Laboratory procedures

Many methods for diagnostic parasitology have been described. 

Great care has to be exercised in the preparation of materials for sample extraction and concentration/clean-up of sample extracts so as to detect any source of contamination and to reduce it to an acceptably low level. All work should be carried out in clean-room laboratories, in clean benches or under pure gas protection. 

1 Cleaning and storage of assware, filters, chemicals and solvents 

All glassware should be washed with detergents overnight, rinsed several times with clean water and heated to 250 °C for 12 h. No (wganic solvents should be used to rinse the glassware prior to use. 

Glass fibre filters retaining particles 1.2 /an (Whatman GF/C) or 0.7 /an diameter (Whatman GF/F) are used for filtration. Solvent extraction is impracticable for filter cleaning as large amounts of solvent are required, and the filters beccnne brittle when wetted with water at a later stage. An effective cleaning method is calcination at 350-370 °C The filters should be well separated from each other in the furnace to allow efficient evaporation of contaminants. The cleaned filters can be stored in clean Petri dishes or wrapped in aluminium foil. 

Sodium sulphate is cleaned conveniently by baking for 10 h in an oven at 350 °C. It is stored in glass-stoppered bottles. 

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Just in case you are not familiar with basic laboratory procedures, this chapter will explain them to you. These are the most basic lab techniques and almost every method in this entire book will require many, if not all, of the protocols to follow. So pay attention ... 

Benzylic brommation is a more commonly used laboratory procedure than chlori... 

Imagine that you find the following instructions in a laboratory procedure Transfer 1.5 of your sample to a 100 volumetric flask, and dilute to volume. How do you do this Clearly these instructions are incomplete since the units of measurement are not stated. Compare this with a complete instruction Transfer 1.5 g of your sample to a 100-mL volumetric flask, and dilute to volume. This is an instruction that you can easily follow. 

A laboratory procedure calls for 250 mb of an approximately 0.10 M solution of NH3. Describe how you would prepare this solution using a stock solution of concentrated NH3 (14.8 M). 

Those general laboratory procedures that, when followed, help ensure the quality of analytical work. 

Manufacture. Furan is produced commercially by decarbonylation of furfural in the presence of a noble metal catalyst (97—100). Nickel or cobalt catalysts have also been reported (101—103) as weU as noncatalytic pyrolysis at high temperature. Furan can also be prepared by decarboxylation of 2-furoic acid this method is usually considered a laboratory procedure. 

In the laboratory or process research section a laboratory procedure for a fine chemical is worked out. The resulting process description provides the necessary data for the determination of preliminary product specifications, the manufacture of semicommercial quantities in the pilot plant, the assessment of the ecological impact, an estimation of the manufacturing cost in an industrial-scale plant, and the vaHdation of the process and determination of raw material specifications. 

Fig. 2. Typical pen etration resistance vs temperature data from laboratory procedure (305 x 305-mm laminates, 0.76-mm PVB 2.27-kg ball impact).

A number of laboratory procedures even more rapid than the accelerated Weather-o-meter have been described for the deterrnination of expected weatherabihty of coating asphalts. Research sponsored by the Asphalt Roofing Manufacturers Association describes a stepwise procedure to determine changes in the cmde asphalt source (see Asphalt). 

In order to define the obese state ia a clinical setting, it is necessary to have a means of estimating the amount of adipose (fat) tissue relative to lean body mass. Whereas highly accurate determiaations of body composition require complex laboratory procedures, large clinical studies typically employ measures of skia-fold thickness (11) or more commonly, body mass iadex (BMl) as a quantitative measure of obesity. 

Acid Chloride Formation. Neopentanoic acid can be converted to neopentanoyl chloride [3282-30-2] by reaction with thionyl chloride (2), phosgene (3), phosphoms pentachloride, phosphoms trichloride, or by the reaction with henzotrichloride ia the presence of Eriedel-Crafts catalysts (4). A laboratory procedure usiag tetramethyl-a-halogenoenamines at room temperature has also been reported (5). 

An equihbrium, or theoretical, stage in liquid-liquid extraction as defined earlier is routinely utilized in laboratory procedures. A feed solution is contacted with an immiscible solvent to remove one or more of the solutes from the feed. This can be carried out in a separating funnel, or, preferably, in an agitated vessel that can produce droplets of about 1 mm in diameter. After agitation has stopped and the phases separate, the two clear liquid layers are isolated by decantation. 

Laboratory procedures for proximate and ultimate analyses are given in the Annual Book of ASTM Standards (Sec. 5, American Society for Testing and Materials, Conshohocken, Pa., 1994) and in Methods of Analyzing and Testing Coal and Coke (U.S. Bureau of Mines Bulletin 638, 1967). 

This is a novel feature of factorial design when compared with the classical laboratory procedure which excludes indications of the interaction of tire variable. The method of airalysis of the data, due to Yates, which is commonly used to evaluate these effects, requires tlrat tire uials are conducted in the sequence shown above, and proceeds as follows. 

Buffers are widely used to maintain nearly constant pH in a variety of commercial products and laboratory procedures (Figure 14.2, p. 384). For these applications and others, it is essential to be able to determine—... 

Had the calculated value for t been less than 1.80 then there would have been no significance in the results and no apparent bias in the laboratory procedure, as the tables would have indicated a probability of greater than 1 in 10 of obtaining that value. It should be pointed out that these values refer to what is known as a double-sided, or two-tailed, distribution because it concerns probabilities of values both less and greater than the mean. In some calculations an analyst may only be interested in one of these two cases, and under these conditions the -test becomes single-tailed so that the probability from the tables is halved. 

Conditioning procedures of test specimens and products are important in order to obtain reliable, comparable, and repeatable data within the same or different testing laboratories. Procedures are described in various specifications or standards such as having a standard laboratory atmosphere [50 2% relative humidity, 73.4 1.8°F (23 1°C)] with adequate air circulation around all specimens. The reason for this type or other conditioning is due to the fact the temperature and moisture content of plastics can affect different properties. 

Caution This reaction involves highly toxic cyanide salts. It may be carried out safely, however, if prudent laboratory procedures are practiced. In particular, cyanide residues should be collected and disposed of separately (Note 1), and the entire sequence should be perform,ed in an efficient hood. 

This system includes measures and activities related to laboratory procedures, testing, analytical methods development and validation or verification, and the stability program. 

Thus each review within the volume critically surveys one aspect of that topic and places it within the context of the volume as a whole. The most significant developments of the last 5-10 years are presented, using selected examples to illustrate the principles discussed. A description of the laboratory procedures involved is often useful to the reader. The coverage is not exhaustive in data, but rather conceptual, concentrating on the methodological thinking that will allow the non-specialist reader to understand the information presented. 

An environmental protocol has been developed to assess the significance of newly discovered hazardous substances that might enter soil, water, and the food chain. Using established laboratory procedures and C-labeled 2,3,7,8-tetra-chlorodibenzo-p-dioxin (TCDD), gas chromatography, and mass spectrometry, we determined mobility of TCDD by soil TLC in five soils, rate and amount of plant uptake in oats and soybeans, photodecomposition rate and nature of the products, persistence in two soils at 1,10, and 100 ppm, and metabolism rate in soils. We found that TCDD is immobile in soils, not readily taken up by plants, subject to photodecomposition, persistent in soils, and slowly degraded in soils to polar metabolites. Subsequent studies revealed that the environmental contamination by TCDD is extremely small and not detectable in biological samples. 

Laboratories handling biologicals have their own special problems. They often have to dispose of small but significant amounts of materials that may be very hazardous. Every laboratory procedure must then be scrutinized with this in mind. 

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