Methyl cellulose identification

Some peak identifications for Figure 7.3.6 found in trimethylsilylated hydroxypropyl methyl cellulose pyrolysate are given in Table 7.3.8. 

The pioneer work on polysaccharide methylation, starting with the methylation of alkali-cellulose with methyl sulfate by Denham and Wood-house, has been reviewed by Irvine and coworkers. An enormous amount of ingenious and time-consuming work has been devoted to S3mtheses of the different methyl ethers of the natural sugars (which are required for identification purposes), and has been summarized in several articles in previous Volumes of this Series. 

In this separation, a 10-mL sample (large volume) containing a solution in tert-butyl methyl ether (tBME) of the pyrolysate of 1 mg cellulose obtained at 600° C was injected (off-line pyrolysis). The PTV injector was programmed at 20° C initial temperature for 2 min. and ramped with 10° C/min at 250° C and kept at this temperature for 1 min. Then the injector was further heated at 300° C. The split vent purge time was 2.5 min. The oven temperature for the first dimension separation was kept at 35° C for 2.5 min. then heated with 30° C/min. at 55° C and further heated with 3° C/min. to 240° C. The detector used in the first dimension was an MS system, which allowed the identification of a series of compounds from this chromatogram. The peak identification is given in Table 5.2.2. 

The type of analysis utilized to determine the composition of a pyrolysate is important because only a certain group of compounds can be seen in one type of analysis. The identification of more volatile compounds found in cellulose pyrolysate can be done very conveniently by on-line Py-GC/MS analysis. The TIC traces of cellulose pyrolysate obtained at 590° C and separated on a Carbowax or on a methyl-phenyl silicone type column were already given in Section 5.2 (Figures 5.2,10, 5.2.11 and 5.2.13). As indicated in Section 5.2, in these chromatograms compounds such as formaldehyde, methanol, or CO were not seen because the mass spectrometer used for the analysis had the mass range detection with a low cut-off at m/z = 32. 

The 2-D TLC was successfully applied to the separation of amino acids as early as the beginning of thin-layer chromatography. Separation efficiency is, by far, best with chloroform-methanol-17% ammonium hydroxide (40 40 20, v/v), n-butanol-glacial acetic acid-water (80 20 20, v/v) in combination with phenol-water (75 25, g/g). A novel 2-D TLC method has been elaborated and found suitable for the chromatographic identification of 52 amino acids. This method is based on three 2-D TLC developments on cellulose (CMN 300 50 p) using the same solvent system 1 for the first dimension and three different systems (11-IV) of suitable properties for the second dimension. System 1 n-butanol-acetone -diethylamine-water (10 10 2 5, v/v) system 11 2-propanol-formic acid-water (40 2 10, v/v) system 111 iec-butanol-methyl ethyl ketone-dicyclohexylamine-water (10 10 2 5, v/v) and system IV phenol-water (75 25, g/g) (h- 7.5 mg Na-cyanide) with 3% ammonia. With this technique, all amino acids can be differentiated and characterized by their fixed positions and also by some color reactions. Moreover, the relative merits of cellulose and silica gel are discussed in relation to separation efficiency, reproducibility, and detection sensitivity. Two-dimensional TLC separation of a performic acid oxidized mixture of 20 protein amino acids plus p-alanine and y-amino-n-butyric acid was performed in the first direction with chloroform-methanol-ammonia (17%) (40 40 20, v/v) and in the second direction with phenol-water (75 25, g/g). Detection was performed via ninhydrin reagent spray. 

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