Study Of Pyrolysis Determination Of S, As, Cl, And F In Soil

Pretreatment is a very important work for the detection of trace elements in soil inthe field of analytical chemical. Compared with the traditional pretreatment method,pyrolysis method with tube furnace is suitable to separate and enrich trace elements insoil. The method is easily coupled with detecting instrument with simple operation andrapid determination. Thus, pyrolysis method with tube furnace will be potentialapplication in monitoring elements in soil.In this paper, pyrolysis pretreatment method coupled with spectrophotometer andion selective electrode was proposed to determine sulfur, arsenic, fluorine and chlorinein soil. The above-mentioned four elements were separated and enriched from complexsoil matrix at high temperature with tube furnace. Spectrophotometer and ion selectiveelectrode were used to determine these elements. In pyrolysis process, the mainparameters were optimized, including pyrolysis system parameters (pyrolysistemperature, pyrolysis time, carrier gas flow rate of each element), absorbing solutionconcentration and absorption solution volume, and soil particle size. In pyrolysis, WO3and NaCl as decomposition accelerator for S and As in soil were studied.Optimization conditions for this system were listed as follow:700-1000℃for tubefurnace temperature,35mins for pyrolysis time,0.1L min-1for gas flow rate,0.1to0.3mol L-1for NaOH absorbing solution concentration,20mL for NaOH absorptionsolution volume, and above200meshes for soil particle size for each element inpyrolysis pretreatment. Under optimum conditions, the proposed method for S has thegood linear range from0.1to0.5mg·g-1and the detection limit (3σ, n=10) is0.02mg·g-1; the proposed method for As has the good linear range from1to6ug·g-1forAs, and the detection limit (3σ, n=10) is0.2ug·g-1; the proposed method for Cl has thegood linear range from10to500ug·g-1and the detection limit (3σ, n=10) is0.5ug·g-1;the proposed method for F has the good linear range from20to1000ug·g-1, and the detectionlimit (3σ, n=10) is5ug·g-1. These studies show that thesw proposed methods had goodlinear range and low detection limit. The testing results in actual soil sample showedthat recovry rate was from81.5%%to116.6%with the method of addition/recovery.Testing results for these elements in GBW07425GBW07454with these proposedmethods are in agreement with standard values for these elements.These studies showed that pyrolysis pretreatment method could overcome theseshortcoming in traditional pretreatment method, such as steps trival, a great backgroundeffect, and time-consuming.