Rapid determination of underivatized amino acids in fertilizers by ultra high performance liquid chromatography coupled to tandem mass spectrometry

Abstract

The analysis of 19 underivatized protein amino acids by ultra high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) is studied. Amino acids were separated by reversed phase, adding to the mobile phase pentadecafluorooctanoic acid as ion pairing reagent. The selected amino acids were eluted in less than 8 min. MS/MS parameters were optimized, using electrospray ionization (ESI) in positive mode for the detection of the amino acids. A simple solid-liquid extraction with water and heptafluorobutyric acid was used for the extraction of the compounds from the fertilizer. All amino acids were extracted with recoveries higher than 70% and relative standard deviation (RSD) lower than 22.5% (inter-day precision). Limits of quantification were always lower than 100 mg kg⁻¹ of sample, for all the compounds. The validated method is simple, fast and sensitive and it has been applied for the determination of amino acids in fertilizers.