Mass spectrometry in structural and stereochemical problems—CCXXIII:ortho interactions of nitro groups

The mass spectra of C¹³ labeled o- nitrobenzoic acid and o-nitrobenzaldehyde were studied. Earlier proposed fragmentations involving group migration to a charge-carrying vacant ortho position were verified. A completely unexpected interaction in o- nitroanisole was uncovered by O¹⁸labeling.     

Determination of trace levels of dinitrophenolic compounds in environmental water samples using hollow fiber supported liquid membrane extraction and high performance liquid chromatography

A hollow fiber supported liquid membrane extraction method for the liquid chromatographic determination of dinitrophenolic compounds at ppt levels has been developed. Different variables affecting the extraction process, such as extraction time, shaking speed, acceptor pH, acceptor buffer concentration, salt content and humic acids have been studied. Enrichment factors up to 7000 times were obtained. Validation of the method included calibration experiments and studies of the linearity of the responses in different matrices. Good linearity was obtained in the environmental matrices evaluated. Detection limits range from 6.0 to 8.0 ng/L, and the relative standard deviations do not exceed 7% in terms of repeatability.     

A simple, sensitive, and rapid method for the determination of cotinine in urine by high-performance liquid chromatography with UV detection

Cotinine levels in biological fluids are a reliable indicator of the presence of nicotine. In this paper, a simple and sensitive high-performance liquid chromatography (HPLC) procedure for the determination of cotinine in urine following liquid-liquid extraction with dichloromethane in an alkaline medium is described. Calibration curves show linearity over the 50 to 3000 ng/mL range with low intra- and interday variability as well as good selectivity and specificity. No solid-phase extraction is performed because the liquid dichloromethane extraction step yields excellent results. This method is a good alternative for routine analysis of urinary cotinine in laboratories where gas chromatography or HPLC-mass spectrometry is not available.     

Mass spectrometry in structural and stereochemical problems: CCXXXVI—corrected electron-impact-induced migratory aptitudes in aryl phenyl carbonates

Corrected relative migratory aptitudes for aryl groups in the electron-impact-induced rearrangement of aryl phenyl carbonates have been determined.     

Polyaniline-ZnO−NiO Nanocomposite Based Non-enzymatic Electrochemical Sensor for Malathion Detection

An electrochemical sensor based on polyaniline-ZnO−NiO (PANI-ZnO−NiO) nanocomposite was developed for the non-enzymatic detection of malathion. The structure, surface morphology, and optical properties of the as-prepared nanocomposite were studied by XRD, FTIR, SEM, and UV-Vis spectroscopy. The electrochemical behavior of the nanocomposite based sensor was first evaluated through cyclic voltammetry (CV). Under optimum conditions, differential pulse voltammetry (DPV) was further utilized for malathion detection, which proved the PANI-ZnO−NiO/GCE electrode as an effective electrochemical sensor. The developed electrochemical sensor showed a low detection limit of 1.0×10⁻⁸ M with a wider linear range of 10 to 70 nM for malathion.     

A novel equilibrium extraction technique employing hollow fibre liquid phase microextraction for trace enrichment of freely dissolved organophosphorus pesticides in environmental waters

A new design of equilibrium hollow fibre liquid phase microextraction (HF-LPME) was developed for the determination of three freely dissolved organophosphorus pesticides (OPPs), i.e. diazinon (O,O-diethyl-O-2-isopropyl-4-methyl-6-pyrimidyl thiophosphate), chlorpyrifos (O,O-diethyl-O-[3,5,6-trichloro-2-pyridyl] phosphorothioate), and fenthion (O,O-dimethyl-O-4-methylthio-m-tolyl phosphorothioate) as model compounds. In this new design a 1.2–1.4 cm length of a hollow fibre (HF), inserted to the end of 20 cm copper wire and impregnated with organic solvent, was used to extract the freely dissolved concentration of OPPs in various water samples. The limits of detection (LOD) in reagent water using gas chromatography-mass spectrometry in the selected ion monitoring (SIM) mode was in the range of 15–80 ng L^?1. The relative standard deviations of the analysis (inter- and intra-day) were 8.7–30%. The method was applied to the extraction of spiked lake and ground water samples. The ground water sample was spiked at 0.1 and 0.2 µg L^?1 concentrations of the analytes under study and the average extraction efficiency at the two concentrations was below 1% showing the non-depletive nature of the extraction, meaning that the freely dissolved concentrations are measured as opposed to total concentrations. Good linearity was obtained for all of the analytes in both reagent water and lake water samples with correlation coefficients, R ², ranging from 0.991 to 0.996, in the concentration ranges of 25–400 ng L^?1. The method was found to be very simple and inexpensive, with the possibility of running hundreds of samples in parallel with very minimal expenses for the determination of freely dissolved OPPs.     

A Novel Rapid MALDI-TOF-MS-Based Method for Measuring Urinary Globotriaosylceramide in Fabry Patients

Fabry disease is an X-linked lysosomal storage disorder caused by deficiency of α-galactosidase A, resulting in the accumulation of glycosphingolipids in various organs. Globotriaosylceramide (Gb3) and its isoforms and analogues have been identified and quantified as biomarkers of disease severity and treatment efficacy. The current study aimed to establish rapid methods for urinary Gb3 extraction and quantitation. Urine samples from 15 Fabry patients and 21 healthy control subjects were processed to extract Gb3 by mixing equal volumes of urine, methanol containing an internal standard, and chloroform followed by sonication and centrifugation. Thereafter, the lower phase was analyzed by MALDI-TOF MS and the relative peak areas of the internal standard and four major species of Gb3 determined. The results showed high reproducibility with intra- and inter-assay coefficients variation of 9.9% and 13.7%, respectively. The limit of detection was 0.15 ng/μL and the limit of quantitation was 0.30 ng/μL. Total urinary Gb3 levels in both genders of classic Fabry patients were significantly higher than in healthy controls (p < 0.0001). Gb3 levels in Fabry males were higher than in Fabry females (p = 0.08). We have established a novel assay for urinary total Gb3 that takes less than 15 min from start to finish.

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An automatic field sampler utilising supported liquid membrane (SLM) for on-site extraction of s-triazine herbicides and degradation products: applied to an agricultural region of Ethiopia

A portable and time-integrating field sampler based on the supported liquid membrane (SLM) extraction technique was constructed. Using two programmable syringe pumps and one programmable valve, the sampler could carry out automatic unattended extraction for up to seven extracts, combining the steps of sampling, trace enrichment and clean-up. The sampler was applied to the extraction of four s-triazine herbicides (atrazine, cyanazine, prometryn and terbutryn) and six major degradation products of s-triazines, including three dealkylated products (deethyl deisopropyl atrazine (DDA), deisopropyl atrazine DIA and deethyl atrazine (DEA)) and three hydroxylated products (hydroxy atrazine (ATOH), hydroxy propazine (PROH) and hydroxy terbutylazine (TZOH)). The donor solution was obtained by mixing sample and buffer, consisting of 1?M phosphate buffer at pH 7.0 and 1.7?M NaCl, in the ratio of 19?:?1 (v/v). Extraction was performed by continuously pumping 10?mL portions of donor along the SLM until 3?L of sample had been extracted. The SLM consisted of di-n-hexylether and the acceptor was 1?M HCl. After extract collection, extracts were neutralised with NaOH and buffered with phosphate. Extracts were analysed with HPLC, using a gradient elution consisting of 3.5?mM phosphate and acetonitrile and UV-detection at 220?nm. Enrichment factors in reagent water ranged from 1.3 (for DIA) to 2739 (for terbutryn). The developed field sampler was tested by carrying out 24-h time-weighted on-site extraction of the ten s-triazine target compounds in Hawassa Lake and its tributary river, located in the agricultural region of the Southern Rift Valley of Ethiopia. Atrazine, cyanazine and terbutryn were generally below the method detection limit, while prometryn was frequently found. Overall, s-triazines were not persistent in the studied environment and degradation products of s-triazines were found in higher concentrations than the parent herbicides in both the river and the lake.