食品中稀土总量测定方法

<正> 本文介绍稀土三元络合物于水溶液中直接用分光光度法测定食品中稀土总量。本方法应用偶氮类试剂(胂Ⅲ、胂K)按比例混合作为络合试剂;利用磺基水杨酸与抗坏血酸作为掩蔽剂和采用基线法测定来消除干扰因素。方法比用萃取分光光度法测定较为简便,仪器设备简单方法灵敏度0.01μg/ml,最低检出0.05ppm,平均回收率91.9％(n=14)。

DETERMINATION OF TOTAL RARE-EARTH METALS IN FOOD BY SPECTROPHOTOMETRIC METHOD

A simple spcctrophotometric method for determination of total rare-earth metals in food is presented. Weigh 5 gm of dry sample in a dish. After soaking the sample more than half an hour with 10 ml 3N H2SO4, evaporate to dryness on a hot plate and ash at 600℃. Dissolve the ash in 1 ml 6N HCl, and evaporate to dryness. Dissolve the residue in 2 ml water, and transfer it to a 10 mi-graduated tube. Wash the dish repeatedly with small amount of water. Transfer the washings to the same tube, and dilute to 10 ml with water. Pipette two portions of aliquots of 4 ml sample solution to two 10ml graduated tubes in which 2 ml of HCOOH-NH3 buffer (pH 3.7) is added. After mixing, add 1 ml each of 10% sulphosalicylic acid solution and 5% ascorbic acid solution. Make volume to 8 ml with water. Mix thoroughly. After 10 minutes, add 1 ml 15% alcoholic diphenylguani-dine solution, mix and add 1 ml 0.025% arsenazo Ⅲ &K solution. Mix, and measure the optical density at 680, 660 and 640 nm against a reagent blank solution. Calculate the total rare-earth metals content with a calibration curve. The sensitivity of the method is 0.01 μg/ml and the detection limit is 0.05ppm (5 gm of sample). The average recovery of added TRExOy is 91.9% (n = 14).