Effects of filtration sterilization on the stability of ketamine, selected benzodiazepines and metabolites in female urine

Benzodiazepines (Benzos) and ketamine (K) are compounds that have been encountered in Drug-Facilitated Sexual Assault (DFSA) cases. Due to the intimate nature of these crimes, evidence collection is often postponed due to delays and/or reluctance in reporting these crimes. Further delays in analysis may be encountered in laboratories with large caseloads and/or backlogs. Drug identification in biological samples is important to determine whether victims knowingly or unknowingly took an impairing substance, however, the results could be negative due to chemical degradation over a long storage period. The purpose of this project was to study if degradation could be prevented with a new preservation method at the time of collection. Urine samples were prepared by the addition of K and metabolites and selected benzos and metabolites that were subjected to different sample pre-treatment techniques, and were analyzed after storage at room temperature (25°C), refrigerator (4°C) and freezer (-20°). The samples were either pre-treated with preservative (0.5% toluene) or filtration sterilization (sterile filter kit) within two hours after sample collection, and a control group with no pre-treatment was incorporated into the study for comparison. The changes in concentrations over 50 days (Benzos group) and 210 days (K group) were evaluated between different pre-treated methods and different temperature conditions. Sample that were treated with 0.5% toluene showed the most degradation: 44% of oxazepam and 96% of diazepam degraded over 10 days, and 80% of dehydronorketamine degraded after storage of 150 days regardless the temperature conditions. Clonazepam and flunitrazepam concentrations were reduced by 80% of the original concentration when stored at room temperature for 10 days. The major benzodiazepines evaluated in this study were stable when stored in the freezer. In K group, ketamine and norketamine that were stored at room temperature and refrigerated over 210 days were stable, however, degradation was observed after 150 days when the samples were stored in the freezer. There was no statistically different change observed among the samples pre-treated with or without filtration sterilization. Each sample pH was measured and it was determined that those stored at room temperature had an average pH of 8.5, while samples stored in the refrigerator and freezer had an average pH of 6.7 and 6.5, respectively. This finding revealed that pH could be the major factor affecting compound degradation rather than the bacterial contamination with high pH contributing to degradation, and low pH potentially preventing sample lost

The heart of a combinatorial model category

We show that every small model category that satisfies certain size conditions can be completed to yield a combinatorial model category, and conversely, every combinatorial model category arises in this way. We will also see that these constructions preserve right properness and compatibility with simplicial enrichment. Along the way, we establish some technical results on the index of accessibility of various constructions on accessible categories, which may be of independent interest.Comment: 44 pages, LaTeX. v4: Extended version of final journal version. (Note that material has been significantly reorganised since v3.

From fractions to complete Segal spaces

We show that the Rezk classification diagram of a relative category admitting a homotopical version of the two-sided calculus of fractions is a Segal space up to Reedy-fibrant replacement. This generalizes the result of Rezk and Bergner on the classification diagram of a closed model category, as well as the result of Barwick and Kan on the classification diagram of a partial model category.Comment: 21 pages, LaTeX. Changes in v3: added some expository material, following suggestions by anonymous referee. (N.B. numbering has changed.