PubMed · 5038122
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R Böhm, E Hannig. 1972. [Cyclic ketals].. https://pubmed.ncbi.nlm.nih.gov/5038122/
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Two new methods for the determination of dithiocarbamate pesticides in occupational hygiene sampling devices are described. Dithiocarbamate spiked occupational hygiene sampling devices, consisting of glass fibre (GF/A) filters, cotton pads, cotton gloves and disposable overalls, were reduced under acidic conditions and the CS2 evolved as a decomposition product was extracted into isooctane. The isooctane was then analysed using gas chromatography with mass spectrometry, for CS2, which provided a quantitative result for dithiocarbamates. Recoveries obtained were generally within a 70-110% range and reproducibilities better than 15% RSD were typically achieved. The method has been successfully applied to samples collected during occupational exposure surveys. A second method employing automatic thermal desorption-gas chromatography-mass spectrometry (ATD-GC-MS) has also been developed and applied to the direct analysis of GF/A (airborne) samples. The method relies on the thermal degradation of dithiocarbamates to release CS2, which is used to quantify the analytes. Thiram spiked GF/A filters gave an average recovery of 107% with an RSD of 4%. The performance of the two analytical methods were directly compared by analysing sub-portions of GF/A filters collected during a survey to evaluate occupational exposures to thiram during seed treatment operations. Both methods performed well for the analysis of airborne (GF/A) samples and produced results in good agreement. ATD-GC-MS is the preferred method for studies involving GF/A (airborne) samples only. Because of the wider applicability of the isooctane method for other sampling devices, it is the preferred choice when carrying out surveys which require a dermal as well as respirable exposure assessment.
The immobilization of cellulose 3,5-dimethylphenylcarbamate derivatives having a polymerizable vinyl group, i.e., 4-vinylphenylcarbamate or 2-methacyloyloxyethylcarbamate, on silica gel was examined under various conditions. The immobilization was basically conducted through the radical copolymerization of the derivatives with a vinyl monomer. Several factors, such as the vinyl monomer content and the type and amount of the vinyl group of cellulose derivatives, were varied. The introduction of a vinyl group onto the silica surface resulted in a more efficient immobilization of the cellulose phenylcarbamate derivatives on the silica gel. As the content of the vinyl group on the cellulose derivatives was reduced, the immobilization became more difficult, although the obtained phase exhibited higher chiral recognition abilities. These immobilized CSPs could be stably used with the eluent containing 10% chloroform, which cannot be used for the phase prepared by coating the derivatives on silica gel. Some racemates were better resolved on the immobilized CSP by using chloroform as a component of the eluent.
The effect of repaglinide on insulin secretion and oxidative stress was evaluated in type 2 diabetic patients in a randomized, controlled, open-label trial. Forty-six patients were treated for 2 months with repaglinide, added to either diet (n=21) or metformin (n=25). A control group of 29 patients, matched for age, weight and glycaemic control, on either diet (n=13) or metformin (n=16) was also followed-up. Phases of insulin secretion (first-FPIS and second-SPIS) ware studied during IVGTT. Total serum antioxidant capacity and serum superoxide dismutase (SOD) activity were measured to assess oxidative stress. HbA(1c) decreased significantly in the repaglinide-treated group (P=0.01), the difference being significant compared with the control group (P=0.01). FPIS increased significantly after repaglinide (P<0.001). The area under the curve (AUC) for FPIS increased significantly (P<0.001), while the AUC for SPIS and for total insulin secretion did not change. Insulin secretion remained unchanged after 2 months in the control group. There was a significant increase after repaglinide in total serum antioxidant capacity (P<0.05) and serum SOD activity (P<0.0004); the difference compared to the control group being significant (P<0.002). Our results demonstrate the physiological effect of repaglinide on endogenous insulin secretion in a controlled, randomized, open-label study-there is a rise only in FPIS, which is the main beta-cell defect in type 2 diabetes mellitus. This improvement in glycaemic control was accompanied by a beneficial effect on oxidative stress in diabetes mellitus.