Pressure Chemical Ionization-tandem Mass Spectrometry Research Articles

Identification of serum metabolites associated with polybrominated diphenyl ethers (PBDEs) exposure in papillary thyroid carcinoma: a case–control study

As the most common endocrine cancer, thyroid cancer (TC) has sharply increased globally over the past three decades. The growing incidence of TC might be counted by genetics, radiation, iodine, autoimmune disease, and exposure to environmental endocrine–disrupting chemicals (EDCs). Polybrominated diphenyl ethers (PBDEs), being typical EDCs, have been widely utilized in plastics, electronics, furniture, and textiles as flame retardants since the 1980s, and research has indicated a significant correlation between their exposure and the risk of TC. Even so, PBDEs exposure impact on the metabolic signature for TC remains unexplored. In this study, eight congeners of PBDEs were determined in serum from 111 patents with papillary thyroid cancer (PTC) and 111 healthy participants based on case–control epidemiology using gas chromatography–atmospheric pressure chemical ionization–tandem mass spectrometry (GC-APCI–MS/MS). Based on the tertile distribution of total PBDEs concentrations in 59 participants, metabolomics analysis was further performed by ultra-high performance liquid chromatography coupled to hybrid quadrupole–Orbitrap MS. In the partial correlation analysis, the 29 identified metabolites were correlated with PBDEs exposure (P < 0.05). In addition, PBDEs disrupted the metabolism of glycerophospholipids, sphingolipids, taurine, and hypotaurine, indicating that neurotransmitters, oxidative stress, and inflammation are the vulnerable pathways affected in PTC. Furthermore, (±)-octopamine and 5-hydroxyindole, both of which modulate the actions of neurotransmitters, emerged as potential disturbed metabolite markers for TC following exposure to PBDEs. This study analyzed the impact of PBDEs on PTC in terms of the metabolic changes and further explored possible biomarkers, which helped us have a deep understanding of the possible mechanism of the effects of PBDEs on TC.

An Analytical Method for Determining N-Nitrosodimethylamine and N-Nitrosodiethylamine Contamination in Irbesartan, Olmesartan and Metformin by UPLC-APCI-MS/MS in Tablet Dosage Form.

N-nitrosamine pollutants are probable carcinogens. Regulatory agencies declared their presence in the drugs unsafe for human consumption and demanded their recall. Using ultra-performance liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry (UPLC-APCI-MS/MS) in tablet dosage form based on International Conference on Harmonization (ICH) tripartite guideline criteria, we aim to develop and test a new approach for identifying and validating nitrosamine-contaminants, N-nitrosodimethylamine (NDMA) and N-nitrosodiethylamine (NDEA) in irbesartan, olmesartan and metformin. The column was Phenomenex Luna-C18, 100 × 3.0mm and 3.0μm. A mobile gradient phase of formic acid in either water or methanol separated the impurities. NDMA and NDEA had retention times of 0.85 and 2.55min, respectively. The detector's linearity was established at concentrations ranging from 0.6 to 100ng/mL. R2 for NDMA and NDEA were 0.9996 and 0.9998, respectively, with a linear response function established at 0.6-100ng/mL. Limit of detection and limit of quantification for NDMA and NDEA were 0.35, 0.29 and 0.55, 0.37ng/mL, respectively. On average, recovery rates for NDMA and NDEA ranged from 96.0 to 98.4 and 96.2 to 98.0%, respectively. The relative standard deviation for NDMA and NDEA was 3.46 and 2.69, respectively. According to the ICH guidelines, the developed method was quick, sensitive and valid. The pharmaceutical formulations of irbesartan, olmesartan and metformin may be regularly examined using the approach provided here.

Determination of eight herbicide residues in foodstuffs of plant origin by gas chromatography–atmospheric pressure chemical ionization–tandem mass spectrometry

This study uses gas chromatography–atmospheric pressure chemical ionization–tandem mass spectrometry (GC–APCI–MS/MS) to detect and identify 8 herbicide residues in foodstuffs of plant origin. In contrast to the extensive fragmentation caused by traditional electron impact ionization (EI) with high energy, APCI is a soft ionization technique. Therefore, more molecular ions and/or protonated molecules are present, improving the sensitivity and selectivity of analytical methods. The standard calibration curves ranged from 0.5 to 50 ng/mL; recoveries were in the range of 76.3–108.5%. The limit of quantification was 1.0 µg/kg for all samples. The results demonstrate the potential of GC–APCI–MS/MS to routinely detect and identify 8 herbicide residues in foodstuffs of plant origin.

Analysis of N-nitrosamines and N-nitrosatable substances from baby bottle rubber teats by liquid chromatography tandem mass spectrometry

A simple and sensitive method based on liquid chromatography-atmospheric pressure chemical ionisation-tandem mass spectrometry (LC-APCI-MS/MS) was developed and validated to determine the levels of 13N-nitrosamines and N-nitrosatable substances migrated from rubber teats into artificial saliva. The migration test from rubber teats was conducted at 40 °C and for 24 h in artificial saliva, and the migrated artificial saliva solution was analysed by liquid chromatography tandem mass spectrometry (LC-MS/MS) without further extracting steps. The sensitivity of N-nitrosamines was examined by applying atmospheric chemical ionisation and electrospray ionisation to optimise the mass spectrometric conditions, and the atmospheric chemical ionisation (APCI) mode exhibited 1.6–19 times higher sensitivity. Method validation showed acceptable linearity, precision, and accuracy, and the detection and quantification limits were 0.07–0.35 and 0.24–1.1 μg kg−1, respectively. The developed liquid chromatography-atmospheric chemical ionisation-tandem mass spectrometry method was applied to 39 domestic and imported rubber teats. From 39 samples, N-nitrosamines [N-nitrosodimethylamine (NDMA), N-nitrosomorpholine (NMOR), and N-nitroso n-methyl N-phenylamine (NMPhA)] were detected in 30 samples, with N-nitrosatable substances in 17 samples give rise to NDMA, NMOR, and N-nitrosodiethylamine. However, the levels were below the specific migration limit of Korean Standards and Specifications for Food Containers, Utensils, and Packages and EC Directive 93/11/EEC.

Simultaneous determination of three components of sodium nitrophenolate in foodstuffs of animal origin by high performance liquid chromatography-tandem mass spectrometry using atmospheric pressure chemical ionization

Sodium nitrophenolate (SNP) is a widely used universal growth regulator consisting of 5-nitroguaiacol sodium (5NG), 4-nitrophenol sodium (PNP), and 2-nitrophenol sodium (ONP). SNP has a positive influence on plants and animals as a feed additive that accelerates growth but is potentially hazardous to humans. SNP has been reported to be cytotoxic and mutagenic, which may increase the risk of cancer and pose a great threat to food safety. There are neither mature detection nor standard methods for the trace analysis of SNP in animal food. Therefore, the development of an accurate and precise analytical method is imperative. This innovative method has theoretical and practical significance for the control of SNP residues, offering advantages such as cost-effectiveness and time efficiency. It will be beneficial for the establishment of detection standards and management measures in foodstuffs of animal origin.In this study, a reliable method for the simultaneous determination of SNP residues in animal food (porcine muscle, chicken tissue, fish, and liver) was developed. For realizing the perfect limit of quantification, the application of back extraction coupled with high performance liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry (HPLC-APCI-MS/MS) was proposed to combine high sensitivity and high selectivity. The optimal method was as follows. First, 2.0 g samples were extracted with 10 mL 0.5 mol/L sodium hydroxide solution, followed by adjustment of the pH to acidity with 3 mol/L hydrochloric acid and the addition of sodium chloride (5.0 g) to saturate the inorganic phase. After back-extraction twice with 16 mL acetonitrile, the solution was merged and again saturated with 5 mL of sodium chloride solution. Second, the merged organic phase was cleaned up with 10 mL of n-hexane for defatting. The middle acetonitrile layer was then concentrated to nearly 1.5 mL at 40 ℃ in a N2 stream before dilution with the mobile phase to a volume of 3.0 mL and filtered. Finally, the analytes were separated on a C18 column (100 mm×4.6 mm, 3 μm) and subjected to gradient elution with a mixed solution of methanol and water. Mass spectrometric analysis, which was quantified using the external standard method, was carried out with an atmospheric pressure chemical ionization negative ion source and based on multiple reaction monitoring (MRM) mode. The key parameters, such as the extraction solvent, extraction steps, and purification method, were optimized.The calibration curves were linear in the ranges of 0.5-10 (5NG), 1.0-20 (PNP), and 2.5-50 μg/L (ONP) with correlation coefficients greater than 0.9999. The limit of quantification (LOQ) for 5NG was 1.0 μg/kg, double for PNP, and five times for ONP. The recoveries of the three different concentration levels in all the four matrices were in the range of 81.5%-98.4%, 81.5%-102%, and 81.4%-95.1%. The repeatability, expressed as the relative standard deviations (RSDs) of the three compounds, ranged from 1.51% to 5.98%, 1.10% to 8.85% and 0.91% to 8.61% (n=6). The developed method is characterized by an excellent purification effect, sensitivity, and accuracy. This method is suitable for the simultaneous and quantitative determination of SNP residues in foodstuffs of animal origin.

Determination of vitamin K encapsulated into lipid nanocarriers by dispersive liquid-liquid microextraction combined with liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry.

Dispersive liquid-liquid microextraction was used in conjunction with liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry to quantitate vitamins K1 and K2 in vitamin-fortified emulsions, and vital microextraction parameters were optimized using response surface methodology coupled with Box-Behnken design. Under optimal microextraction conditions, highly linear (R 2 > .999) calibration curves were obtained for both vitamins in a broad concentration range (1-1000 μg/L), and vitamin recoveries exceeded 90%. The detection and quantitation limits equaled 1.89 and 5.72 μg/L for vitamin K1, respectively, and 5.00 and 15.15 μg/L for vitamin K2, respectively. When applied to vitamin-K-loaded nanoemulsions and solid lipid nanoparticles, the developed method achieved excellent results, outperforming the currently employed Korean Food Code method, and therefore holding great promise for the quantitation of vitamin K in vitamin-fortified food products.

Determination and enantioselective separation of zilpaterol in human urine after mimicking consumption of contaminated meat using high-performance liquid chromatography with tandem mass spectrometry techniques.

The synthetic β-adrenoreceptor agonist zilpaterol is legitimately used as an animal feed supplement in selected countries due to its known effects on lipolysis and protein biosynthesis. These pharmacological characteristics of zilpaterol have contributed to its classification as doping agent in sport by the World Anti-Doping Agency. However, the use as a feed supplement can lead to residues of the drug in edible tissues and, possibly, also in the urine of consumers. To provide urinary elimination profiles of microdosed zilpaterol and to determine whether the ingestion of zilpaterol below or at the acceptable daily intake level of 0.04 μg/kg bodyweight can result in an adverse analytical finding (AAF) in doping controls, healthy volunteers were administered single or multiple oral doses of 0.5μg or 3μg zilpaterol to mimic ingestion of contaminated cattle meat. Urine samples were collected and analyzed using a validated high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS) method and a newly developed chiral high-performance liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry (HPLC-APCI-MS/MS) method. Urinary peak concentrations of zilpaterol were observed for all volunteers 1.5-12.5h after ingestion, and maximum levels >5ng/mL, which would constitute an AAF in doping controls, were found after the intake of 3μg of zilpaterol on five consecutive days in one out of five study participants. Noteworthy, the enantiomeric ratio of excreted zilpaterol remained constant over time. This study provides first insights into the urinary excretion of microdosed zilpaterol. Furthermore, a method was successfully developed and applied for the separation of the zilpaterol enantiomers with mass spectrometric detection.

Cloud point extraction coupled with ultrasound-assisted back-extraction for determination of trace legacy and emerging brominated flame retardants in water using isotopic dilution high-performance liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry

Isotopic dilution high-performance liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry method was developed for determination of seven legacy and emerging brominated flame retardants (BFRs) in water using cloud point extraction coupled with ultrasound-assisted back-extraction. The effects of different experimental conditions on the recovery and matrix effect during cloud point extraction were investigated. Under the optimum conditions (sample volume: 40 mL; Triton X-114 concentration: 1.0 g L−1; equilibration temperature: 40 °C; equilibration time: 10 min; NH4OAc concentration: 0.5 M), the absolute recoveries obtained by cloud point extraction for the seven BFRs ranged from 64.0% to 108.8%, with matrix effect factors ranging between 0.70 and 1.07. Ultrasound-assisted back-extraction combined with isotope dilution mass spectrometry was utilized to enhance the enrichment factor and improve the repeatability. Under the optimized conditions, method limits of detection for BFRs ranged from 0.3 to 3.0 ng L−1. The average recoveries were in the range of 92.9–113.6% and 86.0–99.3% for spiked water samples at 10 and 100 ng L−1 of each BFR. The intra- and inter-day relative standard deviations (n = 6) were less than 5.4% and 8.0%, respectively. The results demonstrated that the proposed method was highly sensitive, efficient and reliable for the determination of trace legacy and emerging BFRs in water samples.

Quantification of anthracene after dermal absorption test via APCI-tandem mass spectrometry.

An analytical method for the detection and quantification of anthracene from interstitial fluid samples was developed by using Atmospheric Pressure Chemical Ionization-Tandem Mass Spectrometry (APCI-MS/MS). The anthracene samples were obtained using intradermal microdialysis to assess dermal absorption of this polycyclic aromatic hydrocarbon (PAH). The experimental considerations were evaluated based on the chemical properties of this PAH and the detection limits of the instrumentation. The addition of an isotopically labeled internal standard allows the reduction of ionization suppression due to instrumental fluctuation and run-to-run deviation. The dermal extraction samples were prepared considering the proceeding conditions for measurement enhancement. Several variables for method validation including coefficient of determination (R2 = 0.993 ± 0.003), percent error (% error = 0 ± 2%), coefficient of variation (% CV = 5 ± 1%), lowest limit of detection (LOD = 39 ± 3 ng mL-1), and lowest limit of quantification (LLOQ = 129 ± 10 ng mL-1) were obtained from the inter- and intra-day measurements for the calibration and the quality control samples. Posterior to this, actual dermal interstitial fluid samples were measured, and it was observed they fitted into the ranges defined from the method development with good accuracy and precision. It was observed that the introduction of an internal standard while performing APCI-MS/MS allows an accurate and precise measurement of the concentration of anthracene to be obtained from dermal extraction samples. This method could be further used for complex mixtures to enhance our understanding of hazardous exposure of PAH on firefighter gear.

Magnetic molecularly imprinted polymers prepared by reversible addition fragmentation chain transfer polymerization for dispersive solid phase extraction of polycyclic aromatic hydrocarbons in water

Magnetic molecularly imprinted polymers (MMIPs) combine nanotechnology and molecular imprinting technology to offer selective and tunable enrichment for water analysis. In this paper, a selective sorbent was prepared by surface polymerization onto magnetic Fe3O4@SiO2 nanoparticles through reversible addition fragmentation chain transfer (RAFT) polymerization. The MMIPs were used for dispersive solid phase extraction (DSPE) of 16 PAHs as priority pollutants in aqueous matrices. After preconcentration, the analysis was performed using gas chromatography with an atmospheric pressure chemical ionization-tandem mass spectrometry (APGC–MS/MS). The extraction method is based on the dispersion of MMIPs in an aqueous sample using an ultrasonic bath which provides rapid equilibrium of analytes between the sorbent and sample solution. The enriched analytes were retrieved by collecting MMIP particles and desorbed into an organic solvent before instrumental analysis. A design of experiment (DOE) approach was applied to optimize several extraction parameters including the mass of MMIPs, the sample volume, salt addition, collection time, desorption volume, and desorption time. A fractional factorial design (FFD) (26-2) was performed to assess the influence of the selected factors on the extracted amount of analytes. The most effective factors including the mass of MMIPs, the volume of sample solution, and salt content was further investigated using central composite design (CCD) and yielded quadratic models between dependent and independent variables. The optimum conditions of DSPE obtained by desirability function (DF) were employed for preconcentration of PAHs in water samples. The evaluation showed that the MMIPs provide higher extraction efficiency compared to nanoparticles such as Fe3O4, Fe3O4@SiO2 and non-imprinted polymer, demonstrating the creation of selective recognition binding sites at the surface of magnetic nanoparticles. The LODs and LOQs ranged from 1 to 100 pg mL−1 and 2 to 200 pg mL−1, respectively. Finally, the MMIP-DSPE method was successfully applied for preconcentration and trace quantification of PAHs in real samples such as produced water and river water samples.

Single-use porous thin film extraction with gas chromatography atmospheric pressure chemical ionization tandem mass spectrometry for high-throughput analysis of 16 PAHs

The need for high throughput, reliable analytical methods for environmental analysis has driven our development of novel sampling technologies that can be used in microextraction devices and integrated into chromatographic systems for fast analysis. Here we report a new method of water analysis for 16 EPA priority polycyclic aromatic hydrocarbons (PAHs) that relies on a tailor made porous polymeric film for extraction with analysis by gas chromatography with atmospheric pressure chemical ionization-tandem mass spectrometry (APGC-MS/MS). The extraction device is user friendly, single-use and gives exhaustive extraction from a relatively small volume (20 mL). The films show good stability, with excellent analytical performance. Critical factors affecting the extraction efficiency such as desorption solvent, desorption time, extraction agitation, and extraction time were studied and optimized. These thin films are cost effective and efficient for single use analysis, but carry-over studies showed that the films can be reused at least 10 times without extensive washing and with no loss in performance. The 16 PAHs were measured with excellent limits of detection ranging from 1 pg mL−1 for BaA to 100 pg mL−1 for Flu and linearity (R2 > 0.997) over the 1–50,000 pg mL−1 concentration range. This high throughput method (1-h extractions, which can be completed simultaneously) showed good reproducibility (<20%) with recoveries in the range of 19.0–40.6% and concentration factors varying between 37.9 and 81.1. Analysis of real seawater and river water samples using matrix-matched calibration in synthetic seawater and river water showed only small matrix effects maintaining high sensitivity (LODs:1–100 pg mL−1), demonstrating that the films are suitable for analysis of real samples without the need for standard addition.

Background levels of dioxin-like polychlorinated biphenyls (dlPCBs), polychlorinated, polybrominated and mixed halogenated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs, PBDD/Fs & PXDD/Fs) in sera of pregnant women in Accra, Ghana

Human exposure data on dioxins and dioxin-like compounds (DLCs) in Ghana are limited. Based on health risks associated with dioxins and DLCs, the impact of maternal body burdens on foetal exposure is significant. This is the first study that assesses polychlorinated, polybrominated and mixed halogenated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs, PBDD/Fs and PXDD/Fs), and dioxin-like polychlorinated biphenyls (dlPCBs) in sera of primiparous Ghanaians. Our sample selection includes 34 participants from two municipalities (Accra and Tema), and explores contributions from environmental and dietary exposures using questionnaire data. Sample preparation involved C18 solid phase extraction, purification with acidified silica and lipid removal cartridges, and detection with gas chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry. The calculated average toxic equivalent concentration was 5.3 pg TEQ/g lw, with contributions from dlPCBs (1.25 pg TEQ/g lw), PCDD/Fs (3.10 pg TEQ/g lw), PBDD/Fs (0.49 pg TEQ/g lw) and PXDD/Fs (0.50 pg TEQ/g lw). The calculated total TEQ concentration was lower than background TEQ concentrations reported in sera of pregnant women globally. Positive correlations were obtained for total dioxins and DLC concentrations with age and Body Mass Index (BMI). Dietary intake of seafood and dairy products had a strong influence on PCDD/F and dlPCB concentrations. Statistically significant differences were observed for dioxins and DLCs in participants from Accra (in close proximity to Agbogbloshie e-waste site) and Tema. Given the significant TEQ contribution of PBDD/Fs and PXDD/Fs (~20%), it is essential to explore these classes of dioxins and DLCs in future biomonitoring studies as they may pose health risks, and add extra diagnostic information in source exposure investigations.

Determination of acrylamide in coffee by ultra performance liquid chromatography-atmospheric pressure chemical ionization tandem mass spectrometry

A method using ultra high performance liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry (UHPLC-APCI-MS/MS) was developed for the determination of acrylamide in coffee. The coffee samples spiked with 13C3-acrylamide as the internal standard were extracted with methanol, and cleaned using HLB solid phase extraction (SPE) cartridges. The liquid chromatography separation was performed on a Brownlee validated AQ C18 column with isocratic elution. Methanol and 0.1% (volume percentage) formic acid aqueous solution were used as the mobile phase. Identification of acrylamide was achieved by APCI-MS/MS with multiple reaction monitoring (MRM) in the positive mode. The quantification analysis was performed by the internal standard method. The calibration curve showed good linearity with a correlation coefficient of 0.999 in the range of 0.5-100.0 μg/L. The limit of detection (LOD) was 5.0 μg/kg. The limit of quantification (LOQ) was 10.0 μg/kg. Recovery of acrylamide from coffee sample was evaluated at concentrations of 100.0, 200.0 and 1000.0 μg/kg. The average recoveries of acrylamide were between 94.6%-115.0% with relative standard derivations (RSDs) in the range of 2.8%-3.6% (n=6). This simple, accurate and sensitive method was proven to be suitable for the determination of acrylamide in coffee.

Determination of polybrominated diphenyl ethers and novel brominated flame retardants in human serum by gas chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry

The accurate detection of brominated flame retardants (BFRs) in humans is an area of high scientific interest and regulatory need due to their potential toxicity. The instrumental analysis of BFRs was commonly performed on gas chromatography-mass spectrometry (GC-MS) operating in electron ionization (EI) or negative chemical ionization (NCI) modes. However, soft ionization techniques, such as atmospheric pressure chemical ionization (APCI), may be more suitable for the analysis of BFRs because the BFRs show high fragmentation in EI and low selectivity in NCI. Additionally, accurate quantifications of BFRs in complex matrices is challenging due to their low concentrations and therefore, a highly sensitive technique is desperately needed. In this study, a new methodology based on gas chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry (GC-APCI-MS/MS) analysis was developed for the determination of thirteen BFRs (eight usually monitored polybrominated diphenyl ethers (PBDEs) congeners and five additional novel BFRs) in human serum. The primary task was to evaluate the potential of the GC-APCI-MS/MS technique for the trace analysis of BFRs in human serum. The results of the spiked recovery test using fetal bovine serum showed that mean recoveries of the analytes ranged from 83.4% to 118% with reduced swing differential signaling (RSDs) of ≤21.1%. The methodological limits of detection (mLOD) of the analytes ranged from 0.04 to 30 pg/mL, and these values were at least one order of magnitude lower than those estimated by the authors in a previous study using GC-NCI-MS or GC-EI-MS/MS, indicating that GC-APCI-MS/MS is more sensitive. Specially, compared to GC-NCI-MS and GC-EI-MS/MS, when GC-APCI-MS/MS was used for the detection of highly brominated BFRs, such as BDE-209 and decabromodiphenyl ethane (DBDPE), a notable improvement in sensitivity and reliability was obtained using a deactivated capillary column connected to the analytical column as the transfer line and maintaining a high temperature to improve the chromatographic behaviors. The developed methodology was successfully used for the analysis of BFRs in human serum collected from residents living in a BFR production area and Beijing.

Identification of organic hydroperoxides and peroxy acids using atmospheric pressure chemical ionization–tandem mass spectrometry (APCI-MS/MS): application to secondary organic aerosol

Abstract. Molecules with hydroperoxide functional groups are of extreme importance to both the atmospheric and biological chemistry fields. In this work, an analytical method is presented for the identification of organic hydroperoxides and peroxy acids (ROOH) by direct infusion of liquid samples into a positive-ion atmospheric pressure chemical ionization–tandem mass spectrometer ((+)-APCI-MS/MS). Under collisional dissociation conditions, a characteristic neutral loss of 51 Da (arising from loss of H2O2+NH3) from ammonium adducts of the molecular ions ([M + NH4]+) is observed for ROOH standards (i.e. cumene hydroperoxide, isoprene-4-hydroxy-3-hydroperoxide (ISOPOOH), tert-butyl hydroperoxide, 2-butanone peroxide and peracetic acid), as well as the ROOH formed from the reactions of H2O2 with aldehydes (i.e. acetaldehyde, hexanal, glyoxal and methylglyoxal). This new ROOH detection method was applied to methanol extracts of secondary organic aerosol (SOA) material generated from ozonolysis of α-pinene, indicating a number of ROOH molecules in the SOA material. While the full-scan mass spectrum of SOA demonstrates the presence of monomers (m∕z = 80–250), dimers (m∕z = 250–450) and trimers (m∕z = 450–600), the neutral loss scan shows that the ROOH products all have masses less than 300 Da, indicating that ROOH molecules may not contribute significantly to the SOA oligomeric content. We anticipate this method could also be applied to biological systems with considerable value.

Enantiomeric separation of triacylglycerols containing very long chain fatty acids

Enantiomers of triacylglycerols (TAGs) containing any combination of very long chain fatty acids (VLCFAs) and/or very long chain polyunsaturated fatty acids (VLCPUFAs) with diolein, dilinolein and didocosahexaenoin were synthesized. Gradient non-aqueous reversed-phase high-performance liquid chromatography/high resolution atmospheric pressure chemical ionization-tandem mass spectrometry (NARP-HPLC/HRMS2-APCI) and chiral liquid chromatography were used for the separation and identification of molecular species of these TAGs. Further, NARP-LC and chiral LC were used to separate natural mixtures of TAGs obtained from four natural sources, i.e. ximenia oil (Ximenia americana), green alga (Botryococcus braunii), breweŕs yeast (Saccharomyces pastorianus) and a dinoflagellate (Amphidinium carterae). The ratio of regioisomers and enantiomers in individual samples was determined and a hypothesis has been confirmed on the biosynthetic pathway of natural TAGs, which is based on the preferential representation of VLCFAs and VLCPUFAs in the sn-1 position of the glycerol backbone.

N-nitrosamines migrating from food contact materials into food simulants: analysis and quantification by means of HPLC-APCI-MS/MS

ABSTRACTIt was the aim of the work described here to develop a validated analytical method for the determination of N-nitrosamines in food simulants. Here, we present the validation of a liquid chromatography–atmospheric pressure chemical ionisation–tandem mass spectrometry method for the determination of 13 N-nitrosamines in the food simulants deionised water, 3% acetic acid and 10% ethanol. Method validation encompassed linearity, LOD, LOQ, recovery, precision and stability of the N-nitrosamines. The method was found to be sufficiently rugged and suitable for routine analysis. In addition, the developed method is on average 10 times more sensitive than the gas chromatography–thermal energy analyser (GC-TEA) method that is currently stipulated in Recommendation XXI for commodities based on natural and synthetic rubber issued by the German Federal Institute for Risk Assessment (BfR). The developed method was applied to determine the N-nitrosamine contents in migration solutions of 12 elastomer samples covering a range of different elastomer types. In 10 out of 12 samples, N-nitrosamines were determined. In most samples, the guidance value of 1 µg/dm2 specified in BfR Recommendation XXI was not exceeded. In conclusion, the analytical method presented here offers a useful alternative to the GC-TEA method currently stipulated in BfR Recommendation XXI. This is of wider relevance, since BfR recommendations are used for compliance assessment of Article 3, paragraph 1 a of the Regulation (EC) No. 1935/2004 with respect to their health safety.

Non-aqueous reversed-phase liquid-chromatography of tocopherols and tocotrienols and their mass spectrometric quantification in pecan nuts

An easy and effective analytical method was developed for the simultaneous quantification of four tocopherols (Ts) and four tocotrienols (T3s) in three pecan nut cultivars (Stuart, Sioux, and Pawnee). The analytes were separated on a C30 column kept at 15°C, under isocratic non-aqueous reversed-phase (NARP) conditions, in only 18min and detected by atmospheric pressure chemical ionization–tandem mass spectrometry (APCI-MS/MS). The HPLC-APCI-MS/MS method was validated, according to the main FDA guidelines, and then applied for the characterization of the real samples. Analytes were extracted by cold saponification with recoveries greater than 87%. The limits of detection (LOD) and limits of quantification (LOQ) were in the range of 0.3–10μg/100mg and 1–30μg/100mg, respectively. Compared to other nuts, vitamin E composition of pecan nuts (Carya illinoinensis) has only partially been elucidated. Results have evidenced the prevalence of γ-forms for both Ts and T3s and clear quantitative differences of the identified vitamers among the studied cultivars. The richest variety in vitamin E was Sioux with a total content of about∼32mg/100g wet weight, followed by Stuart (∼16mg/100g) and Pawnee (∼9mg/100g).

Plasma coenzyme Q10 concentration, antioxidant status, and serum N-terminal pro-brain natriuretic peptide concentration in dogs with various cardiovascular diseases and the effect of cardiac treatment on measured variables.

OBJECTIVE To determine the plasma total antioxidant capacity, erythrocyte superoxide dismutase activity, whole blood glutathione peroxidase activity, and plasma coenzyme Q10 (CoQ10) concentration in dogs with various stages of cardiovascular diseases and in healthy dogs; assess the influence of cardiac treatment on the levels of antioxidant variables, plasma CoQ10 concentration, and serum N-terminal pro-brain natriuretic peptide (NT-proBNP) concentration, and determine any correlation between the disease severity (NT-proBNP concentration) and antioxidant variables or CoQ10 concentration. ANIMALS 43 dogs with various types and stages of cardiovascular diseases (congenital and acquired) and 29 healthy dogs. PROCEDURES Blood samples were collected from all dogs for spectrophotometric assessment of antioxidant variables. Plasma CoQ10 concentration was determined with a high-performance liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry method. Serum NT-proBNP concentration was measured with an ELISA. RESULTS Values for antioxidant variables did not differ among groups of dogs with cardiovascular diseases, regardless of disease stage or treatment. Plasma CoQ10 concentration was significantly increased in treated dogs with congestive heart failure (CHF), compared with untreated patients. However, plasma CoQ10 concentration did not differ among heart failure classes. A significant, negative correlation between serum NT-proBNP and plasma CoQ10 concentrations was identified in treated CHF-affected dogs, suggesting that low plasma CoQ10 concentration may be associated with increased severity of CHF. CONCLUSIONS AND CLINICAL RELEVANCE The antioxidant variables evaluated were not altered in dogs with CHF, regardless of cardiac disease stage or treatment. Further investigation into the possible effects of CoQ10 supplementation in dogs with advanced stages of CHF is warranted.

Atmospheric Pressure Chemical Ionization Gas Chromatography Mass Spectrometry for the Analysis of Selected Emerging Brominated Flame Retardants in Foods

Emerging brominated flame retardants (eBFRs) other than polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs) and their derivatives in foods have been in focus in recent years due to their increasing production volumes, indefinite information on toxicities and the lack of data on occurrence in environments, foods as well as humans. In this study, gas chromatography was coupled to an atmospheric pressure chemical ionization-tandem mass spectrometry (APGC-MS/MS) for the analysis of six eBFRs in pork, chicken, egg, milk and fish. A short section of unpacked capillary column coupled to the end of the analytical column was applied to improve the chromatographic behaviors of high boiling point compounds. The method was comprehensively validated with method limit of quantification (mLOQ) lower than 8 pg/g wet weight (w.w.). Samples from Chinese Total Diet study were quantified following the validated APGC-MS/MS method. 2,3,4,5-pentabromo-6-ethylbenzene (PBEB), hexabromobenzene (HBB), pentabromotoluene (PBT) and 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) were most frequently detected in samples. The highest concentration was found in fish with 351.9 pg/g w.w. of PBT. This is the first report on the presence of PBT in food samples with non-ignorable concentrations and detection rate.