石墨炉原子吸收光谱法测定土壤铝的条件优化

酸性土壤中的活性Al是影响作物生长发育的主要因子之一,土壤Al的测定一直是人们关注的问题。石墨炉原子吸收光谱法测土壤Al所需的样品量少、灵敏度高、离子干扰小,目前在国内外应用较为广泛。由于其测试条件多是应用单因素轮换法来确定,存在实验量大且未考虑交互作用的影响等缺点。采用双因素重复实验及正交实验可显著降低确定最佳测试条件的工作量,且实验条件代表性强,对于准确快捷测定土壤Al具有重要意义。通过双因素（波长和灯电流）重复试验对石墨炉原子吸收光谱仪测定土壤Al的波长和灯电流进行了优化选择,确定最佳波长为309.3nm,最佳灯电流为14mA;应用L2（556）正交试验法对控温程序及基体改进剂、基体酸度条件进行了优化,得出最佳的灰化温度为1400℃、灰化时间为10s,原子化温度为2300℃、原子化时间为5s,最佳基体改进剂为0.1%NH4H2PO4、最佳基体酸度为0.2%硝酸。优化后的方法检出限为1.14μg.L-1,加标回收率达到93.6%~104.1%,相对偏差均小于8%。

Optimizing the Conditions for Soil Aluminum Determination with Graphite Furnace Atomic Absorption Spectrometry

The active Al is one of the main factors that suppressing the growth of plant in acid soil,while the determination of soil Al is concerned by many researchers.It is widely used to determination of soil Al with graphite furnace atomic absorption spectrometry,because of its advantages of requiring less sample content,having higher sensitivity and efficiency and avoiding much more ions interference.The determination conditions for the soil Al using graphite furnace atomic absorption spectrometry,is generally carried out by the single factor rotation method with many disadvantages of taking much more work and without taking the impact of interaction of factors into account.In this paper,both double-factor experiment and orthogonal test,with the significant meaningful for determining Al quickly and accurately because of the deduction of workload and the representative for the test conditions,were all applied to the aluminum determination and resulted in the optimum wavelength of aluminum 309.3 nm and the lamp current 14 mA,and the optimum conditions were also obtained by the application of L25（56） orthogonal test,as follows：the ashing temperature of 1 400 ℃,the ashing holding time of 10 s,the atomization temperature of 2 300 ℃,the atomization holding time of 5 s,the best matrix modifier of NH4H2PO4（0.1%）,and the best matrix acid of 0.2% nitric acid.Moreover,the detection limit was 1.14 μg·L-1,the recoveries was within the range of 93.6%~104.1% and the relative deviation was less than 8% under the above optimum condition of determination.The determination of soil Al under the optimum condition would not only reduce significantly the workload but also get the better accuracy and precision.Furthermore the research result provides probably a new idea for obtaining the optimum determination conditions for other metal elements determination with graphite furnace atomic absorption spectrometry.