AN INVESTIGATION OF THE EFFECTS OF GLASS AND RUBBER ON THE PH OF WATER STORED IN RUBBER CLOSURE-SEALED GLASS VIALS (STABILITY, PHENOL FORMALDEHYDE RESINS, LEACHING)
Abstract
The effects of glass and rubber on the pH of water stored in rubber closure-sealed glass vials were investigated using two methods of accelerated testing--an autoclave test and a 60(DEGREES)C test. The results of this investigation indicated that under autoclave conditions, extractables from the glass container are responsible for the observed increase in pH, and at 60(DEGREES)C the rubber closure extractables are responsible for the observed decrease in pH. The effect of the glass was isolated by sealing the vials with Teflon, rather than rubber, and the pH of the water increased in the three types of glass vials in the order: type I treated < type I < type II. The rubber effect was investigated by finding a UV absorbing compound in the water samples and identifying it as the phenol formaldehyde resin vulcanizing agent from the rubber closure. This ingredient is insoluble in water but is believed to have an increased water solubility by the formation of a zinc chelate. In solution, the phenolic resin is believed to slowly degrade during storage at elevated temperatures to produce carboxylic acid compounds. These compounds may cause the pH of the water to decrease when there is no neutralization by alkaline substances. The pH lowering effect of the closures was demonstrated by storing a potassium chloride solution in the vials at 60(DEGREES)C. The KCI partially inhibits the release of alkali from the glass and the pH decreased in all of the samples. Evidence for degradation of the resin was obtained using IR spectrophotometry and high-performance liquid chromatography. A mechanism was proposed which explains the observed pH changes due to the interactions of water with the glass and rubber.
Degree
Ph.D.
Subject Area
Pharmaceuticals
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