柱前衍生-高效液相色谱-荧光检测法测定白酒中的甜蜜素

Determination of sodium cyclamate in Baijiu by pre⁃column derivatization⁃high performance liquid chromatography with fluorometric detection

白酒中甜蜜素(化学名为环己基氨基磺酸钠)是我国食品安全监督抽检计划中的重点关注项目,生产企业亟需简单、经济、灵敏度高而且可靠的检测方法。本研究建立了柱前衍生-高效液相色谱-荧光检测法测定白酒中甜蜜素的方法。在酸性条件下,通过脱磺酸基反应将样品中的环己基氨基磺酸钠转化为氨基化合物,然后加入400 g/L的氢氧化钠溶液中和样品处理液,再加入邻苯二甲醛衍生试剂与样品溶液中的氨基化合物进行反应,产生具有荧光信号的吲哚取代衍生物。以反相C18色谱柱(250 mm×4.6 mm,5μm)为分析柱,乙腈和磷酸盐缓冲液为流动相进行等度洗脱,荧光检测器检测,外标法定量。结果表明,甜蜜素在0.1~2.0 mg/L范围内呈良好的线性关系,其相关系数(r^(2))大于0.999。基于白酒样品,在0.1~1.0 mg/kg含量范围内进行3个浓度水平的加标回收试验(n=6),平均回收率为90.7%~100.9%,相对标准偏差为3.5%~5.6%,方法的检出限为0.03 mg/kg,定量限为0.10 mg/kg。应用本方法对市售9种白酒样品进行检测,结果与GB 5009.97-2016(第三法)液相色谱-串联质谱法所得结果一致。本方法具有成本低、灵敏度高、专属性强、定量结果准确的特点,适用于大批量白酒中甜蜜素的定量检测,可为生产企业或相关机构进行白酒中甜蜜素的日常监测提供有力的技术支持。

Sodium cyclamate in Baijiu is a key item in the China National Food Safety Supervision and Inspection Plan.A simple,economical,sensitive,and reliable method is urgently needed for routine analysis and internal quality control.A method based on high performance liquid chromatography with fluorescence detection(HPLC-FLD)was developed for the determination of sodium cyclamate in Baijiu by o-phthalaldehyde derivatization.First,the sodium cyclamate in the sample solution was converted into amino compounds using the desulfurization reaction under acidic conditions.Next,400 g/L sodium hydroxide solution was added to the sample solution for neutralization.The amino compounds in the sample solution were then derivatized with o-phthalaldehyde to produce indole-substituted derivatives that are capable of producing fluorescence signals.Separation was carried out on a C18 column(250 mm×4.6 mm,5μm)in isocratic elution mode using a mobile phase consisting of acetonitrile and phosphate buffer.Finally,the eluate was monitored using a fluorescence detector,and an external standard method was used for quantification.A good linear relationship was obtained in the range of 0.1-2.0 mg/L,with correlation coefficients greater than 0.999.The average recoveries of sodium cyclamate spiked at levels of 0.1-1.0 mg/kg in Baijiu samples ranged from 90.7%to 100.9%,with relative standard deviations(RSDs)of 3.5%-5.6%(n=6).The limits of detection and quantification were 0.03 and 0.10 mg/kg,respectively.Nine Baijiu samples collected from the market were tested,and the results demonstrated that the contents of sodium cyclamate detected by the developed method were consistent with those obtained using the liquid chromatography-tandem mass spectrometry(LC-MS/MS)method described in GB 5009.97-2016(the third method).The proposed method is economical,sensitive,specific,and accurate;thus,it provides a basic approach for the determination of sodium cyclamate in Baijiu samples and has great potential for routine analysis in foodstuffs.