A highly sensitive and simple Rayleigh light scattering （RLS） method for the determination of ciprofloxacin hydrochloride has been developed. Ciprofloxacin hydrochloride （CPFH） reacted with tetraphenylboron sodium（TPB） to form an ion-association complex in pH 5.31 aqueous solution, which resulted in a significant enhancement of the RLS intensity, which was linear with the concentration of CPFH in the range of 12.7-419 ng·mL^-1. The limit of detection for CPFH was 6.99 ng·mL^-1. The method is simple, highly sensitive and selective within a wide linear range. Applying this method for the determination of ciprofloxacin hydrochloride in pharmaceutical preparations and biological fluids obtained satisfactory results.
