Reagent quality

Nitrobenzene. Nitrobenzene, of analytical reagent quality, is satisfactory for most purposes. The technical product may contain dinitrobenzene and other impurities, whilst the recovered solvent may be contaminated with aniline. Most of the impurities may be removed by steam distillation after the addition of dilute sulphuric acid the nitrobenzene in the distillate is separated, dried with calcium chloride and distilled. The pure substance has b.p. 210°/760 mm. and m.p. 5 -7°. 

A very large number of both inorganic and organic solvents have been used for non-aqueous determinations, but a few have been used more frequently than most. Some of the most widely applied solvent systems are discussed below. In all instances pure, dry analytical reagent quality solvents should be used to assist in obtaining sharp end points. 

Even inside the controlled conditions of a research laboratory, analyzing clean and standardized test samples PCR procedures requires careful quality control, taking into consideration differences in sample preparation, variation in pipetting, differences in reaction tube thickness, poor calibration or instability of the thermal cycler, and reagent quality. 

Einally, as profiling assays run repeatedly in cycles, unlike HTS campaigns, it is wise to create a reference plate with well characterized, diverse compounds to be tested at a frequency of 3-4 months. This test set ensures that any shift in dynamic range, technical fault associated with plate outlay, alteration of reagent quality or liquid handling is detected. 

Pyridine-Methanol 1 1 mix equal volumes of reagent quality of each solvent containing less than 0.10% water. This must be maintained in a protected system... 

Materials and Apparatus. In general the chemicals are of analytical reagent quality. Water is distilled from glass, with no precautions to exclude CO2 thereafter. 

Materials. Distilled water was used 2-propanol and trihydrous lithium perchlorate, of guaranteed reagent quality from Wako Pure Chemicals Co., were used without further purification. The purity of the 2-propanol was checked by gas chromatography, with Porapak-Q as the column packing, and found to be more than 99.9 mol %. The physical properties of pure solvents were compared with the literature values in a previous paper (2), and the agreement was satisfactory. 

Many factors influence the quality of electrophoretic separations, including gel preparation, reagent quality, instrument assembly, electrophoresis conditions, and the nature and quantity of the sample. 

Since lithium salts obtainable by purchase, even of so-called c.p. or reagent quality, frequently contain impurities totaling about 1 per cent, it is desirable to have a rapid method for obtaining such salts in a reasonably pure state. The following simple procedure for the purification of c.p. or reagent grade lithium carbonate provides such a method, since the resulting pure carbonate may be readily converted by treatment with the proper pure acid into practically any lithium salt desired. The procedure is based upon the fact that lithium carbonate, in contrast to the salts that contaminate it, is much less soluble in hot than in cold water. J In other words, simple recrystallization is employed, but the process is carried out in the reverse direction. 

Composition control is very stringent and ingredients are of analytical reagent quality. 

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