UV assay

Figure 4.47. Drug assay using HPLC respectively UV Spectroscopy. Correlation of HPLC and UV results obtained on four batches of a cream. The vertical error bars each give the mean + standard deviation of 6 HPLC determinations because the Student s t-factor for five d.f. is nearly equal to /6 (see Section 1.3.2), the bars can also be interpreted as 95% confidence limits. The circles connected by a line indicate the corresponding duplicate UV determinations. The proportionality line passes through the origin and the center of mass for the four coordinates. The drug is slightly overdosed (= 103-104% the traditional UV assay apparently is not as selective as it should be an interference adds about 4% to the result.

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. 

In this chapter the validation approach will be explained using a simple and complex example. The simple example is a spreadsheet developed and validated for content uniformity determination by UV assay, while the second one is a routine HPLC potency and related substances determination. The simple example is placed directly into the validation section to further illustrate the validation approach, while the second example is located at the end of the chapter for further reading. Different frames will mark descriptions of these examples. 

The first problem is deciding on which of these two common models to use. It has been argued that for spectrophotometric methods where the Beer-Lambert Law is known to hold, Y = bX + e, the force through zero model is the correct model to choose if the absorbance values are corrected for the blank." The correct way to carry out the calibration regression is to include the blank response at assumed zero concentration and use the model Y = bX + a + instead. This may be a nicety from a practical standpoint for many assays but there are instances where a force through zero model could produce erroneous results. Note that the e denotes the random error term. Table 15 contains a set of absorbance concentration data from a UV assay. 

Kurz, G. and Wallenfels, K. 1974. D-Galactose. UV-assay with galactose dehydrogenase. In Methods of Enzymatic Analysis, 2nd ed. H. U. Bergmeyer (Editor). Academic Press, New York. 

Using the UV assay, very active LOX preparations, such as soybean preparations, can tend to be confusing, because the reaction is essentially over before measurements can be taken. This may lead the novice into the belief that... 

Regarding the UV assay, excessive absorption may be encountered in certain cases. For example, the Good buffers PIPES and HEPES absorb substantially at 234 nm. The optional use of a 9-mm optically transparent quartz spacer inserted into a 1-cm cuvette gives a 10-fold advantage with solutions of high UV absorbance. The spacer also serves as a convenient mixer, whereas mixing is difficult with specialized 1-mm cuvettes. 

The GLC determination of TC, ETC, ATC and EATC in aged TC samples has been reported. Trimethylsilyl derivatives of TCs were formed and gas chromatographed on six different columns, 3% OV-1, 3% JXR, 3% SE 52, 3% OV-17, 10% OV-25 and 10% OV-210. A 6 feet 3% JXR column at 260 °C isotherm separated most of the compounds. Different TC-HC1 powder samples were analysed through GLC for their degradation products and the results compared with those obtained from microbiological and UV assay methods (74). 

E. coli aldolase epPCR/ shuffling UV assay acceptance of phosphate free substrates 41... 

Fiber optic technology for in situ UV assay has received particular interest as it offers significant labor, time, and cost savings by eliminating the sampling and filtering stages of the dissolution test. A fiber optic... 

Table 3 LOD and LOQ estimated for a gradient LC/UV assay with three anal3des ...

In the first multiple-blend study, the multiple-sample bootstrap technique correlated with the reference UV assay, correctly identifying that the appropriate potency was not reached until the 20-min time point, although standard deviations levelled off at 10 min. The 10- and 15-min samples had... 

Derivative spectroscopy may be used in the assay of Ephedrine Elixir BP, which is used as a decongestant. This preparation is an oral solution containing 0.3% w/v of ephedrine hydrochloride in a suitably flavoured vehicle. The elixir is pink in colour and the presence of the pink dye interferes with the simple UV assay, but the preparation may be analysed as follows. 

COMPARISON OF GLC, GLC-COMPUTER, AND UV ASSAY RESULTS OF SOME FORMULATIONS48... 

First, the lack of an aromatic component in 1 meant that decreased immuno-genicity was observed. Second, initial screening assays for highlighting catalytic clones were not readily susceptible to a UV assay. Enantiotopic hydrolysis of 2 to the hydroxyacetate 3 was best accomplished by antibody 37 EB with a turnover number (catalytic rate constant), k =0.007 min and with excellent enantiose-lectivity, 86% ee. 

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