Ivana Kosarac

A novel method for the quantitative determination of free and conjugated bisphenol A in human maternal and umbilical cord blood serum using a two-step solid phase extraction and gas chromatography/tandem mass spectrometry

Bisphenol A is widely used as a monomer in the manufacture of polycarbonates and epoxy resins, as an antioxidant in polyvinyl chloride (PVC) plastics and as an inhibitor of end polymerisation in PVC. Several different methods have been used to quantify total BPA in biological specimens. However, quantification of both free and conjugated BPA continues to present challenges. Moreover, there is limited data concerning fetal exposure. Therefore, the objective of this study was to develop a new method for the analysis of both free and conjugated BPA in human maternal and umbilical cord blood serum. For the analysis of free BPA, the method consisted of a liquid-liquid extraction followed by a two-step solid-phase extraction sample cleanup on Florisil and Oasis HLB sorbents, derivatization of the extract using N-methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA) and analysis by gas chromatography/tandem mass spectrometry (GC/EI-MS/MS). To determine the amount of conjugated BPA in serum samples, bisphenol A-d6 β-glucuronide (4-[1-(4-hydroxyphenyl)-1-methylethyl-d6]phenyl β-D-glucopyranosiduronic acid) was added to each sample prior to enzymatic deconjugation. The MDL and LOQ for BPA were 0.026 ng/mL and 0.087 ng/mL, respectively. The observed recoveries ranged between 65% and 88%. The new method was applied to the determination of paired human maternal and umbilical cord blood serum samples. The results demonstrated that total BPA concentrations in human maternal serum at mid-pregnancy and at delivery ranged from <0.026 ng/mL to 10.425 ng/mL (median 0.548 ng/mL, n=12) and <0.026 ng/mL to 3.048 ng/mL (median 1.461 ng/mL), respectively. Results for matching umbilical cord blood serum BPA concentrations were in the range of <0.026-2.569 ng/mL (median 1.823 ng/mL). The concentrations measured in this study agreed well with BPA levels in human serum reported internationally. Only 2 mid-pregnancy serum samples out of 12 contained quantifiable amounts of conjugated BPA, indicating that BPA-glucuronide is not abundant in either human maternal or umbilical cord blood serum.

Umbilical cord blood levels of perfluoroalkyl acids and polybrominated flame retardants

Perfluoroalkyl acids (PFAAs) and polybrominated diphenyl ethers (PBDEs) are persistent organic pollutants representing two classes of environmental contaminants of toxicological concern, especially for infants. Canadian biomonitoring data on these chemicals are limited. The objectives of this study were to measure PFAAs and PBDEs in umbilical cord blood from approximately 100 hospital deliveries in Ottawa (Ontario, Canada) and examine associations with characteristics of the mother and infant. Geometric means were 1.469 ng/mL for perfluorooctanoate (PFOA) (95% confidence interval of 1.292-1.671 ng/mL), 4.443 ng/mL for perfluorooctane sulfonate (PFOS) (95% CI of 3.735-5.285 ng/mL), 0.359 ng/mL for perfluorononanoic acid (PFNA) (95% CI of 0.318-0.404 ng/mL), and 0.579 ng/mL for perfluorohexanesulfonate (PFHxS) (95% CI of 0.473-0.709 ng/mL). The final multiple regression models indicated that lower gravida, term gestational age, smoking during pregnancy and vaginal delivery were significantly associated with higher levels of PFOS. Similarly, a vaginal delivery was significantly associated with higher PFOA, while weak associations were found with lower gravida and birth weight less than 2500 g. Furthermore, higher PFNA concentrations were significantly associated with older mothers, and vaginal delivery, while weakly associated with term gestational age. Elevated PFHxS concentrations were significantly associated with smoking during pregnancy and lower gravida. Similar to reports from other countries, the preponderant PBDE congener measured in the cord blood was PBDE-47. Questions remain on why various studies have reported conflicting results on the association between PFAAs and birth weight.

Quantitative determination of nine urinary metabolites of organophosphate flame retardants using solid phase extraction and ultra performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS).

Over the last few years, the use of organophosphate flame retardants (OPFRs) has been on the rise; however, there are knowledge gaps in both the human health effects of OPFRs and levels of human exposure. Currently, human biomonitoring data on the levels of OPFR metabolites in the Canadian population are still non-existent. Herein we describe a novel method to measure nine urinary OPFR metabolites using solid phase extraction and ultra performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS). The method detection limits were between 0.08 and 0.25ng/mL for target metabolites. The newly developed and validated method was applied to the analysis of 24 urine samples collected in 2010-12 from pregnant Canadian women. The most frequently detected OPFR metabolite in urine of study participants (detection frequency: 97%) was diphenyl phosphate (DPHP), with concentrations ranging between <0.13-25.2ng/mL, followed (75%) by the sum of two metabolites (DoCP: Di-o-cresyl phosphate and DpCP: Di-p- cresyl phosphate) of tricresyl phosphate, with concentrations between <0.13-4.38ng/mL. With the exception of desbutyl-tris-(2-butoxy-ethyl) phosphate which was not detected in any of the samples, all other OPFR metabolites measured were found among study participants with variable detection frequency, suggesting pregnant Canadian women may be exposed to OPFRs.

The impact of production type and region on polychlorinated biphenyl (PCB), polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) concentrations in Canadian chicken egg yolks

Chicken eggs from five different production types (conventional, omega-3 enriched, free range, organic and free run) were collected, when available, from three regions (west, central and east) of Canada to determine persistent organic pollutant (POP) concentrations. Total polychlorinated biphenyl (PCB) concentrations (∑37 congeners) in yolks from the eggs ranged from 0.162 ng g(-1) lipid to 24.8 ng g(-1) lipid (median 1.25 ng g(-1) lipid) while the concentration of the sum of the 6 indicator PCBs ranged from 0.100 ng g(-1) lipid to 9.33 ng g(-1) lipid (median 0.495 ng g(-1) lipid). Total polychlorinated dibenzo-p-dioxin/dibenzofuran (PCDD/F) concentrations ranged from 2.37 pg g(-1) lipid to 382 pg g(-1) lipid (median 9.53 pg g(-1) lipid). The 2005 WHO toxic equivalency (TEQ) ranged from 0.089 pg TEQ(PCDD/F+dioxin-like[DL]-PCB) g(-1) lipid to 12.8 pg TEQ(PCDD/F+DL-PCB) g(-1) lipid (median 0.342 pg TEQ(PCDD/F+DL-PCB) g(-1) lipid). PCB and PCDD/F concentrations were significantly different (p<0.001) in egg yolks from different regions of collection. In contrast to observations in Europe, PCB and PCDD/F concentrations in Canadian egg yolks were not impacted solely by the production type (e.g., conventional, free range, organic, etc.) used to maintain the laying chickens. Additionally, only one Canadian free range yolk from western Canada (12.8 pg TEQ(PCDD/F+DL-PCB) g(-1) lipid) exceeded the European toxic equivalent concentration limits for eggs (5 pg TEQ(PCDD/F+DL-PCB) g(-1) lipid). This differs from observations in Europe where free range/home produced eggs frequently have higher POP concentrations than eggs from other production types. Median PCB dietary intake estimates based on consumption of eggs were less than 10 ng d(-1) while median PCDD/F intakes were less than 45 pg d(-1).

Simultaneous quantification of bisphenol A, alkylphenols and alkylphenol ethoxylates in indoor dust by gas chromatography-tandem mass spectrometry and a comparison between two sampling techniques

A method based on gas chromatography coupled with triple quadrupole mass spectrometry (GC-MS/MS) was chosen over liquid chromatography coupled with triple quadrupole mass spectrometry (LC-MS/MS) for the simultaneous measurement of bisphenol A (BPA), 4-tert-octylphenol (OP), 4-n-nonylphenol (n-NP), 4-nonylphenol (NP), 4-nonylphenol monoethoxylate (NP1EO), and 4-nonylphenol diethoxylate (NP2EO) in indoor dust. The GC-MS/MS-based method demonstrated high sensitivity, with method detection limits (MDLs) ranging from 0.06 to 0.16 μg g−1. Two types of dust samples were collected using two methods: fresh dust (FD) sampling and household vacuum (HD) sampling. Comparisons of FD and HD samples collected from a subset of 44 homes were based on Spearman rank test. Significant correlations were found for the majority of the target analytes (i.e., BPA, NP, NP1EO and NP2EO), suggesting that household vacuum sampling could be used as an alternative to the expensive fresh dust sampling. Target compounds were then analyzed in 260 HD samples collected from randomly selected urban Canadian single family dwellings as part of the Canadian House Dust Study (CHDS). All target compounds were detected with high frequency (>99%); the most predominant compounds were NP, NP1EO, NP2EO and BPA, with median concentrations (range in parenthesis) of 6.84 (1.0–84.2) μg g−1, 2.13 (0.39–20.4) μg g−1, 2.84 (<0.16–28.1) μg g−1, and 1.78 (0.25–24.0) μg g−1, respectively. High detection frequency and widely scattered concentrations of target analytes in this set of 260 HD samples indicate that indoor house dust may constitute one of the major routes for human exposure to these compounds.

Expanding the number of phthalates monitored in house dust

ABSTRACT Phthalates have been used as plasticisers for several decades in various industry and consumer products. A method was developed for the determination of 13 not commonly monitored phthalates in household dust. The method was based on solvent extraction using sonication, sample clean-up by solid phase extraction (SPE), and analysis using isotope dilution gas chromatography-tandem mass spectrometry (GC/MS/MS). The method was applied to the analysis of dust samples collected using two vacuum sampling techniques from 38 urban Canadian homes: a sample of fresh or ‘active’ dust (FD) collected by technicians and a composite sample taken from the household vacuum cleaner (HD). Spearman rank correlations between HD and FD samples were significant for six phthalates with median concentrations above their method detection limits (MDLs), suggesting that the HD samples provide comparable results with FD samples. Seven phthalates were detected and quantified in a Canada-wide set of 126 household dust samples, among which six phthalates were detected at frequencies higher than 87%, with median (range) concentrations of 1.9 (<0.42–240) (μg/g) for diisohexyl phthalate (DIHxP), 3.8 (<0.16–260) (μg/g) for di-n-heptyl phthalate (DHepP), 6.6 (<1.1–1170) (μg/g) for diisooctyl phthalate (DIOP), 1.1 (<0.12–390) (μg/g) for di-n-octyl phthalate (DOP), 6.3 (<0.16–430) (μg/g) for dinonyl phthalate (DNP), and 1.8 (<0.18–850) (μg/g) for di-n-decyl phthalate (DDP). High detection frequencies and widely scattered concentration levels of these phthalates in this preliminary set of 126 samples suggested a high variability in potential exposure to phthalates in Canadian homes. NIST SRM 2585 (organic contaminants in house dust) was also analysed; eight phthalates were detected, with concentrations ranging from 6.0 μg/g for DOP to 79 μg/g for DIHxP. The results from SRM 2585 may contribute to the certification of phthalate concentration values in this SRM.

Challenges Associated with Sample Preparation for the Analysis of PBDEs in Human Serum.

Polybrominated diphenyl ethers (PBDEs) are used as flame retardants in many applications; however, certain PBDE congeners are persistent, bioaccumulative, and toxic to both humans and the environment. PBDEs have been found in human specimens, and a variety of analytical techniques have been used for their determination in biological matrixes. Nevertheless, obtaining a relatively clean analytical blank sample during PBDE analysis is a big challenge because of the ubiquitous nature of these compounds. Thus, the present study was conducted to compare the PBDE background levels associated with the three most commonly used extraction techniques: liquid-liquid extraction (LLE), SPE, and accelerated solvent extraction (ASE). Conventionally used blank matrixes (HPLC grade water, Milli-Q water, and air) were spiked with internal standards and extracted using LLE, SPE, or ASE. The extracts were analyzed by GC/electron ionization-tandem MS. The ASE method achieved the lowest background levels for nearly all the PBDE congeners analyzed, which may be attributed to the stainless steel and closed-vessel nature of the ASE cells.