Laboratories supplier

For most purposes it is not necessary to follow the procedures given above for the preparation of standard buffer solutions the buffer tablets which are available from laboratory suppliers, when dissolved in the specified volume of distilled (de-ionised) water, produce buffer solutions suitable for the calibration of pH meters. 

The following reagents or their equivalents may be obtained from laboratory suppliers. 

The following reagents are available from laboratory suppliers ... 

Tait24 was determined as 189°C by adiabatic Dewar tests, with an apparent energy of activation of 144 kJ/mol. Dinitrophenol is now classified as an explosive in the UK, and is normally available from laboratory suppliers wetted with 15% water, as is picric acid. 

The easiest substrates to test are acetophenones, as many substituted analogues are commercially available from laboratory suppliers. A large range of results have been reported the best enantiomeric excesses achieved and relevant literature reference are detailed in Tables 35.4 and 35.5. The range of ketones that can be reduced includes substituted diaryl, dialkyl and arylalkyl ketones, alpha-,... 

Various fluoropolymer equipment, for example, connectors and valves, is available from laboratory suppliers (at a high price). The principle of a simple, quick, and inexpensive method for connections of electrochemical cells using PTFE tubes is shown in Fig. 4. 

The laboratory suppliers should be considered as part of the laboratory s quality management system. The type and extend of control applied to the suppliers and the purchased materials shall be dependent upon the effect of the piuehased product on the subsequent output. 

One of the quality aspects of analytical chemical methods is whether they are rugged or robust against extraneous influences or changing conditions. The latter can be a change in analist performing the analysis or a change in instrument, laboratory, supplier of chemicals etc. 

The high-pressure water supply is employed for the operation of the ordinary filter pump , which finds so many applications in the laboratory. Several types of water-jet pumps of glass, plastic or metal construction are available from most laboratory suppliers. These are often fitted with a suitable non-return valve to prevent the apparatus being flooded as a result of fluctuating water pressure. Connection to the water tap in the case of the metal pump is by a direct screw-threaded joint with the glass or plastic models high-pressure tubing of suitable bore is wired to the tap and to the pump. 

Screw-cap containers of fuming nitric acid may develop pressure on storage, owing to attack on the plastic screw cap if the inert protective cap liner fails. Regular pressure release is recommended by one laboratory supplier. For a discussion of the hazards of mixtures of many organic compounds with HN03, see Andrussow.2... 

PEI-thin layer plates Plastic sheets coated with PEI (polyethylene-imine)-cellulose for thin-layer chromatography. 20 x 20 cm sheets Polygram CEL 300 PEI/UV254 obtainable from Macherey-Nagel Co., 516 Diiren, Werkstrasse, 6-8, Postfach 307, West Germany or from laboratory suppliers. 

Other items are from standard laboratory suppliers. 

OECD. No. 5 Compliance of Laboratory Suppliers with GLP Principles, revised 1999. http //www.olis.oecd.org/olis/1999doc.nsf/LinkTo/env-jm-mono(99)21... 

OECD (1992) Compliance of laboratory suppliers with GLP principles, Series on principles of good laboratory practice and compliance monitoring, No. 5 GLP consensus document, environment monograph No. 49, Paris... 

Should solvent extraction be inapplicable as a primary purification stage, adsorption methods should be evaluated. Sequential use of ion exchangers and nonionic polymeric resins will often effect considerable purification. If the resins are to be used regularly such that >50 L will be used during a project, it will be more economical to obtain them directly from the manufacturers rather than from laboratory suppliers. Guidance in the use of ion exchangers is relatively sparse a useful introduction is provided by Harland (14) (see Chapter 5). 

It is possible to take up the problem from the other end and to declare the reproducibility of the procedure, i.e. the inter-laboratory standard deviation jr, as the measurement uncertainty ( top-down procedure). If the same analytical procedure is performed in numerous laboratories at the occasion of a collaborative study it can be assumed that all possible influences add to the inter-laboratory standard deviation which finally is calculated from all data. If no interlaboratory test was performed, it is only the own intra-laboratory standard deviation which is known, a value that may be too small and thus too optimistic, especially when it is necessary to compare the own results with the ones from other laboratories (suppliers, customers, authorities, competitors). 

Contaminants originating in the mineral acids used for digestion are also a significant source of error. Table 5 shows the contaminants present in reagent grade and extra-pure mineral acids available from standard laboratory suppliers. Extra-pure acids have low levels of contaminants but are very expensive. It may be possible to eliminate many of the trace contaminants from reagent grade acids, or at... 

Solutions made by the careful use of the vials of concentrated reagents offered by most laboratory suppliers may generally be assumed to be of the nominal concentration, but for very accurate work it is advisable to standardise them against a primary standard. 

Such an electrode can be made as follows. Capped silver-silver chloride electrodes may be obtained from most laboratory suppliers. 

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