Abstract
Recently, environmental pollution by toxic metals, such as Cd, Pb, Cr, and so on, is getting increasingly worse. In order to increase measurement chances, a portable elemental analyzer is expected to be developed. Conventionally, the measurement of trace metals in environmental pollution was done by atomic absorption spectrometry (AAS), or inductively coupled plasma atomic emission spectrometry (ICP-AES). However those instruments are very expensive, and require a large amount of Ar gas, a nebulizer, and a high power source, and is thus not suitable for portable use. Liquid electrode plasma atomic emission spectrometry (LEP-AES) is a novel atomic emission spectrometry, where a sample solution is put into micro channel whose center is made to be narrower. A high voltage is applied to the solution from both ends, and then a micro-plasma is generated in the channel. This technique is different from ICP-AES due to the following points : it doesn't require a plasma gas or a nebulizer, and an ultra compact and portable element analyzer can be made. In this study, the performance of this analyzer was investigated with a solid phase extraction (SPE) method to measure the Pb concentration in soil. At first, the basic performance was confirmed without SPE. In the result, it is found that the limits of detection (LOD) for Pb by this system is 1.3 mg/L at 405.8 nm, the relative standard deviation is under 10%, and the calibration curve has good linearity at a Pb concentration of less than 800 mg/L. Those values are good enough to measure Pb in soil. Next, heavy metals in standard soil sample (sea bottom material) were extracted into water by the official method. Lead in the extract was separated from other elements by solid-phase extraction, and was then concentrated. By measuring the SPE elution using the LEP-AES system, the original concentration of Pb in the soil was determined to be 80.2 mg/kg (dry), which was close to the certificated value of the soil of 82.7±3.8 mg/kg.
