Fully automated analysis of sterols for food control analytics
A determination of sterols is essential for the control of purity and quality of for example edible oils. According to the ISO 12228 method, the sample first is saponified and then purified by solid phase extraction.
After neutralization and restriction, the obtained analytes are further purified by means of preparative thin-layer chromatography. Next, the manual removal of the fraction from the TLC plate is necessary. Then, the fraction is derivatized and chromatographically analyzed by GC-FID. Due to numerous manual steps during this procedure, the method is highly time-consuming and error-prone.
Axel Semrau® provides a solution for this kind of analysis. It is based on a LC-GC technology which is also used within the MOSH/MOAH system and is in routine use in several laboratories. Saponification of the sample and many further preparative steps are fully automated. For this purpose, a DualPAL (CTC Analytics) is applied. The DualPAL includes two syringes: One syringe is used to meter the required reagents for saponification, the second smaller syringe is used to perform the injection into the HPLC. Subsequently, purification is carried out through HPLC, which is directly connected to the GC-FID detection.
The sterol-containing HPLC fractions are specifically selected and directly transferred to the GC system. Disturbing components are eliminated by this method. By performing LC first, a preparative thin-layer chromatography is not required anymore. Thus, manual steps are limited to the weighing and positioning of the sample within the autosampler. This great level of automation is achieved through the DualPAL concept with two different syringes and the use of LC for purification in the GC.
An extensive validation of this method in customers laboratories was performed. Therefore, numerous samples containing different known concentrations and distributions of sterols were analyzed. The results verified that the presented method is precise and provides reproducible results. Concerning analytical parameters, this method is equally good or even better than the required ISO values.
The entire control of the system is provided through the user-friendly software CHRONOS, which simplifies complex methods.
Advantages of LC-GC coupling
- High sample throughput
- High level of automation
- Low risk of contamination
- Excellent reproducibility
- Best possible sensitivity
- Security of investment
- Expandable to other applications e.g. determination of mineral oil in vegetable oil, determination of the alkyl ester level, determination of PAH
- Short familiarization phase through installation of the entire method including a training course
- Qualified support
Components of the system
- KNAUER Smartline HPLC system
or Agilent 1260 HPLC with UV detector and degasser or Shimadzu LC 20
- CTC DualPAL for automated saponification and purification
- DANI Master GC with FID, alternatively other GCs
- LC-GC Interface for coupling of HPLC to the GC
- Data exchange system including control software and data mining
- Accessories and consumables