Solvent Effects on the 1 H-NMR Chemical Shifts of Imidazolium-Based Ionic Liquids.

The 1 H nuclear magnetic resonance (1 H-NMR) spectrum is a useful tool for characterizing the hydrogen bonding (H-bonding) interactions in ionic liquids (ILs). As the main hydrogen bond (H-bond) donor of imidazolium-based ILs, the chemical shift (δH2 ) of the proton in the 2-position of the imidazolium ring (H2) exhibits significant and complex solvents, concentrations and anions dependence. In the present work, based on the dielectric constants (ϵ) and Kamlet-Taft (KT) parameters of solvents, we identified that the δH2 are dominated by the solvents polarity and the competitive H-bonding interactions between cations and anions or solvents. Besides, the solvents effects on δH2 are understood by the structure of ILs in solvents: 1) In diluted solutions of inoizable solvents, ILs exist as free ions and the cations will form H-bond with solvents, resulting in δH2 being independent with anions but positively correlated with ßS . 2) In diluted solutions of non-ionzable solvents, ILs exist as contact ion-pairs (CIPs) and H2 will form H-bond with anions. Since non-ionizable solvents hardly influence the H-bonding interactions between H2 and anions, the δH2 are not related to ßS but positively correlated with ßIL .

Exposure to metal mixtures and young children's growth and development: A biomonitoring-based study in Eastern China.

Exposure to metal mixtures may affect children's health but the conclusions are controversial. We aimed to investigate the associations of metal mixture exposure with children's physical and behavioral development. 15 metals were detected in the urine samples of 278 preschoolers aged 3-6 years from eastern China. Multiple linear models and restricted cubic splines were used to evaluate dose-response relationships between single metal and children's physical and behavioral development. The Bayesian Kernel Machine Regression (BKMR) models, the weighted quantile sum (WQS) models and Quantile G-Computation were applied to evaluate the joint effects of metal mixtures. The results showed that arsenic (As) was negatively associated with z score of height for age (HAZ) in individual-metal models [ß (95%CI): - 0.22 (-0.38, -0.06), P = 0.006]. Concerning children's behavioral development, multiple-metal models demonstrated a negative association with strontium (Sr) [ß (95%CI): - 0.82 (-1.38, -0.26), P = 0.004], and a positive association with tin (Sn) [ß (95%CI): 0.69 (0.16, 1.21), P = 0.010]. Notably, these associations remained significant or suggestive even after adjustments for multiple tests, sensitivity analyses, and application of different statistical models, including BKMR, WQS, and Quantile G-Computation. Furthermore, the study identified a negative joint effect of the metal mixture on HAZ, as demonstrated by BKMR and Quantile G-Computation models, with As playing an irreplaceable role in this observed impact. In summary, exposure to As appears to have adverse effects on HAZ, while exposure to Sn may hinder children's behavioral development. Conversely, exposure to Sr may have a protective effect on children's behavioral development. Additionally, the combined impact of metal mixtures is implicated in potentially impairing children's physical development, particularly in terms of HAZ.

Polymer solubility in ionic liquids: dominated by hydrogen bonding.

Polymer solubility in ionic liquids (ILs) cannot be predicted by the solubility parameter approach based on the "like dissolves like" principle. According to the Kamlet-Abraham-Taft (KAT) multi-parameter polarity scale, ILs can be categorized on the basis of hydrogen-bond acidity or basicity ones. The experimental observations, that acidic ILs easily dissolve basic polymers and basic ILs dissolve acidic polymers, reflect the complementary nature of hydrogen-bonding interactions. A quantitative hydrogen-bonding analysis is proposed for predicting the solubility by taking the product of ΔαΔß as an indicator of the competition between cross-association and self-association hydrogen bonding (H-bonding), where Δα is the difference of acidity parameters between the polymer and IL, and Δß is the difference of basicity. This solubility criterion has been validated by the solubility data of 19 polymers (11 acidic and 8 basic) in 11 ILs (7 acidic and 4 basic). These principles based on KAT parameters can be applied to other systems dominated by hydrogen bonding.

[Determination of phenoxyacetic herbicides, metabolites of organophosphorus and pyrethroid pesticides in human urine using solid phase extraction coupled with ultra-performance liquid chromatography-tandem mass spectrometry].

Pesticides are widely used in most agricultural areas to protect food crops but adversely affect ecosystems and human beings. Pesticides have attracted great public concern due to their toxic properties and ubiquitous occurrence in the environment. China is one of the largest users and producers of pesticides globally. However, limited data are available on pesticide exposure in humans, which warrants a method for quantification of pesticides in human samples. In the present study, we validated and developed a comprehensive and sensitive method for the quantification of two phenoxyacetic herbicides, two metabolites of organophosphorus pesticides and four metabolites of pyrethroid pesticides in human urine using 96-well plate solid phase extraction (SPE) coupled with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). For this purpose, a systematic optimization of the chromatographic separation conditions and MS/MS parameters was conducted. Six solvents were optimized for the extraction and clean-up of human urine samples. The targeted compounds in the human urine samples were well separated within 16 min in one analytical run. A 1 mL aliquot of human urine sample was mixed with 0.5 mL sodium acetate buffer (0.2 mol/L) and hydrolyzed by ß-glucuronidase enzyme at 37 ℃ overnight. The eight targeted analytes were extracted and cleaned using an Oasis HLB 96-well solid phase plate and eluted with methanol. The separation of the eight target analytes was performed on a UPLC Acquity BEH C18 column (150 mm×2.1 mm, 1.7 µm) with gradient elution using 0.1% (v/v) acetic acid in acetonitrile and 0.1% (v/v) acetic acid in water. The analytes were identified using the multiple reaction monitoring (MRM) mode under negative electrospray ionization (ESI-) and quantified by isotope-labelled analogs. Para-nitrophenol (PNP), 3,5,6-tricholor-2-pyridinol (TCPY) and cis-dichlorovinyl-dimethylcyclopropane carboxylic acid (cis-DCCA) exhibited good linearities ranging from 0.2 to 100 µg/L, and 3-phenoxy benzoic acid (3-PBA), 4-fluoro-3-phenoxy benzoic acid (4F-3PBA), 2,4-dicholorphenoxyacetic acid (2,4-D), trans-dichlorovinyl-dimethylcyclopropane carboxylic acid (trans-DCCA) and 2,4,5-tricholorphenoxyacetic acid (2,4,5-T) showed linearity ranging from 0.1 to 100 µg/L with correlation coefficients all above 0.9993. Method detection limits (MDLs) and method quantification limits (MQLs) of targeted compounds were in the range of 0.02 to 0.07 µg/L and 0.08 to 0.2 µg/L, respectively. The spiked recoveries of target compounds at three levels of 0.5, 5 and 40 µg/L were 91.1% to 110.5%. The inter- and intra-day precisions of targeted analytes were 2.9% to 7.8% and 6.2% to 10%, respectively. This method was applied to the analysis of 214 human urine samples across China. The results showed that all the targeted analytes, except 2,4,5-T, were detected in human urine. The detection rates of TCPY, PNP, 3-PBA, 4F-3PBA, trans-DCCA, cis-DCCA, and 2,4-D were 98.1%, 99.1%, 94.4%, 2.80%, 99.1%, 63.1% and 94.4%, respectively. The median concentration of targeted analytes in a decreasing order were: 2.0 µg/L (TCPY), 1.8 µg/L (PNP), 0.99 µg/L (trans-DCCA), 0.81 µg/L (3-PBA), 0.44 µg/L (cis-DCCA), 0.35 µg/L (2,4-D) and below MDLs (4F-3PBA ). For the first time, we developed a method to extract and purify specific biomarkers of pesticides from human samples based on offline 96-well SPE. This method has the advantages of simple operation, high sensitivity, and high accuracy. Moreover, up to 96 human urine samples were analyzed in one batch. It is suitable for the determination of eight specific pesticides and their metabolites in large sample sizes.

[Determination of 12 typical personal care products in human urine samples by ultra performance liquid chromatography-tandem mass spectrometry].

A rapid and sensitive method based on ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed for the simultaneous determination of 12 typical personal care products (PCPs) in human urine. These PCPs included five paraben preservatives (PBs), five benzophenone UV absorbers (BPs), and two antibacterial agents. Accordingly, 1 mL of the urine sample was mixed with 500 µL of ß-glucuronidase-ammonium acetate buffer solution (enzymatic activities are 500 units/mL) and 75 µL of a mixed internal standard working solution (internal standard contents are 7.5 ng), followed by enzymatic hydrolysis overnight (≥16 h) at 37 ℃ in a water bath. The 12 targeted analytes were enriched and cleaned up using an Oasis HLB solid phase extraction column. Separation was performed on an Acquity BEH C18 column (100 mm×2.1 mm, 1.7 µm) using an acetonitrile-water system as the mobile phase, in negative electrospray ionization (ESI-) multiple reaction monitoring (MRM) mode, for target detection and stable isotope internal standard quantification. The optimal MS conditions were established by optimizing the instrument parameters and comparing two analytical columns (Acquity BEH C18 and Acquity UPLC HSS T3) as well as different types of mobile phases (methanol or acetonitrile as the organic phase) to achieve better chromatographic separation. In order to obtain higher enzymatic and extraction efficiency, different enzymatic conditions, solid phase extraction columns, and elution conditions were investigated. The final results showed that methyl parabens (MeP), benzophenone-3 (BP-3), and triclosan (TCS) showed good linearities in the ranges of 4.00-800, 4.00-800 and 5.00-200 µg/L, respectively, the other targeted compounds showed good linearities in the ranges of 1.00-200 µg/L. The correlation coefficients were all greater than 0.999. The method detection limits (MDLs) were in the range of 0.06-1.09 µg/L, and the method quantification limits (MQLs) ranged from 0.08 to 3.63 µg/L. At three spiked levels, the average recoveries of the 12 targeted analytes ranged from 89.5% to 111.8%. The intra-day and inter-day precisions were 3.7%-8.9% and 2.0%-10.6%, respectively. The results of the matrix effect assessment showed that MeP, ethyl paraben (EtP), and benzophenone-2 (BP-2) exhibited strong matrix effects (26.7%-103.8%); propyl paraben (PrP) exhibited moderate matrix effects (79.2%-112.0%); and the other eight target analytes exhibited weak matrix effects (83.3%-113.8%). The matrix effects of the 12 targeted analytes after correction using the stable isotopic internal standard method ranged from 91.9% to 110.1%. The developed method was successfully applied to the determination of the 12 PCPs in 127 urine samples. Ten typical PCPs were detected, with the overall detection rates ranging from 1.7% to 99.7%, except for benzyl paraben (BzP) and benzophenone-8 (BP-8). The results revealed that the population in this area was widely exposed to PCPs, especially MeP, EtP and PrP; the detection rates and concentrations of these PCPs were found to be very high. Our analytical method is simple and sensitive, and it is expected to be an effective tool for biomonitoring PCPs in human urine samples as part of environmental health studies.