Post-mortem volatiles of vertebrate tissue

Volatile emission during vertebrate decay is a complex process that is understood incompletely. It depends on many factors. The main factor is the metabolism of the microbial species present inside and on the vertebrate. In this review, we combine the results from studies on volatile organic compounds (VOCs) detected during this decay process and those on the biochemical formation of VOCs in order to improve our understanding of the decay process. Micro-organisms are the main producers of VOCs, which are by- or end-products of microbial metabolism. Many microbes are already present inside and on a vertebrate, and these can initiate microbial decay. In addition, micro-organisms from the environment colonize the cadaver. The composition of microbial communities is complex, and communities of different species interact with each other in succession. In comparison to the complexity of the decay process, the resulting volatile pattern does show some consistency. Therefore, the possibility of an existence of a time-dependent core volatile pattern, which could be used for applications in areas such as forensics or food science, is discussed. Possible microbial interactions that might alter the process of decay are highlighted

Can volatile organic metabolites be used to simultaneously assess microbial and mite contamination level in cereal grains and coffee beans?

A novel approach based on headspace solid-phase microextraction (HS-SPME) combined with comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-ToFMS) was developed for the simultaneous screening of microbial and mite contamination level in cereals and coffee beans. The proposed approach emerges as a powerful tool for the rapid assessment of the microbial contamination level (ca. 70 min versus ca. 72 to 120 h for bacteria and fungi, respectively, using conventional plate counts), and mite contamination (ca. 70 min versus ca. 24 h). A full-factorial design was performed for optimization of the SPME experimental parameters. The methodology was applied to three types of rice (rough, brown, and white rice), oat, wheat, and green and roasted coffee beans. Simultaneously, microbiological analysis of the samples (total aerobic microorganisms, moulds, and yeasts) was performed by conventional plate counts. A set of 54 volatile markers was selected among all the compounds detected by GC×GC-ToFMS. Principal Component Analysis (PCA) was applied in order to establish a relationship between potential volatile markers and the level of microbial contamination. Methylbenzene, 3-octanone, 2-nonanone, 2-methyl-3-pentanol, 1-octen-3-ol, and 2-hexanone were associated to samples with higher microbial contamination level, especially in rough rice. Moreover, oat exhibited a high GC peak area of 2-hydroxy-6-methylbenzaldehyde, a sexual and alarm pheromone for adult mites, which in the other matrices appeared as a trace component. The number of mites detected in oat grains was correlated to the GC peak area of the pheromone. The HS-SPME/GC×GC-ToFMS methodology can be regarded as the basis for the development of a rapid and versatile method that can be applied in industry to the simultaneous assessment the level of microbiological contamination and for detection of mites in cereals grains and coffee beans

RIVM Troposferisch Ozon Lidar. Studie van haalbaarheid en definitie.

Abstract niet beschikbaarRIVM will contribute a monitoring network station to the joint European research project TOR (Tropospheric Ozone Research). A planned part of this monitoring station is a tropospheric ozone lidar system that provides vertical ozone profiles from 0 to 15 km altitude. To start the construction of the lidar system, a study of the feasibility of a tropospheric ozone dial system as well as a definition of such a system for RIVM has been made. The feasibility of troposheric ozone measurements is established and a system is proposed. The report further adresses questions like construction, performance, cost and safety for the system.RIV

RIVM Troposferisch ozon LIDAR rapport II. Systeembeschrijving en eerste resultaten.

The construction of a LIDAR system for vertical profiling of tropospheric ozone is described. An overview of the first measurements of the system is given and the status of the system is discussed. The main conclusion are: - The construction of a laboratory version of the system is succesfully completed. - Since the beginning of April 1991 the system has been in use for routine measurements of ozone profiles from an altitude of about 600 m up to 5 km under clear weather conditions. The measurement range is limited to 5 km with analog detection. To achieve greater ranges photon couting is necessary. - It is expected that the system can be made operational in the Dutch TOR measurement network station Kollumerwaard. - Stimulated Raman Scattering (SRS), used for generation of the measurement wavelengths, has been investigated and shifting quantum efficiencies of up tp 77% in hydrogen and 45% for deuterium have been achieved. - The errors in the ozone profiles can be split in statistical errors (precision) and systematic errors. The error sources include differential aerosol backscattering and differential extinction by oxygen, sulphur dioxide, nitrogen dioxide, water vapour, molecules and aerosols. In the table below the present error situation is summarized for an averaging time of 100 seconds (1000 laser shots) and two measurement conditions: a clear, clean day, and a hazy, polluted day with enhanced loading of aerosols, SO2 and NO2. Water vapour is disregarded in the calculation in view of the very uncertain cross sections.- By applying corrective algorithms to the measurements and using longer averaging times the errors can be reduced. The table below gives the estimated situation after correction for systematic errors and 400 seconds averaging (4000 laser shots). - Further improvement of the statistical errors above circa 5 km altitude (i.e. the free troposphere) is possible with installation of photon counting.RIV