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The aim of this study was to develop a method for efficiently extracting eight N-nitrosamines (NAs) from chlorinated drinking water using a solid-phase extraction sorbent. This was achieved by completely drying the sorbent using dry air after passing the water through it and before eluting NAs from it. A 500 mL water sample containing NAs was passed through 2.0 g of Carboxen 572. The sorbent was dried by applying a vacuum (-34 kPa) to the sorbent cartridge for 1 h with a silica gel trap connected to the other end of the cartridge. The NAs were then eluted by passing 15 mL of dichloromethane through the cartridge. The dansyl derivatives of the NAs were analyzed by high-performance liquid chromatography with fluorescence detection using a Microsorb-MV Si column and a mixture of water (40%) and acetonitrile (60%) as stationary and mobile phases, respectively. The coefficients of determination (R2) for five-point linear calibration curves (2-80 ng/L) were 0.9968-0.9997. The relative standard deviations of repeated measurements were mostly less than 5.1%, but were higher for two NAs. The recoveries of all of the NAs when spiked samples were analyzed were > 95.1%, and the estimated method detection limits were 0.5-1.4 ng/L. The method showed much better performance than when the moisture trap was not applied to the cartridge, particularly when the laboratory air had a high level of humidity.
The progress of cartilage decay during joint degeneration is not well monitored with biochemical methods. The role of cathepsin D (CAT-D) in articular cartilage deterioration remains unclear. The aim of this study is to assess the activity of CAT-D and alpha-1 antitrypsin (AAT) in blood in patients with hip or knee osteoarthritis. The activity of CAT-D and AAT in blood serum of 40 women and 21 men with hip or knee osteoarthritis was determined before total joint replacement, on the tenth day after surgery, and once in 54 healthy patients. The preoperative activity of CAT-D in patients with osteoarthritis was lower by 53.6% (11.00 ± 4.54 10-2 nM released tyrosine/mg protein/min, P < 0.001) and after surgery by 55.0% (10.67 ± 4.64 10-2 nM released tyrosine/mg protein/min, P < 0.001) when compared to its activity in healthy patients. There was no significant statistical difference between CAT-D activity before the surgery and its activity on the tenth day after it in the analyzed group (P< 0.496). Simultaneously, the preoperative activity of AAT in the OA (osteoarthritis) patients was by 25.5% (0.93 ± 0.32 mg inhibited trypsin/ml blood serum, P < 0.001) and postoperative was by 44.9% higher (1.26 ± 0.36 mg inhibited trypsin/ml blood serum, P < 0.001) than in healthy patients. The low CAT-D activity in osteoarthritis of big joints is associated with a decrease of cartilage cells during the degenerative process. The higher activity of acute phase protein AAT in OA patients' blood serum confirms the inflammatory component in the osteoarthritis process.
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