Udo A. Th. Brinkman

Review: Biological Activity, Determination and Occurrence of Planar, Mono- and Di-Ortho PCBs

Abstract Some of the 209 polychlorinated biphenyls (PCBs) are stereochemically similar to the planar 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and, because of this similarity, exert biochemical activity and toxicity comparable to that of TCDD. The molecular dimensions and the planarity of the PCB molecule appear to be important for the interaction with the TCDD receptor. These structural requirements, in turn depend on the number of ortho chlorine atoms and the presence of two para and at least two meta chlorine atoms on the biphenyl skeleton. Planar PCBs (i.e., without ortho chlorines), their mono- and some of their di-ortho substituted congeners have inductive properties similar to 3-methylcholanthrene- or mixed-type induction of mixed-function oxidases. These congeners also appear to have the greatest toxic potential. Planar PCBs and some of their mono- and di-ortho substituted congeners occur in very low concentrations in commercial PCB mixtures. Hence, their environmental occurrence is relatively lo...

Analytical separation techniques for the determination of chemical warfare agents

Today, the determination of chemical warfare agents (CWAs) is an important area of application in analytical chemistry. Chromatographic, capillary electrophoretic and mass spectrometric techniques are primarily used for the identification and quantification of a broad field of classical CWAs in environmental samples and neutralization masses, obtained after destruction of CWAs. This overview is illustrative for the state of the art and mainly focuses on the literature published since 1996.

Trace level analysis of micropollutants in aqueous samples using gas chromatography with on-line sample enrichment and large volume injection

In this review article an overview of methods for the analysis of aqueous samples with capillary gas chromatography is presented. The methods can be classified into two approaches: a direct approach in which water is directly introduced onto the GC column, and an indirect approach in which water is eliminated, i.e., by liquid-liquid extraction or solid-phase extraction, prior to introduction of the analytes onto the GC column. The emphasis is on methods in which sample preparation and GC analysis are combined on-line. An outline of methods for large volume injection is also presented as the use of on-line systems often involves the introduction of large volumes of sample extract.

Characterisation of fatty acids in biological oil samples using comprehensive multidimensional gas chromatography

Comprehensive multidimensional gas chromatography can adequately resolve very complex mixtures of analytes such as the fatty acid mixtures which are contained in, e.g., fish and vegetable oils. Well-ordered patterns are obtained in the two-dimensional separation plane which can be used to tentatively identify peaks when no standard is available. The technique which can also be used for quantification, i.e., quantitative ratio analysis, should be especially useful for fingerprinting purposes. Unravelling the composition of complex mixtures such as fish oils appears to be highly rewarding.

Liquid chromatography with atmospheric pressure chemical ionization and electrospray ionization mass spectrometry of flavonoids with triple-quadrupole and ion-trap instruments

With 15 flavonoids as test compounds, the analytical performance of four modes of LC-MS, multiple MS (MSn) and tandem MS operation (atmospheric pressure chemical ionization (APCI), electrospray ionization, positive and negative ionization) was compared for two mass spectrometers, a triple-quadrupole and an ion-trap instrument. Two organic modifiers, methanol and acetonitrile, and two buffers, ammonium acetate and ammonium formate, were used. In general, the use of APCI in the negative ion mode gave the best response, with the signal intensities and the mass-spectral characteristics not differing significantly between the two instruments. The best results were obtained when methanol-ammonium formate (pH 4.0) was used as LC eluent. Under optimum conditions full-scan limits of detection of 0.1-30 mg/l were achieved in the negative APCI mode. Here it needs to be emphasized that up to 2-order response differences were found both between analytes and between modes of ionization. This implies that one should be very cautious when interpreting data on the screening of real-life samples. The main fragmentations observed in the MSn spectra on the ion-trap, or the tandem MS spectra on the triple-quadrupole were generally the same. The advantage of the former approach is the added possibility to ascertain precursor-->product ion relationships.

Determination of isoflavone glucoside malonates in Trifolium pratense L. (red clover) extracts: quantification and stability studies.

Isoflavones, their glucosides and their glucoside malonates were determined in red clover leaf extracts using reversed-phase LC coupled to atmospheric pressure chemical ionisation mass spectrometry (APCI-MS), UV and fluorescence detectors and the stability of the malonates was investigated. Extracts can be stored at least 1-2 weeks at -20 degrees C without loss of malonates. In LC-separated fractions the malonates are most stable when stored at low temperature after evaporation to dryness. The concentrations of eight major isoflavones ranged from 0.04 to 5 mg/g leaves.

Identification of chemicals related to the chemical weapons convention during an interlaboratory proficiency test

In order to test the ability of laboratories to detect and identify chemicals related to the Chemical Weapons Convention (CWC), which prohibits the development, production, stockpiling and use of chemical weapons, and to designate laboratories for this task, the Technical Secretariat of the Organisation for the Prohibition of Chemical Weapons organises proficiency tests. This paper describes the conduct of such a test at the TNO-Prins Maurits Laboratory in Rijswijk, The Netherlands. The analytical strategies and procedures that resulted in the unambiguous identification in the test samples of chemicals relevant to the CWC are discussed.

Accurate mass determinations for the confirmation and identification of organic microcontaminants in surface water using on-line solid-phase extraction liquid chromatography electrospray orthogonal-acceleration time-of-flight mass spectrometry.

The identification of polar microcontaminants in surface water is an important issue in environmental analysis. Liquid chromatography/mass spectrometry (LC/MS) is frequently applied for this purpose. However, even in combination with tandem mass spectrometry (MS/MS), unambiguous identification of the compounds detected is often difficult. The potential of an alternative strategy, based on the ability of an orthogonal-acceleration time-of-flight mass spectrometer to routinely perform accurate mass determination at 10 ppm in on-line LC/MS, is explored. On-line solid-phase extraction LC electrospray orthogonal-acceleration time-of-flight mass spectrometry is shown to enable the determination of pesticides from various compound classes in surface water in the concentration range of 0.1 to 10 micrograms/L. In addition, the ability to discriminate and unambiguously identify pesticides in mixtures of isobaric and/or isomeric compounds is investigated.

Comparison of GC/MSD and GC/AED for the determination of organotin compounds in the environment

SummaryMethods are described for the analysis of environmental samples like water, sediment and suspended matter for the determination of all organotin compounds (OTs) that are currently used as biocides: tributyltin (TBT), triphenyltin (TPT), tricyclohexyltin (TCT) and fenbutatin oxide (FBTO). In water also five degradation products (di and mono substituted analogs) can be determined. Alkylation using a Grignard reagent was used to obtain OT derivatives amenable to gas chromatography (GC). Both methylation and pentylation have been employed for derivatization prior to GC analysis. The present results show that derivatization efficiencies for TPT, TCT and FBTO at trace levels are higher using methylation than pentylation. Detection limits for each type of sample matrix were determined using GC/Mass Selective Detection (GC/MSD) and GC/Atomic Emission Detection (AED). In sediment and suspended matter only tri-substituted OTs (i.e. the parent compounds) could be determined. Detection limits ranged from 0.2 to 10 ng/g dry weight. FBTO, not previously detected in environmental samples, was found at levels of 4 and 11 ng/g in a suspended matter sample and a sediment sample, respectively. In water the OTs and their degradation products were determined at levels of 1–10 ng/l (as tin) using 200 ml water samples.

Enantiomer fractions instead of enantiomer ratios

The use of enantiomer ratios (ERs) to indicate the relative amounts of a pair of enantiomers in a sample has some disadvantages. Enantiomer fractions (EFs) are proposed as an alternative expression to eliminate the difficulties.