Acid chlorides, detection identification

Identification of Salicylic Acid in Horse Urine No statutory limit is prescribed for salicylic acid, but it is normally present in horse urine it is important, therefore, to distinguish between normal concentrations and those arising from medication with aspirin or other salicylates such as topically applied methyl salicylate. Normal urine concentrations rarely exceed 10 LLg/ml, but therapeutic doses of aspirin may give concentrations as much as 500 times greater. Addition of 1 ml of freshly prepared ferric chloride solution to 5 ml of urine will give a detectable violet colour when the concentration of salicylic acid exceeds about 100 ig/ml. A positive result should be followed... 

Qualitatively, these may be quickly detected by the Beilstein test for halogens a copper wire is heated in a gas burner until no color can be seen and the coil plunged into the acetic acid, then brought into the gas flame again. Any trace of green or blue-green flame shows the presence of halogen. The lower identification threshold is about 0.7 ppm for chloride, about 0.65 ppm for bromide, and about 0.55 for iodide. 

GC analysis of LAS is only possible after derivatization into volatile derivatives. Desulfonation of LAS in the presence of strong acids like phosphoric acid leads to linear alkylbenzenes (LAB). The identification of every single LAB isomer by GC-FID is achieved with detection limits lower than 1 /rg/1. In an alternative derivatization method, LAS are converted into their alkylbenzene sulfonyl chlorides by PCI5, which can be directly analyzed by GC-FID. Derivatization reactions for aliphatic anionic surfactants have mainly been described for product analysis. Among the very few methods for environmental analysis, the derivatization of alkyl sulfates to their corresponding trimethylsilylesters followed by determination with GC-FID is mentioned here. ... 

Curtis and Boyd utilized this feature to the full by optimizing NICI conditions for achieving hard ionization, viz., DEA, by which chloride ions are predominantly produced from chlorinated compounds and detected by SIM at m/z 35 and 37. Operated in this way, NICIMS is effectively turned into a chlorine-specific GC detector with selectivity and sensitivity comparable to those of the ELCD. By using this technique, Milley et al. successfully identified dichlor-otetradecanoic acid in a GPC-enriched sample from lobster digestive gland lipids (but with the chlorine position remaining undetermined). The identification of this compound was supported by the mass spectrum obtained with soft NICI optimized for molecular anions, which resembled that of a synthesized 9,10-dichlorotetradecanoic acid. 

Phinney et al. developed three CE-UV methods that allowed the enantiose-paration of ephedrine and pseudoephedrine using neutral HP-pCD, DM-pCD, and charged sulfated pCD as chiral selectors. The combination of negatively charged sulfated pCD (2.8 %) and DM-pCD (1.2 %) under acidic conditions (pH 2.5) provided the best separation of the two couples of enantiomers. Standard reference materials (SRMs) containing ephedra in development at NIST were analyzed by each of three CE methods. In the SRM samples, only the naturally occurring enantiomers ( )-ephedrine and (-l-)-pseudoephedrine were found however, the method proved to be suitable in detecting product adulteration by its potential in identification of specific stereoisomers [56]. The neutral HP-pCD was also found to be a useful chiral selector in the presence of tetrabutylammonium chloride as additive, for the simultaneous enantioseparation of ephedrine, pseudoephedrine, iV-methylephedrine, and norephedrine enantiomers in Ephedra sinica extracts [57]. 

Since chlorine is a structural element in relatively few minerals and rocks, the establishment of its presence or absence may be decisive in identification tests. The procedure given on page 546 for detecting traces of chlorine in fine chemicals can be employed here. The basis of the test is the production of free chlorine from chlorides on warming with chromic-sulfuric acid mixture, followed by exposure of the vapors to the yellow paper that has been impregnated with 4,4 -bis-dimethylaminothiobenzophenone. The paper turns blue if the test is positive. Since the color reaction responds to 0.2 y chlorine, fractions of 1 mg suffice for the detection of chlorine in minerals and rocks. This is shown in Table 5. 

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