Determination of Polyhexamethylene Biguanide Hydrochloride Using a Lactone-Rhodamine B-Based Fluorescence Optode

Abstract

A new determination method for polyhexamethylene biguanide hydrochloride (PHMB) using a lactone-rhodamine B (L-RB) based fluorescence optode has been developed. The optode membrane consists of 2-nitrophenyl octyl ether as a plasticizer, L-RB, and poly (vinyl chloride). The optode responds to tetrakis (4-fluorophenyl) borate, sodium salt (NaTPBF) in the μM range. The fluorescence intensity of the L-RB film for PHMB solution containing 20 μM NaTPBF decreased linearly as the concentration of the PHMB solution increased in the concentration range from 0 to 8.0 μM, which shows that PHMB with a concentration range of 0 to 8.0 μM is determined by the L-RB film optode. The concentration of PHMB in the contact lens detergents by the proposed method was in accord with its nominal concentration.

Keywords: contact-lens detergent; lactone-rhodamine B; optode; polyhexamethylene biguanide hydrochloride.

Figure 1

The absorption spectra of the lactone-rhodamine B (L-RB) film after it was immersed to a NaTPBF solution (pH 4.0, adjusted with a 0.1 M CH₃COOH/CH₃COONa buffer solution) for 30 min, respectively. Concentration of NaTPBF: (1) 0 µM, (2) 1.0 µM, (3) 5.0 µM, (4) 10.0 µM, (5) 50.0 µM, and (6) 100.0 µM.

Figure 2

Calibration curve for NaTPBF obtained by using an L-RB-based optode.

Figure 3

The excitation and fluorescence spectra of the L-RB film after it was immersing to a 5.0 µM NaTPBF solution (pH 4.0, adjusted with a 0.1 M CH₃COOH/CH₃COONa buffer solution) (1: excitation spectrum), (2: fluorescence spectrum), and that of the pH 4.0 buffer solution (0 µM NaDBS solution) (3: excitation spectrum), (4: fluorescence spectrum) for 30 min, respectively.

Figure 4

Calibration curve for polyhexamethylene biguanide hydrochloride (PHMB) in the presence of 20.0 μM NaTPBF obtained by using an L-RB-based fluorescence optode.

Figure 5

Determination of PHMB in a contact lens detergent (A) by the standard addition method. The fluorescence intensity for a solution containing 20.0 μM of NaTPBF and a fivefold diluted contact lens detergent solution (A) through a Sep-Pak CN column was deducted from that for the solutions containing 20.0 μM of NaTPBF and a known amount of PHMB to a fivefold diluted contact lens detergent solution (A) without a Sep-Pak CN column. The deducted fluorescence intensity as the vertical axis was plotted for added PHMB concentration as the horizontal axis.