离子色谱-串联质谱法分析环境水体中痕量人工甜味剂

人工甜味剂被广泛使用并且在环境中持久存在，因此可能成为生活废水污染地表水体及地下水的有力证据。人工甜味剂作为一种新型示踪剂，对其在环境水体中的分析方法的灵敏度和抗干扰能力提出了更高的挑战。本研究采用离子色谱-三重四极杆串联质谱负离子模式实现了4种人工甜味剂的分离检测。经对比考察，采用细内径(2 mm)离子色谱柱( AS19-2 mm)既缩短了保留时间又提高了分离度；采用60 mmol/L NaOH等度洗脱，既实现了简便操作，又克服了传统的反相分离试剂及缓冲盐对离子化效度的负面影响；采用默克固相萃取柱(Merk LiChrolut EN 200 mg 3 mL)对酸化水样(pH<2.0)进行富集，固相萃取柱活化条件为依次加入2 mL甲醇与2 mL水，并采用2 mL甲醇；采用外接水柱后抑制法进一步提高了灵敏度、降低了检测背景值，抑制器电流为75 mA；统一采用多反应监测负离子模式实现了安赛蜜、糖精钠、甜蜜素及三氯蔗糖4种人工甜味剂的同时采集与检测，检出限均在5.0 ng/L以下，不同基质环境样品的加标回收率可控制在65%~120%之间。本方法简便、干扰少、检出限低，既适合于不同基质环境水样的日常分析监测，又适合于地下水污染的示踪研究。

An Innovative Approach to Sensitive Artificial Sweeteners Analysis by Ion Chromatography-Triple Quadrupole Mass Spectrometry

Artificial sweeteners ( ASs ) have gained more and more attention by environmental scientists because some of them such as acesulfame, have the potential to be the ideal tracers of domestic wastewater for environmental monitoring. In contrast to the existing methods of artificial sweeteners, the analytical method of ASs as a new tracer for environmental samples requires better sensitivity and selectivity to avoid matrix interference. A highly sensitive method for the simultaneous determination of four frequently-used artificial sweeteners in water samples using solid-phase extraction and ion chromatography triple quadrupole mass spectrometer with an electrospray ionization source ( IC-MS/MS) in negative ion mode was developed. The separation effect of different separation columns was compared and a 2-mm ion chromatography column AS19 was chosen in the experiment. Chromatographic separation of all the 4 artificial sweeteners was carried out in 9 min in isocratic elution mode using 60 mmol/L sodium hydroxide as eluent. Different kinds of solid phase extraction cartridges were evaluated to obtain satisfactory recoveries of all of the analytes. Merk LiChrolut EN (200 mg, 3 mL) was preconditioned with 2 mL of methanol, followed by 2 mL of H2 O. About 200 mL of sample (pH<2. 0) was passed through the cartridge at a flow rate of 4 mL/min, and then the cartridge was eluted using 2 mL of methanol. 2 mm suppresser (75 mA) was used to reduce the background noise and to remove the matrix interference. The limits of detection were below 5. 0 ng/L for various artificial sweeteners based on 3-fold the S/N. The recoveries of different matrices in the samples were 65%-120%. The method described here is time-saving, accurate and precise, and is suitable for monitoring artificial sweeteners in different water matrices. The method has also the potential to trace other contaminants in groundwater.