UV spectrophotometric method

Selective differential UV spectrophotometric method was presented for the determination of niclosamide in bulk and in its pharmaceuticals [43]. The method was based on measuring niclosamide in alkaline solutions against their neutral ethanolic solutions as blanks. The proposed method was sensitive, highly specific, and advantageous over the conventional UV assays, since the interference of the excipients, impurities, degradation products, or other accompanying drugs was nullified. 

Liu [51] developed a simple and rapid UV spectrophotometric method for determination of niclosamide. The drug, with or without purification by chromatography on a silica gel plate, was dissolved in anhydrous ethanol and the solution or standard was placed in a 1-cm quartz cell and analyzed at 335 nm by spectrophotometry. 

The light-absorbing impurities of oxytetracycline hydrochloride and oxytetracycline dihydrate [2,4,6] are detected using a UV-spectrophotometric method. In all the compendia, the absorbance of a solution of 2.0 mg/mL in a mixture of 1 volume of hydrochloric acid solution (0.1 mol/L) and 99 volumes of methanol at 430 nm not greater than 0.50 is required the absorbance of a solution of 10 mg/mL in the same solvent at 490 nm is not greater than 0.20. The measurements are carried out within 1 h of the preparation of the solutions. 

A few typical examples for the assay of pharmaceutical substances by UV-spectrophotometric method are described below ... 

PLS-UV Spectrophotometric Method for the Simultaneous Determination of Ternary Mixture of Sweeteners (Aspartame, Aeesulfame-K and Saeeharin) in Commereial Produets... 

PLS-UV Spectrophotometric Method for the Simultaneous Determination of Ternary Mixture 307... 

The aim of this study to investigate the effects of Cu(II) ion and PVP concentrations on the oxidation kinetics of H A in aerated and acetate buffered solution, at 25°C, using direct UV spectrophotometric method [14, 15]. 

Edwards and Meacock189, following amide hydrolyses in strong acid solution, used a uv spectrophotometric method. Bunton et al.224 followed the hydrolysis of NN-dimethylbenzamide by adding an alcoholic solution of l-fluoro-2-4-dinitrobenzene and alkali to aliquots of reaction mixture and determining the N,N-dimethyl-2,4-dinitroaniline spectrophotometrically at 381 m/tt. 

Sahu and Patel developed a rapid, simple, accurate, and precise UV spectrophotometric method for the simultaneous determination of amlo-dipine besylate and atorvastatin calcium in a binary mixture. In the method, absorbance values were measured at 238.2 and 246.6 nm that... 

The lack of a well defined UV absorption spectrum for phenytoin makes its determinations by direct UV spectrophotometry difficult nevertheless, the literature describes several methods which depend upon the spectrum of the unchanged drug25 Wallace et al 6 and Fellenberg et al reviewed the use of UV spectrophotometric methods for the analysis of phenytoin. A spectrophotometric method for the quantitative determination of phenytoin has been described by Bgorge et al B based on the difference in absorbance of an alcoholic solution at 233 nm before and after conversion of phenytoin to the sodium salt. Methods that require conversion of the drug to benzophenone have been reported Sf30,31,32 ... 

A derivative UV spectrophotometric method was used by Bonazzi et al. for the determination of benazepril hydrochloride and other angiotensin converting enzyme inhibitors in their pharmaceutical dosage forms [17],... 

Rizk et al. developed a sensitive and selective derivative UV-spectrophotometric method for the determination of three fluoroquinolone compounds, including ciprofloxacin, in formulations and spiked biological fluids (7]. The method depends on the complexation of Cu(II) with the studied compounds in an aqueous medium. A linear correlation was established between the amplitude of the peak and the drug concentration over the range of 35-120 ng/mL. The detection limit was reported as 1.3 ng/mL. The method was used for the determination of the ciprofloxacin bulk drug substance and its tablet formulation, with an overall percentage recovery of 99.22 0.55 to 100.33 1.60. 

Parimoo et al. [18] established a UV spectrophotometric method for the simultaneous determination of mefenamic acid and paracetamol in combination preparations. The determination was carried out in two different solvents, namely methanol and 0.1 N NaOH. The wavelength maximum for mefenamic acid was found at 284 nm, and 248 nm for paracetamol. The wavelength maximum for mefenamic acid in NaOH was found at 219 nm, and 256 nm for paracetamol. There were no interferences in the analyte estimations. 

Dissociation constants of ionizable components can be determined using various methods such as potentiometric titrations [85] CE, NMR, [86] and UV spectrophotometric methods [87]. Potentiometric methods have been used in aqueous and hydro-organic systems however, these methods usually require a large quantity of pure compound and solubility could be a problem. Potentiometric methods are not selective because if the ionizable impurities in an impure sample of the analyte have a pK similar to that of the analyte, this could interfere with determining the titration endpoint. If the titration endpoint is confounded, then these may lead to erroneous values for the target analyte pKa. 

Some work has been done on the kinetics of decarboxylation of aromatic acids in non-aqueous solutions at high temperatures [233]. Usually, the reactions are much faster in aqueous solutions [239] particularly if they are acid catalyzed. Therefore, emphasis in this article will be on decarboxylation in aqueous solution. A brief review has been published in 1968 [240]. In almost all cases, rates can be conveniently followed with the aid of the UV spectrophotometric method. 

Annapurna et al. [13] established simple, accurate, and reproducible UV spectrophotometric methods for fhe assay of buclizine based on the formation of precipitation, charge transfer, and redox products. Precipitation/ charge transfer complex formation of fhe buclizine with I2/p-nitro methyl amino phenol sulfate-sulfanilic acid by method A, the precipitation/complex formation with ammonium molybdate/potassium thiocyanate by method B and precipitation/redox reaction of buclizine with phosphomolybdic acid/Co /EDTA by method C were proposed. Determination of buclizine in bulk form and in pharmaceutical formulations was also incorporated. 

The simplest UV-spectrophotometric method was developed by Rajesh and Reddy [25] to determine ezetimibe as a single compoimd. This method was based only on an absorbance measurement of ezetimibe af one wavelength. Similarly, Jain et al. [26] also employed a simple method to determine ezetimibe in combination with simvastatin. In this method, ezetimibe was observed at a wavelength where simvastatin did not give interference. While no LOD and LOQ values were reported, the linearity of the method was over the range of 5-20 pg/mL. 

TABLE 3.5 Summary of UV-spectrophotometric method used to analyze ezetimibe... 

In the first spectrophotometric method [22] the measurements were carried out using an Agilent 8453 model UV-Vis spectrophotometer with a DAD. The spectra were recorded from 225 to 475 nm. The quantitative analysis were performed at 376 nm for the zero-order derivative UV spectrophotometric method by measuring the height of the peak from zero and at 302 nm, and 281 nm for the first-order derivative UV... 

The United States Pharmacopeia XXII (8) lists a UV Spectrophotometric method for the assay of tolnaftate. The absorbance of tolnaftate solution in methanol (10 pg/ml) is measured at the wave length of maximum absorbance at about 258 nm. Quantitation is based on the net... 

A rapid second-derivative UV spectrophotometric method was developed by Jimena Garcia as a . (1992). This method provided satisfactory results in the analysis of a binary mixture of PBO wilh permethrin, tetramethrin or fenitrothion. 

A convenient UV spectrophotometric method for in-process testing of the active ingredient is usually selected. A UV method can have a turnaround time of a few minutes compared with an HPLC method. Another advantage of the UV spectrophotometric method is that it does not require elaborate instrument and data acquisition systems and can be easily set up in a manufacturing environment. 

The pJCa of medazepam was determined by a UV spectrophotometric method and compared with data obtained from the solubility method. Good correlation was found between the results of the 2 methods."... 

Complexation of metal ions with the carboxyl resin Complexation of the carboxyl resin was carried out towards Fe(II), Fe(III), Co(II), Ni(II) and Cu(II) ions by a batch equilibration technique. A quantity (100 mg) of the resin was stirred in an aqueous metal salt solution (0.05 mol L , 50 mL) for 24 h. The complexed resins were collected by filtration and washed with distilled water to remove uncomplexed metal ions. The concentrations of the metal salt solutions were estimated by UV spectrophotometric methods. 

The DS of the CMC (LC and PH) samples determined by the standard method (Green 1963) was found to be 1.22 and 1.33, respectively, while in case of CMC derived from bamboo cellulose (DCS), this was calculated from its mole fractions after complete depolymerization of polymer chains by HPLC (Heinze et al. 1994) as 0.98. The DS of the optimized CEC sample was calculated from the N content using the equation DS = 162 x %N/1,400 - (53 x %N) was 2.2. Nitrogen content was determined by the KjeldahTs method. The percent hydroxypropoxyl content in HPCs determined by UV spectrophotometric method (Jhonson 1969) were found to be 65.89% (DCS) and 67.75% (PH). 

Xuefeng H. 2002. Determination of total nitrogen in water by alkaline jx)tassium persulfate oxidation-UV spectrophotometric method. Environ. Pollut. Control 24 40-41. 

Wang SX, Oomah DB, McGregor DI. 1998. Application and evaluation of ion-exchange UV spectrophotometric method for determination of sinapine in Brassica seeds and meals. Journal of Agricultural and Food Chemistry, 46(2) 575-579. 

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