Rapid Determination of Available Cobalt & Lead in Calcareous Soils by Inductively Coupled Plasma-Mass Spectrometry with DTPA Extraction

The traditional methods for determining available cobalt and lead in soils by Atomic Absorption Spectrometry and Spectrophotometry have complicated operation and low analysis efficiency and are not applicable to large batches of samples. Advanced equipment has been applied to improve the analysis efficiency, however, the interferences from the extracted fluid affected the sensitivity of the instruments, which resulted in inaccurate determination. In this paper according to the method for determination of available forms of heavy metals in calcareous soil extracted with DTPA, the amounts of available cobalt and lead in soils are determined with Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). A control test was simultaneously conducted with several dilution factors experiments. The results indicate that the measured values of lime standard substances are consistent with the certified values when the extract solution is diluted twice. The measured values are higher than the certified values when the dilution factors for extract solution are 5-10 times higher. If there is no dilution, the measured values are lower than the certified values due to matrix interference. Based on 2 times dilution for extract solution, the detection limit for available cobalt and lead are 0.0130 μg/g and 0.0142 μg/g, respectively. Both the accuracy and precision of the method were validated by analyzing National Standard Reference Materials with RSD (n=9) less than 8% and relative error (n=9) less than 9%. It has been indicated that the method can be used to analyze the calcareous soil and its precision and criterion error were also in line with the limit by geological specification DD2005-03.