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针对煤质复杂,而煤中的镉元素具有低含量且易挥发的特点,提出了采用氧等离子体低温灰化技术对煤进行预处理,再加入硝酸钯作为基体改进剂使镉在灰化过程中生成难离解物质,建立了悬浮液进样石墨炉原子吸收光谱法(GFAAS)测定煤中镉的方法。研究过程中主要探讨了样品基质的影响,通过对比分析低温灰化前后的样品,发现低温灰化处理明显提高了分析的灵敏度和精密度;优化了悬浮液样品的灰化温度和原子化温度及基体改进剂的用量,确定灰化温度和原子化温度分别为650℃和2 200℃,基体改进剂硝酸钯的最佳质量浓度为1.0g/L。实验表明,在优化条件下,标准悬浮液样品中镉在0.1~2.0μg/L范围内呈现较好的线性关系,线性相关系数为0.999 5。方法检出限为0.012mg/kg。对煤实际样品和标准物质进行分析,相对标准偏差(RSD,n=5)为2.9%~5.9%,测定结果与密闭消解法处理样品后的测定值或认定值吻合。
In view of the complicated coal quality and the low content of cadmium in coal and the volatility of cadmium, coal is preconditioned by low temperature ashing of oxygen plasma and palladium nitrate is added as matrix modifier to make cadmium in ashing process In the formation of difficult to dissociate substances, the establishment of a suspension sampling graphite furnace atomic absorption spectrometry (GFAAS) method for the determination of cadmium in coal. In the course of the study, the influence of sample matrix was mainly discussed. By comparing and analyzing the samples before and after low temperature ashing, it was found that the low temperature ashing treatment obviously enhanced the sensitivity and precision of the analysis. The ashing temperature and atomization temperature The amount of matrix modifier used, the ashing temperature and atomization temperature were determined to be 650 ℃ and 2 200 ℃, respectively. The optimum concentration of Pd (NO3) 3 was 1.0g / L. The experimental results showed that the optimum concentration of cadmium in the standard suspension showed a good linearity in the range of 0.1-2.0 μg / L with the linear correlation coefficient of 0.999 5. The detection limit was 0.012 mg / kg. The relative standard deviations (RSD, n = 5) were 2.9% ~ 5.9% for coal samples and reference materials. The results were in good agreement with those measured by confined digestion method.