Biomedical sample analysis

If these methods do prove inconclusive, biomedical sample analysis may provide a unique method for establishing exposure. Due to both the complex technical requirements and the strict forensic approach used it is unlikely that this information will be available in the early phases of response to such an incident. Biomedical sample analysis does however offer another method by which proof of the use of chemical agents can be provided, and thus has a potentially significant role in the overall preparation of a capability for the response to a terrorist chemical agent attack. 

Biomedical sample analysis relies on appropriate sample collection. Although any result is unlikely to guide the response phase of the incident, the emergency response should include consideration of the collection of these samples. The best results are expected to be generated from samples taken as early as possible, and from patients considered to have had the greatest exposure. There is however little clear data available on the urgency of analysis in relation to the stability of markers, and on the effects of lag-times for bringing samples to the laboratory. 

BIOMEDICAL SAMPLE ANALYSIS COMPARED TO ENVIRONMENTAL SAMPLE ANALYSIS... 

Although not yet a mature science, the development of a practical biomedical sampling capability is underway. At present, the OPCW does not have such a capability, and the capability in Member States in this field is also still very limited. Despite a number of practical and technical challenges, biomedical sample analysis has the potential however to be an extremely sensitive and specific method of establishing credible forensic information on the alleged use of chemical agents. 

Column Diameter and Flow 7.3 Biomedical Sample Analysis. 307... 

Biomedical Sample Analysis. 291 11.3 Saxitoxin and Other Marine ... 

Trivalent arsenic forms strong bonds with sulfur, and thiols are therefore used for derivatizing both lewisite and CVAA, forming the same derivative (19). Lewisite reacts with mono and dithiols the reaction with dithiols occurring rapidly at ambient temperature. In a competitive environment, lewisite reacts almost exclusively with dithiols rather than monothiols (35). Three dithiols, 1,2-ethanedithiol, 1,3-propanedithiol and 2,3-dimercaptopropan-l-ol (British Anti-Lewisite, BAL) have been used for biomedical sample analysis of CVAA to form cyclic derivatives (14a, b) and (15). Unlike derivatiza-tion of TDG, CVAA can be derivatized direcdy in an aqueous solution. 2,3-Dimercaptotoluene, which has been used extensively for environmental analysis (19), does not appear to have been used. 

No examples of biomedical sample analysis following human exposure to lewisite have been reported. 

Weapons-grade lewisite consists of lewisite I, (CHC1-CH)AsC12 (90%) and lewisite II, (CHC1-CH)2AsC1 ( 10%), with very small amounts of the non-vesicant lewisite III, (CHCl-CH As (which imparts the characteristic geranium-like odour). Biomedical sample analysis has been directed only at products derived from lewisite I. 

There have been no reported cases where exposure to CS has been confirmed by biomedical sample analysis. In human volunteer trials, with low concentrations of aerosolized CS, neither CS or 2-chlorobenzaldehyde were detected in the blood of six volunteers shortly after termination of the exposure (Leadbeater, 1973). A disadvantage of the major metabolic pathway is that three carbons are lost in the initial hydrolysis. It has yet to be shown if background levels of metabolites... 

Analytical methods continue to be improved, and in some cases adapted for less costly instrumentation. At present, expertise in biomedical sample analysis for CW agents is restricted to a small number of laboratories. Recent interest shown by the OPCW, and the concern for terrorist use of CW, may encourage a larger number of laboratories to acquire expertise. 

Although underivatized TDG can be analyzed by GC, the peak shapes are not ideal, and derivatization is required for analysis at concentrations < 1 ppm. Two types of derivative have been used for TDG. The ones most commonly used are silyl ethers, either trimethylsilyl, or tert-butyldimethylsilyl. Pentafluorobenzoyl and heptafluorobutyryl esters have been used for biomedical sample analysis. The conditions are extensively described by Black et al. ... 

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