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L-抗坏血酸广泛存在于蔬菜、水果等人类食品中,是人的重要的不可缺少的营养成分。含量测定方法常采用分光光度法及容量分析法、作者采用最近国外使用的黄瓜组织膜电极测定维生素C。以三点系列标准法结合微型计算机处理数据,分析结果与“中华人民共和国国家标准——食品中维生素C的测定”比较,结果基本一致。考察最佳测定条件:pH6,温度32℃,黄瓜表皮下3mm处的切片响应值最大,切片厚度以300～500μm为宜(切片太薄,电极寿命短,太厚,则响应时间长),根据浓度-△E曲线测定,其电极线性范围为1.24×10~(-5)～1.86×10~(-4)mol·L~(-1)。该方法的平均回收率为102.7%。用该方法测定Vc含量,用量小(0.1～0.7ml),液样不需脱色处理,不用特殊试剂。但由于生物体是多酶体系,可能存在干扰,如用此电极测定苹果、梨等样品中Vc含量时出现较大误差。
L-ascorbic acid is widely found in human food such as vegetables and fruits and is an important and indispensable nutrient for human. Determination of content often use spectrophotometry and volumetric analysis, the author used the cucumber tissue membrane electrode recently used abroad to determine vitamin C. Three series of standard method combined with microcomputer processing data, the analysis results and the “People’s Republic of China National Standards - Determination of vitamin C in food”, the results are basically the same. The optimum conditions were as follows: pH6, temperature 32 ℃, the slice response value of cucumber subepidermal 3mm was the largest, the slice thickness was 300 ~ 500μm (slice too thin, electrode life is short, too thick, the response time is long) Concentration - △ E curve, the linear range of the electrode is 1.24 × 10 -5 ~ 1.86 × 10 -4 mol·L -1. The average recovery of this method was 102.7%. The method of determination of Vc content, a small amount (0.1 ~ 0.7ml), liquid sample without decolorization, without special reagents. However, because the organism is a multi-enzyme system, there may be interference. For example, when using this electrode to determine the Vc content in apples and pears, there is a big error.