DETERMINATION OF HEXAVALENT CHROMIUM IN INDUSTRIAL-HYGIENE SAMPLES USING ULTRASONIC EXTRACTION AND FLOW-INJECTION ANALYSIS

A simple, fast, and sensitive method was developed for the determinati on of hexavalent chromium (Cr-VI) in workplace samples. Ultrasonic ext raction in alkaline solutions with 0.05 M (NH4)(2)SO4-0.05 M NH3 provi ded good extraction efficiency of Cr-VI from the sample and allowed th e retention of Cr-VI on an ion-exchange resin (95%). The Cr-VI in the sample solution was then separated as an anion from trivalent chromium [Crm] and other cations by elution from the anion-exchange resin with 0.5 M (NH4)(2)SO4 in 0.1 M NH3 (pH 8) buffer solution. The eluate was then acidified with hydrochloric acid and complexed with 1,5-diphenyl carbazide reagent prior to flow injection analysis, By analyzing sampl es with and without oxidation of Cr-III to Cr-VI using Ce-IV, the meth od can measure Cr-VI and total Cr. For optimizing the separation and d etermination procedure, preliminary trials conducted with two certifie d reference materials (CRMs 013-050 and NIST 1633a) and three spiked s amples (ammonia buffer solution, cellulose ester filters and acid wash ed sand) indicated that the recovery of Cr-VI was quantitative (> 90%) with this method, The limit of detection for FIA-UV/VIS determination of the Cr-diphenylcarbazone complex was in the sub-nanogram range (0. 11 ng). The technique was also applied successfully to a workplace coa l fly ash sample that was collected from a power plant and paint chips that were collected from a heating gas pipe and a university building , The principal advantages of this method are its simplicity, sensitiv ity, speed and potential portability for field analysis.