Study On Coupling Optimization Of Atomic Absorption Spectrometry Combining Microwave Digestion Technique For Analysis And Application Of Copper And Chromium In Soils

The environmental behavior of soil is always measured by the total amount of heavy metals,and always judged by the amount to confirm whether being polluted or the degree of pollution.In order to increase the environment quality of the soil,and prevent the high amount of copper and chromium,contained in agricultural waste,animal manure et.as organic fertilizer,gotten into the soil,that lead to contamination,a fast and accurate method for determination of copper and chromium is necessary.Application of agricultural organic fertilizers is traditional tillage method,in which high amout of potential copper and chromium may be contained.In this regard,this paper had investigated the Sajiang Heitu,Red soil and Yellow brown soil,the typical type of soil in Anhui province.Microwave digestion technique combined atomic absorption method were applied and optimized,the main results are as follows.(1)The determing parameters for flame atomic absorption spectrometry were optimized,and those for copper are:slit width is 0.7 mm,air-acetylene ratio 7.5:2.5,lamp current 6 mA,and observation height 0 mm.The standard was determined on the conditions,the limit of quantitation was 0.0111μg/mL,the correlation coefficient 0.9999,and the quantitative range was from 0.0111 to 1.0033μg/mL.(2)The measuring conditions for graphite furnace atomic absorption were optimized,and those for chromiums are:ashing temperature and time are 1200℃ and 20 s respectively,and atomizing temperature and time,2250℃ and 4 s.On range of 4.5349-99.9980 ng/mL for determination of chromium,the correlation coefficient was 0.9994,certifying good linearity.Accurate readings can be obtained on the instrument at a chromium concentration of4.5349 ng/mL.(3)The process and results of dry ashing,heating plate digestion and microwave digestion were compared,it was found that the microwave digestion are the most reliable,not only fast speed,excellent repeatability,but also high recovery,which is over than 99%.(4)Orthogonal experiment was used for optimization of usage amount of acids during digest process.The best combination of acids was 5 mL of nitric acid,2 mL of hydrofluoric acid,and 1 mL of perchloric acid for Shajiang Heitu.And for Red soil,5mL of nitric acid,2 mL of hydrofluoric acid,and 0.5 mL of perchloric acid.as well as for Yellow brown soil,4 mL of nitric acid,2 mL of hydrochloric acid,2 mL of hydrofluoric acid,and 2 mL of chloric acid.The experimental results show that the standard difference of the method is less than 2,and the relative standard difference is less than 4%.It confirms good stability and accuracy,for determination of copper and chromium.(5)Accurate results for relevant projects were obtained for determination of copper and chromium in Sajiang Heitu,Red soil and Yellow brown soil by the microwave digestion technique combined atomic absorption method constructed,those confirmed that the organic fertilizer applied in soil on some areas probably contain different amount of copper and chromium.