Using Theoretical Correction Factors for Quantitative Analysis of Sterols and Sterol Concentrates

Abstract

A common detector for the analysis of sterols and sterol concentrates by gas chromatography is the flame ionization detector (FID). The detector measures the response of ions from a molecule as it is pyrolyzed in a hydrogen flame. The response is relative to the number of hydrogen and carbon atoms in a molecule and it gives different responses for the same amounts of different analytes. Theoretical correction factors (TCF) can be used to account for these differences during data analysis and are based upon the number of active carbons in a molecule and can be calculated from known structures. TCF have been used to provide a more reproducible approach to the analysis of sterol concentrates in raw materials. Use of empirical correction factors (ECF) requires determination of relative responses for each analyte and also a high purity standard (and determination of that purity), which can be expensive or difficult to obtain for the more uncommon sterols. Experiments have been conducted to determine ECF for Ergost-5-en-3-ol, (3b,24R), commonly known as campesterol, Stigmasta-5,22-dien-3-ol, (3b,22E), commonly known as stigmasterol, and Stigmast-5-en-3-ol, (3b), commonly known as b-sitosterol and compared to the calculated TCF for these same sterols. The experiments evaluated differences in concentration, standard purity, and injection technique and found that all three factors had an effect on the determination of ECF. It was also found that cool on column injections gave more accurate ECF values and are preferable for quantitative analysis of sterols.

Crude Palm Oil from Interspecific Hybrid Elaeis oleifera × E. guineensis: Alcoholic Constituents of Unsaponifiable Matter

“…The peak area of each identified component was used to calculate UM composition by using the internal standard addition method. Theoretical correction factors (TCF) relative to squalane (internal standard) were calculated as described by Costin et al [8] for the identified compounds: as pointed out by the authors, the trimethylsilyl group contains three carbons that contribute to the response in the FID, thus they were included in the calculation of TCF for the silylated compounds.…”

Quantitation of Sterols and Steryl Esters in Fortified Foods and Beverages by GC/FID

“…The total sterols are determined by utilizing theoretical correction factors (TCF) to determine the amount of each sterol relative to the internal standard, Epicoprostanol [15]. TCF are used for sterol quantification as they provide more reproducibility compared to empirical correction factors [15].…”

“…The total sterols are determined by utilizing theoretical correction factors (TCF) to determine the amount of each sterol relative to the internal standard, Epicoprostanol [15]. TCF are used for sterol quantification as they provide more reproducibility compared to empirical correction factors [15]. In addition, TCF do not require the preparation and analysis time associated with calibration curves nor the need to acquire pure sterol standards that may be difficult to find [15].…”

“…TCF are used for sterol quantification as they provide more reproducibility compared to empirical correction factors [15]. In addition, TCF do not require the preparation and analysis time associated with calibration curves nor the need to acquire pure sterol standards that may be difficult to find [15]. Since different sterols have different molecular masses, they can give different responses in a FID.…”

“…Formulated foods and beverages include milk, spoonable yogurt, bread, orange juice, apple juice, margarine spread, coffee creamer and puffed corn cereal. Theoretical correction factors (TCF) are used for sterol quantification [15]. There is no evidence to suggest that the methods presented herein could not be used for the quantitation of stanol or stanol ester fortified foods and beverages.…”