氯化铵水溶液浸提-电感耦合等离子体发射光谱法测定石灰性土壤中交换性钠的含量

Determination of exchangeable sodium in calcareous soil by ammonium chloride solution extraction-inductively coupled plasma emission spectrometry

交换性钠是评价土壤碱化度的重要指标之一,传统容量法、重量法和火焰光度计法测定交换性钠手续复杂繁琐,乙醇用量大且对低含量样品有效检出能力不足。本实验将样品采用70%乙醇溶液洗盐后,滤纸及过滤物置于250m L塑料瓶中,加入100m L p H为8.5的氯化铵水溶液,置于摇床以170r·min^(-1)振荡45min后,过滤至已加入5m L浓度为50%盐酸的250m L塑料容量瓶中,用氯化铵水溶液淋洗至刻度,选择589.592nm作为分析谱线,建立了电感耦合等离子体发射光谱法测定石灰性土壤中交换性钠的新方法。在优化的实验条件下,钠的校准曲线在10μg·m L^(-1)以内与对应响应强度呈良好线性关系,线性相关系数为0.9999,方法检出限(3s)为0.0048 cmol·kg^(-1),定量限为0.0192 cmol·kg^(-1)。经国家标准物质验证,测定值与认定值基本相符,相对误差绝对值(∣RE∣,n=7)均不大于8.72%,相对标准偏差(RSD,n=7)均不大于0.6%。交换性钠含量较高试样的加标回收率为97.9%。方法用于农田盐渍化治理工程石灰性土壤样品,测定结果的相对标准偏差(RSD,n=7)均不大于1.5%,与NY/T 1615-2008进行方法间比对,测定结果吻合。本方法样品处理程序简便快捷,乙醇用量大幅降低,检出能力有效提高,分析准确度和精密度好,适用于批量样品分析。

Exchangeable sodium is one of the important indexes to evaluate the degree of soil alkalization.The determination of exchangeable sodium by traditional volumetric method,gravimetric method and flame photometer method is complicated,the amount of ethanol is large and the effective detection ability of low content samples is insufficient.Using ammonium chloride solution as extractant,after washing the salt with 70%ethanol solution,the filter paper and the filter material were placed in a 250mL plastic bottle with a lid,100 mL of ammonium chloride aqueous solution with pH 8.5 was added.After shaked at 170r·min^(-1)for 45 min,the solution was filtered into a 250mL plastic volumetric flask containing 5 mL 50%hydrochloric acid medium,then washed with ammonium chloride aqueous solution to the scale,and 589.592 nm was selected as the analytical spectral line.The exchangeable sodium in calcareous soil was determined by inductively coupled plasma emission spectrometry.Under the optimized experimental conditions,the calibration curve of sodium showed a good linear relationship with the response intensity within 10 ug·mL^(-1),the linear correlation coefficient was 0.9999,the detection limit was 0.0048 cmol·kg^(-1),and the limit of quantitation was 0.0192 cmol·kg^(-1).Verified by national standard substances,the measured values were basically consistent with the certified values,the absolute values of relative errors(|RE|,n=7)were not more than 8.72%,and the relative standard deviations(RSD,n=7)were not more than 0.6%.The recovery rate of the sample with high exchangeable sodium content was 97.9%.The relative standard deviations(RSD,n=7)of determination results were not more than 1.5%for calcareous soil samples from farmland salinization control project.The determination results were consistent with those of the NY/T 1615-2008 method.The sample processing procedure of this method is simple and quick,the amount of ethanol is greatly reduced,the detection ability is effectively improved,the analysis accuracy and precision are good.It is suitable for batch sample analysis.