离子色谱法同时检测大气颗粒物PM_(2.5)中低级脂肪胺和常规阳离子

Simultaneous detection of lower aliphatic amines and conventional cations in atmospheric PM 2.5 particulates by ion chromatography

大气中存在大量的有机胺污染,其中低级脂肪胺是促进颗粒形成和生长成为PM_(2.5)的诱因,会对人体肾脏、心肺功能健康造成损害。而PM_(2.5)是大气中常见的颗粒污染物,是雾霾天气产生的主要原因,其成分非常复杂,测定其中的阳离子和低级脂肪胺,能直接监测环境大气质量,保护人体健康。本研究建立了抑制电导离子色谱法同时测定大气细颗粒物PM_(2.5)中4种低级脂肪胺(甲胺、二甲胺、三甲胺、乙胺)和5种常见阳离子(Na^(+)、NH_(4)^(+)、K^(+)、Mg^(2+)、Ca^(2+)),通过优化色谱条件,实现了K^(+)和甲胺、二甲胺和乙胺等难分离物质的有效分离,分析结果可用于评估空气中的颗粒物污染情况。本研究采用负载石英滤膜的中流量采样器采集大气中的PM_(2.5)颗粒物,裁剪1/2滤膜并剪碎于10 mL超纯水中超声提取2次共60 min,提取液过0.22μm滤膜后用离子色谱检测。比较了3种阳离子色谱柱IonPac^(TM) CS17、IonPac^(TM) CS16和SH-CC-9后,最终选用SH-CC-9阳离子分析柱(200 mm×4.6 mm)进行分离:柱温30℃,检测器温度35℃,进样量25μL,流动相为甲基磺酸(MSA)水溶液,流速为1.1 mL/min。在此色谱条件下,大气中可能存在的其他胺(N,N-二甲基甲酰胺、N,N-二甲基乙酰胺、丙胺、二乙胺、三乙胺、三乙醇胺、异丙胺)对目标离子没有影响。待测的4种低级脂肪胺和5种常见阳离子在各自相应的浓度范围内呈现良好的线性关系,线性相关系数(r)均不小于0.997,检出限(LOD)为0.02~1.90μg/L,定量限(LOQ)为0.07~6.32μg/L, 6个平行样品测定的相对标准偏差(RSD)小于2%,样品加标回收率为93.2%~104%。采用建立的方法对189个大气颗粒物PM_(2.5)样品进行检测,9种离子均有检出,其中Na^(+)、NH_(4)^(+)、Ca^(2+)等离子含量较多,4种低级脂肪胺含量少,但部分样品中乙胺含量偏高。结果表明,本研究建立的离子色谱方法前处理简单,灵敏度高,准确性好,可满足大气颗粒物PM_(2.5)中低级脂肪胺和常规阳离子同时定量检测的需求,能够快速处理大量样品,准确评价空气中颗粒物的污染程度,追溯污染来源,保护人类健康。

Many amine pollutants exist in the atmosphere.Lower aliphatic amines promote the formation and growth of particles into PM_(2.5),which damages the heart,lungs,and kidneys of the human body.PM_(2.5),a common atmospheric particulate pollutant with complex compositions,is the main cause of haze weather.Therefore,measuring the contents of lower aliphatic amines and cations in PM_(2.5) is of great significance for monitoring environmental air quality and protecting human health.This study established a suppressed ion-chromatographic method with conductivity for the simultaneous detection of four lower aliphatic amines(methylamine,dimethylamine,trimethylamine,and ethylamine)and five cations(Na^(+),NH_(4)^(+),K^(+),Mg^(2+),and Ca^(2+))in PM_(2.5).The effective separations of several groups of substances that are difficult to separate,such as K^(+)and methylamine,dimethylamine,and ethylamine,were achieved by optimizing the chromatographic conditions.The results were then used to assess the pollution caused by small particles in the air.A medium-flow sampler loaded with a quartz filter membrane was used to collect PM_(2.5) particles in the atmosphere.The sample flow rate was 100 L/min,and the sampling time was 24 h.Half of the filter membrane was cut and shredded into 10 mL of ultrapure water for two cycles of ultrasonic extraction over 60 min.After membrane filtration,the extract was analyzed using ion chromatography(IC).Three cation-exchange columns(IonPac^(TM) CS17,IonPac^(TM) CS16,and SH-CC-9)were compared,and the SH-CC-9 column(200 mm×4.6 mm)was ultimately used for separation under a column temperature of 30℃,detector temperature of 35℃,and injection volume of 25μL.An aqueous solution of methyl sulfonic acid(MSA)was used as the mobile phase at a flow rate of 1.1 mL/min.Under these conditions,other aliphatic amine ions in air(triethanolamine,diethylamine,triethylamine,isopropylamine,propylamine,N,N-dimethylformamide,and N,N-dimethylacetamide)did not interfere with the separation and detection of the nine target ions.The nine ions showed good linear relationships within the corresponding concentration range,with linear correlation coefficients(r)no less than 0.997.The limits of detection(LODs)were 0.02-1.90μg/L,and the limits of quantification(LOQs)were 0.07-6.32μg/L.The relative standard deviations(RSDs)for the determination of six parallel samples were less than 2%,and the sample recoveries were between 93.2%and 104%.The established IC method was used to detect 189 PM_(2.5) samples collected from the atmosphere,and all nine ions were successfully detected.Among these ions,Na^(+),NH_(4)^(+),and Ca^(2+)showed high concentrations.The contents of the four lower aliphatic amines were low;however,the ethylamine content in some samples was high.The results indicate that the proposed method meets the quantification requirements for cations and lower aliphatic amines in PM_(2.5),with simple processing,high sensitivity,and good accuracy.It can quickly and accurately detect a large number of samples and be used to assess the pollution of small particles in the air as well as trace pollution sources to protect human health.