Investigating the Suitability of UV/Vis Spectrophotometric Methods for Analyzing Arsenic in Urban Soils for use in Undergraduate Laboratory Courses
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Publisher:The Ohio State University
Series/Report no.:The Ohio State University. Department of Chemistry Honors Theses; 2010
Quantifying the concentration of arsenic in soil samples is important for many environmental chemistry investigations, including those characterizing heavy metal in urban settings and examining anthropogenic contributions. Although several approaches for quantifying arsenic in environmental samples have been reported, many of these are poorly suited for use in undergraduate teaching laboratories. The use of UV-Vis spectrophotometric methods are, for both logistical and pedagogical reasons, well-suited for inclusion in the chemistry curriculum. Within this investigation two UV-Vis spectrophotometric methods have been examined to ascertain their applicability for use at the undergraduate level. Criteria for inclusion in chemistry courses, such as time constraints, reproducibility, reagent stability, and dynamic range have been considered for a method employing a Leuco-malachite green dye (Revanasiddappa, 2007) or a method involving a Rhodamine B dye (Pillai, 2000). These two methods were examined in conjunction with two different soil digestion procedures for the analysis of soil samples collected from Columbus, OH. An investigation of the Leuco-malachite green method strongly suggests that it is ill-suited for the analysis of arsenic Columbus' soil due to interference from iron. The Rhodamine B method, in contrast, is less affected by iron or chromium interferrents and statistical analysis indicates good agreement between this method and X-ray fluorescence spectrophotometric analysis. However, poor precision in the Rhodamine B method, attributed in part to the digestion scheme, indicates that additional work is required before this method is included in undergraduate courses.
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