Gas Chromatography-negative Chemical Ionization-mass Spectrometry Research Articles

A-066 Does essential fatty acid deficiency alter ethanolamine plasmalogen concentrations in red blood cells? Implications for clinical testing

Abstract Background Plasmalogens are glycerophospholipids characterized by a fatty alcohol at the sn-1 position, a polyunsaturated fatty acid at the sn-2 position, most commonly docosahexaenoic acid (DHA) or arachidonic acid, and a polar head group at the sn-3 position, mainly phosphoethanolamine. Markedly reduced plasmalogens are seen in peroxisome biogenesis defects, including Zellweger spectrum disorders (ZSD), since the first two steps of plasmalogen synthesis occur in peroxisomes. Disruption of the peroxisomal β-oxidation pathway also causes DHA deficiency in ZSD patients. Since plasmalogens are composed of fatty acids, the deficiency of DHA or other essential fatty acids could further decrease the plasmalogen level in ZSD patients and lower the results of plasmalogen testing in patients without ZSD. To test this hypothesis, we evaluated the impact of essential fatty acid (EFA) deficiency on plasmalogens in patients with ZSD and individuals with EFA deficiency due to unrelated causes. Methods Red blood cell (RBC) samples were obtained from individuals without ZSD referred to ARUP laboratories for clinical EFA testing (n = 80; age range: birth - 89 years), and from patients with ZSD (n = 7; age range birth - 9 years). Three ZSD patients were older and with a less severe phenotype. A total of 18 intact ethanolamine plasmalogen species were extracted from packed RBCs and quantified using a XEVO TQ-XS Mass Spectrometer in conjunction with Ultra-High Performance Liquid Chromatography (Waters). Total plasmalogen values were also calculated; plasmalogen deficiency was defined as ≤60% of age-matched control median. Fatty acids (FAs) were quantified by gas chromatography negative chemical ionization-mass spectrometry (GC-NCI-MS). EFA deficiency was diagnosed by increased Triene/Tetraene ratio (Mead acid/Arachidonic acid). Data was analyzed using Prism v.8.3.0 software (La Jolla, CA). The study was approved by the Institutional Review Board of the University of Utah. Results Out of the 80 samples from individuals without ZSD referred for EFA testing, 18% had normal fatty acid profile, 57% were receiving dietary supplements and 25% had elevated Triene/Tetraene ratio suggesting EFA deficiency. EFA deficiency was accompanied by low DHA only in two individuals without ZSD, whereas it was present in most of the samples from ZSD patients evaluated (5/7). None of the individuals without ZSD were deficient in plasmalogens. Moreover, when compared to individuals without ZSD with a normal FA profile, there was no significant difference observed with EFA deficiency or FA supplementation. Although our ZSD cohort is small, no correlation between EFA deficiency and plasmalogen levels was also seen in ZSD: 2 patients with milder phenotype had EFA deficiency but normal plasmalogens, 2 patients had EFA deficiency and low plasmalogens, 2 patients with low plasmalogens had low DHA without EFA deficiency, and 1 patient had low plasmalogens but normal EFA. Conclusions Plasmalogen quantitation in RBCs by LC-MS/MS is not significantly affected by EFA deficiency. Although more data is warranted to elucidate the correlation between plasmalogen levels and ZSD phenotype, plasmalogens can be within normal reference intervals in ZSD regardless of EFA status.

Determination of three dechloranes in environmental water by magnetic solid-phase extraction-gas chromatography-negative chemical ionization mass spectrometry based on the covalent organic framework material

Dechloranes are additive-type chlorine flame retardants that are widely used in processing industrial products, such as electronic equipment and textiles. Dechloranes, which can enter the human body through various routes, pose significant health risks because of their toxicity, persistence, and bioaccumulation. In 2023, dechlorane plus was listed in the Stockholm Convention on Persistent Organic Pollutants. In the same year, China recognized this compound as a priority-controlled substance. Dechloranes are commonly found at trace levels in water, which is extremely harmful to the environment and human health. Therefore, the development of detection methods for dechloranes is crucial. Magnetic solid-phase extraction (MSPE) has attracted considerable attention because of its low organic solvent consumption, simplicity of adsorbent separation, and ease of operation. In general, the selectivity and efficiency of MSPE depend on the characteristics of the adsorbent. Covalent organic frameworks (COFs) have regular porosity, structural predictability and stability, high specific surface areas, and adjustable pore sizes, which are advantageous for a wide range of separation and analysis applications. In this study, Fe3O4 magnetic nanoparticles and a COF material (TpBD) were combined to prepare Fe3O4@TpBD as an adsorbent for dechloranes. Subsequently, an effective method for analyzing dechlorane in environmental water was established by coupling MSPE with gas chromatography-negative chemical ionization mass spectrometry (GC-NCI/MS). The successful synthesis of Fe3O4@TpBD was confirmed using transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and vibrating sample magnetometry. A single-factor method was used to optimize the extraction conditions, including the Fe3O4@TpBD dosage, pH of water sample, elution solvent type and volume, extraction time, elution time, and ionic strength. The target analytes were separated on a TG-5SILMS column (30 m×0.25 mm×0.25 μm) and quantified using the external standard method in the selected-ion monitoring (SIM) mode. Under the optimal extraction conditions, the method validation results showed a linear range of 2-1000 ng/L. The limits of detection (LODs) and quantification (LOQs) were 0.18-0.27 ng/L and 0.60-0.92 ng/L, respectively, for the three analytes. The intra-day and inter-day precisions at three spiked levels were 4.2%-16.2% and 6.9%-15.7%, respectively. This method was successfully applied to the determination of dechloranes in environmental water samples (laboratory tap water, reservoir water, wastewater treatment plant effluent, and landfill leachate treatment effluent). The recoveries of the three dechloranes at different spiked levels ranged from 77.8% to 113.3% with relative standard deviations (RSDs) of 2.5%-16.3% (n=3). With the advantages of operational simplicity, high sensitivity, and good reproducibility, the proposed method is suitable for the qualitative and quantitative determination of dechloranes in environmental water.

Determination of polybrominated diphenyl ethers in marine sediments by composite chromatography column purification-gas chromatography-negative chemical ionization-mass spectrometry

Polybrominated diphenyl ethers (PBDEs) are used as additive flame retardants. Because they lack the ability to form chemical bonds, PBDEs can easily enter the sediment environment. The accurate qualitative and quantitative analysis of PBDEs in sediments is of great importance for the accurate assessment of PBDE pollution in this environment. Sediments contain many impurities. Therefore, PBDEs in sediment should be purified before analysis to reduce the matrix effect. A method based on gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI/MS) was developed to determine 13 PBDEs in marine sediment samples using a column packed with deactivated silica gel, acidified silica gel, Florisil, and anhydrous sodium sulfate. Sediment samples were extracted by ultrasonication with a mixed solvent of n-hexane-dichloromethane (3∶1, v/v). After two cycles of ultrasonic extraction, the extract was purified by a composite chromatographic column and eluted with n-hexane-dichloromethane (3∶1, v/v). Thirteen PBDEs were determined by GC-NCI/MS in selected-ion monitoring (SIM) mode. The effects of different fillers, eluents, and elution volumes on the purification of PBDEs in the composite column were compared and analyzed, and the GC-NCI/MS analysis conditions were optimized. Three different packing columns were used to purify the sample extract. The first column was packed with 3 g of deactivated silica, 6 g of acidic silica, 3 g of deactivated silica, 3 g of Florisil, and 6 g of anhydrous sodium sulfate; the second column was packed with 3 g of Florisil, 3 g of deactivated silica, 6 g of acidic silica, 3 g of deactivated silica, and 6 g of anhydrous sodium sulfate; and the third column was packed with 3 g of deactivated silica, 6 g of acidified silica, 3 g of deactivated silica, and 6 g of anhydrous sodium sulfate. Among these columns, that packed with 3 g of deactivated silica, 6 g of acidic silica, 3 g of deactivated silica, 3 g of Florisil, and 6 g of anhydrous sodium sulfate showed the best purification effect. The 13 PBDEs showed good linearity in the mass concentration range of 0.1-20 μg/L with correlation coefficients (r2) greater than 0.995 (decabromodiphenyl oxide (BDE-209), r2>0.99). The limits of quantification (S/N=10) was 0.002-0.126 μg/kg. The average recoveries of the 13 PBDEs at three spiked levels of 0.2, 1.0, and 4.0 μg/kg were 85.3%-101.3%, 84.8%-113.6%, and 86.3%-94.7% with relative standard deviations of 4.4%-14.0%, 0.4%-4.9%, and 1.9%-6.6%, respectively. These findings indicate that the method has high sensitivity and accuracy as well as good precision. Finally, the method was applied to the analysis and detection of PBDEs in actual marine sediment samples. The results revealed that the sediment samples contained different contents of the 13 PBDEs, and high detection rates were obtained for lower-brominated PBDE homologs. The detection rate of bis(4-bromophenyl) ether (BDE-15) was 100%, and the detected content of BDE-209 was as high as 60.49 μg/kg. These results demonstrate that the developed method is suitable for the accurate qualitative and quantitative analysis of PBDEs in marine sediment samples.

Quantitative detection of organic mercury in whole blood using derivatization and gas chromatographynegative chemical ionization-mass spectrometry

The Minamata disease, first identified in Japan in the 1950s, is caused by severe methylmercury (MeHg) poisoning. To prevent the development of this disease, routine evaluation of MeHg levels in blood samples is crucial. The purpose of this research was to explore the use of derivatization and capillary gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS) for the quantitative detection of both organic and inorganic mercury in blood samples. Alkyl mercury in standard solutions was extracted as halide salts in toluene with hydrohalic acid. Fat contents in whole blood samples were removed by methyl isobutyl ketone and hexane using a cysteine/alkaline solution and then organic mercury was extracted as a bromide complex using toluene and cupper chloride solution. The linearity of the response ratio vs. concentration curves (R2) was 0.987 for methylmercury bromide and 0.990 for ethylmercury bromide. over the calibration range of 0.02 ng/mL to 20 ng/mL. The recovery of MeHg and ethylmercury (EtHg) was 67.1% and 49.3%, respectively. The concentrations of MeHg in whole blood samples determined using GC with an electron capture detector agreed with those determined using GC-NCI-MS, with a correlation coefficient of 0.923. The mean concentration of MeHg in a certified reference material (NMIJ CRM 7402-a) determined using GC-NCI-MS was 0.64 μg/g, comparable with the certified value of 0.58 μg/g. Our study demonstrates a simple and low-cost approach for analyzing mercury in biological samples, although further optimization is required given the relatively low recovery and the concern about the toxicity of methyl isobutyl ketone.

Determination of four trihalomethanes in ship ballast water by gas chromatography-negative chemical ionization-mass spectrometry

我国每年的船舶压载水排放量巨大,压载水中含有浮游生物、病原体及其幼虫或孢子等,若处理不当,会对排放水域的生态环境造成严重影响。排放压载水前常使用电解法对其进行处理,电解产生的次氯酸钠溶液,能有效杀灭残余的微生物。但电解后会产生副产物三卤甲烷(THMs),其对人体有一定的健康风险,建立船舶压载水中三卤甲烷的测定方法具有重要意义。该研究建立了采用气相色谱-负化学源质谱(GC-NCI-MS)测定船舶压载水中4种三卤甲烷(包括三氯甲烷、二氯一溴甲烷、一氯二溴甲烷、三溴甲烷)的分析方法。船舶压载水样品经过顶空进样技术处理后,通过DB-5MS UI毛细管色谱柱(30 m×0.25 mm×1.0 μm)分离,气相色谱-负化学源质谱仪测定,在选择离子扫描(SIM)模式下分析,采用外标法进行定量。4种三卤甲烷在0.2~50 μg/L范围内线性关系良好,相关系数(r)≥0.995,定量限(S/N=10)为0.1~0.2 μg/L,在0.2、0.5、2.0 μg/L 3个加标水平下,4种THMs的平均回收率为90.3%~106.8%,相对标准偏差(RSD)为1.4%~6.2%。该方法准确、稳定、可靠,可用于测定船舶压载水中4种THMs的含量。使用建立的测定方法对36个船舶压载水进行测定,三溴甲烷、二溴一氯甲烷、一溴二氯甲烷与三氯甲烷的检出率分别为83.3%、69.4%、22.2%和19.4%,检出值分别为34.25~221.5 μg/L、3.52~41.87 μg/L、1.52~8.56 μg/L和0.02~5.46 μg/L。

Quantitation of Fatty Acids in Serum/Plasma and Red Blood Cells by Gas Chromatography-Negative Chemical Ionization-Mass Spectrometry.

Quantitation of long-chain fatty acids in serum/plasma and red blood cells is a useful diagnostic tool in the evaluation of nutritional status and assessment of risk for essential fatty acid deficiency (EFAD). Serum/plasma has been the traditional sample type for this method, yet it requires prolonged fasting which is not compatible with some patient populations. More recently, red blood cells have become an important sample type due to less intraindividual variability and obviating the need for fasting. Here we present a method for the quantitation of 22 fatty acids in serum/plasma or red blood cells. Fatty acids are hydrolyzed and extracted from the biological matrix, followed by derivatization with pentafluorobenzyl bromide and subsequent analysis by gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS).

Silver ion chromatography for the analysis of trans-fatty acid isomers in humans

More than 65 different fatty acids, including positional and geometric fatty acid isomers, have been reported in humans. These isomers have the same molecular mass and very similar chemical structures but can have very different biological functions. The large number of cis- and trans-isomers in human blood pose analytical challenges and require detailed investigations to appropriately determine their effects on health and changes in the amount and composition in people. Silver ion chromatography, a technology used to separate complex fatty acid mixtures, in combination with an expanded version of Centers for Disease Control and Prevention (CDC) gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS) method for fatty acids can effectively separate cis- and trans-fatty acid isomers. This approach has potential for determining comprehensive trans-fatty acid profiles in people.

Effect of fasting status and other pre-analytical variables on quantitation of long-chain fatty acids in red blood cells

Long-chain fatty acids (LCFAs), including omega-3 and omega-6 fatty acids, play essential roles in health maintenance and outcomes. Insufficient intake or the inability to absorb LCFAs from the diet can cause a number of health problems. Evaluation of fatty acid profiles in plasma, serum or red blood cells (RBCs) is routinely used to monitor patients at risk of developing deficiency. Quantitation of LCFAs in RBCs offers advantages over serum/plasma due to low intra-individual variability. Fatty acid composition in RBCs also reflects long-term dietary intake, providing additional information about the patient's nutritional status. However, the literature does not currently address the impact of pre-analytical factors (conditions of RBC collection, sample handling and short-term storage) on LCFA measurements. This study evaluated the effect of several anticoagulants, interferents, different storage conditions and fasting status on quantitation of the twenty-one most abundant LCFAs in RBCs by gas chromatography negative chemical ionization-mass spectrometry (GCNCI-MS). LCFA results were assessed quantitatively (nmol/mL) or as a percent of total. Most common tube types (containing citrate, sodium heparin or EDTA) were all appropriate for blood collection. Whole blood and lysed RBCs were stable at least 24 h at room temperature and up to 7 days refrigerated. Lysed RBCs were also stable for up to three freeze/thaw cycles. The presence of icterus or lipemia did not affect results. LCFAs concentrations in RBCs did not change ~4 h after high-fat intake when the lipid concentration in circulation reaches a peak, while plasma levels of most fatty acids increased up to 40% in response. In summary, RBCs are a reliable sample type for LCFA quantitation in the clinical laboratory. In contrast to plasma or serum, RBCs isolated from non-fasting, hemolyzed or lipemic whole blood specimens are all acceptable for testing. Therefore, RBCs might be a preferable sample type for evaluation of nutritional status of young pediatric patients and in patients with conditions associated with hemolytic anemia or hyperlipidemia.

Umbilical cord serum PBDE concentrations and child adiposity measures at 7 years

BackgroundPolybrominated diphenyl ethers (PBDEs) exist extensively in the environment. Toxicological studies suggested PBDEs may interfere with adipogenic pathways. However, few human evidence addressed PBDE exposures in utero related to childhood adiposity. ObjectiveWe assessed associations between PBDEs concentrations in cord serum and childhood adiposity measures at 7 years. MethodsAmong 318 mother-child pairs from Sheyang Mini Birth Cohort Study (SMBCS) in China, nine PBDE congener concentrations were quantified in umbilical cord serum using gas chromatography-negative chemical ionization mass spectrometry (GC-NCI-MS). Anthropometric indicators of children aged 7 years were measured, including weight, height and waist circumference. Age and sex-specific body mass index (BMI) z scores were calculated based on World Health Organization (WHO)'s child growth standards. Multivariate linear and logistic regression models adjusted for putative confounders were performed to examine associations between PBDE congeners and adiposity parameters. ResultsBDE-209 was the most abundant congener of PBDEs with a median value of 19.5 ng/g lipid. The geometric mean values of nine PBDE congeners ranged from below limit of detection (LOD) to 18.1 ng/g lipid, and the detection rates were 46.5%~96.5%. Cord serum BDE-153 and BDE-154 concentrations were associated with lower childhood BMI z score (regression coefficient, β=-0.15, 95% confidence interval: -0.29, −0.02; p=0.02; β=-0.23, 95%CI: -0.43, −0.03; p=0.03, respectively) and lower waist circumference (β=-0.75 cm, 95%CI: -1.43, −0.06; p=0.03; β=-1.22 cm, 95%CI: -2.23, −0.21; p=0.02, respectively), after controlling for potential confounders. Moreover, prenatal BDE-154 exposure was related to a decreased obesity risk of children aged 7 years (odds ratio, OR=0.46, 95%CI: 0.22, 0.94; p=0.03). These effects were only observed among boys in sex-straitified analyses. ConclusionsCord serum BDE-153 and BDE-154 concentrations were related to reduced adiposity measures at 7 years of age. Further evidence regarding the impacts of prenatal PBDE exposures on childhood development is warranted.

Derivatization gas chromatography negative chemical ionization mass spectrometry for the analysis of trace organic pollutants and their metabolites in human biological samples.

Gas chromatography negative chemical ionization mass spectrometry (GC-NCI-MS) is a preferred instrumental approach for the trace and ultra-trace analysis of various toxic organics and their metabolites in human biological fluids. Specifically, the method has played an important role in the highly sensitive and specific quantitative detection of persistent highly halogenated compounds in environmental matrices and biota during the past few decades. However, for the analysis of toxic metabolites with active hydrogen atoms, such as acids, alcohols, and phenolic compounds, from biological matrixes or organics without electronegative atoms or groups, a derivatization step is often needed prior to GC analysis. Such derivatization aims to change the properties of targets to improve their separation, increase their volatility, and enhance the sensitivity of instrumental detection. This review summarizes three derivatization strategies commonly used for GC methods, i.e., alkylation, silylation, and acylation, together with their application combined with GC-NCI-MS for the high sensitivity analysis of toxic organic metabolites in the human body. The advantages and disadvantages of each derivatization method and potential directions for future applications are discussed. Given the broad variety of applications as well as the compound-specific sensitivity for the ultra-trace analysis of target xenobiotics in human biological fluids, subsequent studies are required to develop convenient, faster derivatization procedures and reagents better suited for routine analysis. Graphical abstract.

Determination of five acylpyrazole pesticide residues in edible vegetable oils using gas chromatography-negative chemical ionization-mass spectrometry

A method was established for the determination of five acylpyrazole pesticide residues in edible vegetable oils using gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS). The pesticides were extracted from a sample with acetonitrile under freezing conditions. A simple cleanup step known as QuEChERS was then conducted. After being identified by GC-NCI-MS, the extracts were quantified using an external standard method that employs a matrix correction standard curve. The linearity of the method was good between 20 and 1000 μg/L, and all limits of quantification were less than 2 μg/kg. Recoveries of all pesticides were in the range of 82.7%-112.4% at the three spiked levels of 0.01, 0.02, and 0.05 mg/kg, and all relative standard deviations were not more than 12.3%. Therefore, this method can be used to determine the residues of acylpyrazole pesticides in edible vegetable oils.

Sugar phosphate analysis with baseline separation and soft ionization by gas chromatography-negative chemical ionization-mass spectrometry improves flux estimation of bidirectional reactions in cancer cells

Precise measurement of sugar phosphates in glycolysis and the pentose phosphate (PP) pathway for 13C-metabolic flux analysis (13C-MFA) is needed to understand cancer-specific metabolism. Although various analytical methods have been proposed, analysis of sugar phosphates is challenging because of the structural similarity of various isomers and low intracellular abundance. In this study, gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS) is applied to sugar phosphate analysis with o-(2,3,4,5,6-pentafluorobenzyl) oxime (PFBO) and trimethylsilyl (TMS) derivatization. Optimization of the GC temperature gradient achieved baseline separation of sugar phosphates in 31 min. Mass spectra showed the predominant generation of fragment ions containing all carbon atoms in the sugar phosphate backbone. The limit of detection of pentose 5-phosphates and hexose 6-phosphates was 10 nM. The method was applied to 13C-labeling measurement of sugar phosphates for 13C-MFA of the MCF-7 human breast cancer cell line. 13C-labeling of sugar phosphates for 13C-MFA improved the estimation of the net flux and reversible flux of bidirectional reactions in glycolysis and the PP pathway.

Determination of short-chain chloroparaffins in synthetic surfacing layers used in sports and diluents by solid-phase extraction coupled with gas chromatography-negative chemical ionization-mass spectrometry

A new method was established to determine short-chain chloroparaffins (SCCPs) in synthetic surfacing layers used in sports and diluents by solid-phase extraction (SPE) coupled with gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS). The analysis conditions for gas chromatography and mass spectrometry were optimized. Then, the samples were extracted by ultrasonication, purified on a Florisil SPE column, monitored in the selective ion monitoring (SIM) scanning mode, and quantified by the external standard method. With this method, a good linear relationship was found over a wide mass concentration range from 0.0501 to 100.17 mg/L, with a linear correlation coefficient (R2) of 0.9995. The detection limit for SCCPs by this method was found to be as low as 0.50 μg/g (i. e. 0.000050%) and the average recoveries for SCCPs spiked in the blank samples varied from 83.2% to 96.3% with relative standard deviations (RSDs) of 1.56%-6.02%. Ten batches of samples were tested and the contents of SCCPs detected in each batch were in the range from 0.016% to 0.55%, which agrees well the European Union limitation requirement for SCCPs. Thus, this method is suitable for qualitative and quantitative analyses of SCCPs in synthetic surfacing layers used in sports and diluents.

Simultaneous determination of cis-permethrin and trans-permethrin in rat plasma and brain tissue using gas chromatography-negative chemical ionization mass spectrometry.

A sensitive method for the simultaneous determination of cis-permethrin (cis-PERM) and trans-permethrin (trans-PERM) in small volumes (100μL) of rat plasma and brain homogenate was developed, using a liquid-liquid extraction for sample preparation and gas chromatography-negative chemical ionization mass spectrometry (GCNCI-MS) for detection. Quantitation of trace levels of the insecticide in small volumes of biological samples is essential to support toxicokinetic studies in small animals. There are currently no validated methods in the literature for determining cis-PERM and trans- PERM in volumes as low as 100μL of rat plasma or brain homogenate. The method provided a linear range of 0.2-150.0ng/mL for analytes in both matrices. The intra- and inter-batch precision (as% relative standard deviation, RSD) and accuracy (as relative error, RE) of the method were better than 20% at the limit of quantitation and better than 15% across the remaining linear range. The validated method was applied in a toxicokinetic study in adult rats with oral dosing of 10mg/kg (cis-PERM) and 100mg/kg (trans-PERM) in corn oil. cis-PERM and trans- PERM were monitored in rat plasma and brain tissue samples for 6h following dosing, and both analytes were detected in all plasma and brain samples.

Determination of fipronil and its metabolites in eggs and egg products with gas chromatography-negative chemical ionization-mass spectrometry

A method was established for the determination of fipronil and its metabolites in eggs and egg products with gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS). The targets were extracted from samples with acetonitrile, and followed by a simple cleanup step known as dispersive solid-phase extraction QuEChERS. The extracts were determined by GC-NCI-MS, and quantified by external standard method with matrix correction standard curves. The recoveries were in the range of 87.0% to 99.3% at four spiked levels (0.1, 2.0, 4.0 and 20.0 μg/kg), and all RSDs were not more than 12.7% for the four analytes. The linearity of the method was good between 0.005 and 0.10 mg/L, and all LOQs were less than 0.10 μg/kg. So this method can be used to determine the residues of fipronil and its metabolites in eggs and egg products.

Quantitation of total fatty acids in plasma and serum by GC-NCI-MS

Polyunsaturated fatty acids (PUFAs), including essential omega-3 and omega-6 fatty acids, play important roles in diverse physiological and pathological processes. Diligent monitoring of PUFAs is recommended for individuals with increased risk of developing essential fatty acid deficiency (EFAD), including premature and very low birth weight infants, patients on prolonged parenteral nutrition, and those with dietary restrictions, for example due to inborn errors of metabolism. Here, we present a gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI‐MS) method for the quantitation of total levels of twenty-two fatty acids (C12‐C22) in serum/plasma, including omega-3 and omage-6 PUFAs. Hydrolysis was used to release esterified fatty acids, which were analyzed by GC-NCI-MS as pentafluorobenzyl esters in selected-ion monitoring (SIM) mode. The calibration curves for all analytes had consistent slopes with R2 of ⩾0.990. Intra- and inter-assay precision CVs were ⩽9.0% and ⩽13.2%, respectively. Samples were found to be stable for 24h at room temperature, at least 7days at 4°C, at least 75days at −20°C, and for three freeze/thaw cycles. No matrix effects or interferences were observed. This method offers improvements over published studies including smaller sample volume, inclusion of additional internal standards, analysis in a single injection, and use of methane reagent gas. This method could be used in a clinical laboratory setting for the diagnosis of EFAD, evaluation of nutritional status, and diet monitoring.

Novel brominated flame retardants in food composites and human milk from the Chinese Total Diet Study in 2011: Concentrations and a dietary exposure assessment

On the basis of the fifth Chinese total diet study (TDS) performed in 2011, the dietary exposure of the Chinese population to novel brominated flame retardants (NBFRs) was assessed. Six NBFRs were determined in 80 composite samples from four animal origin food groups and 29 pooled human milk samples. Based on gas chromatography-negative chemical ionization mass spectrometry (GC-NCI/MS) analysis, the levels of the total NBFRs ranged from <LOD to 70.2ng/g lipid weight (lw) in food composites and from 2.48 to 23.9ng/g lw in human milk samples. Decabromodiphenyl ethane (DBDPE), with mean levels of 9.03ng/g lw in food composites and 8.06ng/g lw in human milk, was the most abundant compound in the total NBFRs. No obvious spatial distribution patterns in China were observed in food samples or human milk. The average estimated daily intake (EDI) of total NBFRs via food consumption for a “standard Chinese man” was 4.77ng/kg bodyweight (bw)/day, with a range of 0.681 to 18.9ng/kgbw/day. Meat and meat products were the main dietary source of NBFRs, although levels of NBFRs in aquatic food were found to be the highest among the four food groups. The average EDI of total NBFRs for nursing infants was 38.4ng/kgbw/day, with a range of 17.4 to 113ng/kgbw/day, which was approximately eight-fold higher than the EDI for adults, suggesting the heavy body burden of NBFRs on nursing infants. The levels and EDI of DBDPE in the present study were similar to or higher than those of legacy BFRs (i.e., PBDEs and HBCD) in the TDS 2007, indicating that DBDPE, as a main alternative to PBDEs, might have become the primary BFR used in China.

Determination of novel brominated flame retardants and polybrominated diphenyl ethers in serum using gas chromatography-mass spectrometry with two simplified sample preparation procedures.

Two simple and efficient pretreatment procedures have been developed for the simultaneous extraction and cleanup of six novel brominated flame retardants (NBFRs) and eight common polybrominated diphenyl ethers (PBDEs) in human serum. The first sample pretreatment procedure was a quick, easy, cheap, effective, rugged, and safe (QuEChERS)-based approach. An acetone/hexane mixture was employed to isolate the lipid and analytes from the serum with a combination of MgSO4 and NaCl, followed by a dispersive solid-phase extraction (d-SPE) step using C18 particles as a sorbent. The second sample pretreatment procedure was based on solid-phase extraction. The sample extraction and cleanup were conducted directly on an Oasis HLB SPE column using 5% aqueous isopropanol, concentrated sulfuric acid, and 10% aqueous methanol, followed by elution with dichloromethane. The NBFRs and PBDEs were then detected using gas chromatography-negative chemical ionization mass spectrometry (GC-NCIMS). The methods were assessed for repeatability, accuracy, selectivity, limits of detection (LODs), and linearity. The results of spike recovery experiments in fetal bovine serum showed that average recoveries ranged from 77.9% to 128.8% with relative standard deviations (RSDs) from 0.73% to 12.37% for most of the analytes. The LODs for the analytes in fetal bovine serum ranged from 0.3 to 50.8pg/mL except for decabromodiphenyl ethane. The proposed method was successfully applied to the determination of the 14 brominated flame retardants in human serum. The two pretreatment procedures described here are simple, accurate, and precise, and are suitable for the routine analysis of human serum. Graphical Abstract Workflow of a QuEChERS-based approach (top) and an SPE-based approach (bottom) for the detection of PBDEs and NBFRs in serum.

Porous lead(II)-based metal organic nanotubes as an adsorbent for dispersive solid-phase extraction of polybrominated diphenyl ethers from environmental water samples

Porous lead(II)-based metal-organic nanotubes (Pb-MONTs) were, for the first time, used as an adsorbent for dispersive solid-phase extraction (d-SPE) of polybrominated diphenyl ethers (PBDEs) at trace levels from environmental water samples. Gas chromatography–negative chemical ionization-mass spectrometry (GC–NCI-MS) was applied for sample detection. Box–Behnken design was performed to investigate and optimize the d-SPE parameters through a response surface methodology. The optimized conditions were obtained as listed: extraction time of 1min, 51.4mg of adsorbent and NaCl concentration of 7.42%. Under the optimized conditions, the new d-SPE-GC–NCI-MS method achieved wide range of linearity (2–1000ngL−1), low limits of detection (0.08–0.22ngL−1), satisfactory repeatability (0.79–8.62%, n=6) and satisfactory reproducibility (3.18–11.0%, n=5), and the possible extraction mechanism was also discussed. The proposed method was used in the analysis of real environmental water samples, and satisfactory recoveries were obtained in the range of 80.5–119.2%. These results indicated that Pb-MONTs have great potential as an adsorbent for the d-SPE of PBDEs at trace levels from environmental water samples.

S1 certification of alpha-endosulfan, beta-endosulfan, and endosulfan sulfate in a candidate certified reference material (organochlorine pesticides in tea) by isotope dilution gas chromatography-mass spectrometry.

This paper presents the certification of alpha-endosulfan, beta-endosulfan, and endosulfan sulfate in a candidate tea certified reference material (code: GLHK-11-03) according to the requirements of the ISO Guide 30 series. Certification of GLHK-11-03 was based on an analytical method purposely developed for the accurate measurement of the mass fraction of the target analytes in the material. An isotope dilution mass spectrometry (IDMS) method involving determination by (i) gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS) and (ii) gas chromatography-electron ionization-high-resolution mass spectrometry (GC-EI-HRMS) techniques was employed. The performance of the described method was demonstrated through participation in the key comparison CCQM-K95 "Mid-Polarity Analytes in Food Matrix: Mid-Polarity Pesticides in Tea" organized by the Consultative Committee for Amount of Substance-Metrology in Chemistry in 2012, where the study material was the same as the certified reference material (CRM). The values reported by using the developed method were in good agreement with the key comparison reference value (KCRV) assigned for beta-endosulfan (727 ± 14μgkg(-1)) and endosulfan sulfate (505 ± 11μgkg(-1)), where the degree of equivalence (DoE) values were 0.41 and 0.40, respectively. The certified values of alpha-endosulfan, beta-endosulfan, and endosulfan sulfate in dry mass fraction in GLHK-11-03 were 350, 730, and 502μgkg(-1), respectively, and the respective expanded uncertainties, due to sample inhomogeneity, long-term and short-term stability, and variability in the characterization procedure, were 27μgkg(-1) (7.8%), 48μgkg(-1) (6.6%), and 33μgkg(-1) (6.6%).