Solution scanometry, a new, simple, fast, available and inexpensive method for the determination of the acidity constant, pKa, of indicators.

A chip was designed for simultaneous extraction of acidic and basic drugs from biological fluids.

In this work, an on-chip electromembrane extraction coupled with the micro solid phase extraction step was developed for extraction, preconcentration, and determination of trace amounts of chromium(vi) in water samples.

In the present research, an on-chip electromembrane extraction coupled with high performance liquid chromatography was developed for monitoring the trace levels of biogenic amines (BAs), including histamine, tryptamine, putrescine, cadaverine and spermidine in food samples. A porous polypropylene sheet membrane impregnated with an organic solvent was placed between the two parts of the chip device to separate the channels. Two platinum electrodes were mounted at the bottom of these channels, which were connected to a power supply, providing the electrical driving force for migration of ionized analytes from the sample solution through the porous sheet membrane into the acceptor phase. BAs were extracted from 2 mL aqueous sample solutions at neutral pH into 50 μL of acidified (HCl 90 mM) acceptor solution. Supported liquid membrane including NPOE containing 10% DEHP was used to ensure efficient extraction. Low voltage of 40 V was applied over the SLMs during extraction time. The influences of fundamental parameters affecting the transport of BAs were optimized. Under the optimized conditions, the relative standard deviations based on four replicate measurements were less than 8.0% and limit of detections were in range of 3.0-8.0 μg L. Finally, the method was successfully applied to determinate BAs in the food samples and satisfactory results (recovery > 95.6) were obtained.

In this work, the magnesium content was determined by the solution scanometric method using titan yellow (TY) as a complexing agent in alkaline media. This method is based on scanning a solution containing the pink-coloured product of the combination of TY and the magnesium hydroxide complex. Hydroxylamine hydrochloride (HA) and starch were utilised as colour stabilizers and protective colloids, respectively. After the cells containing the sample solution were scanned, the colour of each cell was analysed with software written in Visual Basic (VB 6) in terms of the red, green and blue values. The parameters used for optimisation include the reaction time and the concentration of TY, sodium hydroxide, starch and HA. The system had a wide linear range between 0.070 and 30.000 g mL −1 concentrations of magnesium, with a detection limit of 0.058 g mL −1 and a relative standard deviation of 1.90% for the G colour value. In addition, the effects of some foreign species were investigated. The method was successfully applied for the determination of magnesium in almond gum and three water samples.