An environmentally friendly flow-based procedure with photo-induced oxidation for the spectrophotometric determination of chloride in urine and waters

摘要

Chloride determination in urine and natural waters shows clinical and environmental importance because it can be related to human organism dysfunctions and water quality control. It is generally based on argentimetric volumetry or spectrophotometric methods with mercuric salts as reagents. Large amounts of highly toxic wastes then impair the greenness of procedures especially in batch mode. In this work, the use of hazardous chemicals was for the first time avoided in the spectrophotometric determination of chloride. The green procedure was based on a multi-pumping flow system, in which the analyte was on-line photoconverted to chlorine which was spectrophotometrically detected by methyl orange discoloration. The analytical response was linear from 2.0 to 20mgL~(-1) chloride with a detection limit of 0.7mgL~(-1) at the 99.7% confidence level. The coefficient of variation was 1.6% with a sampling rate of 75 determinations per hour. Usual concomitant species did not cause significant interference even in excess in relation to the highest concentration expected in the samples. The results for urine and water samples agreed with those obtained by the reference procedure at the 95% confidence level. The proposed procedure is then a fast, reliable and environmentally friendly alternative for chloride determination.