On-line coupled liquid chromatography-gas chromatography (LC-GC) and LC-LC-GC for detecting irradiation of fat-containing foods

Summary On-line coupled liquid chromatography-gas chromatography-flame ionisation detection (LC-GC-FID) enables efficient and unambiguous determination of irradiation for some fat-containing foods (e.g. meat). Other products, however, contain interfering components or are contaminated, e.g., with mineral oil. Since more selective detection by mass spectrometry has limited success, the determination was improved by a more selective isolation of some key components among the fat degradation products, e.g. the dienes or trienes, by LC-LC-GC-FID. Applications are shown for soup mixes, some spices, fish, and shrimps.

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Nachweis der Bestrahlung fetthaltiger Lebensmittel durch direkt gekoppelte LC-GC und LC-LC-GC

Zusammenfassung Die Bestrahlung einiger fetthaltiger Lebensmittel, z. B. Fleisch, kann mit direkt gekoppelter LC-GC-FID rationell und eindeutig nachgewiesen werden. In anderen Proben wird die Analyse aber durch Inhaltsstoffe des Produktes oder durch Verunreinigungen (z. B. mit Mineralöl) gestört. Da selektivere Detektion durch Massenspektrqmetrie wenig verspricht, wurde der Nachweis durch selektivere Isolierung von Schlüsselkomponenten unter den Bestrahlungsprodukten, z. B. der Diene oder Triene, mittels LC-LC-GC yerbessert. Anwendungen werden gezeigt für Suppenpulver, einige Gewürze, Fisch und Garnelen.

     

GC–MS characterization of oligomers in polyadipates used as plasticizers for PVC in food contact

Fourteen commercial polyadipates and a polysebacate were analysed for their components of a molecular mass below 1000 Da, primarily with the aim of generating the background data for measuring the migration of this type of polymeric additives from plasticized PVC (e.g. cling films and gaskets of lids) into foods or food simulants. Since the composition of the material <1000 Da varies between the polyadipates, the main components must be identified to enable a correct quantification. Polyadipates differ in the diol used as linker, their termination (acid or alcohol) and in the end‐capping (free alcohols, acetylation, acylation with fatty acids, esterification with octanol/decanol). Gas chromatography (GC) provides good separation, but the material remaining in the column up to high temperatures decomposes and forms a hump in the rear part of the chromatogram. Examples of mass spectra are shown, the most indicative fragments pointed out and spectra of 159 components listed. The polyadipates and the sebacate are characterized by their structure, the main components <1000 Da and the fraction of material <1000 Da. Copyright © 2006 John Wiley & Sons, Ltd.     

Recognition of Adulterated Oils by Direct Analysis of the Minor Components

Recognition of adulteration by other oils via direct analysis of the minor components (“sterol fraction”) is shown for olive oil. 10 % of various oils were admixed, the free alcohols silylated and the minor components analyzed by on-line coupled LC-GC-FID. For most oils, even smaller additions can be recognized. Admixed oils can no longer be determined, however, if their minor components have been removed by strong raffination. Bleaching of rapeseed oil with 7% of earth at 180 °C, in fact, completely removed free and esterified sterols.     

On-Line LC-GC for the Analysis of the Minor Components in Edible Oils and Fats – The Direct Method Involving Silylation

The previous on-line LC-GC method for the direct analysis of the minor components in oils and fats (without cleavage of esters) was modified: The free alcohols/sterols were silylated instead of acylated, and the LC fraction transferred to GC is widened to range from the beginning of the LC chromatogram up to the sterol esters. Silylation eliminated the problem that acylation may esterify some free alcohols with free fatty acids from the oil if the oil or fat is of high acidity. Widening of the LC fraction to include squalene and the tocopherols added information to that previously obtained.     

Enrichment for reducing the detection limits for the analysis of mineral oil in fatty foods

A German draft for a regulation requires that there must be no migration of mineral oil aromatic hydrocarbons (MOAH) from recycled paperboard into food. The Federal Institute for Risk Assessment (BfR) is requested to establish the detection limit. It was previously shown that the detection limit of the commonly used methods is below 0.1 mg/kg for the majority of the foods, but substantially higher in fatty products because of limited capacity of the liquid chromatographic preseparation to retain fat, interference by olefins and, if also the mineral oil saturated hydrocarbons (MOSH) should be analyzed, the natural paraffins primarily consisting of odd-numbered n-alkanes. A method is described for the enrichment of the MOSH and MOAH conceived as an auxiliary tool for fatty foods analyzed by the conventional methods, such as on-line HPLC–GC. In a double bed liquid chromatographic column, the lower packing consists of a mixture of activated aluminum oxide, silica gel with silver nitrate and activated silica gel, the upper of activated silica gel. The technical detection limit in edible oils is below 0.3 mg/kg, which translates to less than 0.1 mg/kg in the dry foods packed in recycled paperboard. The distinction between migrated mineral oil and that present before packaging often presupposes the availability of the food prior to packaging.     

Assurance of compliance within the production chain of food contact materials by good manufacturing practice and documentation – Part 3: Lids for glass jars as an example

Parts 1 and 2 of this work outlined the background and the general terms of assuring compliance of food contact materials (FCM) with European legislation by good manufacturing practice (GMP) and compliance declaration (CD). All stages of the manufacturing process are engaged in GMP defined as the process to achieve compliance of the final product with Article 3 of the Framework Regulation 1935/2004 and the specific legislation derived there from. For each relevant aspect, either compliance is concluded (explicitly stating compliance if this is required) or compliance work is delegated to later stages of manufacturing by corresponding instructions in the documentation accompanying the product. A compliance box (CB) is proposed to structure the process and the documentation. Here it is applied to metal closures for glass jars, which are internally coated and contain a gasket of plasticized PVC. A specific composition is assumed and possible compliance work discussed to illustrate how the system is conceived. The system is tested by the problems and issues concerning these lids during the last 10 years: indeed, most of them would have been avoided.     

The two options for sample evaporation in hot GC injectors: thermospray and band formation. optimization of conditions and injector design.

Although classical split and splitless injection is more than 30 years old, we only start to understand the vaporization process in the injector. Solvent evaporation determines much of the process and is the first obstacle to overcome. Videos recorded on devices imitating injectors showed that sample (solvent) evaporation is often a violent process which is poorly controlled and might well explain many of the puzzling quantitative results often obtained. We do not adequately take into account that two vaporization techniques are in use. Partial solvent evaporation inside the syringe needle (optimized as "hot needle injection") produces thermospray: the sample liquid is nebulized upon leaving the needle. The resulting fog is rapidly slowed and moves with the gas. Solute evaporation largely occurs from microparticles suspended in the gas phase. Empty liners are most suitable. Fast autosamplers suppress vaporization in the needle, i.e., nebulization, and shoot a band of liquid into the chamber that must be stopped by a packing or obstacles suitable to hold the liquid in place during the 0.2-5 s required for solvent evaporation. Solute evaporation largely occurs from the surfaces onto which the sample is deposited. Insights into these mechanisms help optimize conditions in a more rational manner. Methods should specify whether they were optimized and validated for injection with thermospray or band formation. The insights should also enable a significant improvement of the injector design, particularly for splitless injection.     

Bracing of patients after fusion for degenerative problems of the lumbar spine--yes or no?

The majority of spine fusions currently performed are for degenerative conditions. Controversy exists regarding whether to routinely brace patients during the postoperative period. The benefits of a rigid orthosis have yet to be documented in a scientific study, and the cost of a custom-molded orthosis can be quite high. An extensive literature search reveals few articles dealing with the subject, and none with an adequate study design to convincingly support or refute the use of external braces. In addition to the questions of whether an external brace is effective, the mechanism of action also remains unclear. It has been difficult to document mechanical effectiveness, so perhaps the effect is psychologic. In addition, it is possible that some, not all, fusion patients may benefit from a brace--yet our ability to select such a patient is poor. As a result, we have solicited the views of two experienced surgeons on the topic. Dr. Connolly argues that an external orthosis is advisable in many cases; Dr. Grob feels that the rigidity of internal fixation should be adequate to obviate the need for external bracing.