Comparison of residual styrene monomer determination of pharmaceutical materials packed with polystyrene using gas chromatography and ultraviolet/visible spectrophotometer

Background: Plastics such as plastic wrapping are an integral part of today’s society. Plastics are made by polymerization of styrene monomers. If the polymerization reaction is not perfect, then there will be unreacted monomer residues. Although styrene is still considered harmless, if there is a metabolic process will form styrene oxide that can cause effects that are carcinogenic. Aims and Objectives: This study aims to determine the residue of pharmaceutical styrene materials packed with polystyrene using gas chromatography (GC) and ultraviolet (UV)/visible spectrophotometers which are usually available in chemical analysis laboratories. Materials and Methods: Orientation of analysis method was performed using latex polystyrene sample. Styrene monomer analysis was performed using a GC and UV/visible spectrophotometer. Then a comparative study was conducted on both methods. Once this method was accepted, it was applied to a polystyrene-containing sample obtained from the market. Styrene was isolated from the sample; then, both methods were tested and compared. Results: Using polystyrene latex sample and varying column temperature, for GC, the optimum condition was obtained at column temperature 110°C, detector temperature 200°C, and temperature of injector 200°C. Using the packing column, we got a repeatability of 96.67%, PRECISION test of 2.81%, 96.49% recovery test, and a detection limit of 0.25 ppm. For the quantitative test of latex polystyrene samples, the average residual content obtained was 0.276%. When using GC with a capillary column, used column DB-17 at 110°C, detector, and injector temperature at 200°C, the average content of styrene residue was 0.278%. When using the spectrophotometer UV/visible, λ maximum at 280.5 nm, the reliability, assay, recovery test, and detection limits were 94.83%, 4.36%, 93.72% and 0.30 ppm, respectively. The residual styrene results obtained with this instrument was an average of 0.271%. Using variance analysis with the fixed model for all three methods (GC with the capillary column, GC with packing column, and spectrophotometer UV/visible) obtained H0 hypothesis was rejected so that it was continued with Duncan test with the result of all three methods could be used for analysis of styrene residue. The result of average analysis for beverage sample with Spectrophotometer UV/visible method was 0.0220%, packed column GC was 0.0221% packing, and capillary column GC of 0.0.223%. For medication samples in each instruments were found 0.0239%, 0.0241%, and 0.0242%, whereas for food samples obtained 0.0236%, 0.0238%, and 0.0239%. Conclusions: A GC method with either a packing column or a capillary column and a spectrophotometer UV/visible could be used to analyze the residual styrene monomer of a polystyrene-grade pharmaceutical sample. The best analysis could use GC with a capillary column. It is recommended to use differential scanning calorimetry and thermogravimetric analysis, if available, as well as infrared spectrophotometer to obtain a cheaper and better method.