Heated flow-cell for gas phase UV-Vis detector in gas chromatography of polycyclic aromatic hydrocarbons.

A detection system for gas chromatography based on gas-phase, molecular absorption measurements is presented, in which the chromatographic column is directly joined to the spectrophotometer flow cell, without heated transfer lines. To maintain polyciclic aromatic hydrocarbons (PAHs) in the gas phase during detection an aluminium heater was constructed. A mixture of 13 PAHs was then separated and analyzed. Parameters affecting separation (temperature program and carrier gas flow) were studied and a program designed to modify the measurement wavelength during the chromatography. The analytical characteristics of each compound were calculated, obtaining detection limits 0.2-1.5 mL-1. Given that some compounds overlaped, it was necessary to resolve their peaks mathematicaly. Finally, the method was applied to a certified synthetic mixture, with good results

The influence of environmental and soil-related variables on the spatial distribution of PCBs in Norwegian and UK soils: implications for global cycling.

This paper reports the influence of environmental variables on soil concentrations of polychlorinated biphenyls (PCBs) and their global fractionation. Soils were sampled from remote woodland (coniferous and deciduous) and grassland locations on a latitudinal transect through the United Kingdom and Norway. Different processes control PCB concentrations and burdens in coniferous, deciduous, and grassland soil systems; these are discussed, with emphasis on the influence of canopy scavenging and soil organic matter (OM) content. In general, concentration differences between sites were 1−2 orders of magnitude for lighter PCBs and 2−3 orders of magnitude for heavier PCBs, when expressed on a pg g-1 dry weight basis. These differences decreased by up to an order of magnitude when expressed as pg g-1 OM. The dataset suggests that the more volatile PCBs are moving toward equilibrium with the OM burden of the soil compartment on a European regional scale, while the distribution of the “stickier”, heavier homologues appears to still be primarily influenced by their preferential deposition closer to source areas. The relative concentration of the tri- and tetra-PCBs increases with latitude, while that of the hepta- and octa-PCBs decreases, consistent with the global fractionation theory. However, the regression slopes are quite shallow, with high scatter, implying that many environmental and soil-related factors (such as precipitation, organic carbon content and type, other soil properties, local sources, etc.) are also influencing the observed congener patterns. Temperature-driven fractionation, while clearly operating and detectable, needs to be considered in this broader context

External Quality Assessment of SARS-CoV-2 Sequencing: an ESGMD-SSM Pilot Trial across 15 European Laboratories

This first pilot trial on external quality assessment (EQA) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) whole-genome sequencing, initiated by the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Study Group for Genomic and Molecular Diagnostics (ESGMD) and the Swiss Society for Microbiology (SSM), aims to build a framework between laboratories in order to improve pathogen surveillance sequencing. Ten samples with various viral loads were sent out to 15 clinical laboratories that had free choice of sequencing methods and bioinformatic analyses. The key aspects on which the individual centers were compared were the identification of (i) single nucleotide polymorphisms (SNPs) and indels, (ii) Pango lineages, and (iii) clusters between samples. The participating laboratories used a wide array of methods and analysis pipelines. Most were able to generate whole genomes for all samples. Genomes were sequenced to various depths (up to a 100-fold difference across centers). There was a very good consensus regarding the majority of reporting criteria, but there were a few discrepancies in lineage and cluster assignments. Additionally, there were inconsistencies in variant calling. The main reasons for discrepancies were missing data, bioinformatic choices, and interpretation of data. The pilot EQA was overall a success. It was able to show the high quality of participating laboratories and provide valuable feedback in cases where problems occurred, thereby improving the sequencing setup of laboratories. A larger follow-up EQA should, however, improve on defining the variables and format of the report. Additionally, contamination and/or minority variants should be a further aspect of assessment.Molecular basis of virus replication, viral pathogenesis and antiviral strategie

External Quality Assessment of SARS-CoV-2 Sequencing: an ESGMD-SSM Pilot Trial across 15 European Laboratories.

This first pilot trial on external quality assessment (EQA) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) whole-genome sequencing, initiated by the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Study Group for Genomic and Molecular Diagnostics (ESGMD) and the Swiss Society for Microbiology (SSM), aims to build a framework between laboratories in order to improve pathogen surveillance sequencing. Ten samples with various viral loads were sent out to 15 clinical laboratories that had free choice of sequencing methods and bioinformatic analyses. The key aspects on which the individual centers were compared were the identification of (i) single nucleotide polymorphisms (SNPs) and indels, (ii) Pango lineages, and (iii) clusters between samples. The participating laboratories used a wide array of methods and analysis pipelines. Most were able to generate whole genomes for all samples. Genomes were sequenced to various depths (up to a 100-fold difference across centers). There was a very good consensus regarding the majority of reporting criteria, but there were a few discrepancies in lineage and cluster assignments. Additionally, there were inconsistencies in variant calling. The main reasons for discrepancies were missing data, bioinformatic choices, and interpretation of data. The pilot EQA was overall a success. It was able to show the high quality of participating laboratories and provide valuable feedback in cases where problems occurred, thereby improving the sequencing setup of laboratories. A larger follow-up EQA should, however, improve on defining the variables and format of the report. Additionally, contamination and/or minority variants should be a further aspect of assessment