Analysis of the ingredients and determination of the residual components of acrylic bone cements

Rapid and reliable methods for the characterization and quantitative determination of ingredients usually present in self‐curing methacrylate bone cements were developed using spectrophotometric, gas chromatographic (GC), and conventional gravimetric procedures. These procedures are applicable to non‐crosslinked methacrylate resins. In the presence of some copolymers, polymer blends or crosslinking agents, or other ingredients which will result in the formation of insoluble methacrylate resins, some modification of the identification procedures and quantitative estimation of the resin components will be required. Molecular weight and molecular weight distribution of the powder and cured cement were obtained from viscosity and gel‐permeation measurements. Residual low molecular weight materials in the cured cement were determined for various storage times. Residual and water‐leachable monomer and residual dimethyl‐p‐toluidine (DMPT) were measured by GC. In air, the monomer content of the cured resin decreased from 3.3% after 1 hr to 2.4% after 215 days. When stored in water at 37°C, over 65% of the extractable monomer is leached out within 10 min. After 6 hr, the rate of diffusion of monomer into the aqueous phase is low. The cured cement contains as much as 0.6% DMPT, which does not leach out. Residual peroxide, estimated spectrophotometrically, amounts to 0.8%, but decreases to 0.14% after 15 months in water at 37°C. A semiquantitative colorimetric test indicated that the hydroquinone content of specimens analyzed within 24 hr after curing amounted to 9 ppm.