Second-derivative spectrophotometr

One technique to assess lipid peroxidation utilizes second-derivative spectrophotometric analysis of cyclohexane or ethanol-reconstituted extracts to determine the cis-trans and trans-trans isomeric forms of conjugated dienes and oxodiene species within synovial fluid. Using this method, a rise in the synovial fluid concentration of conjugated oxodienes, hydroxydienes and hydroperoxy-dienes was found to follow joint exercise (Merry et al., 1991). 

Chen used a second-derivative spectrophotometric method for the determination of miconazole nitrate in Pikangshuang [22]. Sample of miconazole nitrate was dissolved in anhydrous ethanol and the second-derivative spectrum of the resulting solution was recorded from 200 300 nm miconazole nitrate was determined by measuring the amplitude value between the peak at 233 nm and the trough at 228 nm. The recovery was 99.8% with a relative standard deviation (n = 6) of 0.2%. 

A rapid second-derivative spectrophotometric assay procedure was described for the simultaneous determination of niclosamide and thiabendazole in tablets [47]. The derivative absorbances were measured at 354 nm for niclosamide and at 242.5 nm for thiabendazole. 

Olanzapine The first derivative values measured at 222 nm and the second derivative values measured at 230 nm (n=6) were used for the quantitative determination of the drug. Calibration graphs were linear in the concentration range of olanzapine using 2-10 pg mL-i for first and second derivative spectrophotometric method. 18... 

Tatar, S. Saglik, S. Comparison of UV- and second derivative-spectrophotometric and LG methods for the determination of valsartan in pharmaceutical formulation, J.Pharm.Biomed.Anal., 2002,30, 371-375. [capsules losartan is internal standard LOD 200 ng/mL LOQ 1 xg/mL]... 

Fernandez-Gonzales et al. [16] described a method for determination of OTC in medicated premixes and feeds by second-derivative synchronous spectrofluorome-try. The assay based on the reaction of oxytetracycline with divalent metal ion (Ca2+) at pH 6-10 to form a yellow complex that can be analyzed by synchronous spectrofluorometry (AX = 115 nm). Rao et al. [17] described a spectrophotometric method for the determination of OTC in pharmaceutical formulations based on the color reaction with uranium, which was detected at 413 nm. 

A survey of normal and derivative spectra of numerous vitamins, including vitamin Bg, has been reported. The second derivative spectra of these vitamins are especially suitable for their quantitative determinations (132). Quantitative determination by derivative spectroscopy is superior to direct spectrophotometric measurement in many problem situations. 

Panderi used a second-order derivative spectrophotometric method for the simultaneous determination of benazepril hydrochloride and hydrochlorothiazide in tablets [15]. The determination of benazepril hydrochloride in the presence of hydrochlorothiazide was achieved by... 

Barary et al. used a derivative spectrophotometric method for the determination of dipyridamole and carbocromen hydrochloride in the presence of their oxidative degradation products [26], Dipyridamole in 0.1 M hydrochloric acid was determined by first derivative (Di) spectrophotometry at 240 and 260 nm, and by second derivative (D2) spectrophotometry at 246 and 268 nm. For both drugs, 0.1 M-hydrochloric acid was used as a blank. Graphs of Di and D2 were linear for 4-12pg/mL of dipyridamole. The technique effectively corrects for the presence of degradation products. This method was used successfully to determine dipyridamole in persantin tablets. 

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. 

The method for the determination of ruthenium in the presence of Pt using the complexes with tin(II) chloride and second derivative spectrophotometry has been developed [1]. The determination of Ru in Pt-Ru catalysts with carbon support was described. Ruthenium in carbon-supported Pt-Ru-Ge catalyst was determined by simple selective spectrophotometric method using the complex with thiourea [2]. A 18-fold excess of Pd or Rh did not interfere with the determination of Ru. 

Several direct spectrophotometric methods are used for the sulphur dioxide measurement, including non-dispersive infrared absorption, ultraviolet absorption, molecular resonance fluorescence and second-derivative spectrophotometry. 

Ezetimibe First, second and third derivative spectrophotometric methods were proposed and utilised for determination of ezetimibe in pharmaceuticals. 23... 

First derivative spectra of levomepromazine (LV) and its sulphoxide were employed for investigation of LV photodegradation [11]. The degradation process of biapenem was monitored by measurement of first-derivative amplitude at 312 nm [12]. The determined rate constants for studied process were in good agreement with those obtained by HPLC method [12]. The second-order derivative spectrophotometric method was used for investigation of solvolytic reaction 2-phenoxypropionate ester of fluocinolone acetonide [45]. The run of process was observed by measurement the second-order amplitude at 274.96 nm corresponded to fluocinolone acetonide. The solvolysis rate constant was calculated using derivative method and compare with those obtained by HPLC methods [45]. 

Two distinctly different coulometric techniques are available (1) coulometric analysis with controlled potential of the working electrode, and (2) coulometric analysis with constant current. In the former method the substance being determined reacts with 100 per cent current efficiency at a working electrode, the potential of which is controlled. The completion of the reaction is indicated by the current decreasing to practically zero, and the quantity of the substance reacted is obtained from the reading of a coulometer in series with the cell or by means of a current-time integrating device. In method (2) a solution of the substance to be determined is electrolysed with constant current until the reaction is completed (as detected by a visual indicator in the solution or by amperometric, potentiometric, or spectrophotometric methods) and the circuit is then opened. The total quantity of electricity passed is derived from the product current (amperes) x time (seconds) the present practice is to include an electronic integrator in the circuit. 

Erk [20] described a spectrophotometric method for the simultaneous determination of metronidazole and miconazole nitrate in ovules. Five capsules were melted together in a steam bath, the product was cooled and weighed, and the equivalent of one capsule was dissolved to 100 mL in methanol this solution was then diluted 500-fold with methanol. In the first method, the two drugs were determined from their measure d%/dk values at 328.6 and 230.8 nm, respectively, in the first derivative spectrum. The calibration graphs were linear for 6.2—17.5 pg/mL of metronidazole and 0.7—13.5 pg/mL of miconazole nitrate. In the second (absorbance ratio) method, the absorbance was measured at 310.4 nm for metronidazole, at 272 nm for miconazole nitrate and at 280.6 nm (isoabsorptive point). The calibration graphs were linear over the same ranges as in the first method. 

Another spectrophotometric method used the derivative method. Rajput and Raj [19] developed a first-order derivative zero-crossing method to analyze ezetimibe in combination with simvastatin. This method was further applied to determine ezetimibe in combination with lovastatin. The first derivation method also applied to determine ezetimibe in combination with rosuvastatin [20]. Besides the first-derivative method, second- and third-derivative methods were also reported for defermining ezetimibe as a single compound in its dosage form [21]. Flowever, the third-derivative method yielded the lowest limits of defecfion and quantitation relative to other methods used in this research. The maximum wavelength also remained constant regardless of fhe derivative method applied. 

A preliminary chemical investigation of the polysaccharides of M. tuberculosis has recently been undertaken by W. N. Haworth and the authors. It was found that two stable and probably degraded polysaccharide fractions could be isolated from the defatted cells by the action of sodium hydroxide. Both products were serologically active at a dilution of 1 2,000,000 the first fraction ([a] D + 85° in water) was derived mainly from the somatic portion of the cell, while the second + 27° in water) was found in the ether-soluble lipid constituents. Both fractions were intimately associated with deoxyribonucleic acid, which was identified by nitrogen and phosphorus analyses, by the Dische test and by spectrophotometric measurements. 

Derivatisation of samples in HPLC is undertaken principally for two reasons. First, there is no detector for HPLC that has universally high sensitivity for all solutes hence a suitable chemical transformation of the solute can greatly extend the sensitivity and versatility of a selective detector. Second, sample derivatisation may be undertaken to enhance the detector response to sample bands relative to overlapping bands of no analytical interest. This experiment involves the pre-column derivatisation of sample with dinitro-fluorobenzene so enhancing the spectrophotometric response of the sample, that is, the amino acids from a protein hydrolysate. The conversion of the amino acids to their apolar DNP derivatives allows them to be analysed using reverse phase chromatography. Thus, polar DNP-amino acids, such as DNP-aspartate, will elute early whereas apolar DNP-amino acids, such as DNP-alanine, will elute later. The DNP-amino acids are detected by an... 

Gemifloxacin mesylate The proposed methods were based on the reaction of gemifloxacin with chloranilic add and parachloranil to give highly coloured complexes. The coloured products were quantified spectrophotometrically at 530 nm and 540 nm at zero order, 590 and 610 nm for the first derivative and 630 and 650 nm for second order derivative. Beer s law was obeyed in the concentrations range of 10 to 60 pg mL-i, 5 to25 pg mL-i at zero order, 5 to 25 pg mL-i, 5 to 40 pg mL-i at first order and 2 to 20 pg mL-i and 2 to 14 pg mL-i at second order. 17... 

The spectrophotometric data for the immobilized enzymes colloidal systems showed marked light scattering effects. The data were therefore subjected to a smoothing function by curve fitting a (best fit) fourth order polynomial to the data set from 18 to 80 seconds (the time period investing Vmax as determined from the data set of fresh (day 0) free enzyme activity). After curve fitting, the derivatives were calculated and enzyme velocity (VI8-80) was determined for each of the four systems (free enzyme, surface immobilized, inactivated surface immobilized, and immobilized supernatant) over the four time intervals (day 1, 3, 5 and 7). The data were then normalized to the activity of the free enzyme and plotted. 

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