Development and validation of a GC-MS/MS method for the determination of iodoacetic acid in biological samples.

Iodoacetic acid (IAA) is a halogenated disinfection by-product of growing concern due to its high cytotoxicity, genotoxicity, endocrine disruptor effects, and potential carcinogenicity. However, the data on distribution and excretion of IAA after ingestion by mammals are still scarce. Here, we developed a reliable and validated method for detecting IAA in biological specimens (plasma, urine, feces, liver, kidney, and tissues) based on modified QuEChERS sample preparation combined with gas chromatography-tandem triple quadrupole mass spectrometry (GC-MS/MS). The detection method for IAA exhibited satisfactory recovery rates (62.6-108.0%) with low relative standard deviations (RSD < 12.3%) and a low detection limit for all biological matrices ranging from 0.007 to 0.032 ng/g. The study showed that the proposed method was reliable and reproducible for analyzing IAA in biological specimens. It was successfully used to detect IAA levels in biological samples from rats given gavage administration. The results indicated that IAA was found in various tissues and organs, including plasma, thyroid, the liver, the kidney, the spleen, gastrointestinal tract, and others, 6 h after exposure. This study provides the first data on the in vivo distribution in and excretion of IAA by mammals following oral exposure.

Physiologically based pharmacokinetic (PBPK) modeling of BDE-209 following oral exposure in Chinese population.

The wide usage of decabromodiphenyl ether (BDE-209) as additive brominated flame retardant has caused its widespread occurrence in the environment and high exposure risk in humans. Estimating its internal exposure dose and reconstruction of external exposure dose using physiologically based pharmacokinetic (PBPK) modelling approach is a key step in the risk assessment of BDE-209. However, the PBPK model for BDE-209 is currently unavailable. This study has established two oral permeability-limited PBPK models of BDE-209 without enterohepatic recirculation (EHR) (model 1) and with EHR (model 2) for Chinese population. Using the in vitro experiments, the average binding of BDE-209 to human plasma protein (99.64% ± 2.97%) was obtained. Moreover, blood sample analysis and systematic literature review were performed to obtain internal and external exposure data of BDE-209 used for model calibration and validation. The predictions of both models were within 2-fold of the observed, and a longer half-life of serum BDE-209 was observed in model 2 than model 1. Based on the models, a human biomonitoring guidance value (HBM-GV) of 93.61 µg/g lw was derived for BDE-209, and there is no health risk found for Chinese population currently. This study provides new quantitative assessment tools for health risk assessment of BDE-209.

Colorimetric detection uranyl ions based on the enhanced peroxidase-like activity by GO adsorption.

Based on the fact that uranyl ions (UO22+) adsorbed on GO can enhanced the peroxidase-like activity of graphene oxide (GO), a novel colorimetric strategy for visualizing quantitative determination of uranyl ions was established. The peroxidase-like activity of GO-UO22+ nanocomposites was assessed by catalyzing H2O2 oxidation of TMB to produce a distinct color reaction. A good linearity between the UO22+ concentration and absorption at 652 nm was acquired in the range of 5.90 × 10-6 to 9.43 × 10-4 M with a detection limit of 4.70 µM. This strategy was also successfully applied to determination of uranyl ions in environmental water samples.

DNA-AgNCs as a fluorescence turn-off probe for dual functional detection of H2O2 and Fe(II) ions.

A novel fluorescence probe (DNA-AgNCs) was synthesized for dually detecting hydrogen peroxide (H2O2) and ferrous ion (Fe(II)) in water samples. The assay is carried out through a dramatic "turn-off" fluorescence response of AgNCs by hydroxyl radical (OH), which is produced when H2O2 and Fe(II) are present simultaneously. Under the optimal conditions, the degree of fluorescence quenching of the DNA-AgNCs at 525 nm is linearly related to the concentration of H2O2 in the range of 0.3 to 450 pM, and Fe(II) in the range of 0.2 to 6.0 µM. The limit of detection (LOD) of H2O2 and Fe(II) are as low as 99 fM and 60 nM, respectively. Moreover, this method has the advantages of good specificity, high sensitivity, and can be successfully applied for detecting H2O2 and Fe(II) in the real water samples.

Development of a solid phase microextraction-gas chromatography-mass spectrometry method for the determination of pentachlorophenol in human plasma using experimental design.

A new method, headspace solid-phase microextraction (HS-SPME) with in situ derivatization and gas chromatography-mass spectrometry (GC-MS), which was used for the determination of trace amount of pentachlorophenol (PCP) in human plasma was presented. The acetylation derivatization reaction was firstly optimized using a Doehlert design. Then a series of parameters relevant to the headspace SPME procedure, including fiber coating, extraction temperature, extraction time and salt addition, were optimized using a two-level full factorial design expanded further to a central composite design. The validation of method showed that the optimized method had good linearity (R(2)=0.999) within the concentration ranges 0.1-50.0ngml(-1), and was sensitive with the limit of detection of 0.02ngml(-1). Intra- and inter-day precision for pentachlorophenol in human plasma samples were not greater than 11.9% and 12.6%, respectively. The proposed method, to our knowledge, describes the first application of HS-SPME with GC-MS for analysis of PCP in blood plasma sample. Application of the method to real human plasma samples, PCP was successfully detected in some cases at concentration levels 1.2-6.3ngml(-1).