Liquid Chromatography Tandem Triple Quadrupole Research Articles

Comparison of Multiple Bioactive Constituents in the Flower and the Caulis of Lonicera japonica Based on UFLC-QTRAP-MS/MS Combined with Multivariate Statistical Analysis

Lonicerae japonicae flos (LJF) and Lonicerae japonicae caulis (LJC) are derived from different parts of Lonicera japonica Thunb. (Caprifoliaceae), and have been used as herbal remedies to treat various diseases for thousands of years with confirmed curative effects. However, little attention has been paid to illustrating the differences in efficacy from the perspective of phytochemistry. In the present study, a simultaneous determination of 47 bioactive constituents, including 12 organic acids, 12 flavonoids, six iridoids, 13 amino acids and four nucleosides in 44 batches of LJF and LJC samples from different habitats and commercial herbs was established based on ultra-fast liquid chromatography tandem triple quadrupole mass spectrometry (UFLC-QTRAP-MS/MS). Moreover, principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA) and t-test were then performed to classify and reveal the differential compositions of LJF and LJC according to the content of the tested constituents. The results demonstrated that the types and contents of chemical components (e.g., isochlorogenic acid A, chlorogenic acid, neochlorogenic acid, quinic acid, secologanic acid, luteoloside, loganin, secoxyloganin, morroniside and L-isoleucine) were significantly different, which may lead to the classification and the differences in efficacy of LJF and LJC. Our findings not only provide a basis for the comprehensive evaluation and intrinsic quality control of LJF and LJC, but also pave the way for discovering the material basis contributing to the different properties and efficacies of the two medicinal materials at the phytochemical level.

Per- and polyfluorinated compounds in saleswomen's urine linked to indoor dust in clothing shops

This study aims to investigate the characteristics of typical per- and polyfluorinated compounds (PFCs) in indoor dust from clothing shops and urine sampled from saleswomen. A total of 58 indoor dust samples and 73 urine samples from saleswomen were collected from clothing shops in Shanghai, China. All samples were analyzed for PFCs using high-performance liquid chromatography tandem triple quadrupole mass spectrometry (HPLC-MS/MS). The mean PFC concentrations in indoor dust ranged from 0.42 (PFDA) to 5.04 ng g−1 (PFDoA). PFDoA and PFHxS were the most prominent PFCs, with median concentrations of 2.95 ng g−1 and 1.49 ng g−1, respectively. The median PFC concentrations in urine ranged from 10.15 (PFDS) to 666.1 ng l−1 (PFOA) and PFOA was the most abundant chemical with concentrations ranging from 207 to 907 ng l−1. A significant positive correlation was obtained between long-chain PFCs in dust and in urine (p < 0.01). Daily intake values of PFCs via dust ingestion were also calculated, and even under high-end exposure scenarios, the intake of PFOA (36.5 pg day−1) and PFOS (56.7 pg day−1) were well within the tolerable daily intake values. These results are important to both characterize PFC levels and estimate the saleswomen's exposure to PFCs from indoor dust.

Pharmacokinetics, Tissue Distribution, Metabolism, and Excretion of Naringin in Aged Rats.

Aging is an inevitable biological process characterized by the loss of functional capacity and associated with changes in all phases of pharmacokinetic processes. Naringin, a dietary flavanone glycoside, has been proved to be beneficial for the treatment of multiple age-associated chronic diseases. To date, the pharmacokinetic processes of naringin in aged individuals are still unknown. Thus, a rapid resolution liquid chromatography tandem triple quadrupole mass spectrometry (RRLC-QQQ-MS/MS) method was established for the determination of naringin and its metabolite naringenin in rat plasma, urine, feces, and tissue homogenate. The pharmacokinetic parameters were calculated and a higher exposure of naringin and naringenin were observed in aged rats. Naringin and naringenin were mostly distributed in gastrointestinal tract, liver, kidney, lung, and trachea. Furthermore, a total of 39 flavonoid metabolites (mainly glucuronides and sulfates) and 46 microbial-derived phenolic catabolites were screened with ultra-fast liquid chromatography-quadrupole-time-of-flight tandem mass spectrometry (UFLC-Q-TOF-MS/MS). Naringenin, hippuric acid, and 3-(4’-hydroxyphenyl)propionic acid were predominated metabolites. This study systemically investigated the pharmacokinetics, tissue distribution, metabolism, and excretion of naringin in aged rats, revealing age- and gender-related changes in the in vivo behavior of naringin. These results would be helpful for the interpretation of pharmacokinetics and pharmacodynamics of naringin in aged population.

A Validated Ultra-Performance Liquid Chromatography Tandem Triple Quadrupole Mass Spectrometric Method for Fast Determination of Losartan in Rabbit Plasma.

A rapid UPLC-MS-MS method was developed and validated for determination of losartan in rabbit plasma. Protonated adducts of losartan and eprosartan (IS) were monitored in multiple reaction monitoring mode. Molecular masses of daughter species of losartan were m/z 423.19 > 207 and m/z 423.19 > 180; and of eprosartan were m/z 425.11 > 135 and m/z 425.11 > 107. Losartan from plasma samples was extracted by protein precipitation method. The mobile phase comprising water (0.1% formic acid) (A) and acetonitrile (0.1% formic acid) (B) was used in gradient mode. Analytes were eluted on Acquity UPLC®BEH C18 1.7 μm, 2.1 × 50 mm column. Sample run time was 3.0 min. The validation parameters: accuracy, precision and recovery were within recommended limits. Losartan as well as internal standard remains stable in benchtop stability study as well as in post-preparative stability study. Pharmacokinetic parameters such as Cmax (182.79 ± 23.80 ng/mL), Tmax (1.16 ± 0.28 h), AUC0-t (1188.57 ± 404.60 ng h/mL) and Kel (0.0954 ± 0.0140 h-1) of losartan were measured. Method was successfully applied for pharmacokinetic investigation in rabbits and can be used for losartan determination in plasma sample obtained from other animals.

Ultra-high-performance liquid chromatography with tandem mass spectrometry method for determination of four compounds in rat plasma after oral administration of Xanthii fructus and stir-fried Xanthii fructus extracts.

Xanthii fructus (XF), the fruit of Xanthium sibiricum Patr., is a traditional Chinese materia medica commonly used to treat allergic rhinitis and other rhinitis diseases. To uncover the mechanism of the stir-frying process and its effect on the pharmacokinetic behavior of active compounds in model rats, four active compounds-chlorogenic acid, 4-caffeoylquinic acid, 1,5-O-dicaffeoylquinic acid and apigenin-were selected based on previous spectrum-effect experiments. High performance liquid chromatography tandem triple quadrupole mass spectrometry (UPLC-QqQ-MS) technology, an accurate and feasible method, was applied to measure the concentration of these four compounds in rat plasma. This validated method can accurately measure the concentration of each compound at each sampling point of rat plasma. This validated method shows good linearity, extraction recoveries, matrix effects, intra- and inter-day precision and stabilities. Compared with the XF group, the maximum plasma concentration (Cmax ) value of 1,5-O-dicaffeoylquinic acid decreased remarkably (p < 0.05) after oral administration of stir-fried Xanthii fructus (SXF) extract, while the other compounds showed no significant difference. The mean residence time value of chlorogenic acid (p < 0.05) and 1,5-O-dicaffeoylquinic acid (p<0.01) after oral administration of SXF extraction demonstrated significant differences compared with the XF group, while the other two compounds showed no statistical difference, indicating that the stir-frying process prolonged the effect time and delayed the removal time of chlorogenic acid and 1,5-O-dicaffeoylquinic acid. The values of the area under the plasma concentration-time curve from zero to the last quantifiable time-point, the area under the plasma concentration-time curve from zero to infinity, the time to maximum concentration and the elimination half-life of four compounds in the SXF group showed no statistically significant difference from the XF group. From this data, we speculated that the stir-frying process can not only keep the absorption of 4-caffeoylquinic acid and apigenin, but also increase the effect time of chlorogenic acid and 1,5-O-dicaffeoylquinic acid, which could be the mechanism underlying the stir-frying process enhancing the effects of XF.

Comparison of non-anthocyanin polyphenol accumulation in the berry skins of muscadine and European grapes during ripening in China.

The non-anthocyanin polyphenol accumulation in the berry skins of muscadine grapes from South China during ripening was investigated, in comparison to European grapes, for two consecutive years, using ultra-performance liquid chromatography tandem triple quadrupole time-of-flight mass spectrometry. A total of 121 components were tentatively identified, consisting of 48 ellagic acids and precursors (EP), 38 flavonols, 20 hydroxybenzoic acids, 6 hydroxycinnamic acids, 5 flavan-3-ols, and 4 stilbenes. EP (mostly ellagic acid derivatives) and flavonols (mainly isorhamnetin and quercetin derivatives) were, respectively, accumulated abundantly in the muscadine and European grape skins. Additionally, their variation had considerable differences during berry maturation. EP in muscadine cv. "Noble" skins showed a small decrease before veraison and a slight increase post-veraison, yet the flavonols significantly increased as berry maturation in European skins, with a few exceptions. This is the interactional result between genotype and environmental factors, which obviously influences the polyphenol composition and concentration. PRACTICAL APPLICATIONS: Muscadine grapes, indigenous to the southeast of United States, have been introduced to South China in recent years. These grapes have unique polyphenol composition that differs from non-muscadine grapes. Their polyphenol properties have been studied extensively in many but there are a few studies in our knowledge about the variation of these compounds at different berry developmental stages. This article evaluates the accumulation of non-anthocyanin polyphenols in muscadine skins during berry maturation, in comparison to European grapes. The findings exhibit the polyphenol characteristics of these grapes cultivated in new locations across South China, and make further efforts to increase breeding quality and agronomic production, through improving preharvest treatments and agronomic performance during berry developmental stages, that lead to a high increase of polyphenol.

Variations in Physiology and Multiple Bioactive Constituents under Salt Stress Provide Insight into the Quality Evaluation of Apocyni Veneti Folium.

As one of the major abiotic stresses, salinity stress may affect the physiology and biochemical components of Apocynum venetum L. To systematically evaluate the quality of Apocyni Veneti Folium (AVF) from the perspective of physiological and the wide variety of bioactive components response to various concentrations of salt stress, this experiment was arranged on the basis of ultra-fast liquid chromatography tandem triple quadrupole mass spectrometry (UFLC-QTRAP-MS/MS) technology and multivariate statistical analysis. Physiological characteristics of photosynthetic pigments, osmotic homeostasis, lipid peroxidation product, and antioxidative enzymes were introduced to investigate the salt tolerance mechanism of AVF under salinity treatments of four concentrations (0, 100, 200, and 300 mM NaCl, respectively). Furthermore, a total of 43 bioactive constituents, including 14 amino acids, nine nucleosides, six organic acids, and 14 flavonoids were quantified in AVF under salt stress. In addition, multivariate statistical analysis, including hierarchical clustering analysis, principal component analysis (PCA), and gray relational analysis (GRA) was employed to systematically cluster, distinguish, and evaluate the samples, respectively. Compared with the control, the results demonstrated that 200 mM and 100 mM salt stress contributed to maintain high quality of photosynthesis, osmotic balance, antioxidant enzyme activity, and the accumulation of metabolites, except for total organic acids, and the quality of AVF obtained by these two groups was better than others; however, under severe stress, the accumulation of the oxidative damage and the reduction of metabolite caused by inefficiently scavenging reactive oxygen species (ROS) lead to lower quality. In summary, the proposed method may provide integrated information for the quality evaluation of AVF and other salt-tolerant Chinese medicines.

Quality Evaluation of Apocyni Veneti Folium from Different Habitats and Commercial Herbs Based on Simultaneous Determination of Multiple Bioactive Constituents Combined with Multivariate Statistical Analysis.

Apocyni Veneti Folium (AVF) is a kind of staple traditional Chinese medicine with vast clinical consumption because of its positive effects. However, due to the habitats and adulterants, its quality is uneven. To control the quality of this medicinal herb, in this study, the quality of AVF was evaluated based on simultaneous determination of multiple bioactive constituents combined with multivariate statistical analysis. A reliable method based on ultra-fast liquid chromatography tandem triple quadrupole mass spectrometry (UFLC-QTRAP-MS/MS) was developed for the simultaneous determination of a total of 43 constituents, including 15 flavonoids, 6 organic acids, 13 amino acids, and 9 nucleosides in 41 Luobumaye samples from different habitats and commercial herbs. Furthermore, according to the contents of these 43 constituents, principal component analysis (PCA) was employed to classify and distinguish between AVF and its adulterants, leaves of Poacynum hendersonii (PHF), and gray relational analysis (GRA) was performed to evaluate the quality of the samples. The proposed method was successfully applied to the comprehensive quality evaluation of AVF, and all results demonstrated that the quality of AVF was higher than the PHF. This study will provide comprehensive information necessary for the quality control of AVF.

Simultaneous quantitation of multiple contraceptive hormones in human serum by LC–MS/MS

ObjectiveThe objective was to develop a method to simultaneously quantify five commonly used hormonal contraceptives (HCs) and two endogenous sex steroids by liquid chromatography–tandem triple quadrupole mass spectrometry (LC–MS/MS) and apply this method to human serum samples. Study designWe developed a method to simultaneously analyze ethinyl estradiol (EE2), etonogestrel (ENG), levonorgestrel (LNG), medroxyprogesterone acetate (MPA) and norethisterone (NET), along with estradiol (E2) and progesterone (P4), in human serum for a Shimadzu Nexera-LCMS-8050 LC–MS/MS platform. We analyzed serum collected from women self-reporting use of oral contraceptives, contraceptive implants or injectable contraceptives (n=14) and normally cycling women using no HC (n=15) as well as pooled samples from women administered various HCs (ENG, n=6; LNG, n=14; MPA, n=7; NET, n=5). ResultsLimits of quantitation were 0.010ng/mL for E2, EE2 and P4; 0.020ng/mL for ENG, LNG and MPA; and 0.040ng/mL for NET. Precisions for all assays, as indicated by coefficient of variation, were less than or equal to 12.1%. Accuracies for all assays were in the range of 95%–108%. Endogenous hormone values obtained from analysis of human serum samples are in agreement with levels previously reported in the literature for normally cycling women as well as for women taking the appropriate HC. ConclusionsWe have developed a robust, accurate and sensitive method for simultaneously analyzing commonly used contraceptive steroids and endogenous sex steroids in human serum. ImplicationsThis analytical method can be used for quantitating contraceptive steroid levels in women for monitoring systemic exposure to determine drug interactions, nonadherence, misreporting and proper dosing.

Particle size distribution and respiratory deposition estimates of airborne perfluoroalkyl acids during the haze period in the megacity of Shanghai.

This study presents the particle size distribution and respiratory deposition estimates of airborne perfluoroalkyl acids (PFAAs) during the haze period. Size-segregated haze aerosols were collected from an urban location in Shanghai using an eight-stage air sampler. The samples were analyzed for eight PFAAs using ultra-high-performance liquid chromatography tandem triple quadrupole mass spectrometry. The quantification results showed that the concentrations of particle-bound Σ 8PFAAs ranged from 0.26 to 1.90ngm-3 (mean: 1.44ngm-3). All of the measured PFAAs particle size distributions had a bimodal mode that peaked respectively in accumulation size range (0.4<Dp<2.1μm) and coarse size ranges (Dp>2.1μm), but the width of each distribution somewhat varied by compound. The emission source, molecular weight, and volatility of the PFAAs were important factors influencing the size distribution of particle-bound PFAAs. Of these compounds, PFUnDA presented a strong accumulation in the fine size range (average 75% associated with particles <2.1μm), followed by PFOA (69%) and PFDA (64%). The human risk assessment of PFOS via inhalation was addressed and followed the same pattern as the size distribution, with a 2-fold higher risk for the fine particle fraction compared to the coarse particle fraction at urban sites. Approximately 30.3-82.0% of PFAA deposition (∑PFAA: 72.5%) in the alveolar region was associated with particles <2.1μm, although the contribution of fine particles to the total PFAAs concentration in urban air was only 28-57% (∑8PFAAs: 48%). These results suggested that fine particles are significant contributors to the deposition of PFAAs in the alveolar region of the lung.

Quality Evaluation of Prunellae Spica Based on Simultaneous Determination of Multiple Bioactive Constituents Combined with Grey Relational Analysis

Prunellae Spica (PS) is an important traditional Chinese herbal medicine (TCM) with massive consumption because of its therapeutical and seasoning effects. However, little attention has been paid to simultaneous analyze its bioactive components for quality control of PS based on its different growing habitats and different growth periods. In this study, the quality of PS was evaluated based on simultaneous determination of multiple bioactive components combined with grey relational analysis (GRA). A reliable method based on high-performance liquid chromatography tandem triple quadrupole mass spectrometry (HPLC-QTRAP-MS/MS) was established to simultaneously determine the contents of 21 components in PS, including 9 phenolic acids, 3 coumarins, 8 flavonoids and 1 pentacyclic triterpene. Furthermore, GRA was performed to evaluate the quality of PS samples according to the contents of these 21 components. The results showed that the quality of PS harvested on withering period, cultivated in Anhui was better than that of other PS samples. The proposed method is useful for the overall assessment on the quality of PS, and this study provides valuable information for revealing the dynamic change laws of metabolite accumulation in PS and choosing the most suitable harvesting time and genuine producing area of PS to obtain the best quality.

Bioanalysis of farnesyl pyrophosphate in human plasma by high-performance liquid chromatography coupled to triple quadrupole tandem mass spectrometry and hybrid quadrupole Orbitrap high-resolution mass spectrometry

The isoprenoids farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP) are pivotal intermediates for cholesterol homeostasis and cell signaling in the mevalonate pathway. We developed a sensitive and selective high-performance liquid chromatography tandem triple quadrupole mass spectrometry (LC-QQQ-MS) method for FPP in human plasma without the need for a derivatization process. We optimized the sample preparation procedure to extract FPP and 13C5-FPP (as internal standard) from sample fluids using methanol. Phosphate-buffered saline was used as the surrogate matrix for the preparation of calibration curves and quality control samples. Using an XBridge C18 column (3.5μm, 2.1 × 100-mm ID) with gradient elution composed of 10mmol/L ammonium carbonate/ammonium hydroxide (1000:5, v/v) and acetonitrile/ammonium hydroxide (1000:5, v/v) provided the sharp peaks of FPP and 13C5-FPP in human plasma. The calibration curve ranged from 0.2 to 20ng/mL in human plasma with acceptable intra-day and inter-day precision and accuracy. The sensitivity of this bioanalytical method was sufficient for clinical analysis. The endogenous FPP plasma concentrations in 40 human healthy volunteers ascertained by LC-QQQ-MS and high-performance liquid chromatography tandem hybrid quadrupole Orbitrap high-resolution mass spectrometry (LC-Q-Orbi-MS) were comparable. Furthermore, the endogenous GGPP in human plasma was selectively detected for the first time by LC-Q-Orbi-MS. In conclusion, a sensitive bioanalytical method for FPP in human plasma by means of LC-QQQ-MS and LC-Q-Orbi-MS was developed in this study. Taking into account the versatility of LC-Q-Orbi-MS, the simultaneous detection of FPP and GGPP may be feasible in clinical practice.

Profile of Polyphenol Compounds of Five Muscadine Grapes Cultivated in the United States and in Newly Adapted Locations in China.

Polyphenol compositions and concentrations in skins and seeds of five muscadine grapes (cv. “Noble”, “Alachua”, “Carlos”, “Fry”, and “Granny Val”) cultivated in the United States (Tallahassee-Florida, TA-FL) and South China (Nanning-Guangxi, NN-GX and Pu’er-Yunnan, PE-YN) were investigated, using ultra performance liquid chromatography tandem triple quadrupole time-of-flight mass spectrometry (UPLC Triple TOF MS/MS). Fourteen ellagitannins were newly identified in these muscadine grapes. The grapes grown in NN-GX accumulated higher levels of ellagic acid, methyl brevifolin carboxylate, and ellagic acid glucoside in skins, and penta-O-galloyl-glucose in seeds. In PE-YN, more flavonols were detected in skins, and higher contents of flavan-3-ols, ellagic acid, and methyl gallate were identified in seeds. Abundant seed gallic acid and flavonols were found among the grapes grown in TA-FL. Based on principal component analysis (PCA) of 54 evaluation parameters, various cultivars grown in different locations could be grouped together and vice versa for the same cultivar cultivated in different regions. This is the result of the interaction between genotype and environmental conditions, which apparently influences the polyphenol synthesis and accumulation.

Rapid and simultaneous determination of 22 constituents in Menispermi Rhizoma by ultra-performance liquid chromatography tandem triple quadrupole mass spectrometry

A multi-component-assay quality control method, using UPLC-MS/MS, has been developed for the simultaneous quantification of 22 constituents in Menispermi Rhizoma.

Quality Evaluation of Pseudostellariae Radix Based on Simultaneous Determination of Multiple Bioactive Components Combined with Grey Relational Analysis.

Pseudostellariae Radix (PR) is an important traditional Chinese herbal medicine (TCM) with vast clinical consumption because of its positive effects. However, little attention has been devoted to simultaneous analysis of its bioactive components for quality control of PR based on its different harvesting times, different growing habitats, and different processing methods. In this research, the quality of PR was evaluated based on simultaneous determination of multiple bioactive components combined with grey relational analysis (GRA). A reliable method based on ultra-fast liquid chromatography tandem triple quadrupole mass spectrometry (UFLC-QTRAP-MS/MS) was established to simultaneously determine the contents of 30 components in PR, including two cyclopeptides, 12 nucleosides, and 16 amino acids. Furthermore, grey relational analysis was performed to evaluate the quality of PR samples according to the contents of these 30 components. The results showed that the quality of PR harvested in 6 August 2013, cultivated in Jurong, Jiangsu, and treated by oven drying 60 °C was better than that of other PR samples. The proposed method is useful for the overall assessment on the quality of PR, and this study provides valuable information for revealing the dynamic change laws of metabolite accumulation in PR and choosing the most suitable harvesting time and reasonable processing method of PR to obtain the best quality.

Determination of RH-5849 and indoxacarb in rice straw, rice husk, brown rice and soil using liquid chromatography-tandem triple quadrupole mass spectrometry following extraction with QuEChERS method.

A fast and simple analytical method was developed for the simultaneous determination of RH-5849 and indoxacarb in soil, rice straw, rice husk and brown rice. QuEChERS (quick, easy, cheap, effective, rugged and safe) method was used for extraction, and liquid chromatography with tandem triple quadrupole mass spectrometry was used for quantification. The matrix-matched calibration plots were linear in the range between 25 and 5000 μg/L for soil, rice straw, rice husk and brown rice samples. All determination coefficients (R(2) ) were ≥0.9962. The limits of detection and quantification were 1.5 and 5 μg/kg, respectively. Recoveries at three fortification levels ranged between 79.5 and 97.9% with relative standard deviations <11%. The developed method was validated and applied for the analysis of dissipation study samples. For field experiments, the half-lives of RH-5849 and indoxacarb in rice straw were 11.93 and 5.83 days, respectively. The method was demonstrated to be reliable for the routine monitoring of RH-5849 and indoxacarb in rice samples. Copyright © 2016 John Wiley & Sons, Ltd.

Bioconcentration and metabolism of ketoconazole and effects on multi-biomarkers in crucian carp (Carassius auratus)

The tissue distribution, bioconcentration, metabolism and biological effects of the antifungal medication ketoconazole were investigated in fish, crucian carp (Carassius auratus) were exposed to a series of nominal concentrations (0.2, 2 and 20 μg/L) for 14 days. The ultra-high performance liquid chromatography tandem triple quadrupole mass spectroscopy (UPLC/MS/MS) analysis was used to determine the bioconcentration of ketoconazole and its metabolites in fish. The highest tissue concentration of ketoconazole was observed in the liver with the bioconcentration factor of 257.2, which is lower than the estimated BCF value. The ability of crucian carp to metabolize ketoconazole was confirmed and the results pointed out the existence of seven metabolites likely formed via oxidation of imidazole ring and the metabolic alteration of the piperazine rings. In addition, acetylcholinesterase, 7-ethoxyresorufin O-deethylase, superoxide dismutase and glutathione S-transferase changed significantly after 3, 7 and 14 days of exposure (P < 0.05), which indicated that the accumulation and metabolism of ketoconazole in fish tissues may account for the biological effects.

Urinary bromophenol glucuronide and sulfate conjugates: Potential human exposure molecular markers for polybrominated diphenyl ethers

One possible source of urinary bromophenol (BP) glucuronide and sulfate conjugates in mammalian animal models and humans is polybromodiphenyl ethers (PBDEs), a group of additive flame-retardants found ubiquitously in the environment. In order to study the correlation between levels of PBDEs in human blood plasma and those of the corresponding BP-conjugates in human urine, concentrations of 17 BDE congeners, 22 OH-BDE and 13 MeO-BDE metabolites, and 3 BPs in plasma collected from 100 voluntary donors in Hong Kong were measured by gas chromatograph tandem mass spectrometry (GC–MS). Geometric mean concentration of ΣPBDEs, ΣOH-BDEs, ΣMeO-BDEs and ΣBPs in human plasma were 4.45ngg−1lw, 1.88ngg−1lw, 0.42ngg−1lw and 1.59ngg−1lw respectively. Concentrations of glucuronide and sulfate conjugates of 2,4-dibromophenol (2,4-DBP) and 2,4,6-tribromophenol (2,4,6-TBP) in paired samples of urine were determined by liquid chromatography tandem triple quadrupole mass spectrometry (LC–MS/MS). BP-conjugates were found in all of the parallel urine samples, in the range of 0.08–106.49μgg−1-creatinine. Correlations among plasma concentrations of ΣPBDEs/ΣOH-BDEs/ΣMeO-BDEs/ΣBPs and BP-conjugates in urine were evaluated by multivariate regression and Pearson product correlation analyses. These urinary BP-conjugates were positively correlated with ΣPBDEs in blood plasma, but were either not or negatively correlated with other organobromine compounds in blood plasma. Stronger correlations (Pearson’s r as great as 0.881) were observed between concentrations of BDE congeners having the same number and pattern of bromine substitution on their phenyl rings in blood plasma and their corresponding BP-conjugates in urine.

Quantification of bovine β-casein allergen in baked foodstuffs based on ultra-performance liquid chromatography with tandem mass spectrometry

The quantification of allergens in food including baked food matrices is of great interest. The aim of the present study was to describe a non-immunologic method to quantify bovine β-casein using ultra-performance liquid chromatography tandem triple quadrupole mass spectrometry (UPLC-TQ-MS/MS) in multiple reaction monitoring (MRM) mode. Eight of 10 theoretical peptides from β-casein after tryptic digestion were compared and MRM methods were developed to determine five signature peptides. The peptide VLPVPQK was selected as the signature peptide for bovine β-casein because of the high sensitivity. A stable isotope-labelled internal standard was designed to adjust the instability of sample pre-treatment and ionisation caused by matrix effect. Using the present suspension digestion method, the native and denatured β-casein could be digested to release the signature peptide at the maximum extent. The UPLC-TQ-MS/MS method developed based on a tryptic signature peptide led to a reliable determination of bovine β-casein allergen in baked food matrices at a low quantitation level down to 500 μg kg–1 with a satisfactory accuracy (< 8.9%) and recovery (98.8% ± 2.6% to 106.7% ± 3.0%).

Confirmation and quantification of clenbuterol in horse urine using liquid chromatography tandem mass spectrometry triple quadrupole.

Clenbuterol (CLE) is used in horses as a bronchodilator and for its anabolic steroid-like effects. CLE is a Class 3 drug according to current Association of Racing Commissioners International (ARCI) Uniform Classification Guidelines. The Racing Medication and Testing Consortium recommended a urine CLE threshold of 140 pg/mL after careful scientific review of the results of studies describing the disposition of CLE in the horse and this threshold was adopted by the ARCI. Enzyme-linked immunosorbent assay was previously used to screen samples for CLE in Illinois, but could not detect such low concentrations in urine. Thus, a liquid-liquid extraction of CLE from urine followed by quantification by liquid chromatography-tandem mass spectrometry was developed and validated. Method validation included testing stability, ion suppression and enhancement, precision, accuracy and uncertainty. Intra-, interday and total precision and accuracy were calculated for each control and found to be within the ±15% acceptance range. The Guide to the Expression of Uncertainty in Measurement approach was used to calculate uncertainty, which was 11% at the 95% confidence level. In the past 5 years, only 15 samples were reported as positive for CLE in Illinois. This new method was used in a pilot program to screen and confirm samples received from thoroughbred and harness horses.