羰基价测定影响因素考察

Investigation on impact factors of determination of carbonyl group value

目的对羰基价测定影响因素进行考察。方法采用GB/T 5009.37-2003食用植物油卫生标准的分析方法,采用2,4-二硝基苯肼比色法,分别考察测定结果的精密度,显色液稳定性,不同浓度的三氯乙酸溶液、氢氧化钾溶液、2,4-二硝基苯肼溶液、无醛乙醇以及不同的水浴时间、温度对羰基价测定结果的影响。结果该方法的精密度为0.9%~2.4%,显色液在0~90 min内的吸光度呈较快的下降趋势,羰基价的测定结果会随三氯乙酸浓度(3.0~5.0 g/100 mL)、2,4-二硝基苯肼浓度(40~60 mg/100 mL)、水浴时间(20~40 min)、水浴温度(50~70℃)的增大而增大,会随氢氧化钾浓度(3.0~5.0g/100 mL)的增大而降低、90%无醛乙醇会使显色液发生浑浊而无法测定。结论羰基价的检测应严格按照GB/T5009.37-2003中规定的条件进行测定。

Objective To investigate the impact factors in the measurement of carbonyl value. Methods The GB/T 5009.37-2003 Method for analysis of hygienic standard of edible oils was applied to determine the impact factors in the measurement of carbonyl value. The 2,4-dinitrophenylhydrazine colorimetric measurement was adopted, precision test and color liquid stability were studied, the impact of different concentrations of TCA solution, potassium hydroxide solution, 2,4-dinitrophenylhydrazine solution, aldehyde-free ethanol and different water bath time, temperature on carbonyl value were investigated. Result This method showed a good precision of 0.9%~2.4%, color absorbance showed a rapid decline in 90 min, carbonyl value would be increased when the impact factor of TCA concentration (3.0~5.0 g/100 mL), 2,4-dinitro-phenylhydrazine concentration (40~60 mg/100 mL), water bath time (20~40 min) and bath temperature (50~70 ℃) had raised. Meanwhile, carbonyl value decreased as the concentration of potassium hydroxide (3.0~5.0 g/100 mL) dropped, and 90% aldehyde-free ethanol made color liquid could not be measured due to the turbidity. Conclusion The detection of carbonyl value should be strictly carried out under the conditions prescribed in GB/T 5009.37-2003.