Direct atomic absorption mercury determination (without any pre-treatment procedures) in food is complicated by its organics matrix. That is the reason why almost all AAS methods of mercury determination in foodstuff include sample digestion by acids.
Toxicity of pure chemicals is assessed using respirometers by adding increasing concentrations to an active culture. The concentration at which oxygen uptake or gas production begins to decrease is known as the “threshold toxicant concentration.”
Intrinsic kinetic tests involve adding relatively high concentrations of organic substrate to small concentration of acclimated microorganisms so that the COD/VSS ratio typically is greater than 10. Kinetic parameters are then determined by non-linear modeling using well-known relationships between biological growth and oxygen uptake.
Manufacturing of powdered and liquid flavorings and fragrances involves production phases where flavoring chemicals may be released into the ambient air breathed by workers. Exposure control by gas analyzers in the production rooms and laboratories is necessary to ensure that the Time-Weighted Average (TWA) concentrations do not exceed the maximum Permissible Emission Limit (PEL) values.
The mining industry uses chemicals as ‘flotation’ agents in the recovery of sulphide minerals containing metallic elements (e.g., copper, nickel, silver, gold) from ore slurries. Sodium ethyl xanthate (SEX) is one of most common flotation agents, and it decomposes to form ethanol, carbon disulfide CS2, and Carbonyl Sulfide COS. These harmful gaseous compounds must be monitored from the indoor air at the enriching plant.
Phosgene COCl2 is a colorless gas. While it has been used as a Chemical Weapon Agent (CWA) in the past, currently this poisonous gas is also an important reagent in synthesis in the pharmaceutical and chemical industries. The plants using phosgene are typically equipped with gas sensors to detect leaks in the indoor ambient air. The critical situations arise when equipment in contact with the gas at the manufacturing facilities are serviced and maintained. As phosgene is very poisonous, even small gas pockets in...