降水中甲酸、乙酸和草酸的离子色谱法测定及样品保存研究

Determination of Formic Acid,Acetic Acid and Oxalic Acid in Precipitation by Ion Chromatography and Sample Storage

甲酸、乙酸和草酸是降水中有机酸的主要成分。研究选用离子色谱法同时测定降水中的甲酸、乙酸和草酸,并对降水样品中3种有机酸的保存条件进行了研究。优化后的色谱条件为4.0mmol/LNa2CO3和1.2mmol/LNaHCO3混合淋洗液,淋洗液流速为1.0mL/min,进样体积为200μL,电导池温度为30℃,柱温为室温。甲酸、乙酸和草酸的检出限分别为0.002、0.005、0.005mg/L,实际降水样品测定时平行样的相对标准偏差为1.4%~12%,加标回收率为95%~118%。样品采集后需尽快用0.45μm聚醚砜微孔滤膜过滤,4℃以下冷藏密封保存,2d内测定。若用氢氧化钠溶液调节pH至8~10,样品可保存7d。

Formic acid,acetic acid and oxalic acid are the main components of organic acids in precipitation. Ion chromatography was used to simultaneously determine formic acid,acetic acid and oxalic acid in precipitation,and the sample storage conditions of the three organic acids in precipitation were studied. The optimized chromatographic conditions were as follows: The concentration of eluents were 4.0 mmol/L Na 2CO 3 and 1.2 mmol /L NaHCO 3,the eluent flow rate was 1.0 mL/min,the sample volume was 200 μL,the conductivity cell temperature was 30℃,the column temperature was room temperature. The detection limit of formate,acetate and oxalate was 0.002,0.005,0.005 mg /L,respectively. The relative standard deviation of parallel samples in actual precipitation samples was 1.4%-12%,and the spiked recoveries were 95%-118%. After collection,the samples should be filtered with a 0.45 μm polyethersulfone microporous membrane as soon as possible,then stored under 4℃ with tightly resealed and determined within 2 d. Under pH 8-10,the samples can be stored for 7 d.