Factors affecting preparation

Considering the principal factors affecting preparative planar chromatography, described by Nyiredy [101,102], it seems that the most important factors are the stationary and mobile phases with respect to the natural mixtures. 

Precision When the analyte s concentration is well above the detection limit, the relative standard deviation for fluorescence is usually 0.5-2%. The limiting instrumental factor affecting precision is the stability of the excitation source. The precision for phosphorescence is often limited by reproducibility in preparing samples for analysis, with relative standard deviations of 5-10% being common. 

Bailey, A.L, Cardenas-Valera, A.E., Graft copolymers as stabilizers for oil-imwater emulsions. Part 2. Preparation of the emulsions and the factors affecting their stability. Colloids and Surfaces, v.97, pp.1-12, 1995. 

The factors affecting the preparation of the cyclic chlorophosphazenes from phosphorus pentachloride and ammonium chloride continue to receive attention. For example, the yields and reaction times for the preparation of the series, (NPCla) ( — 3—7), varied with the fineness of the ammonium chloride, the nature and volume of the solvent, and added catalysts such as phosphoryl chloride. A procedure, giving due consideration to these factors, was described for the preparation of N3P3CI6 in good yield (88% of cyclic products) and in a relatively short time (2J h). The cyclic chlorophosphazenes can be obtained in even shorter times ca. 10 min) by addition of four moles of pyridine to remove the hydrogen chloride formed ... 

The rate of product to be applied is the critical factor affecting all residue studies. The rate should be the highest recommended rate for that particular crop and should be applied at the limit of the GAP for the specific crop. The test item should ideally be pre-weighed in a laboratory prior to making the application. In most cases, this procedure results in easier accountability of test items, more accurate measurement of required doses, and more accurate application in the field since only the correct amount of water is required to be added by the field operator. This procedure also reduces the quantity of test item required and hence reduces the waste, which has to be disposed of. An additional spare sample, which is weighed at the same time in case of mishap with the original sample may be prepared. 

Wan, L. S. C., and Lai, W. F., Factors Affecting Dmg Release from Drug-Coated Granules Prepared by Fluidized-Bed Coating, Int. J. Pharmaceutics, 72 163-174(1991)... 

Factors Affecting Extraction Yield in SC-CO2 Extraction Sample Preparation... 

A (very rare) genetic deficiency in the production of factor XIII also results in impaired clotting efficacy in affected persons. In this case, covalent links that normally characterize transformation of a soft clot into a hard clot are not formed. Factor XIII preparations, partially purified from human blood, are used to treat individuals with this condition to date, no recombinant version of the product has been commercialized. 

In one experiment the checkers used 3-butyn-l-ol available from Aldrich Chemical Company, Inc., and found that it was of satisfactory purity. In other experiments, both the submitters and the checkers prepared the hydroxy compound from sodium acetylide and ethylene oxide in liquid ammonia according to the procedure described by Schulte and Reiss3 and further attempted to maximize the yield by varying the ratio of sodium ethylene oxide liquid ammonia used ip the reaction. Unfortunately, the checkers failed to obtain consistent results in repeated experiments and consequently could not define the optimum conditions for the reaction. Thus, the yield of 3-butyn-l-ol varied from 15 to 45% and 15 to 31% on the basis of sodium and ethylene oxide, respectively. Unknown and apparently subtle experimental factors affect the yield significantly. 

CEC is a miniaturized separation technique that combines capabilities of both interactive chromatography and CE. In Chapter 17, the theory of CEC and the factors affecting separation, such as the stationary phase and mobile phase, are discussed. The chapter focuses on the preparation of various types of columns used in CEC and describes the progress made in the development of open-tubular, particle-packed, and monolithic columns. The detection techniques in CEC, such as traditional UV detection and improvements made by coupling with more sensitive detectors like mass spectrometry (MS), are also described. Furthermore, some of the applications of CEC in the analysis of pharmaceuticals and biotechnology products are provided. 

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