Prediction of response factors for gas chromatography with flame ionization detection: Algorithm improvement, extension to silylated compounds, and application to the quantification of metabolites

Abstract

We previously showed that the relative response factors of volatile compounds were predictable from either combustion enthalpies or their molecular formulae only 1. We now extend this prediction to silylated derivatives by adding an increment in the ab initio calculation of combustion enthalpies. The accuracy of the experimental relative response factors database was also improved and its population increased to 490 values. In particular, more brominated compounds were measured, and their prediction accuracy was improved by adding a correction factor in the algorithm. The correlation coefficient between predicted and measured values increased from 0.936 to 0.972, leading to a mean prediction accuracy of ± 6%. Thus, 93% of the relative response factors values were predicted with an accuracy of better than ± 10%. The capabilities of the extended algorithm are exemplified by (i) the quick and accurate quantification of hydroxylated metabolites resulting from a biodegradation test after silylation and prediction of their relative response factors, without having the reference substances available; and (ii) the rapid purity determinations of volatile compounds. This study confirms that Gas chromatography with a flame ionization detector and using predicted relative response factors is one of the few techniques that enables quantification of volatile compounds without calibrating the instrument with the pure reference substance.

The essential oil of Achillea ageratifolia (Sm.) Boiss. subsp. serbica (Nyman) Heimerl (Asteraceae) revisited: the stereochemical nomenclature issues, structural elucidation and synthesis of (new) sabinyl esters

“…Each sample was analysed for three consecutive runs. Quantification of other identified essential‐oil components was carried out using peak‐area normalization with response factors from literature . Experimentally obtained values of response factors for representatives of all groups of essential‐oil constituents were in good agreement with those reported in previous reports .…”

Chemical characterization and in vitro antioxidant and antimicrobial activities of essential oil from Commiphora wildii Merxm. (omumbiri) resin

“…The values used in the formula above were calculated using the formula:where is the measured RRF of each of the ISTDs relative to MO and is the predicted RRF of sample constituent i relative to MO. The latter values were calculated for each sample constituent based on their molecular formulae (see Appendix S1) . For the determination of the values, solutions of decane (1.49 mg mL –1 ) and 3‐carene (4.32 mg mL –1 ) were prepared at 50, 100, and 150% levels of the specified concentrations, and each solution contained MO (4.36 mg mL –1 ) as the internal standard.…”

IOFI recommended practice for the use of predicted relative‐response factors for the rapid quantification of volatile flavouring compounds by GC‐FID

“…Low‐boiling solvents (methanol, dichloromethane, pentane, diethyl ether, etc.) yield less accurate results and are not recommended …”

“…The use of experimentally‐determined RRF clearly remains the most accurate means whenever pure authentic standards are available. However, when this is not the case, or when a complex multi‐component mixture makes the experimental RRF measurement too time‐consuming, the predicted RRF are a valid alternative, with a mean accuracy of 6.0% …”

“…This technique, described in a number of publications, with applications reported in the flavour, fragrance, and other domains, can also be used to estimate the purity of chemically‐defined flavouring substances or chromatographic standards using these predicted RRF.…”