RESUMEN
An improved step-by-step colorimetric method for determination of halides has been developed. The method is based on successive selective oxidation of iodide, bromide and chloride into corresponding free halogens, their extraction by airflow and colorimetric detection with different paper test-strips. This procedure can be performed in a single analyzed solution and possesses high selectivity and good sensitivity due to the extraction step. Three types of paper test-strips were examined: paper modified with tetramethylammonium iodide and starch, paper modified with methyl orange and paper modified with silver triangular nanoplates. Limits of detection for iodide, bromide and chloride are 0.01, 0.02, and 0.04 mg L-1 respectively in case of the last mentioned paper. The method was applied to the analysis of samples having complex matrices, such as various seafood, preserves, bread, and natural waters, showing good accuracy of the analysis with recoveries of 95-105% and relative standard deviations not higher than 6%.
RESUMEN
The article describes a novel approach towards improving selectivity of volatile compounds detection using metal nanoparticles. It is based on combination of sensitive optical detection using convenient nanoparticle-modified paper test strips and dynamic gas extraction improving selectivity to volatile compounds. A simple and inexpensive setup allowing for realization of this combination is described. Analytical prospects of the approach are shown by the example of chlorine determination in highly salted aqueous solutions using silver triangular nanoplates and digital colorimetry. The limit of detection is equal to 0.03mgL-1 and the determination range is 0.1-2mgL-1. This determination can be successfully carried out in solutions containing at least 2·105 greater molar amounts of Na+, K+, Zn2+, Cl-, SO42-, and H2PO4- with no sample pretreatment. The approach seems to be compatible with different types of nanoparticles with respect to detection of various analytes, thus having good opportunities for further development.
