PT  - JOURNAL ARTICLE
AU  - Preston, Wendy A.
AU  - Anderson, Neil R.
TI  - Glass and Rubber Closure Effects on the pH of Water II. A Proposed Mechanism of Interaction
DP  - 1985 Jan 01
TA  - PDA Journal of Pharmaceutical Science and Technology
PG  - 28--47
VI  - 39
IP  - 1
4099  - http://journal.pda.org/content/39/1/28.short
4100  - http://journal.pda.org/content/39/1/28.full
SO  - PDA J Pharm Sci Technol1985 Jan 01; 39
AB  - The effects of glass and rubber on the pH of water stored in rubber closure sealed glass vials have been investigated. The effect of the glass was isolated by sealing the vials with Teflon rather than rubber. The effect of the rubber closure on the pH of water was investigated and attributed to the phenolic resin vulcanizing agent of the closure. Phenolic resins are regarded as insoluble in water, but the resin is believed to have an increased water solubility by the formation of a zinc chelate. Once in solution, the phenolic resin slowly degrades during storage at elevated temperatures to produce carboxylic acid compounds. These compounds cause the pH of the water to decrease when there is no neutralization by alkaline substances. The degradation of the resin was demonstrated using infrared spectrophotometry. A high-pressure liquid chromatography analysis of the samples also indicated that degradation products of the resin were present.