Abstract
The analytical GREEnness metric (AGREE) tool is widely used as a reliable greenness assessment method for chromatographic analyses. The AGREE tool has the ability to determine the greenness of analytical methods in terms of both quality and quantity, whereas other commonly used methods assess the greenness either quantitatively or qualitatively. Greenness profiles of six chromatographic methods for simultaneous estimations of serotonin, dopamine, acetylcholine, GABA and glutamate were assessed using AGREE and NEMI tools as a case study. The AGREE assessment tool proved to be user-friendly, and provides a full profile of assessment, hence it can be described as the tool of choice for the assessment of LC-MS chromatographic methods. For optimum application, the weights of 4 of the 12 assessment criteria were set high (weight of four) due to their importance, namely criteria number 7 (waste), number 8 (analysis thruput/number of analytes per run), number 11 (toxicity) and number 12 (operator's safety). Setting proper weights of the assessment criteria contributed significantly to the discrimination of greenness of the compared methods. The selected greenest method for the analysis of the proposed quinary mixture showed an AGREE tool pictogram with a 0.66 score. Additionally, the selected method allows simultaneous estimation of seven constituents in total. It offers high sensitivity, allowing detection of acetylcholine, serotonin and glutamate at levels as low as 2 pg, and dopamine, norepinephrine, GABA and glycine at levels as low as 10 pg, and finally offers fast analysis where all components can be analyzed within 5 min.