Impurities identifying

Statistical analysis" has demonstrated that the demands placed upon the reliability of the chemical shift predictions intrinsic in this automated confirmation of structure, are greater if predicted and experimental stoichiometries cannot be compared. Furthermore, it is inevitable that high throughput environments will not yield pure compounds and the reliable identification of impurities (identified as fractional stoichiometry) will be key. 

Note Impurities identified in refined ingots of commercially available ex-coal tar include naphthalene, 2-methylnaphthalene, fluorene, and methyldibenzofuran (Marciniak, 2002). 

Residues identified on field-treated kale other than malathion included the oxygen analog and the impurity identified by nuclear magnetic resonance and mass spectrometry as ethyl butyl mercaptosuccinate, 5-ester with 0,0-dimethyl phosphorodithioate. This compound did not form as an alteration product of malathion but was present in the 50% emulsifiable concentrate (Gardner et al, 1969). 

An impurity identified in commercially available acenaphthene (Marciniak, 2002). 

Scheme 11.2 Some of the impurities identified in cyanation reaction.

Identify significant impurities and demonstrate the absence of potential or postulated impurities Identify potential degradation products through stress testing and actual degradation products through stability studies... 

The VPO catalyst was prepared by a method described previously [5]. The bulk molar PA ratio of the catalyst was 1.26 and the surface area was 44 m2/g. The catalyst was equilibrated for over 80 hours at the n-pentane/air reaction mixture at the temperature of about 390°C before measurements. Silicium carbide (Prolabo, purity > 99 % grain fraction 0.35 mm), n-pentane (Aldrich, purity > 99 % impurity identified as 2-pentenes) and methyl-tert-butyl ether (MTBE) (Aldrich, purity > 98 %) were used without further purification. 

Diethyl N,N-dimethylphosphoramidate Diethyl dimethylphosphoramidate c6h16no3p 2404-03-7 Major impurity, identified in soil ... 

Bismuth chloride is a good catalyst for veratrole acylation by RCOC1 (entries 1,2), but the crude product may contain about 5 % of an impurity identified (GC-MS) as compound fi, which would arise from cleavage of an ether group by HC1. The reaction is more difficult with acid anhydrides (entries 4,5) relative to anisole (Table 4, entries 2,4). 

TNT was removed prior to the analysis by fractional crystallization. The impurities, identified by their El mass spectra, included isomers of dinitrobenzene (DNB), DNT and TNT, as well as TNB, 2,4,6-trinitroxylene (TNX), and 1-nitro-naphthalene. 

Because some of the impurities identified in AMS are not available commercially, this test method is based on the use of theoretical response factors calculated with the use of effective carbon numbers (see Table 2). ... 

Connect the gas sample to the G.C. sample port. Flush the loop for a period of 30 s. Close the sample cylinder shut-off valve and inject the sample the moment the loop reaches atmospheric pressure. Integrate the areas of the impurities. Identify the impurities by comparing their retention time to that obtained with the standard mixture. A typical sample chromatogram is shown in Fig. 5. 

---