Journal of Oil Palm Research Vol. 24 (1) April 2012, p. 1287-1295


CHEONG Mei Yee* ; HAZIMAH Abu Hassan* ; ZAFARIZAL ALDRIN Azizul Hassan* ; ROSNAH Ismail*


Crystalline metal-based glycerol complexes, such zinc (Zn), cobalt (Co), iron (Fe), nickel (Ni) and manganese (Mn) complexes, are formed by heating certain metal oxides, hydroxides or salts with glycerol at temperatures above 110°C. In this study, zinc glycerolate were synthesised using zinc oxide and excess glycerol at 240°C. The characterisations done were Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis and differential thermal analysis (TGA-DTA), scanning electron microscopy (SEM), X-ray diffraction, in vitro dermal irritection assay and determination of sun protection factor (SPF). The hydrolysis property of zinc glycerolate in aqueous condition was also investigated. The hydrolysis of zinc ions followed a rather simple path unlike in the case of most polyvalent cations. The reaction of Zn2+ with OH ions resulted first in the formation of Zn(OH)+ species followed by precipitation of zinc hydroxide which easily redissolved in an excess of base to form a soluble complex. Quantitative TGA-DTA analysis was used to determine the amount of glycerol required in aqueous solution that could presumably minimise the hydrolysis of zinc glycerolate. Aqueous solutions that were subjected to high heat needed up to 60% of glycerol in order to preserve the zinc glycerolate. Therefore based on this study, zinc glycerolate is more suited to be incorporated in dry or anhydrous formulations such as powders and ointments. It has SPF of 1.07 ± 0.004 and ultraviolet A (UVA) ratio of 0.29, which is a moderate (one star) Boots star rating for UVA protection. Zinc glycerolate is classified as non-irritant, and therefore has good potential for use in the pharmaceutical and personal care product industries.


* Malaysian Palm Oil Board,
P. O. Box 10620, 50720 Kuala Lumpur, Malaysia.