Liquid Chromatography Inductively Coupled Plasma Mass Spectrometry Research Articles

LC‐ICP‐MS analysis of inositol phosphate isomers in soil offers improved sensitivity and fine‐scale mapping of inositol phosphate distribution

Abstract Organic forms of phosphorus (P) prevail in soils and their quantification is vital to better understand global biogeochemical cycles. P speciation in soil is commonly assessed by 31P NMR spectroscopy of sodium hydroxide‐EDTA (NaOH‐EDTA) extracts. A liquid chromatography‐inductively coupled plasma‐mass spectrometry (LC‐ICP‐MS) method that employs NaOH‐EDTA is described. Comparison with 31P NMR shows that LC‐ICP‐MS is up to three orders of magnitude more sensitive. It allows measurement in samples as small as 1 mg. We reveal variation of inositol phosphate distribution in Swedish boreal forest soil and identify myo‐ and scyllo‐inositol hexakisphosphates and other isomers including scyllo‐inositol pentakisphosphate. Speciation of the major inositol phosphates was not altered by long‐term nitrogen fertilization.

Combination of isotope dilution with liquid chromatography-inductively coupled plasma mass spectrometry for the simultaneous monitoring and evaluation of cadmium and inorganic arsenic in polished rice.

A new monitoring and evaluation technique for cadmium (Cd) and inorganic arsenic (i-As) in rice was developed, where the isotope dilution (ID) method was applied in combination with high performance liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS), following heat-assisted extraction. Cadmium and i-As in a rice sample were extracted using the HNO3-H2O2 extractant, and an appropriate amount of enriched 111Cd was spiked into it. Cadmium and As species were measured simultaneously by LC-ICP-MS. The cadmium concentration was calculated from the isotope dilution analysis, and i-As was determined by the comparison (1 point calibration) method using additional 111Cd as an internal standard. The proposed method provides accurate and precise determination of Cd based on the isotope dilution analysis. Moreover, it can be applied to a rapid screening test to find contaminated rice samples, by means of monitoring the intensity ratios of natural 111Cd and i-As to the additional 111Cd. The developed technique was applied to analyzing multiple rice reference materials, and the measurement results of Cd and i-As agreed with the certified values within the uncertainty range. It is noted that the grain size of rice samples does not affect the extraction data, when the rice sample is crushed into powder less than 850 μm. The proposed method was very useful for the monitoring and evaluation of Cd and i-As in rice as a precise analytical method as well as a screening method.

Determination of Arsenic Species in Edible Insects by LC-ICP-MS.

Edible insects may contain arsenic. Analysis of arsenic species is necessary in order to accurately assess arsenic exposure. An analytical method was validated and used to determine and quantitate arsenic species in edible insects. Arsenic species were extracted from edible insects by heating at 100 °C in 0.3 mol/L nitric acid. The concentration of arsenic species was then determined by liquid chromatography inductively coupled plasma mass spectrometry (LC-ICP-MS) using an octadecylsilane (ODS) column with a mobile phase containing an ion-pair reagent. The limit of detection (0.007-0.012 mg/kg), limit of quantitation (0.021-0.038 mg/kg), repeatability (1.2-3.2%), intermediate precision (2.8-4.5%), and trueness (recoveries 97-102% based on spiked samples) of the proposed method were satisfactory for inorganic arsenic, dimethylarsinic acid, and arsenobetaine in edible insects. Total arsenic was detected in all samples obtained in Japan (Asian forest scorpion, diving beetles, giant water bug, grasshoppers, June beetles, mole crickets, male rhino beetle, female rhino beetle, sago worms, and silkworm pupae) and consisted of mostly inorganic arsenic. Beetles in particular showed relatively high levels. Arsenic content varies among edible insect species. Feed control is important, as arsenic concentrations in edible insects may be feed dependent. Arsenic species in edible insects were analyzed by LC-ICP-MS using an ODS column with a mobile phase containing an ion-pair reagent. Inorganic arsenic was detected in most samples, with concentrations ranging from <0.04 to 29.3 mg/kg.

Speciation and determination of inorganic antimony in tea infusion by using solid-phase extraction-based liquid chromatography-inductively coupled plasma-mass spectrometry

In this work, we developed a method to separate and detect inorganic antimony (iSb) in tea infusions based on liquid chromatography-inductively coupled plasma-mass spectrometry (LC-ICP-MS). Considering that iSb was present in tea infusions in trace amounts, a commercial solid-phase extraction (SPE) column was employed to enrich iSb(III) and iSb(V). In this study, we found that iSb exists in tea infusions in a bound state with an unknown substance rather than in a free state. Therefore, the enrichment step was combined with oxidation and reduction processes. Because of the enrichment process and the high sensitivity of LC-ICP-MS, the LODs of iSb(III) and iSb(V) were both as low as 0.03 μg L−1. The RSDs (n = 6) of iSb(III) and iSb(V) were all below 8.1%, and the recoveries (n = 6) were 92–96% and 90–94%, respectively. Then, a total of six tea infusion samples were inspected. The data revealed that the total Sb in the tea infusions ranged from 0.22 to 0.97 μg L−1, and we found that 50–83% of the total Sb in the tea infusion was iSb. This method is worth promoting since it has satisfying methodological performance.

Dissolved organic matter mediated dark- and photo-aging processes of Hg(II): Critical impacts of binding sites and sulfidation on Hg(II) abiotic reduction and microbial methylation

Dissolved organic matter (DOM)-mediated divalent mercury (Hg(II)) aging kinetics play a crucial role in controlling Hg(II) transformation and bioavailability in natural aquatic environments. However, the differential environmental behaviors of new and aged Hg(II) in a same reaction system remains unknown. In this study, multi-isotope tracing was used to investigate the impacts of binding site and sulfidation during DOM-mediated Hg(II) aging processes on Hg(II) reduction and microbial methylation in the same reaction system. Stepwise reduction approach and liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS) demonstrate that DOM-mediated dark aging processes are mainly driven by the rearrangement of DOM binding sites with Hg(II), but not the formation of mercury sulfide nanoparticles (HgSNP). The abundant but weaker RO/N (carboxyl and amino) Hg(II)-binding sites are replaced with stronger RSH (thiol) moieties towards Hg(II) binding with aging, resulting in a decrease in Hg(II) reduction. In contrast, besides reduction, DOM-mediated Hg(II) photoaging induces the formation of HgSNP, as revealed by LC-ICP-MS, which in turn decreases the microbial methylation potential of Hg(II). These findings help better understand and predict the kinetic characteristics of Hg(II) reactivity and its influence on Hg cycle within natural aquatic environments.

Quantitative Separation of Unknown Organic-Metal Complexes by Liquid Chromatography-Inductively Coupled Plasma-Mass Spectrometry.

Dissolved organic matter (DOM) is widely recognized to control the solubility and reactivity of trace metals in the environment. However, the mechanisms that govern metal-DOM complexation remain elusive, primarily due to the analytical challenge of fractionating and quantifying metal-organic species within the complex mixture of organic compounds that comprise DOM. Here, we describe a quantitative method for fractionation and element-specific detection of organic-metal complexes using liquid chromatography with online inductively coupled plasma mass spectrometry (LC-ICP-MS). The method implements a post-column compensation gradient to stabilize ICP-MS elemental response across the LC solvent gradient, thereby overcoming a major barrier to achieving quantitative accuracy with LC-ICP-MS. With external calibration and internal standard correction, the method yields concentrations of organic-metal complexes that were consistently within 6% of their true values, regardless of the complex's elution time. We used the method to evaluate the effects of four stationary phases (C18, phenyl, amide, and pentafluoroylphenyl propyl) on the recovery and separation of environmentally relevant trace metals (Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb) in Suwannee River Fulvic Acid and Suwannee River Natural Organic Matter. The C18, amide, and phenyl phases generally yielded optimal metal recoveries (>75% for all metals except Pb), with the phenyl phase separating polar species to a greater extent than C18 or amide. We also fractionated organic-bound Fe, Cu, and Ni in oxidized and reduced soils, revealing divergent metal-DOM speciation across soil redox environments. By enabling quantitative fractionation of DOM-bound metals, our method offers a means for advancing a mechanistic understanding of metal-organic complexation throughout the environment.

Thymine-mediated electrochemical aptasensor for sensitive and simultaneous detection of Hg2+ and CH3Hg+ in fish samples

In this study, a thymine-mediated electrochemical aptasensor was constructed for instantaneous detection of Hg2+ and CH3Hg+ in fish muscle using ferrocene (Fc) and methylene blue (MB) as electrochemical tags. In the presence of Hg2+, a HP-Fc (ferrocene and thiol-labeled hairpin DNA) was opened and hybridized with a complementary S1 (single-stranded DNA) to form a stable thymine-Hg2+-thymine (T-Hg2+-T) structure. Then, the Fc tag got far away from the gold electrode surface, inducing a distinct decrease of its electrochemical signal. Meanwhile, SA−MB (methylene blue labeled single-stranded DNA) was designed to complement with S2 (thiol-labeled single-stranded DNA). When CH3Hg+ was present, the double-stranded DNA was dissociated, and a more stable CH3Hg+-T structure was generated by binding of screened S2 and CH3Hg+. Thus, the SA−MB was away from electrode surface and the significantly reduced current of MB was observed. As a result, Hg2+ and CH3Hg+ were differentiated through the thymine-mediating, realizing the simultaneous detection of Hg2+ and CH3Hg+ without extra separation procedure. Such a sensing strategy allowed sensitive and selective detection of Hg2+ and CH3Hg+ down to the picomolar level, with limits of detection (LOD, S/N = 3) of 0.06 pM and 0.13 pM, respectively. The sensor was finally successfully applied for the detection of Hg2+ and CH3Hg+ in fish samples, and the results were in good agreement with those obtained by liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS). This technology provides a sensitive and simple method for speciation analysis and monitoring of Hg2+ as well as CH3Hg+ in biological samples.

Risk assessment of methylmercury and species identification in shark meats ingested by Taiwan children

Human exposure to methylmercury (MeHg) is through consumption of carnivorous fish and seafood to cause neurotoxicity. Carnivorous fish, especially fresh shark meat and its product are often used in Taiwan. This study is first to determine the shark species from fresh shark meats and smoked shark meats using genome sequencing. Additionally, the level of MeHg in a part of these shark meats was measured by using liquid chromatography/inductively coupled plasma mass spectrometry (LC/ICP-MS). Based on these MeHg levels, the risk of MeHg exposure of the shark meat consumption was assayed by utilizing the estimated weekly intake (EWI) and hazard quotient (HQ) of MeHg for the children of 3–18 ages. The results indicate the major species of fresh shark meats is Prionace glauca, and the minor species includes critically endangered species Rhynchobatus australiae and vulnerable species Alopias superciliosus. The level of MeHg was below 2 mg/kg in most shark meats, which is consistent with the Taiwan standard limit. However, the level of MeHg in some samples of shark meats was more than 2 mg/kg. Importantly, higher level of MeHg was found in smoked shark meat than that in fresh shark meat. Another, the level of HQ was more than 1, which is a criterial risk point, for children to ingest a little shark meat for children of 3–12 ages. The results indicate that the dietary intake of shark meat or smoked shark meat is danger for 3–12 years old children.

Simultaneous determination of iodide and iodate in salty spices by liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS)

In this study, iodide and iodate species in food were simultaneously determined by LC-ICP-MS after sample treatment with Deion water based on ultrasonic extraction. The conditions of the instrument and the extraction procedure were investigated. The method was validated with calibration curves that have the coefficient of determination (R2) higher than 0.995. The method limits of detection (LOD) of iodide and iodate were 0.079 and 0.060 mg/kg respectively meeting the regulatory requirements for food safety management. The recoveries were in the range of 83.5 - 108% and the relative standard deviations (RSDr) were between 2.57 and 5.22%. These parameters met the requirements specified by AOAC. A total of 43 salty spice samples including table salts, iodized seasoning soup powders, seasoning seeds, oyster sauces, soy sauces, fish sauces were collected and analyzed for research purposes. The results showed that a high percentage (76.9%) of table salt and seasoning soup powder samples had total iodate and iodide content lower than the specified level. Meanwhile, other salty spice samples, especially seasoning seeds and soy sauces, had a significant content of iodide in the range of 2.0 to 13.2 mg/kg. This study has contributed to the preliminary assessment of the current status of iodine content in salty spice products collected in Hanoi city.

Simultaneous determination of borax and polyphosphates content in food by liquid chromatography inductively coupled plasma mass spectrometry (LC-ICP-MS)

A new method based on LC-ICP-MS technique has been developed and validated for&amp;nbsp;the simultaneous determination of borax and polyphosphates (phosphate, pyrophosphate,&amp;nbsp;tripolyphosphate) in foods. The analytes were extracted from the samples with 18 mM&amp;nbsp;sulfuric acid solution using ultrasonic vibration extraction technique before being filtered and&amp;nbsp;analyzed by LC-ICP-MS system. The method was validated with calibration curves that have&amp;nbsp;the coefficient of determination (R2) higher than 0.995. The method limits of detection (LOD)&amp;nbsp;of borax, phosphate, pyrophosphate (Pyro-P), and tripolyphosphate (Tripoly-P) were in the&amp;nbsp;range of 2.5 to 15.0 mg/kg. The recoveries were in the range of 86.0 to 107.0% and the relative&amp;nbsp;standard deviations were below 5.23%. A total of 83 samples of cereal, meat, and seafood-based&amp;nbsp;food were analyzed for research purposes. The results did not indicate a risk of using borax&amp;nbsp;and polyphosphates in most rice products. Meanwhile, meat products including pork paste and&amp;nbsp;roasted pork sold in traditional markets had a borax detection rate of over 60%. This study&amp;nbsp;showed that there was still a risk of using borax in food processing and the use of polyphosphates&amp;nbsp;in food products collected in some districts in Hanoi city.

Comparison of Simultaneous Quantitative Analysis of Methylmercury and Inorganic Mercury in Cord Blood Using LC-ICP-MS and LC-CVAFS: The Pilot Study of the Japan Environment and Children's Study.

Prenatal exposure to methylmercury (MeHg) affects child development after birth. However, many epidemiological studies have evaluated total mercury levels without analyzing speciation. Biomonitoring of MeHg and inorganic mercury (IHg) is essential to reveal each exposure level. In this study, we compared a high-throughput analysis for mercury speciation in blood using liquid chromatography-inductively coupled plasma-mass spectrometry (LC-ICP-MS) and liquid chromatography-cold vapor atomic fluorescence spectrometry (LC-CVAFS). The validated LC-ICP-MS method was applied to 101 maternal blood and 366 cord blood samples in the pilot study of the Japan Environment and Children’s Study (JECS). The accuracy of the LC-CVAFS method ranged 90–115% determined by reference material analysis. To evaluate the reliability of 366 cord blood samples, fifty cord blood samples were randomly selected and analyzed using LC-CVAFS. The median (5th–95th percentile) concentrations of MeHg and IHg were 5.4 (1.9–15) and 0.33 (0.12–0.86) ng/mL, respectively, in maternal blood, and 6.3 (2.5–15) and 0.21 (0.08–0.49) ng/mL, respectively, in cord blood. Inter-laboratory comparison showed a relatively good agreement between LC-ICP-MS and LC-CVAFS. The median cord blood:maternal blood ratios of MeHg and IHg were 1.3 and 0.5, respectively. By analyzing speciation, we could focus on the health effects of each chemical form.

Method validation for As speciation in rice using LC-ICP-MS and the inorganic arsenic limit for Brazilian rice

A methodology for As speciation in rice using liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS) was optimised and validated. Chromatographic separation and elution of As(III), DMA(V) (dimethylarsenic acid), MMA(V) (monomethylarsenic acid) and As(V) were achieved in less than 8 min using 10 mmol L−1 (NH4)2HPO4 as the mobile phase, at pH 6 and a flow rate of 1.4 mL min−1. The limits of detection for As(III), DMA(V), MMA(V) and As(V) in rice were 1.87, 2.89, 0.54 and 3.00 ng g-1, respectively. The method’s accuracy was assessed through analyte recovery tests and analysis of certified reference materials, which included white and brown rice flours. The validated method was applied for As speciation in 640 rice samples, comprising polished (white) rice, parboiled rice and brown rice collected from different mesoregions in the Rio Grande do Sul State in Brazil. By comparing the total concentration of As (tAs) found in the acid digested samples with the As species sum, the average extraction efficiencies were 98 ± 13%, 93 ± 12% and 86 ± 6%, for white, parboiled, and brown rice, respectively. The average concentrations of inorganic arsenic (iAs, that is As(III) + As(V)), DMA and tAs in brown and parboiled rice were not different but differed from those in white rice; the average concentrations of tAs, iAs and DMA in brown and parboiled rice were higher than those found in white rice were. The iAs concentration in all rice samples was lower than 200 ng g−1, which could be recommended as the maximum iAs concentration for Brazilian rice.

LC/ICP-MS AND COMPLEMENTARY TECHNIQUES IN BESPOKE AND NONTARGETED SPECIATION ANALYSIS OF ELEMENTS IN FOOD SAMPLES.

Chemical elements speciation analysis of food samples has been among the most important scientific topics over the last decades. Food samples are comprised of high variety of chemical compounds, from which many can interact with metals and metalloids, forming complex elemental species with various influence on the human body. It is particularly important not only to determine the amount of certain chemical element in food sample but also to identify the form in which given element occurs in given sample. Employment of bespoke and nontargeted speciation methods, with the use of liquid chromatography inductively coupled plasma mass spectrometry (LC/ICP-MS) and complementary techniques, provides more complete picture on the metals and metalloids speciation in food. This review discusses issues concerning speciation analysis of metals and metalloids in food samples with the use of LC/ICP-MS as a leading technique in elemental speciation nowadays and a complimentary technique intended for their identification. © 2020 John Wiley & Sons Ltd. Mass Spec Rev.

Determination and generating study on monoiodoacetic acid and diiodoacetic acid in water by liquid chromatography-inductively coupled plasma mass spectrometry

In this study, we have developed a method to directly detect monoiodoacetic acid (MIAA) and diiodoacetic acid (DIAA) in drinking water using liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS). MIAA and DIAA were qualitatively analyzed based on the retention time and quantitatively measured using the peak area integral. The figures of merit from five independent labs reveal that the LODs of the method were 0.06 ~ 0.22 μg/L for MIAA and 0.04 ~ 0.18 μg/L for DIAA, and the recovery rates were 95% ~ 107% and 94% ~ 103% for MIAA and DIAA, respectively. Concomitant anions such as 200 mg/L of SO42−, NO3−, BrO3−, and F−, 300 mg/L of Cl− and 2.0 mg/L of chlorine or bromine based haloacetic acids (HAAs) could not interfere with this method. Additionally, the results for the quality control samples from five labs were consistent with one another. The verification data from five independent labs proved that the method is accurate and adaptable. Since the method does not use pretreatments or toxic organic reagents, the greenness of the method is guaranteed compared to that of conventional methods. Hence, the method used to detect MIAA and DIAA in drinking water is qualified as a standard method for wide application. Furthermore, the generation study of iodoacetic acids (IAAs) in Cl2 and UV275-Cl2 disinfection systems was performed. The results showed that the amount of IAAs was significantly higher when UV275-Cl2 was used to disinfect the high-iodium water than when only Cl2 was applied, especially in weak acid conditions. This conclusion is of great importance in suggesting how to reduce the potential risk of IAAs when producing drinking water when chlorine or a UV275-Cl2 disinfection process is applied.

Simultaneous determination of Cr (III) and Cr (VI) in functional foods using liquid chromatography - inductively coupled plasma mass spectrometry (LC-ICP-MS)

Chromium is often added in some functional foods to aid in the treatment of diabetes or in fortified dairy products. The toxicity of chromium depends on the oxidation state. Therefore, it is necessary to identify or quantify chromium species to assess food safety hazards. In this study, the species of Cr (III) and Cr (VI) were determined by liquid chromatography (LC) with collision cell inductively coupled plasma mass spectrometry (ICP-MS). The main parameters such as the concentration of complexing agents, the effect of pH, the mobile phase flow rate, the extraction solvents as well as the extraction time and temperature were optimized. The method detection limits (MDLs) of 20 &amp;micro;g/kg for Cr (III) and 10 &amp;micro;g/kg for Cr (VI) obtained based on peak hight at mass 52 for injections at low level spiked samples. The repeatability of Cr (III) was 1.96 % while that of Cr (VI) was 7.78%. The recovery of Cr (III) and Cr (VI) at 1 mg/kg was in the range of 91.3 - 98.4% and 89.3 - 96.7% respectively. The validated parameters were completely meeting the Association of Official Analytical Collaboration (AOAC) performance requirements, which was applied to analyze Cr species in some functional food samples collected on the market. The content of Cr (III) was found in accordance with products label declaration while Cr (VI) was not detected.

A simple spectrophotometric method for rapid quantitative screening of arsenic bio-transforming bacteria

Abstract A simple spectrophotometric technique for inorganic arsenic speciation of known total arsenic has been developed for application in quantitative screening of arsenite-oxidizing and arsenate-reducing bacteria from the wide range of environmental isolates. The technique is based on the spectrophotometric absorbance measurement of the color intensity in the arsenic and potassium permanganate mixture. Since arsenate does not react with potassium permanganate, the intensity of color decreases proportionately with the increasing concentration of arsenite in the total arsenic. The speciation method can be used over a pH range of 4–9. The validity of the results obtained from this spectrophotometric method was confirmed with the Liquid Chromatography-Inductively Coupled Plasma-Mass Spectrometry (LC-ICP-MS). This method has great potential for the screening of arsenite-oxidizing bacteria.

Development of a liquid chromatography-inductively coupled plasma mass spectrometry method for the simultaneous determination of methylmercury and inorganic mercury in human blood

We developed and validated a liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS) method for simultaneous determination of methylmercury (MeHg) and inorganic mercury (I-Hg) in human blood samples. Thallium was used as an internal standard for determination of MeHg and 196Hg was used as an internal standard for I-Hg determination. The blood samples were extracted using a 7% (v/v) HCl solution containing 1.5% (w/v) l-cysteine. A 10% (w/v) trichloroacetic acid solution was used to precipitate proteins in the extract. Mercury species were measured by LC-ICP-MS. The linear range of the assay was 0.08–60 ng/mL for MeHg and 0.05–2.5 ng/mL for I-Hg. The method was validated with the Certified Reference Materials Blood Mercury (Institut National de Santé Publique Québec, Quebec, Canada) and Seronorm™ Trace Elements Whole Blood (Sero AS, Billingstad, Norway). Additional validation was performed by comparing the results obtained with those from a widely used gas chromatography method with electron-capture detection. The proposed method was applied to the simultaneous determination of MeHg and I-Hg in human blood samples. The LC-ICP-MS method provides precise, accurate, and robust determination of MeHg and I-Hg levels in human blood over a long period and has a simple and quick sample preparation. We expect that this method will contribute to large-scale evaluation of human exposure to mercury compounds in future.

Arsenolipids in the green alga Coccomyxa (Trebouxiophyceae, Chlorophyta)

Lipid-like compounds containing a dimethylarsinoyl group, i.e. Me2As(O)-, have been identified by liquid chromatography/inductively coupled plasma mass spectrometry (LC/ICP-MS) and non-aqueous reversed-phase high-performance liquid chromatography (positive and/or negative high-resolution tandem electrospray ionization mass spectrometry (NARP-HPLC/HR-ESI+(−)-MS/MS) from three strains of green algae of the genus Coccomyxa (Trebouxiophyceae, Chlorophyta). The algae were cultivated in a medium containing 10 g arsenic/L, i.e. 133.5 mmol/L of Na2HAsO4.7H2O. After extraction by methyl-tert-butyl ether (MTBE), total lipids were analyzed by ICP-MS or ESI-MS without any further separation or fractionation. A total of 39 molecular species of arsenic triacylglycerols (AsTAG), 15 arsenic phosphatidylcholines (AsPC), 8 arsenic phosphatidylethanolamines (AsPE), 6 arsenic phosphatidylinositols (AsPI), 2 arsenic phosphatidylglycerols (AsPG) and 5 unknown lipids (probably ceramides) were identified. The structures of all molecular species were confirmed by tandem MS. Dry matter of the individual strains contained different amounts of total arsenolipids, i.e. C. elongata CCALA 427 (0.32 mg/g), C. onubensis (1.48 mg/g), C. elongata S3 (2.13 mg/g). On the other hand, there were only slight differences between strains in the relative abundances of individual molecular species. Possible biosynthesis of long-chain lipids with the end group Me2As(O) has also been suggested.

Arsenic Speciation of Edible Shrimp by High-Performance Liquid Chromatography-Inductively Coupled Plasma-Mass Spectrometry (HPLC-ICP-MS): Method Development and Health Assessment

This study aimed at developing an accurate method for determining the levels of total arsenic (As) and arsenic species in edible shrimp with the collision/reaction cell (CRC) in the O2 mass-shift mode to remove interferences. The microwave-assisted extraction method demonstrated satisfactory efficiency (86.9%), and As species were separated rapidly within 11 min when the optimized chromatographic conditions were adopted. During the study, the limits of detection, precision, and spike recovery for six arsenic species were in the ranges from 0.010 to 0.028 μg/L, 1.89 to 3.14%, and 96.9 to 103.2%, respectively. The analytical methods were successfully applied to determine the concentrations of total arsenic and As species in eight shrimp samples. The results showed that arsenobetaine was the predominant As species, and inorganic arsenic contents were below 0.5 mg/kg in the shrimp samples analyzed. The health risk assessment indicated that the shrimp samples detected posed no particular risk of As to local consumers.

A comparative assessment of water-soluble selenium metabolites in commercial selenised yeast supplements by liquid chromatography-electrospray ionisation QTOF-MS

Liquid chromatography-inductively coupled plasma-mass spectrometry (LC-ICP-MS) was utilised for the screening of organoselenium metabolites in the water extracts of selenised yeast products. Four different commercially available yeast products and a reference Se-enriched yeast standard, (SELM-1) were analysed. Total selenium and selenomethionine concentrations were determined by ICP-MS and LC-ICP-MS, respectively. Ultrafiltration using a 3 kDa molecular weight cut-off membrane was used in the present study for sample clean-up. The water-soluble extracts were lyophilised to increase analyte concentration, resuspended in water and analysed by liquid chromatography-electrospray ionisation quadrupole time-of-flight mass spectrometry (LC-ESI-QTOF-MS). Selenium-containing species were confirmed using selenium’s unique isotopic pattern. This approach allowed for the detection of approximately 129 previously unreported selenium metabolites across the different yeast samples. Determination of the elemental composition of 14 previously unreported selenocompounds was advanced through MS2 analysis and accurate molecular mass determination (Δ ppm<1.6 for all proposed elemental compositions).