs) is an established transplacental agent known to affect fetal development in animal studies. However, iAs has not been adequately studied in the general population with respect to iAs exposure during pregnancy and its impact on the health status of newborns. The aims of this study were to 1) elucidate the association between arsenic exposure and oxidative/methylated DNA damage in pregnant women, and 2) determine the association with birth outcomes. A birth cohort study of 299 pregnant mother-newborn pairs was recruited during 2001–2002 in Taiwan. We collected maternal urine samples during the 3rd trimester for measuring iAs and its metabolites. We used high-performance liquid chromatography/inductively coupled plasma mass spectrometry (HPLC-ICP-MS) for quantifications of the arsenic species. Liquid chromatography/tandem mass spectrometer (LC-MS/MS) was used to measure the 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) and N7-methylguanosine (N7-MeG) DNA damage biomarkers. Birth outcomes were collected to assess the associations with maternal arsenic exposure and the DNA damage biomarkers. Multiple regression analyses showed that maternal urinary iAs had positive associations with the methylated N7-MeG (beta = 0.35, p<0.001) and oxidative 8-oxodG (beta = 0.24, p<0.001) DNA damage biomarkers, and a decreased one-minute (1-min) Apgar score (beta = -0.23, p = 0.041). Maternal N7-MeG was also associated with a decreased 1-min Apgar score (beta = −0.25, p = 0.042). Mutual adjustment for iAs and N7-MeG showed an independent and significant prediction for a decreased 1-min Apgar score of iAs (beta = −0.28, p = 0.036). Maternal iAs exposure was associated with both maternal DNA damage and adverse newborn health. Maternal N7-MeG levels might be a novel biomarker for monitoring fetal health related to iAs.

셀레늄이 강화된 이스트에서 셀레늄 단백질의 분리 및 확인

Selenium-containing proteins were separated from selenium-enriched yeast (SEY) using Trizol<TEX>$^{(R)}$</TEX> reagent followed by anion exchange (AE) chromatography. This method is simpler and less time consuming than electrophoresis. Five selenium containing proteins were identified by on-line AE HPLC-ICP/MS (high performance liquid chromatography-inductively coupled plasma/mass spectrometry). Each protein was enzymatically hydrolyzed to seleno-amino acids and separated with RP (reverse phase) HPLC for the identification of selenoproteins.

Arsenic speciation in water by high-performance liquid chromatography/inductively coupled plasma mass spectrometry-method validation and uncertainty estimation

In order to obtain reliable analytical results for the separation and determination of arsenic species by high-performance liquid chromatography/inductively coupled plasma mass spectrometry (HPLC/ICP-MS), the analytical procedure must be fully validated and the measurement uncertainty of the analytical result should be estimated. The total arsenic concentration of the samples was determined by ICP-MS. Separation of the arsenic species, AsB, As(III), DMA, MMA and As(V), was accomplished by liquid chromatography, which was hyphenated to inductively coupled plasma mass spectrometry, used for detection purposes. Automated handling of these systems was achieved with Chromera software. The separation capability between the analytical signals of arsenic species, AsB-As(III), As(III)-DMA, DMA-MMA and MMA-As(V), was 1.3, 1.1, 5.1 and 4.6, respectively. The limit of detection (LOD) values ranged from 0.070 µg L(-1) for DMA to 0.13 µg L(-1) for MMA. The expanded uncertainty U [%] values for coverage factor k = 2 estimated for AsB, As(III), DMA, MMA and As(V) were 12 %, 13 %, 5.6 %, 9.6 % and 8.6 %, respectively. This study reports, for the first time, building the uncertainty budgets for five arsenic species and estimation of the expanded uncertainty (for k = 2). The qualitative and quantitative parameters determined in the validation process indicate that the presented analytical procedure can be applied for the determination of AsB, As(III), DMA, MMA and As(V) in water.

Characterization of Arsenic Biotransformation Products from an Open Anaerobic Degradation of Fucus distichus by Hydride Generation Gas Chromatography Atomic Absorption Spectrometry and High Performance Liquid Chromatography Inductively Coupled Plasma Mass Spectrometry

This work reports on the isolation and determination of biotransformation products obtained from the organoarsenic compounds that are present in Fucus distichus when it was subjected to an open anaerobic decomposition by using the Hydride Generation Gas Chromatography Atomic Absorption Spectrometry (HG-GC-AAS) and High Performance Liquid Chromatography Inductively Coupled Plasma Mass Spectrometry (HPLC-ICP-MS). The seaweed and filtrate residues obtained from the open anaerobic degradation procedure were extracted in methanol and partitioned in phenol-ether-water mixtures to obtain water soluble extracts. The water soluble extracts were cleaned up and separated on a gel permeation Sephadex G15 column. Arsenic species concentrations were determined by using HG-GC-AAS. Final characterization of the biotransformation isolates was carried out on HPLC-ICP-MS. Only two arsenic species, 2-dimethylarsinoyl ethanol (DMAE) and dimethylarsinic acid (DMAA), were positively identified in the water soluble extract of the marine brown algae. The two arsenic species are strong intermediate candidates in the biosynthesis of arsenobetaine from oceanic arsenate in marine food webs.

Closed Anaerobic Biotransformation Products of Organoarsenic Compounds inFucus distichus

The closed anaerobic decomposition extracts ofFucus distichusincubated with seawater and sediment, and without sediment as control, were subjected to extractions and isolation on Sephadex LH 20 and Cellulose Thin Layer Chromatography. The decomposition extracts and isolates were analyzed by using both the Hydride Generation Gas Chromatography Atomic Absorption Spectrometry (HG-GC-AAS) and High Performance Liquid Chromatography Inductively Coupled Plasma Mass Spectrometry (HPLC-ICPMS) to identify the arsenic species in the equilibrium mixtures of the seaweed and filtrates separately. In the methanol seaweed extract, equilibrium mixture of arsenosugars (AS) AS1 and AS2 and their biotransformation products of dimethylarsinoylethanol (DMAE) and dimethylarsinic acid (DMAA) were identified. In the methanol filtrate extract of the mixture, only DMAE and DMAA were identified. However, in the control methanol filtrate extract five organoarsenic species, AS1 and AS2, one unidentified hidden organoarsenic species, DMAE and DMAA were identified in the equilibrium mixture. This result confirmed that the hidden organoarsenic species inFucus distichus, AS1 and AS2, and an unidentified organoarsenic compounds are biotransformed to only DMAE and DMAA under an anaerobic condition. This also suggests that DMAE and DMAA are strong intermediate candidates for the generation of arsenobetaine, from arsenoribosides in the marine food webs.

Mercury distribution and speciation in different brain regions of beluga whales (Delphinapterus leucas)

The toxicokinetics of mercury (Hg) in key species of Arctic ecosystem are poorly understood. We sampled five brain regions (frontal lobe, temporal lobe, cerebellum, brain stem and spinal cord) from beluga whales (Delphinapterus leucas) harvested in 2006, 2008, and 2010 from the eastern Beaufort Sea, Canada, and measured total Hg (HgT) and total selenium (SeT) by inductively coupled plasma mass spectrometry (ICP-MS), mercury analyzer or cold vapor atomic absorption spectrometry, and the chemical forms using a high performance liquid chromatography ICP-MS. At least 14% of the beluga whales had HgT concentrations higher than the levels of observable adverse effect (6.0mgkg−1 wet weight (ww)) in primates. The concentrations of HgT differed between brain regions; median concentrations (mgkg−1 ww) were 2.34 (0.06 to 22.6, 81) (range, n) in temporal lobe, 1.84 (0.12 to 21.9, 77) in frontal lobe, 1.84 (0.05 to 16.9, 83) in cerebellum, 1.25 (0.02 to 11.1, 77) in spinal cord and 1.32 (0.13 to 15.2, 39) in brain stem. Total Hg concentrations in the cerebellum increased with age (p<0.05). Between 35 and 45% of HgT was water-soluble, of which, 32 to 41% was methyl mercury (MeHg) and 59 to 68% was labile inorganic Hg. The concentration of MeHg (range: 0.03 to 1.05mgkg−1 ww) was positively associated with HgT concentration, and the percent MeHg (4 to 109%) decreased exponentially with increasing HgT concentration in the spinal cord, cerebellum, frontal lobe and temporal lobe. There was a positive association between SeT and HgT in all brain regions (p<0.05) suggesting that Se may play a role in the detoxification of Hg in the brain. The concentration of HgT in the cerebellum was significantly associated with HgT in other organs. Therefore, HgT concentrations in organs that are frequently sampled in bio-monitoring studies could be used to estimate HgT concentrations in the cerebellum, which is the target organ of MeHg toxicity.

Comparative oxidation state specific analysis of arsenic species by high-performance liquid chromatography-inductively coupled plasma-mass spectrometry and hydride generation-cryotrapping-atomic absorption spectrometry

The formation of methylarsonous acid (MAsIII) and dimethylarsinous acid (DMAsIII) in the course of inorganic arsenic (iAs) metabolism plays an important role in the adverse effects of chronic exposure to iAs. High-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) and hydride generation-cryotrapping-atomic absorption spectrometry (HG-CT-AAS) have been frequently used for the analysis of MAsIII and DMAsIII in biological samples. While HG-CT-AAS has consistently detected MAsIII and DMAsIII, HPLC-ICP-MS analyses have provided inconsistent and contradictory results. This study compares the capacities of both methods to detect and quantify MAsIII and DMAsIII in an in vitro methylation system consisting of recombinant human arsenic (+3 oxidation state) methyltransferase (AS3MT), S-adenosylmethionine as a methyl donor, a non-thiol reductant tris(2-carboxyethyl)phosphine, and arsenite (iAsIII) or MAsIII as substrate. The results show that reversed-phase HPLC-ICP-MS can identify and quantify MAsIII and DMAsIII in aqueous mixtures of biologically relevant arsenical standards. However, HPLC separation of the in vitro methylation mixture resulted in significant losses of MAsIII, and particularly DMAsIII with total arsenic recoveries below 25%. Further analyses showed that MAsIII and DMAsIII bind to AS3MT or interact with other components of the methylation mixture, forming complexes that do not elute from the column. Oxidation of the mixture with H2O2 which converted trivalent arsenicals to their pentavalent analogs prior to HPLC separation increased total arsenic recoveries to ~95%. In contrast, HG-CT-AAS analysis found large quantities of methylated trivalent arsenicals in mixtures incubated with either iAsIII or MAsIII and provided high (>72%) arsenic recoveries. These data suggest that an HPLC-based analysis of biological samples can underestimate MAsIII and DMAsIII concentrations and that controlling for arsenic species recovery is essential to avoid artifacts.

Ionic liquid based carrier mediated hollow fiber liquid liquid liquid microextraction combined with HPLC-ICP-MS for the speciation of phenylarsenic compounds in chicken and feed samples

A novel method of ionic liquid based carrier mediated hollow fiber liquid liquid liquid microextraction (IL-carrier mediated HF-LLLME) combined with high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) has been developed for the speciation of five phenylarsenic compounds and arsenate in chicken and feed samples. The target arsenic species were extracted from 6 mL aqueous samples (pH = 10.2) into an organic phase (20% (v/v) [MTOA]+[Cl]− in toluene) impregnated in the pores of a hollow fiber, then back extracted into a 10 μL acceptor phase of 0.3 mol L−1 NaBr in the lumen of the hollow fiber. The main driving force for the extraction was the gradient concentration of the counter ion from the donor phase to the acceptor phase. Factors affecting the extraction of the target arsenic species were investigated in detail. Under the optimal conditions, the limits of detection (LODs, 3σ) for five target phenylarsenic compounds and arsenate were in the range of 1.4–16.0 ng L−1 with the relative standard deviations (CAs(V),4-OH,3-NHPAA,PA,4-NPAA = 0.05 μg L−1, Cp-ASA = 0.10 μg L−1, n = 7) ranging from 3.6 to 10.0%, and the enrichment factors were varied from 86 to 372-fold. The proposed method of IL-carrier mediated HF-LLLME-HPLC-ICP-MS was successfully applied to the determination of five phenylarsenic compounds and arsenate in chicken and feed samples with the recoveries of 79.2–105.4% and 81.1–117.8% for the spiked chicken and spiked feed samples, respectively.

Chromate in food samples: an artefact of wrongly applied analytical methodology?

Recently several papers were published in highly ranked journals on the presence of Cr(VI) in tea infusions, bread samples and plants. These statements were made on the basis of determination of total Cr concentrations in alkaline and aqueous sample extracts by ETAAS, without applying any speciation analysis. If Cr(VI) really exists in bread samples and tea infusions, consumption of bread and tea would represent long-term chronic exposure to Cr(VI) and a health threat for the majority of the human population. It is well accepted that due to the presence of organic matter foodstuffs of plant and animal origin cannot contain Cr(VI). Therefore, to show that the reported data on the presence of Cr(VI) in foodstuffs are an artefact of inappropriately applied analytical methodology, investigation of speciation was carried out by high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS). 50Cr(VI) and 53Cr(III) stable isotopes were used to follow species interconversions during the extraction procedures. Separated Cr species eluted from the column were followed at m/z 50, 52 and 53. The high sensitivity of the HPLC-ICP-MS method (LOD for m/z 52, 0.03 μg Cr(VI) L−1) enabled reliable determination of Cr(VI) at concentration levels that were much lower than the total Cr content present in sample extracts. The speciation analysis data demonstrated that in all samples analysed Cr(VI) concentrations were below the LOD. In tea infusions 50Cr(VI) was almost completely reduced due to the presence of antioxidants, while the high content of organic matter in bread appreciably reduced 50Cr(VI) even in highly alkaline (pH 12) bread extracts. The data confirmed that Cr(VI) does not exist in foodstuffs of plant origin and provided some conclusive evidence that the same can be expected for foods of animal origin.

A New Metal Tag for Highly Selective and Sensitive Analyses of Amino Acids and Dipeptides by HPLC/ICP-MS

We have developed a novel metal tag, bis(ethylenediamine)-4'-methyl-4-carboxybipyridine-ruthenium N-succinimidyl ester (ECRS) for sensitive analysis of amino acids using high performance liquid chromatography/inductively coupled plasma mass spectrometry (HPLC/ICP-MS). ECRS is a functional reagent, containing an ester group at one end that can be activated to bind to amino group and a chelated ruthenium at the other. The activated ester was reacted briefly with amino groups under weakly alkaline conditions. The ruthenium was detected sensitively by ICP-MS. ECRS was reacted with 17 proteinogenic amino acids in borate buffer. The derivatives were separated by reversed phase HPLC and identified by quadrupole-based ICP-MS. ECRS was suitable for speciation; low molecular weight compounds containing amino groups. We have thus established a quantitative analytical method for amino acids and dipeptides. The detection limits of branched amino acids (signal-to-noise ratio of 3) were 1.5 nmol·L-1 in the standard solution (100 amol per injection).

Determination of 6 Selenium Species in Selenium-Enriched Food by Hyphenated Technique of High Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry

A method for the determination of 6 selenium species in selenium-enriched food by hyphenated technique of High Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry( HPLC-ICPMS) has been developed. The 6 selenium species were separated on a Hamilton PRP-X100 analysis column using20 mmol / L citric acid as the mobile phase with pH 6. 0 under gradient elution within 15 min. This method was easy to operate and with remarkably high sensitivity. The detection limits of SeO2!4,SeO2!3,selenomethionine( SeMet),selenocystine( SeCys2),selenourea( SeUr) and selenoethionine( SeEt) were found to be 0. 7,0. 5,4. 1,1. 3,13. 6,11. 9 μg / L for 100 μL injection volume in He collision cell mode of mass spectrometry. Selenium-enriched corn flour containing SeMet was used to investigate the results of different extraction methods. This method has been used to determine selenium species in some kinds of selenium-enriched food,including rice,yeast,tea and ganoderma lucidum spore powder. The results were satisfactory.

Determination of Bromine Flame Retardants in Polymers by High Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry

A study was performed to determine decabromodiphenyl ether( BDE209),decabromobiphenyl( BB209) and hexabromobenzene( HBB) in polymers by high performance liquid chromatography-inductively coupled plasma mass spectrometry( HPLC-ICP-MS).Agilent TC-C18column( 250 mm×4.6 mm,5 μm) was used with isopropanol/methanol/water( 60∶ 30∶ 10,V/V) as mobile phase at flow rate of 0.8 mL/min.Samples were extracted with toluene,using ultrasonic-assisted extraction( UAE),and then precipitated by isooctane and methanol.Chromatographic separation and mass spectrometric conditions were optimized,and matrix effect of polystyrene( PS),acrylonitrile-butadiene-styrene copolymer( ABS) and polyethylene( PE)were evaluated.The calibration curve was linear within the range from 0.25 mg/L to 10 mg/L with a correlation coefficient of 0.9999.The recoveries of addition standard were in the range of 75.9%-103.8%.The LOD( S/N=3) and the LOQ( S/N=10) were within the range of 0.097-0.1 mg/L and 0.243-0.250 mg/L.The matrix inhibitions of HBB,BB209 and BDE209 in PE,ABS and PS were 25%,10% and3%,respectively.The results proved that the method is simple,selective,specific and suitable for determination of bromine flame retardants in polymers.