Retention time materials

Similarly, small (0.2—0.6 mm) air bubbles are introduced into a 2.6-m Deister Flotaire column at an intermediate level allowing rapid flotation of readily floatable material in the upper recovery zone. The bottom air permits longer retention time of the harder-to-float particles in the presence of micrometer-sized bubbles at a reduced downward velocity. The first commercial unit went on stream in 1986. It was used to improve the recovery of <0.6 mm (—28 mesh) coal in the plant s tailings. An average of 5.5% increase in coal recovery resulted from its use (14). The second commercial use processed <0.15 mm (—100 mesh) coal feed. 

The plate dryer may vary in size from 5-35 vertically stacked plates with a heat-exchange area between 3.8-175 m". The largest unit available has overall dimensions of 3 m (w) by 4 m (1) by 10 m (h). Depending upon the loose-bulk density of the material and the overall retention time, the plate dryer can process up to 5,000 kg/hr of wet product. 

When a flocculated feed is added to a filter tank, there is a definite time lag before this material reaches the surface of the filter medium. Since this lag time is not known at the time of testing, a lag time of 8 to 10 minutes should be allowed before starting the first leaf test on a flocculated shiny. Two, or perhaps three, tests can be run before the elapsed time exceeds the probable retention time in the full-scale filter tank. With knowledge of the elapsed time after flocculation and data relating to the rate of degradation, the rates obtained on the leaf test runs can be adjusted to some constant lag time consistent with the anticipated full-sc e design. 

They include the combustion chamber, gas burners, burner controls, and exit temperature indicator. Usual exit temperatures for the destruction of most organic materials are in the range of 650°-825°C, with retention times at the elevated temperature of 0.3-0.5 sec. 

Reservoir. Retention time should be 5-8 minutes. Stainless steel material is recommended. 

Analytical information taken from a chromatogram has almost exclusively involved either retention data (retention times, capacity factors, etc.) for peak identification or peak heights and peak areas for quantitative assessment. The width of the peak has been rarely used for analytical purposes, except occasionally to obtain approximate values for peak areas. Nevertheless, as seen from the Rate Theory, the peak width is inversely proportional to the solute diffusivity which, in turn, is a function of the solute molecular weight. It follows that for high molecular weight materials, particularly those that cannot be volatalized in the ionization source of a mass spectrometer, peak width measurement offers an approximate source of molecular weight data for very intractable solutes. 

Occasionally, samples are run that adsorb onto the packing material. Generally, if one of the performance characteristics of the column changes by 10% or more, it is prudent to clean the column. These performance characteristics are (1) asymmetry factor, retention time, resolution, and theoretical plates. 

From 3-0-acetyl-5-deoxy-5-iodo-1,2-0-isopropylidene-/ -l-ara-binofuranose (38). Treating 100 mg. of (38) in pyridine (1 ml.), with anhydrous silver fluoride (200 mg.) for 4 hours and isolating the product as described above afforded crystalline 34 in 87% yield. Pure material had m.p. 31°-33°C. and [ ]D24 — 6.5° (c, 4 in acetone). Both samples had identical infrared spectra and had the same g.l.c. retention time at 100°C. 

The contents of the receiver and trap are combined with the aid of a few drops of dichloromethane and distilled through a 15-cm. Vigreux column under reduced pressure. After only a few drops of forerun, the main fraction is 2.87-3.17 g. (60-66%) of 5-hexynal, b.p. 61-62° (30 mm.), w20d 1.4447, df 0.875 (Notes 11-13). Cas chromatographic analysis (Note 14) shows this material to contain 3-5% of unidentified impurities with longer retention times (Note 15). 

The structure of the last eluting peak (Fig. ID, peak 10), structure is easily deduced to be 2,2, 3,3, 4,4, 5,5, 6,6 decabromo DPF from the bromine content of the pure sample, lack of proton spectrum and long retention time. Indeed, a recrystallized standard serves as reference material for a quantitative HPLC assay to be described elsewhere. 

In many analyses, fhe compound(s) of inferesf are found as par of a complex mixfure and fhe role of fhe chromatographic technique is to provide separation of fhe components of that mixture to allow their identification or quantitative determination. From a qualitative perspective, the main limitation of chromatography in isolation is its inability to provide an unequivocal identification of the components of a mixture even if they can be completely separated from each other. Identification is based on the comparison of the retention characteristics, simplistically the retention time, of an unknown with those of reference materials determined under identical experimental conditions. There are, however, so many compounds in existence that even if the retention characteristics of an unknown and a reference material are, within the limits of experimental error, identical, the analyst cannot say with absolute certainty that the two compounds are the same. Despite a range of chromatographic conditions being available to the analyst, it is not always possible to effect complete separation of all of the components of a mixture and this may prevent the precise and accurate quantitative determination of the analyte(s) of interest. 

The submitters used a 2.1 m. x 0.64 cm. column with 5% fluorosilicone (FS-1265) supported on Diatoport S as stationary phase. With a column temperature of 170° and a helium flow rate of 60 ml. per minute, 2-ethoxypyrrolin-5-one has a retention time of 2.2 minutes. The analysis was carried out at 160° by the checkers, using a column of 5% diethylene glycol succinate-Bentone supported on Diatoport S. The starting material had a retention time of 3.9 minutes under these conditions. Bentone is available from Applied Sciences Laboratory, Box 440, State College, Pennsylvania 16801. 

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