The determination of cholesterol is routinely performed in egg-containing foods. The aim is to determine the amount of the ingredient whole egg or egg yolk, as these are valuable components. This determination according to the Paragraph 64 method involves time-consuming, manual steps. The CHRONECT Workstation Cholesterol allows the fully automated determination of the egg content in food.
Advantages at a glance
- Comparable results to the reference method
- Measurement of up to 18 samples within 24 hours
- Improvement of the analysis quality
- Improvement of the turnaround time
- Reduction of resource consumption
- Reduction of manual effort
- Reduction of solvent consumption
Comparison with the reference method
The determination of the egg content with the CHRONECT Workstation Cholesterol is largely based on the specifications of the official method. The samples are saponified, extracted and starch-containing samples are subjected to enzymatic starch hydrolysis. For the automated approach, the processes were partially adapted. In an extensive comparison of the automated method with the official approach, good matches of the results were found for different matrices.
Basis of the CHRONECT Workstation Cholesterol is the LC-GC technology of Axel Semrau in combination with an automated sample preparation. The LC-GC technology connects an HPLC via a special interface with a GC equipped with a FID. The coupling is done via an interface consisting of a control unit and a heatable valve unit.
The temperature of the valve unit can be varied from room temperature to 150 °C. The temperature control effectively prevents condensation of the HPLC solvent in the valve unit and improves the stability of the system significantly. An integrated flushing of the valve unit with carrier gas prevents tailing of the solvent and possible carryover.
The HPLC system consists of a binary pump and a UV detector, which is used to check the HPLC chromatogram and to verify the correct fractionation. HPLC is used to separate cholesterol from matrix components. A fraction of the HPLC containing the cholesterol is then transferred from the LC directly to the GC. The measurement of cholesterol is performed as in the official method with a FID.
The control of the whole system is done user-friendly by the software CHRONOS by Axel Semrau. The XYZ robot CHRONECT Robotic integrated in the system takes over the sample preparation steps, which are based on the manual procedure of the Paragraph 64 method. The sample is saponified automatically. After neutralization an automated liquid-liquid extraction is performed. This is followed by automated drying using Na2SO4. Afterwards the again diluted extract is injected into the LC-GC-FID system. After the analysis, the HPLC is backwashed. This removes any remaining matrix and significantly improves the operational reliability and lifetime of the chromatographic columns.
If samples containing starch are analyzed, the described automatic procedure is extended by an enzymatic starch hydrolysis; this is also part of the Paragraph 64 method.
The use of LC-GC technology allows the elimination of a derivatization step. The obtained peak form of the cholesterol is very good even without derivatization.
All CHRONECT Workstations are commissioned in advance. In the course of a comprehensive Factory Acceptance Test not only the correct technical function but also the analytical performance is checked. This test run is repeated after the installation in a Site Acceptance Test during installation in the customer's laboratory. In this way, the analytical accuracy is verified and the system is ready for use immediately after installation.
Application from practice
The CHRONECT Workstation Cholesterol is a common development of Landeslabor Berlin-Brandenburg and Axel Semrau. The system received the Application Award from Laborpraxis at analytica virtual 2020.