Measurements of cadmium in soil extracts using multi-variate data analysis and electrochemical sensors
There is a growing awareness of potential health risks due to exposure to heavy metals. One source of uptake is via agriculture, when heavy metals in the soil are taken up by the crop. The metal cadmium holds a special position, since it is considered to be a health risk, even at the low concentrations observed in our food supply, furthermore, it is ranked as eight on the top 20 hazardous substances list. Two measurement systems are described based on stripping voltammetry for analysis of cadmium. One is based on a three metal direct probe system (TMDPS) with three working electrodes (platinum, gold and rhodium), combined with a polishing unit, the other is an automatic flow through system, using one working electrode of gold, also equipped with a polishing unit. A number of different soils were extracted with an ammonium-lactate solution and analyzed with the systems, and the data obtained were subjected to multi-variate data analysis (MVDA). Using modeling based on partial least square (PLS), concentrations of cadmium in the soil extracts could be predicted for the TMDPS in the concentration area 0.5–10 μg/l with a root mean square error of prediction (RMSEP) of 0.8 μg/l and a relative predicted deviation (RPV) of 2.0. One sample could be analyzed in 4 min. It was also shown that by using different PLS models, the concentration of the elements copper, aluminum, lead and iron could be predicted. The possibilities of using the technique for field use were also evaluated by studies of mixtures of different soils in 0.1 M HNO3 solution, the time for an analysis was, however, rather large, around 20 min.
KeywordsCadmium Stripping voltammetry Multi-variate data analysis Soil Soil extracts
Swedish Farmers’ Foundation for Agricultural Research, the VL foundation and S-SENCE of Linköping University are gratefully acknowledged for financial support. The Swedish Sensor Centre (S-SENCE) is supported with grants from the Swedish National Board for Industrial and Technical Development and Swedish Industry.
- Bard, A. J., & Faulkner, L. R. (1980). Electrochemical methods–fundamentals and applications. New York, USA: Wiley.Google Scholar
- Barregård, B., Svalander, C., Schütz, A., Westberg, G., Sällsten, G., Blohmé, I., et al. (1999). Cadmium, mercury, and lead in kidney cortex of the general Swedish population: A study of biopsies from living kidney donors. Environmental Health Perspectives, 107, 867–871. doi: 10.2307/3454473.PubMedCrossRefGoogle Scholar
- Daniele, S., Bragato, C., & Baldo, A. M. (1997). An approach to the calibrationless determination of copper and lead by anodic stripping voltammetry at thin mercury film microelectrodes. Application to well water and rain. Analytica Chimica Acta, 346, 145–156. doi: 10.1016/S0003-2670(97)00114-1.CrossRefGoogle Scholar
- Eriksson, J., Andersson, A., & Andersson, R. (1997). Current status of Swedish arable soils. Swedish Environmental Protection Agency, Report 620-4778-7.Google Scholar