UV—visible spectrophotometry

Colored ion-pair complexes were found useful for extractive spectrophotometric assays of a number of analytes oseltamivir [20], nortriptyline hydrochloride in pharmaceutical formulations [21], zolmitriptan in tablets [22], finasteride in tablets [23], and dosage forms of amoxycillin and flucloxacillin [24]. In all cases, the chromoge-nic reagent and analyte formed ion-pairs that obeyed Beer s law and were suitable for quantitative determinations. 

FIG U RE 15.1 SFC-ELSD of phospholipid mixture with modified COj on the four stationary phases. The modifier consisted of methanol with 5 mM ammonium acetate. Chromatographic conditions flow rate of 2 mL/min, methanol/additive concentration raised from 15 to 55% at 4 min and held for 5 min at 55%. (From Yip, H.S.H. et al. Chromatographia 2007, 65, 655-665. With permission of Vieweg Verlag.) 

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The evaluation of instrumentation for molecular UV/Vis spectroscopy is reviewed in the following pair of papers. Altermose, 1. R. Evolution of Instrumentation for UV-Visible Spectrophotometry Parti, /. Chem. Educ. 1986, 63, A216-A223. 

Hydantoin derivatives show weak absorption in the uv-visible region, unless a part of the molecule other than the imidazohdinedione ring behaves as a chromophore (13) however, piC values have been determined by spectrophotometry in favorable cases (14). Absorption of uvby thiohydantoins is more intense, and the two bands observed have been attributed to n — tt and n — tr transitions of the thiocarbonyl group (15,16). Several piC values of thiohydantoins have been determined by uv-visible spectrophotometry (16). 

UV-visible spectrophotometry and fluorescence spectrophotometry are also used for the direct observation of radical species and their reactions in some... 

Other methods reported for the determination of beryllium include UV-visible spectrophotometry [80,81,83], gas chromatography (GC) [82], flame atomic absorption spectrometry (AAS) [84-88] and graphite furnace (GF) AAS [89-96]. The ligand acetylacetone (acac) reacts with beryllium to form a beryllium-acac complex, and has been extensively used as an extracting reagent of beryllium. Indeed, the solvent extraction of beryllium as the acety-lacetonate complex in the presence of EDTA has been used as a pretreatment method prior to atomic absorption spectrometry [85-87]. Less than 1 p,g of beryllium can be separated from milligram levels of iron, aluminium, chromium, zinc, copper, manganese, silver, selenium, and uranium by this method. See also Sect. 5.74.9. 

It therefore became more convenient to monitor the reaction progress with UV/Visible spectrophotometry, because all the pyridine N-oxides have strong absorption bands near 330 nm, with e 103Lmol 1cm 1. Two approaches for the analysis of the kinetic data were used. In the first but much less precise method, the initial reaction rates were calculated from the objective method of fitting the experimental values of [PyOL to this function (30) ... 

Figure 7.5 Schematic diagram of a high performance liquid chromatography (HPLC) system. The solvent(s) are pumped through the system, and the sample injected just before the column where separation occurs. Detection is often by UV/visible spectrophotometry at a fixed wavelength.

Chapter 1 is an introduction to the field of molecular fluorescence, starting with a short history of fluorescence. In Chapter 2, the various aspects of light absorption (electronic transitions, UV-visible spectrophotometry) are reviewed. 

The study of molecular complexation was then extended to other aromatic nitro derivatives125. Although, as was described before, one of the more frequent methods of studying the formation of molecular complexes is by UV-visible spectrophotometry, the author did not observe detectable differences in the UV-visible absorbance spectra between the 2-hydroxypyridine-l-fluoro-2,4-dinitrobenzene (FDNB) mixtures and the sum of their separate components. The author observed that the signals of the 1II NMR spectra of FDNB in apolar solvents were shifted downward by the addition of 2-hydroxypyridine from solutions where [2-hydroxypyridine] [FDNB] he calculated the apparent stability constants, which are shown in Table 13. 

A new water-soluble calix[4]arene-triacid-monoquinone (99) has been synthesized and its ion-binding properties in aqueous solution were investigated by means of voltammetry and UV-visible spectrophotometry. The electrochemical behaviour of (99) is dependent on the concentration of Ca + ion rather than that of other alkaline... 

Chloromethane, vibrational spectra, 692 /fteto-Chloroperbenzoic add (m-CPBA) diastereoselectivity, 1144 transition metal peroxides, 1090, 1091 p-Chlorophenol, quinoneimine dyes, 630 Chlorophyll, UV-visible spectrophotometry, 664... 

Dialkyl peroxides (continued) colorimetry, 707-8 flame ionization detection, 708 NMR spectroscopy, 708 titration methods, 707 UV-visible spectrophotometry, 707-8 enthalpies of reactions, 153-4 graft polymerization initiation, 706 hydroperoxide determination, 685 peroxide transfer synthesis, 824-5 stmctural characterization, 708-16 electrochemical analysis, 715-16 electron diffraction, 713 mass spectrometry, 714 NMR spectroscopy, 709-11 thermal analysis, 714-15 vibrational spectra, 713-14 X-ray crystallography, 711-13 synthesis... 

Oxidation indices, 656-72 peroxide determination, 762-3 peroxide value, 656, 657-64 colorimetry, 658-61 definition, 657 direct titration, 657 electrochemical methods, 663-4 IR spectrophotometry, 661-3 NIR spectrophotometry, 663 UV-visible spectrophotometry, 658-61 secondary oxidation products, 656, 665-72 tests for stability on storage, 664-5, 672 thermal analysis, 672 Oxidative amperometiy, hydroperoxide determination, 686 Oxidative cleavage alkenes, 1094-5 double bonds, 525-7 Oxidative couphng, hydrogen peroxide determination, 630, 635 Oxidative damage... 

Vinylsilanes, ozonolysis, 275-6 Vimses, ozone disinfection, 616 Visible spectrophotometry see UV-visible spectrophotometry... 

Diclofenac sodium, famotidine and ketorolac were analysed utilising their formation of a coloured charge transfer complex with 2,4 dichloro-6-nitrophenol. The complexes were detected by UV/visible spectrophotometry at 450 nm. The method was not affected by the presence of common excipients in the formulations analysed. The precision and accuracy of the method was comparable to that of HPLC methods used to analyse the same samples. ... 

Pharmacopoeial methods rely heavily on simple analysis by UV/visible spectrophotometry to determine active ingredients in formulations. These methods are usually based on the use of a standard A (1 %, 1 cm) value for the active ingredient being assayed and this relies on the UV spectrophotometer being accurately calibrated as described earlier in the chapter. Such methods also presume that there is no interference from excipients (preservatives, colourants, etc.) present in formulations and that the sample is free of suspended matter, which would cause light scattering. 

UV/visible spectrophotometry is a standard method for determining the physicochemical properties of drug molecules prior to formulation and for measuring their release from formulations. The type of properties which can be usefully determined by the UV method are listed as follows. 

Deng, H. and Van Berkel, G.J., Electrospray mass spectrometry and UV/visible spectrophotometry studies of aluminium(III)-flavonoid complexes, J. Mass Spectrom., 33, 1080, 1998. 

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