Comparison of different mass spectrometric approaches coupled to gas chromatography for the analysis of organochlorine pesticides in serum samples

Biomonitoring of organochlorine pesticides and cancer survival: a population-based study

Organochlorine pesticides (OCPs) are endocrine-disrupting chemicals (EDCs) that even at very low levels can cause cancer by increasing the activity of tumor cells and suppressing the immune system. There is also little information on OCPs and survival after diagnosis. The aim of this study was to monitor the concentration of OCPs in the blood serum of cancer patients and its relationship with their socio-demographic characteristics and ultimately that impact on survival time and hazard ratio (HR). This cross-sectional study included 89 diagnosed patients with cancer in Isfahan, Iran. 12 types of OCPs were measured in serum by gas chromatography (7GC) with an electron capture detector and equipped with mass spectrometer (MS). Also, participants' questionnaire was completed to collect information. T-test, ANOVA, and Chi-square tests were used to evaluate the association between serum levels of OCPs and quantitative and qualitative information of patients. Survival analysis was also examined based on Kaplan-Meier method, log-rank test, and Cox model. The mean of total OCPs in patients' serum was calculated to be 1.82 ± 1.36 μg/L. Concentration of 2,4' DDE had a significant relationship with body mass index (BMI) (kg/m²) (P < 0.05). In addition, gender revealed a significant correlation in estimating survival time (P < 0.05). Non-exposure to OCPs showed a positive effect on increasing the life expectancy of patients. Lindane and endosulfan increased the risk of death by 16% and 37%, respectively, with insignificant P value (P > 0.05). The findings of the present study showed adverse effects of OCPs on patients' survival time and increased mortality of HR. Moreover, as the first research conducted in the study area, it is suggested management of environmental, individual and social factors that could be influenced the biological accumulation of OCPs in humans and cause health promotion.

Pesticides monitoring in biological fluids: Mapping the gaps in analytical strategies

Pesticides play a key-role in the development of the agrifood sector allowing controlling pest growth and, thus, improving the production rates. Pesticides chemical stability is responsible of their persistency in environmental matrices leading to bioaccumulation in animal tissues and hazardous several effects on living organisms. The studies regarding long-term effects of pesticides exposure and their toxicity are still limited to few studies focusing on over-exposed populations, but no extensive dataset is currently available. Pesticides biomonitoring relies mainly on chromatographic techniques coupled with mass spectrometry, whose large-scale application is often limited by feasibility constraints (costs, time, etc.). On the contrary, chemical sensors allow rapid, in-situ screening. Several sensors were designed for the detection of pesticides in environmental matrices, but their application in biological fluids needs to be further explored. Aiming at contributing to the implementation of pesticides biomonitoring methods, we mapped the main gaps between screening and chromatographic methods. Our overview focuses on the recent advances (2016-2021) in analytical methods for the determination of commercial pesticides in human biological fluids and provides guidelines for their application.

Multiresidue analysis of 85 persistent organic pollutants in small human serum samples by modified QuEChERS preparation with different ionization sources in mass spectrometry

In this study, a multiresidue analytical method was developed, validated, and applied for quantifying 85 persistent organic pollutants (POPs), including 38 polychlorinated biphenyls (PCBs), 23 polybrominated diphenyl ethers (PBDEs), and 24 organochlorine pesticides (OCPs) from 200 μL of human serum. A modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method was applied to minimize the required sample amount and optimize various conditions including the extraction solvent and the number of extractions. The extraction efficiency was optimized using double extraction with an ethyl acetate/hexane/acetone mixture. Gas chromatography coupled with triple-quadrupole mass spectrometry was used for analysis, and two different ionization sources, electron impact ionization (EI) and atmospheric pressure chemical ionization (APCI), were used to compare their sensitivity. The APCI source employed soft ionization at atmospheric pressure, producing abundant molecular ion formation with minimal fragmentation, in contrast to extensive fragmentation caused by EI. Of the 85 POPs analyzed, 59 target compounds (69.4%) showed lower limits of detection that were two- to fifty-fold lower in APCI than those determined using EI. The developed method was validated for its detection limit (0.5-10 pg/mL for PCBs, 2-20 pg/mL for PBDEs, and 2-40 pg/mL for OCPs), precision (0.8%-34.3% of coefficient of variation), recovery (49.6%-77.1%), matrix effect (46.7%-156.9%), and accuracy (81.2%-113.1% for PCBs, 85.8%-112.2% for PBDEs, and 55.2%-113.9% for OCPs). Its linearity was R² > 0.99 for 84 compounds, and 96% average accuracy (for APCI) was obtained using the National Institute of Standards and Technology (NIST) standard reference materials (NIST 1957 and 1958). These ionization methods were compared by analyzing 25 real human serum samples. The observed species were 1.1-24.6 pg/mL of 28 PCBs, 2.5 pg/mL of BDE-47, and 6.5-195.1 pg/mL of 6 organochlorine pesticides (median concentration for each species), and only 11 compounds were detected with APCI owing to its enhanced sensitivity.

Understanding the relative performance of SCAN, SIM, PMRM and MRM methods for quantifying polycyclic aromatic hydrocarbons in crude oil samples

RATIONALE

Polycyclic aromatic hydrocarbons (PAHs) present in oil spill samples are analyzed by gas chromatography/mass spectrometry (GC/MS) and gas chromatography/tandem mass spectrometry (GC/MS/MS) using four different methods: (1) full scan (SCAN), (2) selected ion monitoring (SIM), (3) multiple reaction monitoring (MRM), and (4) pseudo multiple reaction monitoring (PMRM). This study quantifies the relative performance of these methods.

METHODS

Novel experiments were designed to measure the signal-to-noise (S/N) ratios of all four methods. This was accomplished by spiking the crude oil with five deuterated PAHs (dPAHs) in two distinct ways: (1) varying the background noise by changing crude oil concentrations before spiking the samples with 1 ng/mL of dPAHs, and (2) varying the signal by spiking dPAHs concentrations of 0.5 and 5 ng/mL into a crude oil sample.

RESULTS

The MRM method is the most selective and sensitive of the four methods. It also provides the lowest limit of detection (LOD) and limit of quantitation (LOQ). MRM is the optimal approach for quantifying PAHs in complex petroleum samples containing high levels of background noise. Also, our data show that the PAHs in complex oil spill samples can be quantified by MRM without using any complicated sample preparation steps.

CONCLUSIONS

Based on our experimental data, the relative performance of the four methods used for quantifying PAHs in crude oil samples can be ranked as MRM > PMRM > SIM > SCAN.

Association of in utero hexachlorocyclohexane exposure with gestational age

As endocrine disrupting chemicals, hexachlorocyclohexane (HCH) isomers were reported to impair the intrauterine growth. Although the findings of HCHs with preterm birth were well established, the associations with gestational age were limited. In the present study, we examined whether exposure to HCHs would influence gestational age. The study population included 1028 pregnant women and their offspring who were born in 2014-2015 from a birth cohort in Wuhan, China. Associations of the cord serum HCH levels with gestational age were estimated using generalized linear models. We found higher HCH levels in pregnant women, who were elder, had higher body mass index (BMI) before pregnancy, received higher education, or were exposed to smoking passively. For term birth, the 3rd tertiles of α-HCH and γ-HCH were significantly associated with shorter gestational age [crude β = -1.017, confidence interval (CI): - 2.017, - 0.018 for α-HCH, crude β = -1.068, CI: - 2.067, - 0.070 for γ-HCH], and relationships were similar after adjusted by covariates. Stratified analysis showed positive associations between α-HCH and gestational age for mothers younger than 25 years old (adjusted β = 0.610, CI: 0.061, 1.158), while showing negative relationships for mothers elder than 35 years old (adjusted β = -1.365, CI: -2.414, -0.317). In summary, our results indicated cord serum levels of HCHs were associated with gestational age at birth.

Evaluation of gas chromatography-atmospheric pressure chemical ionization tandem mass spectrometry as an alternative to gas chromatography tandem mass spectrometry for the determination of polychlorinated biphenyls and polybrominated diphenyl ethers

A method for the analysis of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in serum was developed using gas chromatography coupled to tandem mass spectrometry with atmospheric pressure chemical ionization (GC-APCI-MS/MS). The ionization and fragmentation performance of APCI were evaluated and compared with those of electron ionization (EI). In contrast to extensive fragmentation caused by EI with high energy, soft ionization achieved by APCI produced mass spectra dominated by molecular ions from the first stage of MS analysis. Better sensitivity and selectivity achieved by the GC-APCI-MS/MS method allowed to analyze serum samples with a low volume (100 μL). The limits of detection (LODs) ranged from 0.067 to 14 pg/mL for the analysis in serum samples. The developed method was evaluated at three spiking levels (0.05, 0.5 and 5 ng/mL for PCBs), showing good recoveries and repeatability. The recoveries ranged from 74.0% to 130.5%, and the relative standard deviations (RSDs) were less than 20%, for all analytes. The determination of PCBs and PBDEs in the human serum samples by GC-APCI-MS/MS was compared with gas chromatography-tandem mass spectrometry with EI (GC-EI-MS/MS). BDE-99 and BDE-100 were successfully quantified by GC-APCI-MS/MS, while these two PBDE congeners were not detected by GC-EI-MS/MS. The GC-APCI-MS/MS method had a clear advantage when analyzing compounds at low levels.

Association of prenatal exposure to organochlorine pesticides and birth size

There has been substantial evidence showing the adverse effects of organochlorine pesticide (OCP) exposure on human, but studies focused on the prenatal exposure effects at low OCP levels on infant birth size were scarce and controversial. In this study, cord serum samples were collected at the delivery from 1028 pairs of mothers and newborns in Wuhan, China and investigated the associations of prenatal exposure to OCPs and birth size. The prenatal exposure of hexachlorocyclohexane isomers (HCHs), p,p'-dichlorodiphenyltrichloroethane (p,p'-DDT) and its metabolites were analyzed. The associations between birth size and prenatal OCP exposure were examined by multiple linear regressions. A sex-specific relationship between the OCP exposure and birth size was observed. β-HCH was negatively associated with birth weight and ponderal index for boys [adjusted β = -28.61; 95% confidence interval (CI): -54.84, -4.37 and adjusted β = -0.17; 95% CI: -0.32, -0.01, respectively], whilst no significant associations with prenatal exposure of OCPs were found among girls. The inverse association of prenatal exposure to low levels of β-HCH was shown sex-specific difference, which was only observed significantly in boys. The findings strengthened the evidence that the fetal development was influenced by prenatal exposure to certain OCPs and the effects might be different in the newborn sex.

Concentrations of organochlorine pesticides in cord serum of newborns in Wuhan, China

Organochlorine pesticides (OCPs) had been widely used in China before they were banned decades ago due to the concern of the toxicology to human. Previous reports showed that OCPs were still often detectable in human bodies. However, there is limited study concerning the body burden of OCPs in infants and fetus in China. In this study, the prenatal exposure to OCPs was evaluated by measuring OCPs in cord serum. A total of 1046 cord serum samples were collected in Wuhan during 2014 and 2015, and analyzed for the concentrations of hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs), dichlorodiphenyldichloroethanes (DDDs) and dichlorodiphenyldichloroethylenes (DDEs) by using gas chromatography-tandem mass spectrometry (GC-MS/MS). The median levels of ∑HCHs and ∑DDTs were 10.1 ng/g lipid (with the range from <LOD to 1910 ng/g lipid) and 35.5 ng/g lipid (with the range from 0.18 to 11,100 ng/g lipid), respectively. β-HCH and p,p'-DDE were found to be the major OCPs presenting in the cord serum samples. A minor positive association between the serum levels of α-HCH and β-HCH was observed, and the concentrations of o,p'- and p,p'-DDT isomers were found positively associated. The OCP exposure levels obtained in this study were comparable to those data from other areas in China and much lower than some of highly polluted countries. The prenatal exposure to OCPs would be of concern since fetuses were more vulnerable than adults and the cord serum is an accurate non-invasive matrix for monitoring of prenatal exposure.