Optimization of turbidimetric method for detecting soil available sulfur and comparison with ICP-OES method
The 3rd National Soil Survey is of great significance.In order to ensure the authenticity and reliability of the data,the standard detection methods need to be repeatedly verified to optimize the method suitable for nationwide promotion.Due to poor linearity of the standard curve of turbidimetric method in NY/T 1121.14-2006 to detect soil available sulfur,it is urgent to optimize the extraction and determination conditions to improve the accuracy and precision of the method.In view of this,it was explored the influence of the state and brand of precipitator and the method of linear fitting on the linearity of the standard curve of the turbidity method in the paper.The result showed that the correlation coefficient(r)of the standard curve can be＞0.999 and meet the requirements of analysis if the freshly prepared 40 g/L BaCl2 is used.At the same time,the determination of soil available sulfur by inductively coupled plasma spectroscopy(ICP-OES)was verified and compared.The detection limits of turbidimetric method and ICP-OES were 1.20 and 0.80 mg/kg,respectively,which satisfied the requirements of analysis and test.The results of accuracy and precision verification showed that turbidimetric method and ICP-OES could be used for the detection of soil available sulfur and there was no significant difference in the results.The turbidimetric method was suitable for the determination the samples with concentration below 48 mg/kg,and the ICP-OES was better to the samples ranging of 0-150 mg/kg samples.Based on the experience in detection of 3rd National Soil Survey pilot work,it was suggested that ICP-OES should be as the standard method for the determination of soil available sulfur,which could provide reference for the 3rd National Soil Survey.
the 3rd national soil surveyavailable sulfurturbidimetryinductively coupled plasma emission spectrometer
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