Gas Chromatography-tandem Mass Spectrometry Research Articles

Investigation of the Relationship between Spontaneous Abortion, Serum Pesticides, and Polychlorinated Biphenyl Levels.

Occupational and environmental chemical exposure have been associated with adverse reproductive consequences. This study investigates the relationship between spontaneous abortion and blood pesticide and polychlorinated biphenyl (PCB) levels. A survey was conducted, and blood samples were collected from 200 patients, consisting of 100 cases with spontaneous abortion and 100 cases with normal deliveries. A total of 150 different pesticides, including organophosphates, organochlorines, carbamates, and pyrethroids, were screened in the collected blood samples and analyzed quantitatively using Tandem mass spectrometry-specifically in combination with liquid chromatography and gas chromatography-tandem mass spectrometry methods. Eight types of PCBs were analyzed with the gas chromatography-tandem mass spectrometry method. The groups were compared based on these analyses. The mean age of the participants was 28.09 ± 4.94 years. In 59% of the spontaneous abortion group, 5.05 ± 1.97 chemicals were detected in different amounts. (p < 0.05). Analysis of the samples identified the presence of β-Hexachlorocyclohexane (β-HCH), delta-hexachlorocyclohexane (δ HCH), Hexachlorobenzene (HCB), Pentachlorobiphenyl-28 (PCB-28), Pentachlorobiphenyl-52 (PCB-52), o,p'-Dichlorodiphenyldichloroethylene (o,p'-DDE), p,p'-Dichlorodiphenyldichloroethylene (p,p'DDE), o,p'-Dichlorodiphenyldichloroethane (o,p'-DDD), p,p'-Dichlorodiphenyldichloroethane (p,p'-DDD), Pentachlorobiphenyl-118 (PCB-118), Pentachlorobiphenyl-101 (PCB-101), Pentachlorobiphenyl-153 (PCB-153), Pentachlorobiphenyl-138 (PCB-138), Pentachlorobiphenyl-202 (PCB-202), Pentachlorobiphenyl-180 (PCB-180) as well as Fibronil, Buprimate, Acetoclor, Acemiprid, Pentimanthalin, and Triflokystrobin. The spontaneous abortion group had significantly higher exposure to PCB-101, PCB-52, PCB-138, and δ-HCH (p < 0.05). Women included in the study had high pesticide and PCB exposure rates. Many of the blood samples contained multiple pesticides with endocrine-disrupting effects. Higher exposure to organochlorine compounds in the serum was identified in the group with spontaneous abortions.

Geographical Indication Characteristics of Aroma and Phenolic Acids of the Changping Strawberry

Strawberry is the most consumed berry fruit worldwide due to its unique aroma and high nutritive value. This fruit is also an important source of phenolic compounds. Changping strawberries are recognized as a national agricultural product of geographical indication (GI) due to their unique flavor. Widely accepted standards for identifying GI strawberries from non-GI strawberries are currently unavailable. This study compared the aroma and phenolic acid composition of GI and non-GI strawberries. Furthermore, the characteristic aroma and phenolic acid markers of GI strawberries were determined. A classification model based on the markers was established using Fisher discriminant analysis (FDA). In this study, six groups of strawberries with variety name of “Hongyan”, including GI strawberries from Changping and non-GI strawberries from Changping, Miyun, Pinggu, Shunyi, and Tongzhou, were collected. A total of 147 volatile substances were discovered using gas chromatography–tandem mass spectrometry. The contents of a few compounds principally responsible for the distinctive aroma in GI strawberries were in the top three of the six groups, providing GI strawberries with a generally pleasant fragrance. OPLS–DA identified isoamyl butyrate and trans-2-octen-1-ol as characteristic markers. Enrichment analysis indicated that beta-oxidation of very long-chain fatty acids, mitochondrial beta-oxidation of very long-chain fatty acids, fatty acid biosynthesis, and butyrate metabolism played critical roles in volatile compound biosynthesis. The total phenolic content was 24.41–36.46 mg/kg of fresh weight. OPLS–DA results revealed that cinnamic acid could be used as a characteristic phenolic acid marker of GI strawberries. Based on the three characteristic markers, FDA was performed on the different groups, which were then divided. The separation of strawberry samples from different origins using the three characteristic markers was found to be feasible. These findings help effectively understand the aroma and phenolic acid composition of strawberries and contribute to the development of strawberries with a pleasant fragrance and health benefits.

Evaluation of pesticide residues in selected vegetables from Kuala Lumpur, Malaysia using modified QuEChERS and assessment of washing methods

Growing population in Malaysia has resulted in increased production of local vegetables as well as pesticide usage. This constitutes a health risk to human health. In the present work, the level of ten pesticide residues namely chlorpyrifos, profenofos, aldrin, endrin, cypermethrin, lambda-cyhalothrin, carbendazim, propamocarb, imidacloprid, and thiamethoxam in ten types of vegetables collected from six local markets were measured using modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) coupled with gas chromatography-tandem mass spectrometry (GC-MS/MS) and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Results showed that 13.3% samples contained pesticide residues above the maximum residue limit (MRL) prescribed by the Malaysian Food Regulations 1985, 55.0% of samples contained pesticide residues below the MRL, and no pesticide residues were detected in 31.7% of samples. Carbendazim and chlorpyrifos were among the highest pesticides detected in the samples. For the type of vegetables, kale and spinach contained high concentrations of pesticide residues above the MRL. In order to produce safe vegetables, the efficiency of different washing methods (tap water, 10% sodium bicarbonate solution, and 10% acetic acid solution) in reducing carbendazim and chlorpyrifos residues in a kale model system was evaluated. Results showed that the levels of carbendazim and chlorpyrifos reduction for all three methods were significantly different (p &lt; 0.05) with 10% acetic acid solution being the most effective followed by 10% sodium bicarbonate solution, and tap water. Washing kale with 10% acetic acid reduced 76.0 and 41.2% of carbendazim and chlorpyrifos, respectively. Therefore, it is recommended for consumers to practice 10% sodium bicarbonate washing method by soaking vegetables with an acidic solution followed by rinsing with tap water to reduce pesticide residues, and minimise the exposure to hazardous pesticides.

Source characteristics of polycyclic aromatic hydrocarbons and polychlorinated biphenyls in surface soils of Shenyang, China: A comparison of two receptor models combined with Monte Carlo simulation

The surface soil concentrations of 16 PAHs and 15 PCBs were simultaneously determined by gas chromatography-tandem mass spectrometry in 21 locations of urban areas of Shenyang. The average concentrations of PAHs and PCBs were 26.40 ± 34.68 mg/kg and 48.03 ± 27.47 μg/kg, respectively. Factor analysis with nonnegative constraints (FA-NNC) and absolute principal component score with multiple linear regression (APCS-MLR) model were used to explore and evaluate the sources of PAHs and PCBs in the study area. The results of FA-NNC showed that PAHs in soils were mainly from traffic emissions (49.64%), coal combustion (46.88%) and petrogenic source (3.49%). The PCBs in soils were mainly from commercial and high temperature combustion mixed sources (20.3%), combustion and industry emission mixed sources (21.1%), electrical equipment sources (22.2%) and traffic emission sources (36.4%). The results of APCS-MLR were consistent with those of FA-NNC. The uncertainty of FA-NNC and APCS-MLR model was analyzed by Monte Carlo simulation method. The results revealed the reliability of the two receptor models on source apportionment. The estimated carcinogenic risks indicated that the risks of PAHs in soils exceed the acceptable range (10−6-10−4), while the risks of PCBs were below the acceptable risk level of 10−6.

Global Analysis of 2-Hydroxy Fatty Acids by Gas Chromatography-Tandem Mass Spectrometry Reveals Species-Specific Enrichment in Echinoderms.

Abnormal levels of 2-hydroxy fatty acids (2-OH FAs) are characterized in multiple diseases, and their quantification in foodstuffs is critical to identify the sources of supplementation for potential treatment. However, due to the structural complexity and limited available standards, the comprehensive profiling of 2-OH FAs remains an ongoing challenge. Herein, an innovative approach based on gas chromatography-tandem mass spectrometry (GC-MS/MS) was developed to determine the full profile of these FA metabolites. MS and MS/MS spectra of the trimethylsilyl (TMS) derivatives of 2-OH fatty acid methyl esters (FAMEs) were collected for peak annotation by their signature fragmentation patterns. The structures were further confirmed by validated structure-dependent retention time (RT) prediction models, taking advantage of the correlation between the RT, carbon chain length, and double bond number from commercial standards and pseudostandards identified in the whole-brain samples from mice. An in-house database containing 50 saturated and monounsaturated 2-OH FAs was established, which is expandible when additional molecular species with different chain lengths and backbone structures are identified in the future. A quantitation method was then developed by scheduled multiple reaction monitoring (MRM) and applied to investigate the profiling of 2-OH FAs in echinoderms. Our results revealed that the levels of total 2-OH FAs in sea cucumber Apostichopus japonicas (8.40 ± 0.28 mg/g dry weight) and starfish Asterias amurensis (7.51 ± 0.18 mg/g dry weight) are much higher than that in sea urchin Mesocentrotus nudus (531 ± 108 μg/g dry weight). Moreover, 2-OH C24:1 is the predominant molecular species accounting for 67.9% of the total 2-OH FA in sea cucumber, while 2-OH C16:0 is the major molecular species in starfish. In conclusion, the current innovative GC-MS approach has successfully characterized distinct molecular species of 2-OH FAs that are highly present in sea cucumbers and starfish. Thus, these findings suggest the possibility of developing future feeding strategies for preventing and treating diseases associated with 2-OH FA deficiency.

Multi-residue pesticides determination in complex food matrices by gas chromatography tandem mass spectrometry

An analytical method for determination of GC-amenable pesticides in complex matrices, was validated based on QuEChERS sample preparation and gas chromatography tandem mass spectrometry. Performance of the method was tested according to the EU SANTE guidelines for 172 pesticides belonging to different chemical classes, in three representative complex matrices. Three concentration levels were tested in order to establish the lowest limit of quantification possible. For some matrix/pesticide combination, careful selection of the quantification/confirmation transitions was key to avoid interferences. Accurate quantification was achieved by standard addition. The number of compounds fulfilling EU SANTE criteria at 10 µg/kg and 100 µg/kg were 93 and 148 for roasted coffee, 93 and 112 for green tea and 98 and 111 for curry respectively. The method was further evaluated in different matrices (chili, clove, cumin, paprika and rosemary) with 50–90 % of the compounds fulfilling the validation criteria depending on the matrix.

Simultaneous Determination of Sodium Pentachlorophenolate and Its Metabolites in Swine Samples

Pentachlorophenol (PCP) is a persistent organic pollutant usually present in the form of sodium salts (PCP-Na) that has been banned for many years, but it can still be detected in animal food. The present study established a method of detecting PCP-Na and its metabolites—tetrachlorocatechol (TCC), pentachlorophenol acetate (PCP-acetate), and pentachloroanisole (PCA)—in swine samples (pork, fat, liver, heart, lungs and kidney), simultaneously using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and gas chromatography-tandem mass spectrometry (GC-MS/MS) based on the modified QuEChERS pre-treatment method. The validation results exhibited a good sensitivity with limits of quantitation (LOQs) of 1 μg/kg–2 μg/kg. The recoveries of spiked samples were in the range of 60.5–119.9%, with a relative standard deviation (RSD) between replicates (n = 5) of between 0.70% and 12.06%.

Simple quantification of propofol and its metabolites in blood and urine using gas chromatography–tandem mass spectrometry (GC–MS/MS)

An analytical method which was used for the simultaneous detection and quantification of propofol and its metabolites in human blood and urine by gas chromatography-tandem mass spectrometry (GC–MS/MS) was newly established and applied to authentic human samples obtained from the deceased. The QuEChERS method was employed, and then analyzed by GC–MS/MS. We separately used sulfatase and β-glucuronidase to hydrolyze the urine sample and calculated the increase of propofol and 4-hydroxypropofol before and after the hydrolysis. The results of urinary concentrations in urine from the subject were: 4.88 μg/mL for propofol, 0.53 μg/mL for 4-hydroxypropofol, 3.35 μg/mL for propofol-glucuronide, 0.31 μg/mL for the total concentration of 1-(2,6-diisopropyl-1,4-quinol)-glucuronide plus 4-(2,6-diisopropyl-1,4-quinol)-glucuronide, and 0.39 μg/mL for 4-(2,6- diisopropyl-1,4-quinol)-sulfate. The lower limit of quantification was 10 ng/mL for all determined compounds; the extraction recoveries were not less than 57.2 %. Intraday and interday precisions and accuracies were all less than 10 %. The calibration curves for propofol and 4-hydroxypropofol in human urine showed the correlation values of not less than 0.999; propofol and 4-hydroxypropofol in blood also presented good linearities in the concentration ranges of 0.1–10 μg/mL. The two compounds had good stability within 7 days at 25, 4, and −20 ℃. To our knowledge, this is the first trial to establish a simple and reliable method to simultaneously detect and quantify of propofol and its phase I and II metabolites in human blood and urine samples by GC–MS/MS.

Allergens and Other Harmful Substances in Hydroalcoholic Gels: Compliance with Current Regulation.

Hydroalcoholic gels or hand sanitisers have become essential products to prevent and mitigate the transmission of COVID-19. Depending on their use, they can be classified as cosmetics (cleaning the skin) or biocides (with antimicrobial effects). The aim of this work was to determine sixty personal care products frequently found in cosmetic formulations, including fragrance allergens, synthetic musks, preservatives and plasticisers, in hydroalcoholic gels and evaluate their compliance with the current regulation. A simple and fast analytical methodology based on solid-phase microextraction followed by gas chromatography-tandem mass spectrometry (SPME-GC-MS/MS) was validated and applied to 67 real samples. Among the 60 target compounds, 47 of them were found in the analysed hand sanitisers, highlighting the high number of fragrance allergens (up to 23) at concentrations of up to 32,458 μg g-1. Most of the samples did not comply with the labelling requirements of the EU Regulation No 1223/2009, and some of them even contained compounds banned in cosmetic products such as plasticisers. Method sustainability was also evaluated using the metric tool AGREEPrep, demonstrating its greenness.

Analysis of organochlorine pesticides in contaminated soil by GC-MS/MS using accelerated solvent extraction as a green sample preparation

ABSTRACT Organochlorine pesticides (OCPs), persistent organic pollutants, in the contaminated soil have been analysed by a gas chromatography-tandem mass spectrometry (MS) in this work. OCPs were extracted with a mixture of dichloromethane and n-hexane by using accelerated solvent extraction at elevated temperature and high pressure. The extractant was concentrated by a rotary vacuum evaporator and cleaned up by silica gel solid phase extraction. OCPs were then separated by a gas chromatography in combination with an electron impact ionisation MS in MS/MS mode. The limit of detection, limit of quantification and other important parameters of the GC-EI-MS/MS analytical method, such as repeatability, recovery and so on, have been investigated and presented. Limit of detection and limit of quantification have been achieved from 0.005 ng g−1 (p,p’-DDE) to 0.405 ng g−1 (dieldrin) and 0.016 ng g−1 to 1.216 ng g−1, respectively. The repeatability of this method was achieved below 8.3% and 13.7% for short- and long-term stability. Recovery of all OCPs ranged from 78.1% ± 1.5% to 117.5% ± 3.2%. The developed analytical method was validated by spiking experiments in the real samples. The validated method has been then used for the analysis of OCPs in the soil samples that were collected from the contaminated areas in Vietnam. Results showed the presence of hexachlorocyclohexane isomers and p-p’-DDT in all analysed samples at elevated levels.

Accumulation of organophosphorus pollutants in adipose tissue of obese women - metabolic alterations

Organophosphorus pesticides (OPPs) and organophosphate esters (OPEs) are organophosphorus compounds created as substitutes for persistent environmental pollutants, namely organochlorines pesticides and brominated flame retardants, respectively. However, there is evidence that organophosphorus compounds are also widespread across the environment and have adverse effects on biota. In humans, OPPs and OPEs were reported to be carcinogenic, neurotoxic, hepatotoxic, nephrotoxic, amongst others. As lipophilic compounds, these accumulate in fat tissues as adipose tissue. Yet biomonitoring studies and analytical methodologies to assess these compounds in the human body are scarce, particularly in adipose tissue. In this study, the presence of six OPPs and seven OPEs was determined in samples of subcutaneous adipose tissue (scAT) and visceral adipose tissue (vAT) from 188 adult obese women. OPPs and OPEs were quantified by gas chromatography (GC) flame photometric detection and confirmed in GC tandem mass spectrometry. The detection frequencies ranged between 0.5-1.6% and 48–53%, respectively for OPPs and OPEs. Organophosphorus pollutants were present in both adipose tissues and median concentrations were 0.008 ± 0.020 μg/g scAT and 0.009 ± 0.020 μg/g vAT. A total of 32 Spearman's correlations were found between organophosphorus pollutants concentrations in adipose tissue and several biochemical parameters (18 positive and 14 negative). Our results show that anthropometric and hormonal parameters, cholesterol, glycaemia, macrominerals, urea and sedimentation velocity might be influenced by the presence of these compounds. The presence of organophosphorus pollutants in the environmental and their possible effect on female metabolic processes is concerning. Particularly because presently OPEs usage is not controlled or limited by any regulation. More studies are needed to fully understand these pollutants behaviour and hazard effects on human health, biota, and the environment so control regulations can be drawn to prevent and lessen their effects.

Dynamics of Organic Acids during the Droplet-Vitrification Cryopreservation Procedure Can Be a Signature of Oxidative Stress in Pogostemon yatabeanus.

Cryopreservation in liquid nitrogen (LN, -196 °C) is a unique option for the long-term conservation of threatened plant species with non-orthodox or limitedly available seeds. In previous studies, a systematic approach was used to develop a droplet-vitrification (DV) cryopreservation protocol for Postemon yatabeanus shoot tips that includes preculture with 10% sucrose, osmoprotection with C4-35%, cryoprotection with A3-80% vitrification solution, and a three-step regrowth starting with the ammonium-free medium. The tricarboxylic acid (TCA) cycle is a crucial component of plant cell metabolism as it is involved in redox state regulation and energy provision. We hypothesized that organic acids (OAs) associated with the TCA and its side reactions indirectly indicate metabolism intensity and oxidative stress development in shoot tips under the cryopreservation procedure. In this study, the contents of 14 OAs were analyzed using gas chromatography-tandem mass spectrometry (GC-MS/MS) in P. yatabeanus shoot tips in a series of treatments including individual steps of the DV procedure, additional stress imposed by non-optimum protocol conditions (no preculture, no osmoprotection, various vitrification solution composition, using vials instead of aluminum foils, etc.) and regrowth on different media with or without ammonium or growth regulators. The possible relation of OA content with the total cryoprotectant (CPA) concentration and shoot tips regeneration percentage was also explored. Regeneration of cryopreserved shoot tips reduced in descending order as follows: standard protocol condition (91%) > non-optimum vitrification solution (ca. 68%) > non-optimum preculture (60-62%) > regrowth medium (40-64%) > no osmoprotection, cryopreservation in vials (28-30%). Five OAs (glycolic, malic, citric, malonic, and lactic) were the most abundant in the fresh (control) shoot tips. The dynamic pattern of OAs during the DV procedure highly correlated (r = 0.951) with the total CPA concentration employed: it gradually increased through the preculture, osmoprotection, and cryoprotection, peaked at cooling/rewarming (6.38-fold above control level), and returned to the fresh control level after 5 days of regrowth (0.89-fold). The contents of four OAs (2-hydroxybutyric, 3-hydroxypropionic, lactic, and glycolic) showed the most significant (10-209-fold) increase at the cooling/rewarming step. Lactic and glycolic acids were the major OAs at cooling/rewarming, accounting for 81% of the total OAs content. The OAs were categorized into three groups based on their dynamics during the cryopreservation protocol, and these groups were differently affected by protocol step modifications. However, there was no straightforward relationship between the dynamics of OAs and shoot tip regeneration. The results suggest that active modulation of OAs metabolism may help shoot tips to cope with osmotic stress and the chemical cytotoxicity\ of CPAs. Further intensive studies are needed to investigate the effect of cryopreservation on cell primarily metabolism and identify oxidative stress-related biomarkers in plant materials.

Determination of fipronil and its three degradates in water using stir bar sorptive extraction–thermal desorption–gas chromatography–tandem mass spectrometry

A method was developed for determination of fipronil (FIP) pesticide and its three major degradates (fipronil desulfinyl, fipronil sulfide, fipronil sulfone) in water at the levels required by the EU Commission in the Decision 2022/1307. The method combines solvent-free stir bar sorptive extraction (SBSE) with thermal desorption–gas chromatography–tandem mass spectrometry (TD–GC–MS/MS). Simple sample processing involves 16 h of stirring a 100 mL water sample with a polydimethylsiloxane-coated sorptive stir bar, followed by TD of the trapped analytes into the GC. The greenness assessment by analytical Eco-Scale approach resulted in classification of the entire analytical method as "an excellent green analysis". The obtained limits of quantification for all FIPs determined in tap, lake, MilliQ water and artificial seawater were in the range of 0.12–0.30 ng L–1. The recoveries ranged between 81.7 and 109% with relative standard deviations from 2.8 to 14%. The results show that the method is suitable for screening and monitoring the studied analytes in selected matrices.

Characterization of CBD oils, seized on the Belgian market, using infrared spectroscopy: Matrix identification and CBD determination, a proof of concept.

The availability of cannabidiol (CBD) oil products has increased in recent years. No analytical controls are mandatory for these products leading to uncertainties about composition and quality. In this paper, a methodology was developed to identify the oil matrix and to estimate the CBD content in such samples, using mid-infrared and near-infrared spectroscopy. Different oils were selected based on the information labeled on products and were bought in food stores in order to create a sample set with a variety of matrices. These oils were spiked with CBD to obtain samples with CBD levels from 0% to 20%. The first part of the study was focused on the qualitative analysis of the oil matrix. A classification model, based on Soft Independent Modeling of Class Analogy, was build using the spiked oils to distinguish between the different oil matrices. For both spectroscopic techniques, the sensitivity, the specificity, the accuracy and the precision were equal to 100%. These models were applied to determine the oil matrix of seized samples. The second part of the study was focused on the quantitative estimation of CBD. After determination of CBD in seized samples using gas chromatography-tandem mass spectrometry, partial least square regression (PLS-R) models were built, one for each matrix in the sample set. Both techniques were able to classify unknown oily samples according to their matrix, and although only few samples were available to evaluate the PLS-R models, the approach clearly showed promising results for the estimation of the CBD content in oil samples.

Method validation, household cooking effect on pesticide residues, and evaluation of processing factors in rice

An experiment shows the reduction of pesticide residues using common household cooking techniques. The estimation of seven pesticides was performed using the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method with liquid chromatography tandem mass spectrometry (LC-MS/MS) and Gas Chromatography Tandem Mass Spectrometry (GC-MS/MS) in rice. The method validation study was carried out with linearity (R2 > 0.99), average recoveries of all pesticides ranged from 82.00 to 102.36%, with a precision of 3.78–6.84% and 1.25–7.24% inter and intraday, respectively. The limit of quantification was 0.01 mg/kg for all tested pesticides. The processing factors (PF) were calculated for seven pesticides from various processing of rice grains collected from the plot applied with pre-mixed pesticides. To decrease pesticide residues in rice grains, processing techniques, including pressure cooking rice, traditional cooking without drained water, and traditional cooking with excess water, were investigated. The overall percent reductions of fipronil, imidacloprid, pymetrozine, flonicamid, bifenthrin, clothianidin, and cartap hydrochloride were 71.96–90.01, 69.07–86.60, 79.78–91.05, 69.37–84.08, 68.95–88.77, 71.73–85.44, and 61.23–89.67 percent, respectively. The calculated PFs for all pesticides were less than 1, indicating that the residue magnitudes of all pesticides decreased after each process and all the processing techniques were effective. The data showed that the traditional technique of cooking rice with excess water was the most efficient technique to reduce pesticides, proving effective in minimizing pesticide residues and reducing human exposure to pesticides through diet.

B-201 Development of a Quantitative Gas Chromatography Tandem Mass Spectrometry Method for Metabolic Profiling of Urine Organic Acids

Abstract Background Urine organic acids (UOA) analysis is an essential investigation for inborn errors of metabolism (IEMs). The vast majority of methods use gas chromatography mass spectrometry (GC-MS) and are only qualitative. Gas chromatography tandem mass spectrometry (GC-MS/MS) offers greater sensitivity and selectivity, and enables the combination of qualitative screening with quantitative analysis. We describe the development and preliminary validation results of a quantitative GC-MS/MS method. Methods Urine creatinine concentrations were measured (CobasPro, Roche Diagnostics) and normalized to 1.25 mmol/L. After internal standard addition, each urine specimen, calibration standard and QC were incubated with a hydroxylamine solution followed by a liquid-liquid extraction. Further sample concentration permitted the isolated UOA to be derivatized using N,O-bis(trimethylsilyl)trifluoroacetamine (BSTFA) with 1% chlorotrimethylsilane (TMCS) prior to injection. GC-MS/MS analysis was performed using a GC-MS-TQ8050 triple quadrupole system (Shimadzu) with a 30 m DB-5MS (Agilent J&amp;W) capillary column (0.25 mm, ID of 0.25 µm). Split injection mode was deployed with an initial column temperature of 70°C. The mass spectrometer was operated in electron ionization (EI) and multiple reaction monitoring (MRM) modes. The linear concentration ranges of the targeted metabolites within the devised GC-MS/MS protocol were determined. Results The optimal temperature gradient for high-resolution UOA separations was derived and their respective retention times determined. MS/MS detection parameters were optimized to permit the identification of precursor and production ions for all (N = 38) derivatized UOA. Total analysis time was 33.8 min per injection. The achieved linear concentration ranges for each metabolite was respectively determined. Linear concentration ranges and correlation coefficients of representative UOA: 3-hydroxyisovaleric acid (range = 9 to 708 µmol/L, R2 = 0.9874); lactic acid (range = 15 to 751 µmol/L, R2 = 0.9936); 3-hydroxybutyric acid (range = 15 to 751 µmol/L, R2 = 0.9991); and 2-methyl-3-hydroxybutyric acid (range = 10 to 501 µmol/L, R2 = 0.9996). The correlation coefficients for all remaining UOA ranged from R2 = 0.9458 (4-hydroxyphenylpyruvic acid) to R2 = 0.9998 (3-methylglutanoic acid and ethylmalonic acid). Conclusion The devised GC-MS/MS protocol permits the unbiased identification and quantification of UOA used to investigate IEMs. The linear concentration ranges for all analytes were determined and are appropriate for monitoring these markers of inherited enzyme deficiencies. The analytical performance of this UOA GC-MS/MS method must be further validated and its diagnostic performance for selected IEMs characterized.

Determination of blood:air, urine:air and plasma:air partition coefficients of selected microbial volatile organic compounds

Partition coefficients (PCs) are essential parameters for understanding the toxicokinetics of chemicals in the human body since they are used in the description of different processes of absorption, distribution, and excretion in physiologically based pharmacokinetic (PBPK) models used in chemical exposure and risk assessment. The goal of this study was to determine urine:air, blood:air and plasma:air partition coefficients (PCs) of microbial volatile organic compounds (mVOCs) previously selected as having high potential as biomarkers of indoor mold exposure. To achieve this goal, the vial-equilibration technique was used, and quantification was performed using headspace gas chromatography tandem mass spectrometry (HS-GC-MS/MS) analysis. Matrix:air PCs of 19 different mVOCs have been successfully determined and their values ranged between 14 and 3586 for urine:air, 78 and 4721 for blood:air and 64 and 5604 for plasma:air PCs. Water:air PCs were also determined, and their values varied between 16 and 2210, showing a good correlation with urine:air PCs for 17 compounds of the selected mVOCs (R2 = 0.97, slope close to unity) indicating that water:air PCs below 103 may be a good surrogate for urine:air PCs. All studied mVOCs have high blood:air PCs (greater than 78) indicating strong pulmonary uptake. Due to their high blood:urine PCs, some mVOCs may be more easily measured in blood than in urine. This work is an important preliminary step toward the use of mVOCs as potential biomarkers of indoor mold exposure. The data obtained in this study will help to determine the most appropriate matrix to use in this biomonitoring approach and will eventually facilitate the development of PBPK models for these chemicals.

Isotope-labeling in situ derivatization and HS-SPME arrow GC-MS/MS for simultaneous determination of fatty acids and fatty acid methyl esters in aqueous matrices.

Fatty acids (FAs) and fatty acid methyl esters (FAMEs) co-occur in many samples, and analysis of both substance classes is frequently of high interest. To this end, this study introduces the first method for simultaneous determination of FAs and FAMEs including fully automated solvent-free solid-phase microextraction (SPME) arrow headspace extraction combined with isotope-labeling in situ FA derivatization with deuterated methanol (CD3OD). By using the chromatographic isotope effect (ΔRt = 0.03min) and the + 3m/z mass shift, FAs can be selectively differentiated from the FAMEs during gas chromatography tandem-mass spectrometry (GC-MS/MS) operated in the multiple reaction monitoring (MRM) aquisition mode. Additionally, an approach is presented to predict the retention times of deuterated compounds. Optimization of the derivatization conditions was accomplished by design of experiments and found to be 20min, 50°C, 4v/v% CD3OD, and pH 2.1. During method validation, FAs and FAMEs were calibrated in different concentration ranges by standard addition in five real matrices and ultrapure water leading to good linearities and method detection limits for FAs ranging from 1-30µgL-1 and for FAMEs from 0.003-0.72µgL-1. FAs and FAMEs were detected in real samples from surface water, wastewater treatment plant effluent, and three different bioreactor samples and could be quantified in concentrations ranging from 2-1056µgL-1 for FAs and 0.01-14µgL-1 for FAMEs.

Determining Polycyclic Aromatic Compounds in Bird Feathers Using Pressurized Fluid Extraction

Due to their ease of collecting and transporting from the field and their ability to accumulate pollutants, bird feathers are increasingly being used as a non-invasive biomonitoring tool for environmental monitoring programs. Polycyclic aromatic compounds (PACs) are a diverse class of environmental pollutants, and because of their deleterious impacts on biological species, monitoring these compounds in wildlife is of high importance. Current approaches to measuring PACs in bird feathers involve a time-consuming acid treatment with a concomitant solvent extraction step. Here, a validated method for measuring a suite of PACs in bird feathers using pressurized fluid extraction and identification and quantitation by gas chromatography-tandem mass spectrometry is presented. Chicken (Gallus domesticus) feathers were purposely fortified with a suite of 34 PACs separately at three fortification levels and placed inside a pressurized fluid extraction cell containing silica gel/deactivated alumina to provide in situ clean-up of the sample. Except for anthracene and naphthalene, the accuracy of our method ranged for PAHs from 70–120% (irrespective of fortification level), and our intra- and inter-day repeatability was smaller than 28%. For APAHs, our accuracies ranged from 38–158%, and the inter- and intra-day repeatability was less than 35%. Our limits of detection and quantitation for both groups of compounds ranged from 0.5–13 and 1.5–44.3 ng/g, respectively. Overall, the developed method represents an effective and efficient approach for the extraction and quantitation of PACs from bird feathers that negated the need for the time-consuming and potentially harmful acid treatment.

Covalent organic framework-based magnetic solid-phase extraction coupled with gas chromatography-tandem mass spectrometry for the determination of trace phthalate esters in liquid foods.

Covalent organic framework-coated magnetite particles (Fe3O4@COF) were synthesized and applied as the adsorbent tothe selective capture of phthalate esters (PAEs) in liquid foods. Combined with the magnetic solid-phase extraction (MSPE) technology, a gas chromatography-tandem mass spectrometry (GC-MS/MS) method was employed for the separation and quantification of PAEs. Following optimization of the magnetic extraction and elution parameters, the developed analytical method offered a satisfactory linear range (0.1-5 μg L-1) with determination coefficients ranging from 0.9934 to 0.9975 for the five different PAEs studied. The limits of detection (LOD) were in the range1.9-12.8ng L-1. The recoveries ranged from 70.0 to 119.8% with a relative standard deviation (RSD) less than 9.7%. Density functional theory (DFT) calculations established that the dominant adsorption mechanism used by the COF to bind PAEs involved π-π stacking interactions. Results encourage the wider use of COF-based adsorbents and MSPE methods in the analytical determination of PAEs in foods.