Oxalic acid is a kind of dicarboxylic acid. It widely exists in the plant kingdom. It has different functions
in different fields. In medicine, printing and dyeing, plastics and other industrial production, oxalic acid
can be used as pharmaceutical raw materials, complexing agents, bleaching agents, precipitants and
reducing agents. From the perspective of food, long-term consumption of vegetables with high oxalic acid
content is easy to cause arthritis, low blood calcium, bladder stones, kidney stones and other diseases.
Therefore, it is considered to be an antagonist of mineral elements.
Fe3+ can form purple complex with sulfosalicylic acid at pH is 2. It has a characteristic absorption peak at
510 nm. Fe3+ and sulfosalicylic acid can produce a purple complex. Oxalic acid and oxalate can make it
lighter. At the same time, the absorbance of Fe3+ and sulfosalicylic acid complex decreases with the
increase of oxalic acid. Accordingly, the content of oxalic acid in the sample can be calculated from the
reduced absorbance value.
Required but Not Provided:
Spectrophotometer, desk centrifuge, water-bath/constant temperature incubator, transferpettor, 1 mL glass
cuvette, mortar/homogenizer, EP tube, ice and distilled water.
Protocol
I. Preparation:
Tissue: according to the tissue weight (g): the volume of the distilled water (mL) is 1:5-10. It is suggested
that add 1 mL of distilled water to 0.1 g of tissue. Homogenize on ice. Then add a little reagent IV (about
3-5 mg). After shaking and mixing, put it into a 75℃-water bath to decolorize for 30 min. Shake 2-3 times
during this period. Centrifuge at 3000 rpm for 15 minutes at room temperature after decolorization. Take
the supernatant on ice for test. (If the tissue precipitation and reagent IV cannot be removed by one-time
