Rapid spectrophotometric determination of benzalkonium in pharmaceuticals by extraction/ FIA

• Published in: BUNSEKI KAGAKU Vol. 39; no. 2; pp. 73 - 77
• Main Authors: MIYAJI, Toshihiko, HIBI, Kiyokatu, SAKAI, Tadao
• Format: Journal Article
• Language: Japanese; English
• Published: Tokyo The Japan Society for Analytical Chemistry 1990; Japan Science and Technology Agency
• Subjects: FIA coupled with solvent extraction; formation of ternary ion associate by quinine, BPB and benzalkonium; selective and rapid assay of benzalkonium in pharmaceuticals
• ISSN: 0525-1931
• DOI: 10.2116/bunsekikagaku.39.2_73

Bivalent BPB anion reacts with 10-5 M quinine in neutral media to form a 1:2 charge transfer complex in 1, 2-dichloroethane, but not with 10-6 M benzalkonium. However, trace amounts of benzalkonium could be extracted into 1, 2-dichloroethane with BPB only when 10-410-5 M quinine was added in the extraction system giving a blue product. The molar absorptivity of the product was 50500 mol-1cm-1l at 610 nm. The blue product can be used for selective and rapid spectrophotometric determination of benzalkonium by the FIA method. The carrier solution (0.8 M phosphate buffer, pH 7.5) was pumped at a 0.75 ml/min flow rate and 1×10-4 M quinine standard solution and 5×10-5 M BPB were pumped at 0.25 ml/min each. Sample solutions (100 μl) were injected into the carrier stream by a six-way injection valve and mixed with the reagents in a 1 m reaction coil. The ion associate formed by quinine, BPB and benzalkonium was extracted into the organic phase in a 4 m extraction coil. The organic phase was separated by a phase separator with either a microporous polytetrafluoroethylene (PTFE) membrane (pore size 0.5 μm) or PTFE tubing (pore size 2 μm), and put through a 8-μl flow cell. Then the absorbance was measured at 610 nm and recorded as peak-shaped signals. Benzalkonium in the range of 5×10-6 M to 1.5×10-4 M could be determined and the relative standard deviation was 1.1% for 10 determinations of 1×10-4 M benzalkonium. The sample throughput was 24/h. The FIA method proposed here can be applied to the selective and rapid assay of benzalkonium in pharmaceuticals.