IOP Conference Series: Materials Science and Engineering PAPER • OPEN ACCESS Spectrophotometric Determination of Benzocaine via Oxidation and Bleaching Colour of Rifampicin Dye To cite this article: Mohammed M. Mohammed et al 2020 IOP Conf. Ser.: Mater. Sci. Eng. 928 052032 View the article online for updates and enhancements. This content was downloaded from IP address 170.106.33.14 on 24/09/2021 at 17:37 2nd International Scientific Conference of Al-Ayen University (ISCAU-2020) IOP Publishing IOP Conf. Series: Materials Science and Engineering 928 (2020) 052032 doi:10.1088/1757-899X/928/5/052032 Spectrophotometric Determination of Benzocaine via Oxidation and Bleaching Colour of Rifampicin Dye Mohammed M. Mohammed, Nabeel S. Othman * and Faiz M. AL-Abady Department of Chemistry, College of Science, University of Tikrit ,Tikrit ,Iraq Department of Chemistry, College of Science, University of Mosul, Mosul ,Iraq Department of Chemistry, College of Science, University of Tikrit ,Tikrit ,Iraq [email protected] Abstract Benzocaine(BENZ) has been estimated by indirect spectrophotometric method. The suggested method based on oxidation of BENZ via N-bromosuccinamide (NBSA) in presence of hydrochloric acid, then the unreacted or the excess NBSA was immerse in bleaching the colour of rifampicin dye(REFPD),the absorbance of unreacted REFPD has been estimated at wavelength 476 nm (the highest absorption of REFPD) .The measured absorbance is directly proportional to the amount of BENZ in the solution. All parameters affected the oxidation of BENZ and bleaching the colour of REFPD and the optimum values have been fixed. Beer's law(linearity) of the method is in the range of 2 to 15 μg.ml-1, the molar absorptivity value equal to 4.295 x10 3 l.mol-1.cm-1 and the Sandall's index for sensitivity is calculated and equal to 0.0384 μg.cm - 2.The suggested method has an application part included estimation of BENZ in its pharmaceutical formulation (sterile ear drops). Keywords: Benzocaine, rifampicin, N-bromosuccinimide, spectroscopy, bleaching. Introduction BENZ is one of a local anesthetic drug for local and temporal relief of pain .BENZ is used as a local to loss the sensitivity and to eliminate sensation of the hard pain ,also it so-called pain sensitivity [1,2]. BENZ is ethyl p-aminobenzoate ; ethyl 4- aminobenzoate or it called ethylaminobenzoate,it is white crystal, colourless and odorless has the following structure in Scheme 1 [3]. M.wt =165.2 g/mol. Chemical formula : C9H11NO2 Scheme 1 .The chemical formula and structure of BENZ Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Published under licence by IOP Publishing Ltd 1 2nd International Scientific Conference of Al-Ayen University (ISCAU-2020) IOP Publishing IOP Conf. Series: Materials Science and Engineering 928 (2020) 052032 doi:10.1088/1757-899X/928/5/052032 Various techniques or method have been used in estimation BENZ as free or in its pharmaceutical formulations .These techniques included ,HPLC[4,5], HPLC-FIA-amperometric detector[6],batch injection analysis-amperometric detector [7],single sweep polarography[8],capillary electrophoresis[9].According to availability of devises used in spectroscopy and are not expensive, and also BENZ contains the amine group in its structure that is considered one of the encouraging groups for researchers, as it enters into many known reaction that are sensitive analytically [10-18]. The dye used in this investigation is rifampicin dye , a reddish-brown or brownish-red, crystalline powder, slightly soluble in acetone, water and soluble in methanol[3], REFPD has been used in estimating paracetamol via the, oxidation and bleaching the coloure[19]. The main objective of the current research is to estimate BENZ in an easy and sensitive spectrophotometric method and apply it in estimation BEBNZ in its pharmaceutical preparation( sterile ear drops). Experimental Apparatus A JASCOV – 630 UV / VIS spectrophotometer (Japan), with matched quartz cells(1cm) were used for all measurement. The balance BEL ENGNEERING was used in this investigation. Material and solution All material used in this research are of analytical grad. -1 Benzocaine solution,100 μg .ml -1 BENZ in 100 μg .ml was prepared by dissolving 0.0100 g of BENZ [C9H11NO2 ]in 5 ml ethanol and then the volume was completed to mark of the 100 ml volumetric flask with distilled water . N-bromosuccinimide solution (0.01M) This solution was prepared by dissolving 0.1779 g of NBSA in a 30 ml of distilled water, then complete the volume to the mark of 100 ml volumetric flask with distilled water. Rifampicin solution (0.1%) This solution was prepared by dissolving 0.05 g of REFPD with 2 ml ethanol (95%), then the volume was completed with distilled water in a 50 ml volumetric flask. Hydrochloric acid solution (1M) 8.4 ml of concentrated hydrochloric acid was diluted to 100 ml with distilled water in a volume flask. Pharmaceutical preparation,100 μg .ml-1 Three container of otocol sterile ear drops were mixed (each ml contain50 mg of BENZ ,1 ml of the mixture was mixed with 2 ml of ethanol and then the volume was completed with 2 2nd International Scientific Conference of Al-Ayen University (ISCAU-2020) IOP Publishing IOP Conf. Series: Materials Science and Engineering 928 (2020) 052032 doi:10.1088/1757-899X/928/5/052032 distilled water to100 ml in a volumetric flask, 5 ml from above solution diluted into 25 ml in a volume flask with distilled water to prepare 100 μg BENZ .ml-1 solution. Standard and curved working method The calibration curve for the suggested method was prepared by adding various volumes of BENZ (100 μg .ml-1) to cover the range of BENZ concentration from 2 to 15 μg .ml-1 to a serious of 10 ml volumetric flasks ,then 1 ml of 1M HCl, and 0.3 mL of NBSA (0.01M) were added and after a period waiting for 20 minutes, 0.5 ml of REFPD solution then 2 ml of ethanol (95%) for each flask (to increase stability) were added. Let the flasks for 5 minutes before the volume completed with distilled water to the mark. The absorbance of solutions was measured at the wavelength of 476 nm and the results were as in Figure 1 indicated that the linearity is from 2 to 15 μg .ml-1 Figure 1. The calibration curve of determination BENZ via suggested method. The molar absorptivity and the Sandall's index values are calculated and equal to 4.295 x10 3 l.mol-1 cm-1 and 0.0384 μg . cm-2 respectively. Results and discussion : The preliminary experiment involved knowing the maximum wavelength for REFPD by taking 1 ml of (0.1%) solution and diluting it into 10 ml with DW, and the spectrum from 250- 700 nm against DW (Fig. 2) indicated that 476 nm was the maximum absorption of REFPD, and it is fixed in the next experiments. 3 2nd International Scientific Conference of Al-Ayen University (ISCAU-2020) IOP Publishing IOP Conf. Series: Materials Science and Engineering 928 (2020) 052032 doi:10.1088/1757-899X/928/5/052032 Figure 2.The spectrum of REFPD. The optimum amount of REFPD Absorbance values for solutions prepared from various amount of REFPD were used in the constructing of standard curve of REFPD(Fig 3). Figure 3.The calibration curve of REFPD REFPD volume 0.5 ml was adopted in subsequent experiments . Selection of oxidizing agent Also, one of the preliminary experiments that must be performed is to know the type of oxidizing agent that gives a highest colour bleaching of REFPD . Figure 4 shows that the NBSA solution gives the best results (maximum bleaching) when compared with KIO4 ,and was chosen in subsequent experiments 4 2nd International Scientific Conference of Al-Ayen University (ISCAU-2020) IOP Publishing IOP Conf. Series: Materials Science and Engineering 928 (2020) 052032 doi:10.1088/1757-899X/928/5/052032 Figure. 4. The bleaching of REFPD colour's. The optimum conditions for the reaction: In order to obtain the ideal conditions that give the highest sensitivity and the highest stability of the unbleached – REFPD using NBSA as an oxidant , the optimum conditions that achieve this have been studied as follows: The optimum amount of NBSA Different volumes of 100 μg . ml-1BENZ solution(to cover the concentration from 25-200 μg BENZ .10 ml-1) have been added to several 10 ml volumetric flasks then 0.5 ml of 1M HCl has been added. NBSA solution was added with various volumes then after good shaking, left these volumetric for a waiting period of 10 minutes and then 2 ml of the REFP (0.1%) and 2 ml of ethanol (95%) were added. After waiting for 5 minutes, complete the volume with distilled water and the absorbance was measured against the blank solution at 476 nm and the results were as in Table 1. Table 1. The optimum amount of NBSA. 0.01M of μg of Benzocaine /10 ml NBSA R2 (ml) 25 50 100 150 200 0.1 0.3392 0.3955 0.4057 0.4085 0.4106 0.5667 0.2 0.2104 0.2962 0.3753 0.3951 0.4038 0.8077 0.3 0.0731 0.1366 0.2513 0.3652 0.3995 0.9685 0.4 0.0194 0.0639 0.2107 0.2785 0.3318 0.9621 0.5 0.0180 0.0283 0.0831 0.2130 0.2667 0.9623 From the results in Table 1,although 0.1 and 0.2 ml of NBSA gave highest intensity ,but the stability is bad and they gave lowers values of determination coefficient(R2) ,therefore 0.3 ml of the oxidant (NBSA) was chosen to give it the highest absorbance of the excess REFPD and 5 2nd International Scientific Conference of Al-Ayen University (ISCAU-2020) IOP Publishing IOP Conf.