对不同种类的食品提出了不同的试样预处理方法,并对预处理中提取各被测化合物的溶剂的选择,提取时试样溶液酸度(pH值)的选定,以及除去干扰物质的试液净化条件等因素作了较深入的试验.经预处理后的澄清试液供高效液相色谱法(HPLC)分析.分析时采用ODS C18色谱柱对被测化合物(苯甲酸、山梨酸、水杨酸及糖精钠)进行分离,所用流动相为由甲醇及0.02 mol·L-1乙酸铵溶液按9比91(体积比)混合组成的溶液.测量中用二极管阵列检测器(DAD),检测波长为230 nm,按保留时间及特征光谱图进行定性.定量测定采用外标法,测量与各化合物浓度相对应的峰面积.四种化合物的检出限均小于0.000 1 g·L-1,用标准加入法进行了回收率试验,所得结果在82.3%~109.5%之间,计算得相对标准偏差(n=8)小于10%.

Different procedures for pretreatment of foodstuff samples were described and chosen according to different kinds of foodstuff.Conditions of sample pretreatment,including the choice of solvents for extraction of the 4 additive compounds to be determined (benzoic acid,sorbic acid salicylic acid,soluble saccharin),the choice of suitable acidity (pH value) of the sample solutions and the purification condition to remove the interfering substances,were studied thoroughly.After pretreatment of the sample,the clear sample solution was submitted to HPLC analysis.Separation was performed by using ODS C18 column and mobile phase composed of methanol and 0.02 mol·L-1 ammonium acetate solution mixed in the ratio of 9+91 by volume.Diode array detector at 230 nm was used in the measurements.Qualitative analysis was carried out according to the retention time and checking with characteristic spectra.External standard method was used in the determination by measuring the peak area in respect to the concentration of the compound determined.Detection limits for all the 4 compounds were found to be less than 0.000 1 g·L-1.Values of recovery of the compounds found by the standard addition method were in the range 82.3%-109.5%.Precision of the method was also tested,giving values of RSD′s (n=8) less than 10%.