碱稳定样品法测定降水中3种有机酸

Determination of Three Organic Acid Anions in the Rainfall Samples Based on Alkali Stabilization Method

建立了氢氧化钠稳定样品的离子色谱梯度淋洗测定大气降水中3种有机酸(乙酸、甲酸、草酸)的分析方法。用淋洗液在线发生器(RFC-30)产生梯度氢氧化钾溶液,以及IonPacAS19分离柱、IonPacAG19保护柱,确定了最佳梯度淋洗程序,可在36 min内同时测定大气降水中有机酸(乙酸、甲酸、草酸)和无机阴离子。并探讨了乙酸、甲酸、草酸标准溶液的稳定性,在有机酸标准溶液调为碱性(pH≥10)条件下,且于4℃下冷藏密封保存,乙酸、甲酸、草酸在10天内具有较好的稳定性。如空白试验中有微量甲酸、氯离子,实际样品和标准溶液测定时需相应扣减。乙酸、甲酸和草酸线性回归方程相关系数均大于0.9995,方法检出限分别为0.002、0.003、0.002 mg/L,实际降水样品测定时乙酸、甲酸、草酸的相对标准偏差在0.3%~3.3%,加标回收率在93.0%~105.0%。本方法检出限低、精密度、准确度好,操作简便、灵敏、实用,可应用于实际大气降水分析,为相应标准方法(HJ1004-2018)提供了参考。

A method for determination of three organic acid anions(acetate,formate and oxalate)in the rainfall samples by gradient elution ion chromatography and samples storaged by NaOH solution was developed.Using the gradient potassium hydroxide solution generated by elution generator on-line(RFC-30)and high capacity anion exchange column(IonPacAS19,IonPacAG19),the optimized gradient elution programs were established.Organic acid anions(acetate,formate and oxalate)and inorganic anions can be satisfactorily separated and simultaneously determined by gradient elution ion chromatography(IC)within 36 minutes.The stability of the three organic acid anions standard solutions was discussed.Under the conditions,the three organic acid anions standard solutions was adjust to alkaline(pH≥10)and stored under 4℃ with tightly resealed,the standard solutions had good stability within 10 days.The trace amounts of formate and chloride ions in the blank test should be deducted when the actual samples and standard series solution were determined.The linear correlation coefficients of acetate,formate and oxalate were greater than 0.9995,the detection limits were 0.002,0.003 and 0.002 mg/L respectively.The relative standard deviations of spiked samples were between 0.3% to 3.3%,quantitative recoveries of spiked samples were from 93.0% to 105.0%.This method has low detection limit,good precision and accuracy,easy operation,sensitivity and effective.This new method had been applied to the determination of these anions in actual rainfall samples in China,and provided reference application of national standard method HJ1004-2018.