Fast and sensitive method to determine parabens by capillary electrophoresis using automatic reverse electrode polarity stacking mode: application to hair samples

A meta-analysis highlighting the increasing relevance of the hair matrix in exposure assessment to organic pollutants

Owing to a wide range of advantages, such as stability, non-invasiveness, and ease of sampling, hair has been used progressively for comprehensive biomonitoring of organic pollutants for the last three decades. This has led to the development of new analytical and multi-class analysis methods for the assessment of a broad range of organic pollutants in various population groups, ranging from small-scale studies to advanced studies with a large number of participants based on different exposure settings. This meta-analysis summarizes the existing literature on the assessment of organic pollutants in hair in terms of residue levels, the correlation of hair residue levels with those of other biological matrices and socio-demographic factors, the reliability of hair versus other biomatrices for exposure assessment, the use of segmental hair analysis for chronic exposure evaluation and the effect of external contamination on hair residue levels. Significantly high concentrations of organic pollutants such as pesticides, flame retardants, polychlorinated biphenyls and polycyclic aromatic hydrocarbon were reported in human hair samples from different regions and under different exposure settings. Similarly, high concentrations of pesticides (from agricultural activities), flame retardants (E-waste dismantling activities), dioxins and furans were observed in various occupational settings. Moreover, significant correlations (p < 0.05) for hair and blood concentrations were observed in majority of studies featuring pesticides and flame retardants. While among sociodemographic factors, gender and age significantly affected the hair concentrations in females and children in general exposure settings, whereas adult workers in occupational settings. Furthermore, the assessment of the hair burden of persistent organic pollutants in domestic and wild animals showed high concentrations for pesticides such as HCHs and DDTs whereas the laboratory-based studies using animals demonstrated strong correlations between exposure dose, exposure duration, and measured organic pollutant levels, mainly for chlorpyrifos, diazinon, terbuthylazine, aldrin, dieldrin and pyrethroid metabolites. Considering the critical analysis of the results obtained from literature review, hair is regarded as a reliable matrix for organic pollutant assessment; however, some limitations, as discussed in this review, need to be overcome to reinforce the status of hair as a suitable matrix for exposure assessment.

Exposure estimates of parabens from personal care products compared with biomonitoring data in human hair from Northeast China

Parabens (PBs), a class of endocrine-disrupting chemicals (EDCs), are extensively used as additives in personal care products (PCPs); however, distinguishing between endogenous and exogenous contamination from PCPs in hair remains a challenge. We conducted a comprehensive analysis of the levels, distribution patterns, impact factors, and sources of PBs in 119 human hair samples collected from Changchun, northeast China. The detection rates of methylparaben (MeP), propylparaben (PrP), and ethylparaben (EtP) in hair samples were found to be 100%. The concentration of PBs in hair followed the order of MeP (57.48 ng/g) > PrP (46.40 ng/g) > EtP (6.80 ng/g). The concentration of PrP in female hair was significantly higher (65.38 ng/g) than that observed in male hair (7.82 ng/g) (p < 0.05). The levels of excretion rates of MeP (ERMeP) and excretion rates of PrP (ERPrP) in the hair-dying samples (ERMeP: 17.89 ng/day; ERPrP: 14.15 ng/day) were found to be 2.52 and 2.40 times higher, respectively, compared to the non-hair-dying samples (ERMeP: 7.09 ng/day; ERPrP: 6.05 ng/day). However, the system exposure dosage (SED) results revealed that although hair dyes exhibited higher PBs, human exposure was found to be lower than certain PCPs. The results of the correlation analysis revealed that toner, face cream, body lotion, and hair conditioner were identified as the primary sources of PBs in male hair. Furthermore, the human exposure resulting from the utilization of female hair dye and serum exhibited a positive correlation with hair ERMeP and ERPrP levels, indicating in the screening of samples, excluding hair samples using hair dye and haircare essential oil can effectively avoid the interference caused by exogenous contamination from PCPs.

Determination of contamination levels for multiple endocrine disruptors in hair from a non-occupationally exposed population living in Liege (Belgium)

Today, the interest in hair as alternative matrix for human biomonitoring of environmental pollutants has increased, but available data on chemical levels in hair remain scarce. In this study, the measurement of 2 bisphenols (A and S), 3 parabens (methyl-, ethyl- and propylparabens) and 8 perfluroralkyl compounds (PFCs) namely perfluoroctanesulfonate (PFOS), perfluorohexanesulfonate (PFHxS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluroroheptanoic acid (PFHpA), perfluoropentanoic acid (PFPeA) and perfluorohexanoic acid (PFHxA) was carried out, using a thoroughly validated UPLC-MS/MS method, in the hair from 114 adults living in Liege (Belgium) and surrounding areas. The most frequently quantified compounds in the population were: bisphenol S (97.4%, median = 31.9 pg·mg^-1), methylparaben (94.7%, median = 28.9 pg·mg^-1), bisphenol A (93.9%, median = 46.6 pg·mg^-1), ethylparaben (66.7%, median = 5.2 pg·mg^-1), propylparaben (54.8%, median = 16.4 pg·mg^-1) and PFOA (46.4%, median < 0.2 pg·mg^-1). The other PFCs were detected only in few samples although current exposure of the Belgian population to PFCs was previously demonstrated using blood analyses. Nonparametric statistical analyses were performed to evaluate the influence of gender, hair treatments and hair length, but no significant difference was observed. Only age was positively correlated with the propylparaben contamination. Although blood seems to remain more suitable for PFCs exposure assessment, the results of this study suggest that hair can be an appropriate matrix for biomonitoring of organic pollutants such as parabens or bisphenols.

Exposure assessment to parabens, bisphenol A and perfluoroalkyl compounds in children, women and men by hair analysis

Population is continuously exposed to endocrine disrupting compounds present in everyday products such as parabens, bisphenol A (BPA), and perfluoroalkyl compounds (PFCs). The aims of this study were, first, to evaluate human exposure to three parabens (methylparaben (MeP), ethylparaben (EtP) and propylparaben (PrP)), BPA and six PFCs (perfluorobutanoic acid, perfluoropentanoic acid, perfluorohexanoic acid, perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS)) through the analysis of hair samples from children, women and men and, then, to evaluate possible relationships between pollutant concentration in hair and age, gender, smoking and dyeing habits or hair colour. Hair samples were collected from 42 volunteers from Seville (Spain) (10 children, 16 women and 16 men). Six of the monitored pollutants (MeP, EtP, PrP, BPA, PFHpA and PFOS) were detected in at least 76% of the samples analysed. The highest concentrations and frequency of detection (100% of the samples) corresponded to MeP and PrP (up to 14,187 and 9009 ng/g, respectively). BPA was found in 83% of the samples at concentrations in the range from 24 to 1427 ng/g whereas PFCs were detected at concentrations in the range from 0.6 to 15.5 ng/g, being PFHpA and PFOS the ones most frequently detected (86% and 76%, respectively). Concentrations of BPA and parabens in adults were statistically higher than those in children. The results of this study reveal the suitability of hair for biomonitoring endocrine disrupting compounds of high concern (PFCs, parabens and BPA) to which population is internally or/and externally but continuously exposed.

A New Sensor for Methyl Paraben Using an Electrode Made of a Cellulose Nanocrystal-Reduced Graphene Oxide Nanocomposite

A new cellulose nanocrystal-reduced graphene oxide (CNC-rGO) nanocomposite was successfully used for mediatorless electrochemical sensing of methyl paraben (MP). Fourier-transform infrared spectroscopy (FTIR) and field-emission scanning electron microscopy (FESEM) studies confirmed the formation of the CNC-rGO nanocomposite. Cyclic voltammetry (CV) studies of the nanocomposite showed quasi-reversible redox behavior. Differential pulse voltammetry (DPV) was employed for the sensor optimization. Under optimized conditions, the sensor demonstrated a linear calibration curve in the range of 2 × 10^-4-9 × 10^-4 M with a limit of detection (LOD) of 1 × 10^-4 M. The MP sensor showed good reproducibility with a relative standard deviation (RSD) of about 8.20%. The sensor also exhibited good stability and repeatability toward MP determinations. Analysis of MP in cream samples showed recovery percentages between 83% and 106%. Advantages of this sensor are the possibility for the determination of higher concentrations of MP when compared with most other reported sensors for MP. The CNC-rGO nanocomposite-based sensor also depicted good reproducibility and reusability compared to the rGO-based sensor. Furthermore, the CNC-rGO nanocomposite sensor showed good selectivity toward MP with little interference from easily oxidizable species such as ascorbic acid.

Development of a liquid chromatography/tandem mass spectrometry method for monitoring of long-term exposure to parabens

RATIONALE

Parabens, the alkyl esters of 4-hydroxybenzoic acid, are a family of compounds widely used as preservatives in cosmetic products, including for children, and some are permitted in foods. Parabens are known to be weak endocrine disruptors because they interfere with the function of endogenous hormones through binding to estrogen receptors. Therefore, the levels of parabens in biological samples indicate endocrine-disruptive exposure. In particular, hair samples can provide information on accumulated exposure to parabens.

METHODS

For monitoring of long-term exposure to parabens, an improved analytical method for rapid and direct determination in hair sample was developed involving ultra-performance liquid chromatography-tandem mass spectrometry using on-line extraction. Five parabens (methyl-, ethyl-, propyl-, butyl- and benzylparaben) were separated within 10 min after incubation with 1 N HCl. Parabens were separated using a Waters BEH C₁₈ column (2.1 mm × 100 mm, 1.7 μm) and a mobile phase consisting of 10 mM ammonium acetate in water and acetonitrile with a gradient program at a flow rate of 300 μL/min. The analysis of the separated parabens was monitored with electrospray negative ionization tandem mass spectrometry.

RESULTS

The linearity of the method was demonstrated by r²  ≥ 0.994. The limits of detection as defined by a signal-to-noise ratio of 3 were 1-5 ng/g. The mean concentration of the five parabens in hair of human subjects was measured to be 55.6 ± 24.3 to 136.9 ± 48.5 ng/g.

CONCLUSIONS

The levels of parabens in hair samples may play an important role in understanding probable endocrine-disruptive exposure, and the described method could be used to evaluate and monitor long-term exposure to parabens as endocrine disruptors.

Biomonitoring of 21 endocrine disrupting chemicals in human hair samples using ultra-high performance liquid chromatography-tandem mass spectrometry

Rapid industrial growth has increased human exposure to a large variety of chemicals with adverse health effects. These industrial chemicals are usually present in the environment, foods, beverages, clothes and personal care products. Among these compounds, endocrine disrupting chemicals (EDCs) have raised concern over the last years. In the present work, the determination of 21 EDCs in human hair samples is proposed. An analytical method based on the digestion of the samples with a mixture of acetic acid/methanol (20:80, v/v) followed by a solid-liquid microextraction and analysis by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was developed and validated. The most influential parameters affecting the extraction method were optimized. The method was validated using matrix-matched calibration and recovery assays. Limits of detection ranged from 0.2 to 4 ng g^-1, limits of quantification from 0.5 to 12 ng g^-1, and inter- and intra-day variability was under 15% in all cases. Recovery rates for spiked samples ranged from 92.1 to 113.8%. The method was applied for the determination of the selected compounds in human hair. Samples were collected weekly from six randomly selected volunteers (three men and three women) over a three-month period. All the analyzed samples tested positive for at least one of the analyzed compounds.

Recent progress of sample stacking in capillary electrophoresis (2014-2016)

The term "sample stacking" comprises a relatively broad spectrum of techniques that already form an almost inherent part of the methodology of CZE. Their principles are different but the effect is the same: concentration of a diluted analyte into a narrow zone and considerable increase of the method sensitivity. This review brings a survey of papers on electrophoretic sample stacking published approximately since the second quarter of 2014 till the first quarter of 2016. It is organized according to the principles of the stacking methods and includes chapters aimed at the concentration adjustment principle (Kohlrausch stacking), techniques based on pH changes, micellar methods, and other stacking techniques. Not reviewed are papers on transient ITP that are covered by another review in this issue.

Current trends in sample preparation for cosmetic analysis

The widespread applications of cosmetics in modern life make their analysis particularly important from a safety point of view. There is a wide variety of restricted ingredients and prohibited substances that primarily influence the safety of cosmetics. Sample preparation for cosmetic analysis is a crucial step as the complex matrices may seriously interfere with the determination of target analytes. In this review, some new developments (2010-2016) in sample preparation techniques for cosmetic analysis, including liquid-phase microextraction, solid-phase microextraction, matrix solid-phase dispersion, pressurized liquid extraction, cloud point extraction, ultrasound-assisted extraction, and microwave digestion, are presented. Furthermore, the research and progress in sample preparation techniques and their applications in the separation and purification of allowed ingredients and prohibited substances are reviewed.