Contamination in laboratories

Aging of soil-contaminant mixtures prior to the addition of microbes reduced bio availability of such contaminants in laboratory studies and aging reduced herbicidal activity in various field studies. 

To date the Occupational Safety and Health Administration (OSHA) has had little involvement with GLP labs other than as a part of normal workplace safety evaluations. Increasingly however, OSHA has expressed concerns about the possible exposure of workers to biological and viral contaminants in laboratory environments. No doubt a good deal of this concern is a result of concerns following the September 11 disaster, and subsequent (so far unrealized) fears of related biological warfare. 

Bogomolov, D.M., Chen, S.K., Parmelee, R.W., Subler, S. and Edwards, C.A. (1996) An ecosystem approach to soil toxicity testing a study of copper contamination in laboratory soil microcosms. Applied Soil Ecology, 4, 95-105. 

In all areas where raw materials, in-process drugs, or drugs are exposed, the following considerations apply to the extent necessary to prevent contamination. In laboratories these considerations only apply to the extent necessary to ensure the validity of test results. 

In countries with contaminated air from industrial origin, the atmospheric zinc contamination can be overcome using laminar flow hoods or cleanrooms [64]. It should be noted that air contamination in laboratories often originates from vapors emitted by copying machines [65]. 

What is the concentration of a contaminant in laboratory air . Let s assume that we accidentally leave an uncapped container of an organic solvent on a lab bench (not in the hood). We can easily calculate the (equilibrium) vapor pressure of the solvent at the temperature of the lab. (see Chemical Connection 3.1.1.1.) but we don t really know how long it takes to reach this equilibrium. This is a question about rate of vaporization and that rate will also be affected by the surface area of the solvent and the size of the uncapped opening. But, even if the solvent vaporizes rapidly, the actual concentration in lab air will be greatly affected by the ACH since that value tells us about the rate of removal of air in the lab. The actual partial pressure of the chemical will be less than the equilibrium vapor pressure, but we don t know by how much. 

Although chloroform is an analyte, it also can be interferent. Due to its volatility, chloroform present in the laboratory air may diffuse through the sample vial s Teflon septum, contaminating the samples. How can we determine whether samples have been contaminated in this manner ... 

Occurrence of Plasticizers in the Environment. The contamination of laboratory chemicals and equipment causes problems in the analysis of very low concentrations of phthalates in environmental samples. Strenuous efforts have been made to overcome these difficulties in recent studies but the results of many earHer investigations must be treated with caution. 

Another difficulty sometimes encountered in laboratory tests is that contamination of the testing solution by corrosion products may change its corrosive nature to an appreciable extent. 

Variable Air Volume Fume Cupboards This type of cupboard incorporates a variable air volume (VAV) controller that regulates the amount of air exhausted from the cupboard such that the face velocity remains essentially constant irrespective of the sash position. A sensor detects either the sash position, the pressure differential l>etween the fume cupboard interior and the room, or the vekxity at some point in the cupboard. This information is used to control either the exhaust fan speed or the position of a control damper. The supply air volume flow rate into the laboratory or workspace should also be regulated. It should be remembered that with the sash in the closed position the amount of air to dilute contaminants in both the fume cupboard and the laboratory is reduced and that there could, for example, be difficulty in reducing contaminant levels below the lower exphasive level. 

Different protection factors have been defined. One method is to define it as the ratio of the concentration of a contaminant in the exhaust duct (CJ to the concentration in the breathing zone (C[,) of a person standing in front of the enclosure, for example, a laboratory fume hood ... 

After a chromatogram has been developed the TLC plate is removed from the developing chamber and the status quo is fixed by removing the mobile phase remaining in the layer as quickly as possible. This is properly performed in the fume cupboard so as not to contaminate the laboratory with solvent fumes. If possible the TLC plate should be laid horizontally because then as the mobile phase evaporates the separated substances will migrate evenly to the surface where they can be the more readily detected. A fan or hair dryer (hot or cold air stream)... 

Anionic end-to-end cyclizations have been carried out in several laboratories 66 67,8 ) jjie cydization yields range from 20 to 60%, and the molecular weights accessible reach up to 300,000. Above this limit, separation between polycondensate and cycles becomes increasingly difficult. The presence of some linear contaminant in the cyclic polymer cannot be disregarded. 

The varying metabolic activities of bacteria and their response to immediate environmental factors have been exploited in the design of special diagnostic and selective media. Recipes for these run into many hundreds such media are used in hospital and public health laboratories for identifying organisms found in samples believed to be contaminated by them, and as an aid to diagnosis and treatment. In addition they are used to detect contaminants in pharmaceutical products (British Pharmacopoeia 1993). A few examples will be given to illustrate the principle. 

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