Extraction and determination of the potato glycoalkaloid α-solanine in soil

The toxic glycoalkaloids alpha-solanine and alpha-chaconine are produced in all parts of the potato plant, and post-harvest potato tubers may represent a source of soil and water contamination. A new method was developed for extraction and purification of alpha-solanine in soil samples. Soil samples were extracted with THF : H2O : ACN : CH3COOH (50 : 30 : 20 : 1) and the extract purified by SPE before HPLC determination of alpha-solanine. The limit of detection was 2.4 mg of alpha-solanine kg(-1) soil. The new procedure was used for determination of alpha-solanine in spiked soils with varying content of organic matter and texture. Recovery for soil samples spiked with alpha-solanine 1 h before extraction was 61-68% for soils low in organic carbon (< 2.2% C), and to 47% for soil high in organic carbon. Similar recoveries were obtained for alpha-chaconine. The reproducibility of the method shown by the relative standard deviation varied from 1.7 to 10.1%, depending on the soil type. No decrease in extractable alpha-solanine was observed until day 17 for soil samples spiked with pure alpha-solanine kept at 5 degrees C, while the content in samples spiked with potato materials showed a faster decline. This indicates that the degradation and/or ageing processes proceed relatively slowly for glycoalkaloids in soil matrices. This is the first method reported for determination of potato glycoalkaloids in soil.