Analysis of Food Contact Materials using Comprehensive Gas Chromatography in combination with High Resolution Time-of-flight Mass Spectrometry.

Food contact materials are materials, that are intended to be in contact with food. These can be things, that are quite obvious like a glass, a can for soft drinks, but also machinery in a food factory or a coffee machine. Food contact materials can be constructed from a variety of materials like plastics, rubber, paper, coatings, metal etc. In many cases a combination is used; for example a carton box for juices can include (from the inside to the outside): plastic layer, aluminium, paper, printing and top coating. During the contact of the food contact materials with the food, molecules can migrate from the food contact material to the food. Because of this, in many countries regulations are made to ensure food safety. In Europe the framework Regulation (EC) No. 1935/2004[1] applies to all food contact materials. Leachable substances are subdivided into Intent&Listed, Intent&Non-Listed and Non-Intent&Non-Listed.
Especially for the last group (NIAS), established analysis methods using an LC-GC-FID system do not provide enough information. In this study comprehensive two-dimensional gas chromatography (GCXGC) in combination with high resolution time-of-flight mass spectrometry was evaluated.
Beside liquid injections, sample introduction techniques like static/dynamic headspace and thermal desorption were included. A greater amount of information can be gained by pairing an additional complementary separation with two-dimensional gas chromatography (GCxGC). The Consumable Free (CF) LECO GCxGC system takes advantage of a dual-stage, quad-jet thermal modulator positioned between the two columns and a secondary oven allows independent temperature control of the second dimension column. The addition of a high resolution multi-reflecting TOFMS, with a resolving power greater than 25000 (FWHM) and sub ppm mass accuracies, provided  accurate mass data adding more confidence in analyte identification. Besides traditional EI ionization chemical ionization (CI positive) was used to confirm the mass to charge ratio of the molecular ion.The data processing focused on both targeted and non-targeted analysis. Advanced software features like a comparison tool (Reference) were used to contrast and identify differences between two samples.

 

Analysis of Contaminants in Surface Water using Comprehensive Two-Dimensional Gas Chromatography with different Time-of-Flight Mass Spectrometers

The monitoring of water samples for the presence of organic pollutants at trace level requires sensitive and selective analytical methods. Due to the wide polarity range, thermolability and chemolability, liquid chromatography–mass spectrometry (LC-MS) is the preferred technique for this application. However, the usage of LC-MS for specific compound groups to be monitored is not really satisfactory due to the low efficiency of electrospray ionization and/or APCI.
In actual practice, capillary gas chromatography (GC) is still an important separation technique, which easily can be combined with selective and sensitive thermionic, flame-photometric  and MS detectors. As sample complexity increases, additional resolution can be gained by comprehensive two-dimensional  gas chromatography coupled to time-of-flight mass spectrometry (GCxGC-TOFMS).
Real-life water samples, spiked at (sub) ppb-level, have been subjected to this instrument configuration with solid-phase extraction (SPE) as sample preparation step. SPE is generally preferred over liquid–liquid extraction, because it is less laborious, uses less organic solvent, yields better analyte enrichment and is easier to couple to chromatographic systems for online operation. Combining the sample cleanup potential of an optimized SPE method with the large peak capacity of GCxGC and detection capabilities of a TOF mass spectrometer with nominal mass resolution leaded to a confident separation and detection of defined target compounds. Special attention has been paid to the similarity of the acquired spectra (absence of skewing).
Confident identification of non-target analytes was best accomplished by the use of high resolution mass spectrometry. The LECO multi-reflecting TOFMS, with a resolving power greater than 25000 (FWHM) and sub ppm mass accuracies, proved to be the ideal solution for confident analyte identification within a complex sample matrix, based on accurate mass data.

Juergen Wendt

Dr. Juergen Wendt is the European Technical Product Specialist for LECO’s High Resolution Time of Flight Systems, based at the new European Application and Technology Centre in Berlin. A position he has held since 2011.
Prior to that he worked as a Senior Application Chemist in the European Application
Lab of Agilent Technologies. Here he was responsible for small molecule applications
in the fields of environmental, food safety and forensics.
Dr. Wendt holds a PhD degree in analytical and inorganic chemistry from the Johannes Gutenberg University of Mainz, Germany.