Study on the Water of the Inner Epidermis of the Bulb of Onion by Infrared Spectra

Abstract

An infrared spectrophotometer was developed for the direct method of structural study of water contained in the inner epidermis of the bulb of onion. The direct method was to replace potassium chloride tablet method which was also discussed in the aspect of the effect of water on the infrared spectra.
The results may be summarized as follows:
1. The mixing of only potassiam chloride powder by agate mortar for 3min to form tablet increased the it absorption, especially at 3.0μ (3340cm^-1).
2. The effect of the mixing method of potassium chloride powder and soybean flour on the it spectra was found that the use of agate mortar intensified the absorption of it rays at 3.0μ (3340cm^-1) and 6.1μ (1630cm^-1). The vibration after agate mortar mixing did not remarkably increase the it absorptions.
3. There was no significant difference between the it spectrum of red bean flour of 1.56% moisture content and that of 12.57% moisture content.
4. On the whole the ir spectra of rice flour and wheat flour were similar to each other in appearance, while the it spectra of red bean flour, dwarf red cranberry bean flour and white kidney bean flour resembled each other. The it absorptions of soybean flour were relatively sharp in the spectral regions 2900-2800cm^-1 and 1740-1730cm^-1.
5. The increase of number of polyethylgne films (thickness of 0.03mm) increased the sharpness of ir absorption, but it did not obstruct the study of the structure of water.
6. Two layers of polyethylene covered water films indicated about twice the it absorption of mono layer of water film at 1630cm^-1, and the same relation was observed also at 3340cm^-1.
7. The ir absorption by the proper vibration of polyethylene was eliminated more in two layers of its film than in one layer. The ir absorption in the range1445-1435cm^-1 was related to proper vibration of polyethylene, and the absorption of free OH was at lower frequencies (3280-3240cm^-1) than that of absorbed water (3340cm^-1).
8. At 3240-3200cm^-1 the it absorption was observed in the case of the inner epidermis of the bulb of onion, while the it spectra of freewater was not so clear.
9. The ir spectra of fresh inner epidermis of the bulb of onion indicated that there was much adsorbed water, but that the amount of free water did not differ from those of the inner epidermises which were vacuum-dried or died in the space over 95% sulfuric acid respectively.
The quantitative analysis, therefore, of water adsorbed to the surface of various epidermises may be possible, while the free water may require to be scanned beginnig at 1650cm^-1.
10. Since heating of the fresh inner epidermis of the bulb of onion did not change its ir spectra, the adsorbed water to the surface of it may be similar to bound water in character.