Sequential injection method for the determination of hexavalent chromium in soils and ground water

Hexavalent chromium (Cr (VI)), a known carcinogen, is present as a contaminant of soil and ground water at a large number of sites. The need to quickly and accurately screen samples in the field is increasing as restoration efforts escalate. A Sequential Injection (SI) analysis method has been developed utilizing the 1,5-diphenylcarbazide spectrophotometric method for Cr(VI). The SI system was computer interfaced, allowing for the automation of the analysis and providing electronic collection of the test results. A relative standard deviation for all analyses of less than 3% was obtained and the limit of detection was determined to be 25 {mu}g/liter (ppb) in deionized water. An automated SI procedure which can leach the available Cr(VI) from a soil sample into solution ready for the described analysis in less than five minutes has been developed. The methods were coupled into a single automated SI system. The analysis of lab produced and field soil samples is presented. Data concerning the effect of the storage of Cr(VI) solutions in an acidic form is presented and discussed.