A validated LC–MS/MS method for quantitative determination of L-dopa in Fagioli di Sarconi beans (Phaseolus vulgaris L.)

An analytical method based on ultrasound assisted extraction (UAE) and liquid chromatography 36 coupled to electrospray tandem mass spectrometry (LC–ESI/MS/MS) was validated and applied for 37 determining L-dopa in four ecotypes of Fagioli di Sarconi beans (Phaseolus vulgaris L.), marked 38 with the European label PGI (Protected Geographical Indication). The selectivity of the proposed 39 method was ensured by the specific fragmentation of the analyte. Simple isocratic chromatographic 40 conditions and mass spectrometric detection in multiple reaction monitoring (MRM) acquisition 41 mode were used for sensitive quantification. The LC–ESI/MS/MS method was validated within a 42 linear range of 0.001–5.000 μg/mL. Values of 0.4 and 1.1 ng/mL were obtained for limit of detection 43 and limit of quantification, respectively. The repeatability, inter-day precision and recovery values 44 ranges were 0.6-4.5%, 5.4-9.9%, 83-93 %, respectively. Fresh and dried beans cultivated exclusively 45 with organic methods avoiding any synthetic fertilizers and pesticides, as well as pods, were analyzed 46 showing a L-dopa content ranging from 0.020±0.005 μg/g to 2.34±0.05 μg/g dry weight.