Oxalate Determination: Analytical Problems Encountered with Certain Plant Species

Abstract

Accurate quantitative determination of oxalate in chemical analyses of edible plants is important because oxalate is a poisonous compound. The traditional KMn04-oxalate reduction-oxidation (Dye) method of analyzing for plant oxalate content presents two problems: (a) Plant pectins are not entirely separated in the determination of watersoluble oxalate and interfere in the oxidation of oxalate; and (b) a brownish-black precipitate containing ferrous iron is precipitated at the same pH as calcium oxalate and the precipitate interferes in determination of both water- and acid-soluble oxalate. Our modification of the Dye method consists of (a) using double-distilled water as the diluting medium, (6) increasing the acidity of the water-soluble oxalate medium after plant digestion to obtain complete removal of pectins, and (c) eliminating the ferrous iron-containing precipitate by filtration. Oxalate in the ferrous iron-containing precipitate is determined as calcium and magnesium salts by atomic absorption spectrophotometry; the value thus obtained is added to the oxalate value from the oxidation- reduction method. An indirect analytic method for oxalate, in which all of the oxalate was precipitated as the calcium salt and then measured by atomic absorption spectrophotometry, proved to be inaccurate

Antioxidant Activities, Nutritional Composition and Antinutritional Properties of Two Leafy Vegetables (Cleome rutidosperma and Cassia tora) Consumed in Adamawa State, Nigeria

“…The oxalate content of powdered samples was determined by the modified method of [20], alkaloid content of samples was determined using the gravimetric method [15].…”

Chemical composition of toasted and fermented earth ball (<i>Icacinia manni</i>) meals: Determination of their feeding value using broiler chickens

“…Titration of distillate was carried put with 2.02m sodium thio-sulphate using 1ml iodine and a drop of starch as the indicator. Total oxalate content was determined by the procedure of Abaga et al (1968), while the extraction and precipitation of phytic acid was performed according to the method described by Grewal and Jood (2006).…”

Effects of different heat processing methods on the antinutritional factors (ANFS) level of<i>P. reticulatum</i> seed meal

“…Antinutritional factors of the seed were determined using diverse standard methods viz: saponin was estimated using Hudson and El-Difrawi (1979) method, tannin (AOAC, 1980), cyanide (AOAC, 1984), oxalate (Abeza et al, 1968), phytate (Reddy et al, 1982 and phenols by Obadoni and Ochuko (2001).…”