Nitrogen retention time

In 1959 Clinton and coworkers reported the first synthesis of some pyrazole fused androstane derivatives and described their biological activity (B-76MI40404). Stanazolol (695) or 17-methyl-2iT-5o -androst-2-eno[3,2-c]pyrazol-17/3-ol was 10 times as active as 17a -methyltestosterone in improving nitrogen retention in rats (B-80MI40406), and its myotrophic activity was only twice that of 17a-methyltestosterone. It is used as an anabolic steroid with no lasting adverse side effects. 

These calculations indicate that both the methyl group and the nitrogen atom increase the electron density around the carbon atom in the double bond which is /3 to the substituent (models 143 and 144). Therefore, when both of these groups are bonded to the same carbon atom of the double bond, this increase of electron density about the jS-carbon atom is intensified (as in model 146 and compound 142). This type of compound, then, is more strongly held by the stationary phase, and hence its retention time is longer than that of compound 141, where the effects of the methyl substituent and the nitrogen counteract each other (model 145). 

For example, only those dihydropyrimidines that contained a hydrogen-bonding donor at position 3 next to the chiral center were separated. Remarkably, dihydropyrimidines with non-substituted nitrogen atoms at positions 1 and 3 resulted in separations with longer retention times and decreased separation factors a. Increas-... 

Hint To distinguish these compounds without elemental composition or standards for GC retention time, split the GC effluent to a FID, a nitrogen-phosphorus detector, and the mass spectrometer, simultaneously. Using this splitter system, it is easy to determine if the GC peak contains nitrogen. Also, the analyst can differentiate between azobenzene and benzophenone by using the methoxime derivative. 

You can vary the composition of the eluent (mobile phase) in HPLC a lot more than in GC, so there s not really much correspondence. Substitute nitrogen for helium in GC and usually the sensitivity decreases, but the retention times stay the same. Changing the mobile phases—the gases—in GC doesn t have a very big effect on the separation or retention time. 

For gas chromatographic analysis of the products, the submitter used a 3 ft. x 0.125 in. stainless steel column of 5% LAC-446 (cross-linked diethylene glycol-adipic ester) on Diatoport S (60-80 mesh), which was heated at 140° and swept with prepurified nitrogen at 30 ml. per minute. The four isomers were observed as three peaks at retention times of 3.08, 3.69, and 4.07 minutes. The checkers used aim. x 4 mm. glass column of 10% DECS on Gas Chrome Q (60-80 mesh), which was heated at 200° and swept with prepurified nitrogen at 75 ml. per minute. 

Table 13.11 Typical GLC retention times for organomercury dithizonates. (I) 2% polyethyleneglycol succinate on Chromosorb G (acid-washed, DMCS-treated, 60-80 mesh) in glass column 1.5m long, 3mm I.D. carrier gas, nitrogen... 

The prediction of retention times in a given eluent from log P has been proposed for aromatic hydrocarbons.19 The log A values of phenols21 and nitrogen-containing compounds22 were also related to their logP, and the calculated log P was used for the qualitative analysis of urinary aromatic acids, i.e. for the identification of metabolites in urine from the differences of log P in reversed-phase liquid chromatography.23,24... 

Gas chromatographic data was obtained on a Tracor Model 220 gas chromatograph equipped with a Varian Model 8000 autosampler. The analysis column was a 1.7 m "U column, 4 mm id, filled with 3% SP-2250 packing (Supelco, Inc., Bellefonte, PA) held at 200 C. The injection temperature was 250 and the nitrogen carrier gas flow rate was 60 mL/min. The detector temperatures were 350 for electron capture and 190 for flame photometric. Detector signals were processed by a Varian Vista 401 which gave retention times and peak areas. 

A relatively new design of a high-rate DAF unit uses a shallow bed system (Supracell) with only 3 minutes of retention time and operated at an overflow rate of 140Lpm/sqm (3.5 gpm/sq ft) [42]. This unit has been used for industrial and municipal wastewater treatment and offers lower capital cost and headroom requirements. It was installed at a petrochemical complex in Texas as a secondary clarifier to improve the operation and the capacity of an existing activated sludge system [43]. In recent years, nitrogen has replaced air in covered DAF systems because of the potential for explosion. These systems are called dissolved nitrogen flotation (DNF) systems. The operations of DAF and DNF are similar. 

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