The CHRONECT Workstation PAH and the newly developed imPAHct method (innovative multidimensional PAH clean-up technology) by Axel Semrau® provide a high level of automation.

Polycyclic aromatic hydrocarbons (PAHs) are formed during partial combustion and pyrolysis processes. They enter the environment through fumes, bound to dust particles or mineral oil residues. PAHs contaminate foodstuff either from the environment (e.g. dust particles on broad-leaf vegetables) or by roasting and smoking processes.

Laboratories analyze PAHs regularly. The reason for this is the partly very high carcinogenicity of the substance group and their broad distribution. European guidelines set limiting values which vary depending on the foodstuff. For the marker substance benzo[a]pyrene the value lies between 1-6 μg/kg while the total limit value for the PAH4 (this term summarizes benzo[a]pyrene, benzo[a]anthracene, chrysene and benzo[b]fluoranthene) is 1-35 μg/kg. The analysis of polycyclic aromatic hydrocarbons (PAH) is a great analytical challenge, due to the variety of food matrices and the detection limits demanded by the European Food Safety Authority (EFSA).

Due to the required sensitivity and complex matrices, PAH determination is a great challenge for analytics. As an analytical method either HPLC with fluorescence detection or GC-MS are used. Sample preparation is often extensive and time-consuming. Conventional analysis methods are using HPLC with fluorescence detection or GC-MS. In both cases, the sample preparation is often extremely extensive and complex. Recent requirements to laboratories include a reduction in sample handling time (Turn-Around-Time) and an increase in the sample throughput. Still, no losses within the analytical parameters, e. g. sensitivity, precision and accuracy are desired. Consequently, highly automated analytical procedures are necessary.

The CHRONECT LC-GC technology by Axel Semrau® has been established for many years in the routine analysis of foodstuff. It forms the ideal base for the solution presented here. The analytics of PAHs is done by a LC-LC-GC-MS/MS system and with the imPAHct method. To measure PAHs, a simple yet fast extraction of the sample is performed. The extract is quickly manually treated and then transferred to the CHRONECT Workstation PAH. Here, the extract is purified by a two-step LC separation (LC-LC Clean-Up) and subsequently analyzed via GC-MS. Edible oils may be measured straightforwardly.

Applying this intelligent matrix management, it is possible to determine the PAHs which are prescribed by EFSA fully automated. Depending on the detector, detection limits are reached which are even lower than the required European values for infant formula by a factor of 100.

The LC-GC solutions by Axel Semrau® are pre-installed and tested in our application laboratory. They are delivered in a ready-for-use condition. The installation includes a Site Acceptance Test as well as a briefing which enables the user to start working with our solution immediately. This ensures the fastest possible start of the routine measuring operation.

Benefits of the CHRONECT Workstation PAH and the imPAHct method

"Our expert in CTC PAL know-how and programming, and more than 20 years experience in the field of chromatography. Contact me if you have questions or need a quotation"

System Components

LC-LC-GC-MS/MS measurement of cocoa butter which was doted to 0.04 μg/kg with PAH

LC-LC clean-up: first and second purification

Calibration curve for benzo[a]pyrene between 0.04 - 4 μg/kg

This system has been designed for the sensitive and fast detection of mineral oil contaminants in different matrices such as cosmetics, foodstuff, oils and fats, feeding stuff and packagings.

The method is thoroughly published and tested. In an article in FoodProductionDaily the method was described as the most efficient one: "According to EFSA, the most effective method to detect MOH levels in food is through pre-separation by high performance liquid chromatography (HPLC) online coupled to GC with flame ionisation detection (FID)." (Source).

"Our expert in CTC PAL know-how and programming, and more than 20 years experience in the field of chromatography. Contact me if you have questions or need a quotation"

Special advantages of the LC-GC-System MOSH/MOAH

Technical setup of the device

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.

"Our expert in CTC PAL know-how and programming, and more than 20 years experience in the field of chromatography. Contact me if you have questions or need a quotation"

Advantages of LC-GC coupling

Components of the system

The illustrations below show exemplary chromatograms.
The LC-GC coupling provides two chromatograms simultaneously:

Signal of the UV detector from the HPLC
FID signal of the sterols

HPLC chromatogram: Separation of Δ5- and Δ7-sterols, an impossible process using the manual method. After analysis, the HPLC column rewinds and reconditions during the parallel GC run. This ensures the best sample throughput and steady initial conditions.

GC chromatogram from sunflower oil:

GC chromatogram from rapeseed oil: