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

Abstract

The toxic glycoalkaloids α-solanine and α-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 α-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 α-solanine. The limit of detection was 2.4 mg of α-solanine kg⁻¹ soil. The new procedure was used for determination of α-solanine in spiked soils with varying content of organic matter and texture. Recovery for soil samples spiked with α-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 α-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 α-solanine was observed until day 17 for soil samples spiked with pure α-solanine kept at 5°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.

Keywords:

• Solanum tuberosum
• Glycoalkaloids
• α-Solanine
• Soil
• Extraction
• SPE

Acknowledgements

The authors wish to thank Kristina Egede Budtz for skilled technical assistance with the laboratory experiments.