On-line lab-in-syringe cloud point extraction for the spectrophotometric determination of antimony

Abstract

Most of the procedures for antimony determination require time-consuming sample preparation (e.g. liquid–liquid extraction with organic solvents), which are harmful to the environment. Because of the high antimony toxicity, a rapid, sensitive and greener procedure for its determination becomes necessary. The goal of this work was to develop an analytical procedure exploiting for the first time the cloud point extraction on a lab-in-syringe flow system aiming at the spectrophotometric determination of antimony. The procedure was based on formation of an ion-pair between the antimony–iodide complex and H+ followed by extraction with Triton X-114. The factorial design showed that the concentrations of ascorbic acid, H2SO4 and Triton X-114, as well as second and third order interactions were significant at the 95% confidence level. A Box–Behnken design was applied to obtain the response surfaces and to identify the critical values. System is robust at the 95% confidence level. A linear response was observed from 5 to 50µgL−1, described by the equation A=0.137+0.050CSb (r=0.998). The detection limit (99.7% confidence level), the coefficient of variation (n=5; 15µgL−1) and the sampling rate was estimated at 1.8µgL−1, 1.6% and 16h−1, respectively. The procedure allows quantification of antimony in the concentrations established by environmental legislation (6µgL−1) and it was successfully applied to the determination of antimony in freshwater samples and antileishmanial drugs, yielding results in agreement with those obtained by HGFAAS at the 95% confidence level.