HPLC-MS/MS in der Rückstandsanalytik von Pflanzenschutzmitteln

Goal and Scope

Increasing demands from the regulatory authorities of plant protection products for residue analytical methods on the one hand and the need for cost reduction by shorter development times on the other hand have led to a significant displacement of conventional methods (e.g. HPLC-UV or GC-MS) by HPLC-MS/MS with atmospheric pressure ionization (API) in residue analysis since the mid of the 1990s. This development started in the pharmaceutical industries where HPLC-MS/MS had already been used for the quantitation of drugs and their metabolites in plasma since the late 1980s.

Methods

The reason for the high acceptability of HPLC-MS/MS with electrospray ionisation (ESI) or chemical ionization at atmosheric pressure (APCI) compared with alternative methods are shown with respect to analytical quality parameters, compliance with international registration guidelines and economic reasons.

Results and Conclusion

HPLC-MS/MS is being applied for solving ca. 75% of all analytical problems occuring in modern residue analytical laboratories. This technique offers convincing advantages for the determination of plant protection products and their metabolites in various matrices. These are a reduced number of or no clean-up steps after extraction of the samples, high throughput besides high ruggedness, low limits of detection and a large linear measuring range. In addition, several analytes of various chemical classes can be determined within one chromatographic run. Due to the high selectivity there is only little need for additional confirmatory methods. For enforcement purposes HPLC-MS/MS is accepted by the European authorities since 2002. However, due to high costs for instrumentation and specially skilled personnel only few enforcement laboratories have invested into this technology, so far.

Recommendation and Perspective

The importance of HPLC-MS/MS in residue analysis will further increase, as new ionization techniques will enable the analysis of more analytes and as the investment costs will decrease in the future. However, proven conventional methods will still survive in some cases. New concepts, such as parallel HPLC-MS/MS or on-line purification of extracts by column switching which are already widely used in the pharmaceutical industry could help to further increase the throughput. However, for a sound evaluation with respect to their applicability in residue analysis there is so far too little experience.     

Limit of safety against flame transmission for sintered metal flame arrester elements in the case of flashback in fuel gas/oxygen mixtures

In autogenous welding, cutting and allied processes, so-called dry safety devices are used to protect the outlet terminals of gas distribution lines. To prevent flame transmission, these units are fitted with sintered metal flame arrester elements. At the Federal Institute for Materials Research and Testing (BAM), extensive investigations have been carried out with an experimental flame arrester to determine the limits of safety against flame transmission for sintered metal flame arrester elements in the case of flashback in fuel gas/oxygen mixtures. On the basis of the results of these investigations, it is possible to estimate the pore sizes up to which a sintered metal element can prevent any flame transmission with a given fuel gas.     

N2O emissions from agricultural soils in the North China Plain:the effect of chemical nitrogen fertilizer and organic manure

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Biodegradation potential of cyano-based ionic liquid anions in a culture of Cupriavidus spp. and their in vitro enzymatic hydrolysis by nitrile hydratase

Biodegradation tests with bacteria from activated sludge revealed the probable persistence of cyano-based ionic liquid anions when these leave waste water treatment plants. A possible biological treatment using bacteria capable of biodegrading similar compounds, namely cyanide and cyano-complexes, was therefore examined. With these bacteria from the genera Cupriavidus, the ionic liquid anions B(CN)₄ ^?, C(CN)₃ ^?, N(CN)₂ ^? combined with alkaline cations were tested in different growth media using ion chromatography for the examination of their primary biodegradability. However, no enhanced biodegradability of the tested cyano-based ionic liquids was observed. Therefore, an in vitro enzymatic hydrolysis test was additionally run showing that all tested ionic liquid (IL) anions can be hydrolysed to their corresponding amides by nitrile hydratase, but not by nitrilase under the experimental conditions. The biological stability of the cyano-based anions is an advantage in technological application, but the occurrence of enzymes that are able to hydrolyse the parent compound gives a new perspective on future cyano-based IL anion treatment.     

Epilithic Lichen—Atmospheric Deposition Monitors of Trace Elements and Organohalogens?

ABSTRACT

Epilithic lichen (Xanthoria elegans in Canada, Lecanora muralis in Germany) were gathered from 17 locations in Ontario, Canada (from Lake Ontario to James Bay) and 43 locations in Germany (from the Alps to the North Sea and from the Baltic Sea to the Erzgebirge). Sample aliquots were digested in nitric acid and trace elements were analyzed by inductively coupled plasma-mass spectrom-etry techniques. The organohalogens were determined as absorbable organic halogens (AOXs) by coulometry. Concentration ranges from Germany for trace element samples and AOXs were determined. The lichen showed high spatial resolution in their element enrichment patterns. This allowed for differentiation between natural and anthropogenic dominance in ambient air concentrations. This biomonitoring method has proven to be very sensitive, fast, and reliable. No clear relationship could be found between trace element and AOX concentrations. The AOX values may reflect individual metabolic rates of the fungal partner in lichen symbionts.     

Complete mineralization of benzene by a methanogenic enrichment culture and effect of putative metabolites on the degradation

Microbial degradation of benzene under anaerobic conditions plays an important role in remediation of contaminated sites but the microorganisms and metabolic pathways involved remain poorly understood. In this study, we evaluated degradation of benzene by a methanogenic enrichment culture obtained from non-contaminated lotus field soil, alone and in the presence of several putative metabolic intermediates, that is, toluene, benzoate and phenol. Using stable isotope (¹³C) labeled substrate, benzene was shown to be degraded almost completely to equimolar concentrations of methane and carbon dioxide, without detectable accumulation of extracellular metabolites. Concurrently, toluene, benzoate and phenol were also effectively mineralized, but probably by microorganisms other than the benzene degraders. The latter included Hasda-A, which is putative benzene-degrading deltaproteobacterium present in the culture. While toluene and benzoate did not affect benzene degradation, phenol had a moderate inhibitory effect although it was not a major metabolic intermediate of benzene in our culture. Finally, 4-hydroxycoumarin was detected as a compound formed from phenol but further experiments are required to elucidate its relationship to degradation of phenol.