Development of a multicommutated flow system with chemiluminometric detection for quantification of gentamicin in pharmaceuticals

Abstract

A new flow procedure based on multicommutation with chemiluminometric detection was developed to quantify gentamicin sulphate in pharmaceutical formulations. This approach is based on gentamicin's ability to inhibit the chemiluminometric reaction between luminol and hypochlorite in alkaline medium, causing a decrease in the analytical signal. The inhibition of the analytical signal is proportional to the concentration of gentamicin sulphate, within a linear range of 1 to 4 μg mL(-1) with a coefficient variation <3%. A sample throughput of 55 samples h(-1) was obtained. The developed method is sensitive, simple, with low reagent consumption, reproducible, and inexpensive, and when applied to the analysis of pharmaceutical formulations (eye drops and injections) it gave results with RSD between 1.10 and 4.40%.

Figure 1

(a) scheme of the multicommutated flow system employed. S: sample; R₁: hypochlorite solution (carrier solution); R₂: luminol solution; Pp: peristaltic pump; V₁, V₂, and V₃: solenoid valves; X and Y: confluence points; RC: reaction coil; D: chemiluminometric detector; W: waste. (b) schematic representation of solenoid valves actuation during each analytical cycle. V₁, V₂, and V₃: solenoid valves; ts: sampling time; td: insertion time of luminol, reaction of this with the mixture sample/hypochlorite and signal detection.

Figure 2

Influence of hypochlorite's pH in the analytical signal. Dotted line: Reference signal; Continue line: Gentamicin standard solution (1 μg mL⁻¹).