Validation of a rapid ultra‐high‐performance liquid chromatography–tandem mass spectrometry method for quantification of chlorogenic acids in roasted coffee

Abstract

Chlorogenic acids (CGAs) are a large class of esters formed between quinic acid and hydroxycinnamic acids. They are present in coffee as a complex mixture of positional and geometric isomers, where caffeoylquinic acids (CQAs) are the most abundant, followed by dicaffeoylquinic acids (diCQAs), feruloylquinic acids (FQAs), and p-coumaroylquinic acids (p-CoQAs). The aim of this work is to develop a new reliable and fast liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for simultaneous identification and quantification of total amount of 11 CGAs in roasted coffee. Regarding sample preparation step, aqueous methanol and 100% aqueous ultrasonic extractions were evaluated. For the filtration Step 4, different membranes were tested, in order to fill the void of complete evaluation of extractables recovery when using different membranes, highlighting an incomplete recovery when using nylon filters. An LC/electrospray ionization (ESI)-MS/MS method was developed and validated following the European rules in terms of specificity, linearity, concentration range, limit of detection (LOD) and limit of quantification (LOQ), precision, and trueness, in order to obtain a useful quality control tool for roasted coffee. The method was applied for quantification of CGAs of a roasted coffee sample previously characterized by an interlaboratory circuit (LVU), and results were compared with the quantitation of CGAs via UHPLC-DAD. The quantitative results were expressed as 5-CQA equivalents, and the validation of this approach opens the way to reliable, cheap, and environmental-friendly tools for quality control purposes.

LC–MS methods combination for identification and quantification of trans‐sinapoylquinic acid regioisomers in green coffee

“…Quantitative analysis was performed; the concentration of each SiQA isomer in the samples was calculated as 5‐CQA equivalent using an external standard method through calibration curves. The method was validated in terms of specificity, linearity, concentration range, accuracy, and repeatability according to the criteria specified in EU Commission Decision 2002/675/EC following the procedure previously published 25 . To evaluate the linearity of the method, six standard solutions approximately equally spaced with concentrations ranging from 0.068 to 6.8 μg/mL of 5‐CQA were analyzed in duplicate on three different days.…”

“…CEs were optimized to maximize the transition signals (precursor ion to product ion). The method was validated in terms of specificity, linearity, concentration range, LOD, limit of quantification (LOQ), precision, and trueness following the guidelines previously reported 25 . All data were processed using MultiQuant 3.0.2. software (Sciex, Framingham, MA, USA), and statistical analysis were carried out using XLSTAT 2018 (Microsoft, Sunnyvale, California USA).…”

“…The method was validated in terms of specificity, linearity, concentration range, accuracy, and repeatability according to the criteria specified in EU Commission Decision 2002/675/EC following the procedure previously published. 25 To evaluate the linearity of the method, six standard solutions approximately equally spaced with concentrations ranging from 0.068 to 6.8 μg/mL of 5-CQA were analyzed in duplicate on three different days. To avoid errors, the individual solutions were prepared by dilution from the common stock solution, kept in amber glass.…”

“…From a functional point of view, CGAs have been suggested to be involved in the defense mechanism against environmental aggressions, 10 a complete and exhaustive chemical characterization of plant metabolites in different botanical species appears crucial for the future of the coffee sector. For identification of SiQAs, different green coffee samples were analyzed as well as Gardeniae Fructus samples to check its use as a possible “surrogate standard.” After identification by UHPLC‐ESI‐QqTOF‐MS/MS in different samples, and then, thanks to the high resolution, by bypassing the obstacle of the lack of commercially available standards for this class of CGAs, implementation of a previously optimized UHPLC‐ESI‐MS/MS method for quantification of CGAs was applied 25 in order to quantify SiQAs. In addition, to confirm the presence of all three SiQA regioisomers in Robusta coffee, Arabica coffee samples from different geographical origins and samples of different botanical wild species ( Coffea liberica and Coffea pseudozanguebariae ) have been characterized.…”