Liquid chromatography with diode array detection combined with spectral deconvolution for the analysis of some diterpene esters in Arabica coffee brew

Abstract

14In this manuscript, the separation of four kahweol esters and four cafestol esters that are present in 15Arabica coffee brews was investigated using HPLC/DAD. Those compounds could not be baseline 16 separated in a single chromatogram using RP-LC but the kahweol esters could be selectively detected by 17 setting the wavelength at 290 nm. In this case the four kahweol esters were baseline separated allowing 18 for their quantification. Such approach was not possible for the cafestol esters and spectral deconvolution 19 was used to obtain deconvolved chromatograms that were specific to cafestol and kahweol esters 20 respectively. In each of those chromatograms, the 4 esters were baseline separated allowing for the 21 quantification of the eight targeted compounds. Because kahweol esters could be quantified either using 22 the chromatogram obtained by setting the wavelength at 290 nm or using the deconvolved chromatogram, 23 those compounds were used to compare the analytical performances. Slightly better LOD were obtained 24 using the deconvolved chromatogram (average LOD of 5.7 mg/L against 6.7 mg/L). Identical 25 concentrations were found in a real sample with both approaches. The peak areas of the different diterpene 26 esters in the deconvolved chromatograms were proven to be repeatable with an average intra-day 27 repeatability of 0.8 % (6 replicates) and an inter-day repeatability of 1.0% (3 successive days, two 28 replicates each day). This work demonstrates the accuracy of spectral deconvolution in conjunction with 29 HPLC-DAD (HPLC-DAD/SD) to mathematically separate co-eluting compounds using the full spectra 30 recorded by the DAD. 31 32

The Occurrence of Cafestol and Kahweol Diterpenes in Different Coffee Brews

“…Another study from the UP by Erny, Moeenfard and Alves (2015) showed that most studies on the subject were performed after saponification of kahweol and cafestol esters. But to better understand the composition of the diterpene esters in boiled Arabica coffee drinks, the authors performed the quantification by HPLC-DAD combined with spectral deconvolution, since the kahweol and cafestol esters eluted together.…”

Chromatographic Methods for Coffee Analysis: A Review

“…Prior to the analysis, the diterpenes were extracted from coffee beans using organic solvents, such as n-hexane, diethyl ether, petroleum ether, followed by saponification by an alcoholic KOH solution. Diterpene compounds were also determined in Arabica coffee by HPLC-DAD (Erny, Moeenfard & Alves, 2015). In Arabica and Robusta coffee beverages, previously unknown compounds affecting their flavor were identified by high resolution HPLC-MS (Nascimento et al, 2015).…”

Variability of some diterpene esters in coffee beverages as influenced by brewing procedures

“…Those files were opened using Matlab R2013b and the chromatographic data loaded into a two-dimensional (2D) array. The Matlab function was programmed using Matlab R2013b and can be found in previous published study (Erny et al 2015). Through applying spectral deconvolution to every spectrum, deconvoluted chromatograms were obtained that are specific to the cafestol and kahweol esters.…”

“…Free diterpenes (either originally present or after cleavage of the esters) can be analyzed using liquid or gas chromatography (Erny et al 2015) as well as spectrophotometric method (Dias et al 2013). However, to provide information on individual esters, diterpene esters should be analyzed through HPLC only after gel permeation chromatography or solid phase extraction (Kurzrock and Speer 2007).…”

“…Deconvolution aims to extract from the original data chromatographic and spectroscopic profiles of each individual component (Van Hoeylandt et al 2014). Deconvolution has been successfully implemented in order to identifying or quantifying several compounds (Erny et al 2015;Namara et al 2007;Van Hoeylandt et al 2014). This approach designated as HPLC-DAD with spectral deconvolution (HPLC-DAD/ SD) which allowed quantifying each diterpene esters despite an important co-elution (Erny et al 2015).…”