Interference of Amino Acids in Pulsed Amperometric Detection of Peanut Sugars1

Abstract

High performance anion exchange chromatography and pulsed amperometry were used to separate and quantify peanut sugars extracted with methanol: chloroform:water (60:25:15, V/V/V), a highly polar sol vent which solubilizes other seed components including amino acids. Free sugars were separated on an anion exchange column using a sodium hydroxide gradient and detected with a pulsed amperometric detector equipped with a gold electrode. Free amino acids in the seed extract interfered with sugar analysis by causing peak shifting and co-elution of some amino acids with sugars. Free arginine co-eluted with inositol resulting in a peak area which was 42% of the actual total area for both compounds. Proline co-eluted with fructose. Serine eluted on the leading edge of sucrose. Peak areas of these interfering amino acids were either "additive" or "subtractive" to sugar peaks. Altering the gradient elution or using cation syringe filters to remove contami nant amino acids permitted the accurate identification and quantification of peanut seed sugars. Results from this study suggest applications that can be applied in other biological systems containing free amino acids and sugars.

Investigations into Genotypic Variations of Peanut Carbohydrates

“…Retention times for arabinose, mannose, and galactose did not match any of the unknown components. The use of the cation syringe filters (Singleton et al, 1996) on the rehydrated extract before analysis eliminated the possibility of interfering amino acids in the unknowns. Verbascose and ajugose have been reported as carbohydrate components in peanuts by Tharanathan et al (1975Tharanathan et al ( , 1976 and Amaya et al (1978).…”