Infrared spectroscopy hydroxyl content

Analysis of oligomers for phenolic hydroxyl end groups was conducted by quantitative infrared spectroscopy. Hydroxyl absorbance at 3580 cm-1 was measured for a number of synthetic mixtures of bisphenol-A and bisphenol-A homopolycarbonate. A calibration curve for hydroxyl absorbance vs. weight percent hydroxyl end groups was constructed. Hydroxyl content of bisphenol-A oligomers was calculated from the calibration data. 

The acetyl content of cellulose acetate may be calculated by difference from the hydroxyl content, which is usually determined by carbanilation of the ester hydroxy groups in pyridine solvent with phenyl isocyanate [103-71-9J, followed by measurement of uv absorption of the combined carbanilate. Methods for determining cellulose ester hydroxyl content by near-infrared spectroscopy (111) and acid content by nmr spectroscopy (112) and pyrolysis gas chromatography (113) have been reported. 

Detailed near-infrared spectra of PET exposed to different relative humidities indicated three different subbands of the first overtone of water at 7080 cm 7010 cm and 6810 cm The comparison with the water spectmm of bulk water suggested that most of the water is only weakly bonded with PET (89). The analysis of difference spectra of dry nylon and nylon exposed to different humidities, indicated that there were distinct populations of hydrogen-bonded water in it (90). Recently, Musto et al. (91) investigated the nature of molecular interactions of water in epoxy resins by means of near-infrared spectroscopy as proposed by Eukuda et al. (89,90). They found three subbands at 7076 cm 6820 cm and 6535 cm evidencing two kinds of water adsorbed in the polymer (mobile water localized in micro vide and water molecules firmly bonded to the network). However, hydroxyl groups of epoxy may complicate the analysis of water content in polymers because they absorb also in the same overtone region as water. 

Considerable effort in the past few years has been devoted to the development and the study of rapid and efficient analytical methods for the determination of functionality in coal and coal derived products (2-11). The determination of phenol and alcohol moieties by acetylation has been used routinely for several years (1,3-7). Recently several groups have used silylation in combination with Infrared,(10) proton NMR (2) and atomic adsorption spectroscopy (3) to determine phenolic and alcoholic content of coal and coal derived products. Triethylborane activated by pivalic acid has been used very recently as a reagent for the determination of hydroxyl groups in lignites (11). 

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