Collaborative swab performance comparison and the impact of sampling solution volumes on DNA recovery.

The collection of DNA traces marks the first step determining the success of genetic analysis. This study aimed to identify and validate a suitable alternative to the currently used ForensiX Evidence Collection Kit containing a cardboard box for swab storage. This box has to be folded at the crime scene, which is time-consuming and carries the risk of potential contamination and handling difficulties. A collaboration study involving three police departments and one laboratory for forensic genetics was performed to compare the currently used swab against three challenger swabs: ForensiX SafeDry, Copan 4N6FLOQSwab™ Genetics and Copan 4N6FLOQSwab™ Crime Scene. Mock samples consisted mainly of touch DNA, but also blood, saliva and semen were applied to twelve items with different surfaces. Every organisation contributed with three DNA collectors, whose individual collection efficiencies were investigated. The challenge of preparing homogenous traces, especially touch DNA, was addressed by enhancing hand contact frequency and sampling area. As a further part of the swab comparison study, we describe for the first time the influence of different swabbing solution volumes on the sampling efficiency of the different swabs. The application of touch DNA was also tested for a further swab type, the Sarstedt Forensic Swab, which yielded such low DNA concentrations that it was excluded from the collaboration study. The Copan Genetics and Copan Crime Scene swabs yielded significantly lower DNA concentrations than the currently used ForensiX Evidence Collection Kit and ForensiX SafeDry swab. The inter-individual performance results of the operators revealed significant differences in sampling skills. Comparing different swabbing solution volumes showed higher DNA yields or no significant difference for the ForensiX Evidence Collection Kit and ForensiX SafeDry than the Copan Genetics, depending on the item or trace type swabbed. Our results highlight the importance of validating first-step components that are decisive to the success of DNA typing in the context of specific sampling procedures and laboratory methods. Also, the significance of individuals' securing variations, principally unknown for crime scene investigation and laboratory teams, is emphasised for the first time, offering a practical approach for improving and training DNA collecting activities and ensuring the optimal securing evidence process. These findings increase the knowledge of impacts on DNA collection and, thus, benefit other laboratories and forensic services, particularly when using the same extraction methods.

Fast online emission monitoring of volatile organic compounds (VOC) in wastewater and product streams (using stripping with direct steam injection).

Open-loop stripping analysis (also referred to as dynamic headspace) is a very flexible and robust technology for online monitoring of volatile organic compounds in wastewater or coolant. However, the quality and reliability of the analytical results depend strongly on the temperature during the stripping process. Hence, the careful and constant heating of the liquid phase inside the stripping column is a critical parameter. In addition, this stripping at high temperatures extends the spectrum of traceable organics to less volatile and more polar compounds with detection limits down to the ppm-level. This paper presents a novel and promising approach for fast, efficient, and constant heating by the direct injection of process steam into the strip medium. The performance of the system is demonstrated for temperatures up to 75 °C and traces of various hydrocarbons in water (e.g., tetrahydrofuran, methanol, 1-propanol, n-butanol, ethylbenzene).

Kinetics and rate constants of the reaction CH2OH+O2-->CH2O+HO2 in the temperature range of 236-600 K.

The kinetics and absolute rate constants of the gas-phase reaction of the hydroxymethyl radical (CH2OH) with molecular oxygen have been studied using laser photolysis/near-IR absorption spectroscopy. The reaction was tracked by monitoring the time-dependent changes in the production of the hydroperoxy radical (HO2) concentration. For sensitive detection of HO2, two-tone frequency modulation absorption spectroscopy was used in combination with a Herriott-type optical multipass absorption cell. Rate constants were determined as a function of temperature (236 K

Quantitative determination of combustion intermediates with cavity ring-down spectroscopy: systematic study in propene flames near the soot-formation limit.

Cavity ring-down spectroscopy (CRDS) was applied in several fuel-rich, one-dimensional, premixed C3H6/O2/Ar flames at 50 mbars (37.5 torr) to measure absolute OH, HCO, and 1CH2 concentration as well as temperature as a function of stoichiometry. Although these flames near the sooting limit present a complex chemical environment, significant spectral interferences were found to be absent. Specific aspects of the CRDS technique for measurement of temperature and radical concentration profiles are discussed; and the results are analyzed in comparison with flame model simulations.