Confirmation liquid chromatography-infrared

Reference substances can be used for confirmation of identity of the substance by, e.g. infrared spectrophotometry where the spectrum of the substance to be examined must be concordant with the spectrum of the GRS, or by thin layer chromatography where the migration and appearance of the spots of both the substance to be examined and the GRS are the same, or by liquid chromatography where the retention time of both the substance to be examined and the GRS are the same. 

Biphenyl Fraction. The low molecular weight compounds, soluble in isooctane and hot methanol, were primarily biphenyl and o-, m-, and p-terphenyl. These products were identified by gas-liquid chromatography using a silicone gum rubber column (Figure 4) and a Carbowax 20M column with appropriate standards. The components were trapped and analyzed by infrared and NMR spectroscopy for confirmation. Biphenyl was present in sufficient quantity to be readily detected in the initial infrared spectrum and was isolated by sublimation. Quantitative data, obtained using the silicone column with appropriate calibration curves are presented in Table III. With the possible exception of biphenyl, the yields are very low considering the overall conversion noted. The o-, m-, and p-terphenyl ratio (1/0.4/1) indicates a preference for the para position beyond that expected for random attack. 

Walters, M.J. Ayers, R.J. Brown, D.J. Analysis of illegally distributed anabolic steroid products by liquid chromatography with identity confirmation by mass spectrometry or infrared spectrophotometry. J.Assoc.Off.Anal.Chem., 1990, 73, 904-926... 

Confirmation of any positives is advisable by using techniques such as liquid chromatography (LC) in conjvmction with MS or by infrared (IR) spectroscopy and GC in combination with MS. 

In all instances, there is a need to confirm the purity or stability of a particular sample before and after testing. Generally, the sponsor will assume these functions, but many private testing laboratories are associated with sophisticated analytical chemistry laboratories equipped with infrared spectrometry, gas chromatography, high-pressure liquid chromatography, and gas chromatography-mass spectroscopy instruments. 

Reactions were carried out in the liquid phase using 100 % HNOj from MERCK. Acidic clays (Slid CHEMIE - Munich FRG) and dessicants (PROLABO) were of commercial grade and used without further purifications, besides thermal treatments if needed. All compounds were analysed by gaz chromatography and their structures confirmed by mass spectrometry and infrared spectroscopy. 

About 10 g of VLB (vincaleucoblastine or simply vinblastine) sulfate were converted by standard procedures to VLB free base. The free base, obtained as a residue after evaporation of the dried ethereal solvent, was dissolved in about 200 ml of anhydrous methanol. Anhydrous liquid ammonia (300 ml) was added, and the reaction mixture sealed and maintained at about 100°C for 60 hours. The reaction vessel was opened, and the contents removed and evaporated to dryness in vacuo. The resulting residue, containing 4-desacetyI VLB C-3 carboxamide, as shown by thin layer chromatography, were combined and the solvent evaporated therefrom in vacuo, yielding asa residue purified 4-desacetyl VLB C-3 carboxamide free base. The NMR and IR spectra of the solid free base confirmed the structure indicated. The free base showed a band in the infrared at 1,687 cm-1, characteristic of the amide function. The molecular weight of the free base determined by mass spectroscopy was 753 which is in agreement with theoretical value calculated for C43H55N5O7. 

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