Determination of 6 Extractable Heavy Metal Elements in Soil by Inductively Coupled Plasma Mass Spectrometry with Constant Temperature Oscillation Extraction

A method for the determination of extractable heavy metal elements including chromium, nickel, copper, zinc, cadmium, and lead in soil by inductively coupled plasma mass spectrometry (ICP-MS) with constant temperature oscillation extraction was proposed. The soil sample was dried naturally and passed through a 2 mm nylon sieve. 10.0 g of the sieved soil sample was taken and placed into a stoppered centrifuge tube. 100 mL of 0.01 mol·L⁻¹ calcium chloride solution was added and the mixture was placed in a vertical intelligent precision shaker. The extraction temperature was set at (20±2) ℃, with the horizontal oscillation speed of (180±20) r·min⁻¹, and the extraction time of 120 min. After extraction, the mixture was centrifuged and the supernatant was filtered. The resulting filtrate was collected into a 10 mL colorimetric tube, in which 6 extractable heavy metal elements were determined by ICP-MS under the conditions of integration time of 0.5 s and collision pool mode,using internal standard ⁷²Ge to correct ⁵³Cr,⁶⁰Ni,⁶³Cu and ⁶⁶Zn, as well as ¹⁰³Rh to ¹¹⁴Cd and ¹⁸⁵Re to ²⁰⁸Pb. As shown by the results, linear relationships between the corresponding signal intensity and the internal standard signal intensity ratios and mass concentrations of chromium, nickel, copper, zinc, cadmium, and lead elements were found in definite ranges, with detection limits (2.764s) of 0.076, 0.075, 0.074, 0.15, 0.010, 0.050 mg·kg⁻¹, respectively. The method was used for the analysis of national standard substances. For elements with the certified values above the detection limits, the determined values were basically consistent with the certified values. RSDs (n=6) of the determined values of elements above the detection limits were not more than 5.0%.