Determination and Correction of Analytical Biases and Study on Chemical Mechanisms in the Analysis of Cr(VI) in Soil Samples Using EPA Protocols

Abstract

EPA Methods 3060A (alkaline extraction) and 7196A (colorimetric measurement) currently constitute a pair of protocols for the measurement of Cr(VI) in environmental soil samples in EPA RCRA SW-846 Update III. To identify the sources of possible biases, we applied the newly developed Speciated Isotope Dilution Mass Spectrometry (SIDMS) as an alternative detection method to Method 7196A. SIDMS is capable of correcting for species transformation, while Method 7196A is not. In Method 3060A, soluble Cr(III) could be oxidized during extraction, resulting in positive errors of Cr(VI); Cr(VI) could be lost or reduced during neutralization, leading to negative errors of Cr(VI). When sand and soil extracts were analyzed, low recoveries were obtained with Method 7196A. However, SIDMS achieved approximately 100% recoveries. The influence of some soil matrix components on the detection of Cr(VI) using Method 7196A has been evaluated. As expected, reducing agents could cause low recoveries of Cr(VI). Surprisingly, we found that strong oxidizing agents could also result in low recoveries. We identify these method biases and discuss the mechanisms in this paper.

A screening method for detection of hexavalent chromium levels in soils

“…According to the literature, extraction procedures using NaOH/Na 2 CO 3 solution, both using heat and at ambient temperature, do not induce either Cr(VI) reduction, or oxidation of Cr(III). 15,16,23 Before the extractant solutions is discharged, it is advisable to use a solution of concentrated ascorbic acid to reduce the Cr(VI) present in solution, followed by the recovery of Cr(OH) 3 after adjusting the pH to 8.…”

“…While Cr(VI) is relatively mobile in the environment and acutely toxic, mutagenic, teratogenic and carcinogenic, Cr(III) is relatively immobile under moderately alkaline to slightly acidic conditions, and has a relatively low toxicity. [1][2][3][4] Analysis for total chromium is straightforward, however, successful analysis for Cr(VI) in soil matrices can be more complex. An optimal extraction procedure should completely release Cr(VI) species without disturbing the species distribution.…”

“…An optimal extraction procedure should completely release Cr(VI) species without disturbing the species distribution. 3,4 Because Cr(VI) is a strong oxidizer, there are certain conditions in the environment that preclude chromium from existing in the hexavalent state. Under highly reducing conditions Cr(VI) is rapidly reduced to Cr(III).…”

Direct Fluorescence Quantification of Chromium(VI) in Wastewater with Organic Nanoparticles Sensor

“…Several techniques, such as flame atomic absorption spectrometry (FAAS), [2][3][4] electrothermal atomic emission spectrometry (ETAAS), 5,6 inductively coupled plasma atomic emission spectrometry (ICP-AES), 7 luminescence, 8 chemiluminescence, 9 spectrophotometry, [10][11][12] chromatography, 13 X-ray fluorescence spectrometry 14 and electrochemical methods 15,16 have been used for the determination of chromium. Among the available methods, spectrophotometry [17][18][19] has been widely used for the determination of Cr(VI). However, the technique is liable to various interference effects, e.g., the presence of colloidal particles, turbidity and colored species.…”

A Study of Interference Factor of Analysis Method of Hexavalent Chromium in Soil using UV/VIS Spectrometry and Application of Ion Chromatography

“…그리고 분해용액 중의 6가 크롬과 DPC 용액을 반응시켜 발색하기 위해 황산으로 pH 2 ± 0.5로 조작하는 전처리 과정에서 6가 크롬이 DPC 용액과 반응하기 전에 유기물, Fe 등에 의해 3가 크롬으로 환원 될 수 있다 (Huo et al, 1998;James et al, 1995; Table 3). (Bowen, 1979).…”