Environmentally Sustainable Achiral and Chiral Chromatographic Analysis of Amino Acids in Food Supplements

Abstract

Two LC methods were developed for the achiral and chiral reversed-phase (RP) analysis of an amino acid (AA) pool in a food supplement, in compliance with the main paradigms of Green Chromatography. A direct achiral ion-pairing RP-HPLC method was optimized under gradient conditions with a water-ethanol (EtOH) eluent containing heptafluorobutyric acid (0.1%, v/v), to quantify the eight essential AAs (Ile, Leu, Lys, Met, Phe, Thr, Trp, and Val) contained in the food supplement. Thus, the usually employed acetonitrile was profitably substituted with the less toxic and more benign EtOH. The method was validated for Leu and Phe. The chiral LC method performed with a teicoplanin chiral stationary phase was developed with a water-EtOH (60:40, v/v) eluent with 0.1%, v/v acetic acid. The enantioselective analysis was carried out without any prior derivatization step. Both developed methods performed highly for all eight AAs and revealed that: (i) the content of six out of eight AAs was consistent with the manufacturer declaration; (ii) only L-AAs were present. Furthermore, it was demonstrated that a two-dimensional achiral–chiral configuration is possible in practice, making it even more environmentally sustainable. A molecular modelling investigation revealed interesting insights into the enantiorecognition mechanism of Lys.

Optimization of analytical method greenness scores: a case study of amino acid enantioseparations with carbonated aqueous systems

“…18 The authors of method 3 did not perform any quantitative metrics of greenness to compare the proposed method to the original one and simply replaced methanol with the “less toxic and more benign EtOH”. 21 The effort is commendable, but the resulting separations had longer run times with ethanol (max. 50 min) than methanol (max.…”

“…), 5 µm FPP) and an ethanol water MP (40/60, pH 3.9 by FA). 21 With this large column and a flow rate of 0.8 mL min −1 , the deadtime is >3.1 minutes alone, and the run times reach ∼50 minutes for lysine. These slow separations result in a large amount of waste generated and high AMGS, reaching 61 and averaging 22 for the AAs tested.…”

“…16 The importance of the chirality of amino acids has driven many analytical procedures to be reported in the literature over the past five decades, [9][10][11][17][18][19][20] with some of this research focusing on or mentioning greenness/sustainability. [21][22][23][24] The chirality of AAs in space is a key area of research as a possible origin of Earth's biological homochirality, biomarkers for potential extraterrestrial life, or evidence of assymetric photolysis. The United States National Aeronautics and Space Administration (NASA) has special interests in developing lightweight and small instruments for extraterrestrial in situ chiral/ achiral chemical analysis.…”

“…16 The importance of the chirality of amino acids has driven many analytical procedures to be reported in the literature over the past five decades, 9–11,17–20 with some of this research focusing on or mentioning greenness/sustainability. 21–24…”

A Green Liquid Chromatography Method for Simultaneous Quantification of Caffeine and its Three Major Metabolites in Urine, Drinks, and Herbal Products

“…This issue can be overcome by increasing the temperature of the mobile phase, by using ultra-performance liquid chromatography instrumentation, or by adopting monolithic stationary phases [1,7]. The use of ethanol has been explored recently by Varfaj et al [6,8]. Another green mobile phase proposed is pure water without additives, used at ambient temperature, but this approach requires polarembedded specific stationary phases [7].…”