Determination of procaine, benzocaine and tetracaine by sequential injection analysis with pel-manganate-induced chemiluminescence detection

Local anaesthetics procaine hydrochloride (I), benzocaine (II), and tetraca ine hydrochloride (III) were determined by the technique of sequential inje ction analysis (SIA) with chemiluminescence (CL) detection. The CL was emit ted during the oxidation of the analytes by permanganate in aqueous sulphur ic acid in the presence of various CL enhancers (4-hydroxybiphenyl, Rhodami ne B, glycolaldehyde, glutaraldehyde and formic acid). The optimum enhancer or reagent concentrations: order and volumes of the injected zones were: 0 .37 M formic acid (40, 23 or 28 mu l for I-III, respectively), sample (40 m u l), 2.3 M H2SO4 (20, 16 or 18 mu l for I-III, respectively), and 0.5 mM K MnO4 (19, 13 or 15 mu l for I-III, respectively). After a double (or single for III) reversal of the flow the mixed zone was pushed into the detector at a flow rate of 100 mu l s(-1). The transient CL signal was recorded at g reater than or equal to 390 nm. The calibration graphs relating the intensi ty of the emission (peak heights) to the concentration of the analytes were curvilinear (a second order polynomial showed the best fit) and they were suitable for determining I-III in the ranges 0.5-50, 0.5-25 and 0.2-25 mu g ml(-1), respectively. The limits of detection (3 sigma) were 0.3 mu g ml(- 1) for I and II and 0.1 mu g ml(-1) for III. The sample throughput was 120 h(-1). The relative standard deviations were less than or equal to 3.8% (n = 10) when determining 5 mu g ml(-1) of I-III in prepared pure test solutio ns. The I and II were assayed in pharmaceutical dosage forms by the propose d method and the SIA results did not show any statistically significant dif ference from those obtained by standard titrimetry with sodium nitrite. (C) 2000 Elsevier Science B.V. All rights reserved.