The hydrophobic azo dye 6-hexyl-4-(2-thiazolylazo)resorcinol (HTAR, H2L) was studied as part of a system for the centrifuge-less cloud point extraction (CL-CPE) and spectrophotometric determination of traces of cobalt. The extracted 1:2 (Co:HTAR) complex, [CoIII(HL−)(L2−)]0, shows an absorption maximum at 553 nm and contains HTAR in two different acid–base forms. Optimum conditions for its formation and CL-CPE were found as follows: 1 × 10−5 mol L−1 of HTAR, 1.64% of Triton X-114, pH of 7.8, incubation time of 20 min at ca. 50 °C, and cooling time of 30 min at ca. −20 °C. The linear range, limit of detection, and apparent molar absorptivity coefficient were 5.4–189 ng mL−1, 1.64 ng mL−1, and 2.63 × 105 L mol−1 cm−1, respectively. The developed procedure does not use any organic solvents and can be described as simple, cheap, sensitive, convenient, and environmentally friendly. It was successfully applied to the analysis of artificial mixtures and real samples, such as steel, dental alloy, rainwater, ampoules of vitamin B12, and saline solution for intravenous infusion.
Summary Background. Reactive oxygen species (ROS) are produced in the body during normal metabolism by means of enzymes and non-enzymatic chemical reduction of molecular oxygen. In case of prevalence of ROS formation over their elimination, highly reactive free radicals can be accumulated and can cause multiple damages to the biomolecules and cells. Determination of isoprostanes in biological matrices is most often used to register free radical damage and requires selective, sensitive and specific techniques. Methods. This study presents the development and validation of an LC-MS/MS method for the determination of 8-iso-Prostaglandin F2α in human plasma utilising a modified liquid-liquid extraction procedure with phase separation. Results. Modified sample preparation procedure assured higher extraction yield, clear separation of organic layer from plasma water phase and protein precipitates, and better purified product for instrumental analysis. Linearity was validated in the range 0.1 – 5.0 µg/L with R2>0.996; normalised matrix varied between 86.0 and 108.3%, accuracy ranged from 90.4 % to 113.9% and precision both within-runs and between-runs was less than 7%. With a run time of 10 min, a throughput of over 50 samples per working day could be performed. Conclusion. The method meets all the current industrial validation criteria and allows the accurate and precise determination of 8-iso-PGF2α in human plasma at diagnostically significant concentration range.
The ion-associated complex formed between the anionic chelate of Co(II)-4-(2-thiazolylazo)resorcinol (TAR) and the monotetrazolium cation of 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl-2H-tetrazolium chloride (INT) in the liquid-liquid extraction system Co(II)-TAR-INT-H 2 O-CHCl 3 was studied by the spectrophotometric method. The optimum extraction conditions of Co(II) were established and the extraction equilibria were investigated. The equilibrium constants, the recovery factor and some analytical characteristics were calculated. The validity of Beer's law was checked. The molar ratio of the components in the ternary ion-associated complex Co(II)-TAR-INT was determined and the general formula of the complex was suggested. The effect of various foreign ions and reagents on the process of complex formation in the liquid-liquid extraction system was studied.
The complex formed between an anionic chelate of Mo(VI)-3,5-dinitrocatechol (3,5-DNC) with the cation of 3,3'-(3,3'-dimethoxy-4,4'-biphenylene)bis(2,5-diphenyl-2H-tetrazolium chloride) (Blue Tetrazolium Chloride, BTC) in the liquid-liquid extraction system Mo(VI)-3,5-DNC-BTC-H 2 O-CHCl 3 was studied. The optimum conditions for the complex formation and extraction of the ion-associated complex were established by spectrophotometry. The molar ratio of the reagents was determined by independent methods. The validity of Beer's law was checked and some analytical characteristics were calculated. The association process in aqueous phase and the extraction equilibria were investigated and quantitatively characterized. The following key constants of the processes were calculated: association constant, distribution constant, extraction constant and recovery factor. Based on this, a reaction scheme, a general formula and a structure of the complex were suggested.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.