Combination of On-Line Solid-Phase Extraction with LC-MS for the Determination of Potentially Hazardous Glycoalkaloids in Potato Products

A simple and rapid method for the determination of naturally occurring, potentially hazardous glycoalkaloids (GAs) in potatoes and their products has been developed. The procedure is based on the on-line solid-phase extraction of the acetic acid extracts from potato products and combined with liquid chromatography (LC)-mass spectrometry (MS) in a fully automated system (Symbiosis (TM), Spark Holland Instruments, Emmen, The Netherlands). As sorbent material HySphere (TM) 18HD was used for alkaloid enrichment. GAs were eluted with the LC gradient and directly analysed by MS. Detection of the analytes was achieved in the sensitive multiple reaction monitoring mode using two characteristic ions (m/z 98 as a qualifier for GAs and m/z 868.3 as a quantifier for alpha-solanine or m/z 852.4 for alpha-chaconine). Typical validation data for method precision (nu(k) alpha-solanine=5.3- 6.5, nu(k) alpha-chaconine=3.4-15.4), accuracy ( average recovery of alpha-solanine=84%, average recovery of alpha-chaconine=87%) and linearity over the range from 1 to 1,000 ng ml(-1) (R-2=0.9915 for alpha-solanine, R-2=0.9939 for alpha-chaconine) with detection limits of 0.3 ng ml(-1) for alpha-chaconine and 0.5 ng ml(-1) for alpha-solanine were obtained. GA contents of commercial potato products were determined by the new on-line method and afterwards compared with those obtained with an established high-performance LC routine procedure. Better performance of the on-line procedure was obvious from the standard deviations of both methods. Other advantages included a strong reduction of overall analysis time, human intervention and solvent consumption as well as waste production. The time required for the on-line analysis was 5 min, which would allow processing of almost 100 samples in 8 h.