Fast and simple MEKC sweeping method for determination of thiosulfate in urine

Abstract

A new method for determination of thiosulfate in human urine has been developed and validated. Analytical procedure is very simple and consists of only few steps: derivatization of thiosulfate with 2-chloro-1-methylquinolinium tetrafluoroborate, centrifugation of a mixture, separation of so-formed derivative by micellar electrokinetic chromatography with sweeping and UV detection at 375 nm. A fused-silica capillary with an inlet to detector length of 51.5 cm and a total length of 60 cm (75 μm id) was served as a separation column. The separation voltage of 20.5 kV (∼160 mA) and buffer solution consisting of 0.055 mol/L sodium phosphate (pH 8), 25% acetonitrile, and 0.035 mol/L sodium dodecyl sulfate were found to be the most suitable conditions for the effective separation. The limit of quantification for thiosulfate was 4 μmol/L urine. The method was validated and calibrated for thiosulfate in the range of 4-64 μmol/L (R(2) = 0.9997). The relative standard deviation of the points of the calibration curve varied from 1.2 to 4.8% RSD.

Recent progress of sample stacking in capillary electrophoresis (2016–2018)

“…A new method for determination of thiosulfate in human urine was described by Kubalczyk et al. . The analytical procedure consists of derivatization of thiosulfate with 2‐chloro‐1‐methylquinolinium tetrafluoroborate, injection of the non‐micellar sample solution, MEKC sweeping and separation in a BGE containing 55 mM sodium phosphate at pH 8 with 35 mM SDS and 25% ACN.…”

Extraction, preconcentration and spectrophotometric determination of trace levels of thiosulfate in environmental waters

“…When compared to the analytical performance properties of the current VA-CPE method with those of other detection methods in literature such as LODs, linear working range, precision, preconcentration and sensitivity enhancement factors [4,5,13,14,30,32,33], except for IC method based on catalytic effect of thiosulfate onto photometric reaction between I 3 − and N 3 − at pH 5.0 [1] in Table 4, it shows many advantages such as simplicity, minimum solvent consumption, reasonable repeatability/reproducibility, a linear working range of 600-fold, a low detection limit with comparatively little interference with a highly good calibration sensitivity. IC as detection tool has disadvantages such as long analysis time (>15 min), expensive analysis equipment and chemicals, poor recovery due to peak tailing and/or peak overlapping especially at high concentrations, so as to lead to recalibration of instrument.…”

“…In these studies, thiosulfate was separated from other species by ion chromatography (IC) [1], capillary electrophoresis (CE) [4], micellar electrokinetic chromatography (MEKC) [13] and capillary zone electrophoresis (CZE) [14]. A great disadvantage of IC with universal detection techniques such as conductivity and indirect UV is interference by the high concentrations of co-eluting matrix anions such as chloride and sulfate [15].…”

“…In this sense, a separation and preconcentration step is necessary especially for UV-Vis spectrophotometry with low sensitivity, in which the thiosulfate levels of samples are lower than detection limit of spectrophotometry as detection tool. In order to determine low contents of thiosulfate of real samples, the traditional separation and preconcentration procedures such as SPE [17], sweeping, which is based on in-line and online preconcentration of neutral and charge analytes in capillary and/or microchips or which is based on partition of the analytes between pseudo-stationary phase and the surrounding phase what promotes separation of analytes from matrix in MEKC [18,19], solvent extraction [20], electrosorption before detection by cathodic stripping differential pulse voltammetry (CS-DPV) at pH 4.4 [21], electrochemical accumulation on a miniaturized modified mercury drop electrode before detection by cathodic stripping voltammetry (CSV) [22], electrochemical deposition before detection by linear sweeping voltammetry (LSV) in a study, which is based on anodic depolarization reaction between sulfur and the mercury electrode at pH 8.3 [23] as well as column-switching separation/preconcentration before analysis by suppressed IC [24] have been used. But these preconcentration procedures have generally limitations such as time-consuming and cumbersome to perform, utility of columns with a narrow internal diameter limiting the flow rates to a range of 1-10 mL min −1 , so as to large trace-enrichment time for large sample volumes, plugging the cartridge of samples with particulate matter, unsatisfactory enrichment factors, using toxic organic solvents, forming secondary waste for extraction.…”

Novel MEKC method for determination of sodium 2-mercaptoethanesulfonate in human plasma with in-capillary derivatization and UV detection

“…Micellar electrokinetic chromatography (MEKC) in the last few years become in many laboratories routine analytical tool for determination of biologically active compounds [21,[30][31][32]. Despite the huge analytical potential of electromigration techniques, namely quick separation, good resolution, high selectivity and little requirements as regards the size of the sample, they have some important limitations which arise especially when very complex biological samples should be analyzed.…”