Spectrophotometry differential

Gupta, R.C. and Lundberg, G.D., Qualitative determination of theophylline in blood by differential spectrophotometry, Anal Chem., 45,2402,1973. 

A third technique involves gas chromatography to separate water from UDMH. The fourth assay procedure is also used to determine water in UDMH, but by differential spectrophotometry at 1.9 nanometers. Water concns of from 0.1 to 15 wt % are detd. The fifth analysis technique is a near IR procedure which can be used to determine water in UDMH and diethylenetriamine, or the individual compds in a mixt. 

Barrosa (133) has reported the analysis of a mixture of pyridoxine and isoniazid in tablet formulation. Pyridoxine is determined by differential spectrophotometry at 324 nm. 

El-Yazbi et al. reported an application of a derivative-differential ultraviolet spectrophotometric method for the determination of oxazepam or phenobarbitone in the presence of dipyridamole [24]. Tablets containing the drugs were powdered and dissolved in ethanol. For solutions of oxazepam and dipyridamole, two portions of each were diluted with 0.1 N sulfuric acid and 0.05 M sodium borate, and subjected to differential spectrophotometry with measurements being made at 283, 292, 298 and 282, and 307, and 296 nm. First derivative (ADi)... 

Four electron carriers (A, B, C, and D) are required in the electron transport system of a recently discovered aerobic bacterium. You find that in the presence of substrate and 02, four inhibitors (I, II, III, and IV) block respiration at four different sites. From differential spectrophotometry of the electron carriers, you find that these inhibitors yield the patterns of oxidation state of the carriers shown below. What... 

Ferredoxin-NADP" oxidoreductase is a flavoprotein bound to the membrane that can nevertheless be isolated as a water soluble homogeneous preparation [247]. The isolated enzyme has a molecular weight of 40000 and contains one mol of FAD per mol of apoprotein [248] its midpoint potential is -0.38 V at pH 7 [249]. The enzyme can also accept NAD" " as electron acceptor, but is very specific for ferredoxin as donor the formation of a 1 1 complex with this latter protein could be demonstrated by differential spectrophotometry [250]. Immunological studies have revealed the location of this flavoprotein on the stromal surface of the membrane, in the vicinity of the ATPase complexes and therefore predominantly on... 

In this method salicylic acid is determined in its compound preparations. A sample of 1 g of ointment or 1 ml of liquid preparation, containing 6% of salicylic acid and 12% of benzoic acid is dissolved in boiling water. The cooled solution is diluted to 500 ml with H20 and filtered, and a 100 ml portion of the titrate is diluted to 100 ml with H20. Salicylic acid is determined in the resulting solution by differential spectrophotometry at 297 nm (22). 

K2. Kalckar, H. M., Differential spectrophotometry of purine compounds by means of specific enzymes. J. Biol. Chem. 167, 429-443 (1947). 

Differential spectrophotometry [22,23] consists in the measurement of the absorbance of a solution of the given element, not with reference to the solvent used, but with reference to a solution of this element (in the form of a coloured complex) of known concentration, slightly lower than the concentration of the solution studied. In this technique, the measuring error is in proportion to the difference of concentrations (and not to the concentration of the analyte in the solution under test), which enables one to reduce the relative error. Grey filters of appropriate absorbance have been proposed as references [24]. 

The theoretical bases of differential spectrophotometry have been presented [22]. The relative error of absorbance measurement is 0.2-0.5%, and is less in differential spectrophotometry [25-28] than in the regular method. Hence, the precision of differential spectrophotometry is comparable with that of gravimetric and titrimetric methods. This fact enables the technique to be applied in the determination of higher contents of the analytes. 

Spectrophotometric methods are characterized by high versatility, sensitivity, and precision. They may be used for the determination of almost all chemical elements over a wide range of concentrations, from macroquantities (by means of differential spectrophotometry) to traces ranging from 10 -10 % (after suitable preconcentration). Spectrophotometric methods are among the most precise instrumental methods of chemical analysis. 

The Chrome Azurol S method was used to determine aluminium in water [82], steel [83,84], uranium alloys [85], iron ores [86], and magnetic alloys [87]. Higher contents of aluminium (-10%) in magnesium and titanium compounds were determined by the differential spectrophotometry techniques [88]... 

Tantalum has been determined using Methyl Violet in concentrates [135]. Larger amounts of tantalum were determined by differential spectrophotometry [136]. Other basic dyes were used in determination of tantalum in ores [94], niobium and its compounds [97], and uranium and zirconium [96]. 

The tin(II) method has been used for determining platinum in catalysts [63,64] and ores [65]. Differential spectrophotometry was used for determining platinum in its alloy with ruthenium [66] and in catalysts [67]. The contents of platinum in catalysts have also been determined by derivative spectrophotometry [68]. 

Silicon has been determined as molybdosilicic acid in sewage [48], organic compounds [49], rocks and minerals [19,50,51], bauxites [52], cast iron and steel [53], high purity copper [23], copper alloys [21], various metals [54], refractory materials [55], vanadium pentoxide [22], and semiconductors [56]. The method has been applied also in the differential spectrophotometry [57] and flow injection [58,59] techniques. 

Titanium has been determined with the use of chromotropic acid in sea-water [87], rocks [88], bauxites [89], steels [90], magnetic alloys [91], and alkalies [4], Differential spectrophotometry has been used in the determination of titanium in the tobacco industry products [92]. 

T for the blank. For differential spectrophotometry, the lowest standard is used instead the blank [8]. 

Of relevance from a practical point of view are publications dealing with the t.l.c.-quantitative analysis of twelve Rauwolfia bases, " t.l.c.-colour reactions for analysis of 38 indole alkaloids from some Vinca species, the quantitative determination of Cinchona quinoline alkaloids by t.l.c.-differential spectrophotometry, and the high-speed liquid-liquid chromatography of ergot alkaloids " and Mitragyna alkaloids. ... 

Precision spectrophotometry (differential spectrophotometry) is a technique that involves comparing an unknown solution with a reference. The reference scale is set at zero using a solution of a highly colored (radiation-adsorbing) species in place of a reagent blank. Concentrations of the unknown higher than the reference are then measured against this zero in the usual way. 

This book has wide variety of topics in spectroscopy including spectrophotometric apparatus and techniques. Topics covered absorption, emissions, scattering, causes of non-linearity, monochromators, detectors, photocells, photomultipliers, differential spectrophotometry, spectrophotometric titration, single beam, dual and multi wave length spectrophotometry, and diode array spectrophotometers. 

The simultaneous detection of benzoic, citric, and lactic acid in soft drinks (168), benzoic acid in textile fibers (169), in Chinese traditional medicine from Daemonorops draco (170), in foods (171-173), and by fluorimetric detection and quantification (173a) have been effected. Alkyl 4-hydroxybenzoates have been separated by circular HPTLC (174), on silufol (preferred visualization, iodine vapor) (175), by reflectance spectrophotometry at 272 nm on sil G HR UV plates (176), and by remission photometry (177). Hydroxybenzoic acids in grape leaves, berries, and wine have been separated on micropolyamide layers (178), and preservatives in wine (179) on polyamide layers containing a fluorescent pigment. Silanized silica gel H (F254) has been employed for the quantitative analysis of alkyl 4-hydroxybenzoates by off the plate differential spectrophotometry (180). Salicylic acid and its derivatives have been analyzed by a variety of TLC procedures (181-190), Sources of error have been discussed (191) and manipulative problems examined (192). 

The sources of error in this method have intrigued many authors. An editorial in 1954 took a rather dim view of the technique. Gridgeman published a critique of the transmittance ratio method and another paper on errors in differential spectrophotometry. Neal Mortimer and Cannon [ ] have also discussed errors. Fridovich et aL caution that in differential meth-... 

Lothe used indirect differential spectrophotometry employing a partially decolorized reference. 

Lueck determined phosphorus by indirect ultraviolet spectrophotometry. Lothe discussed indirect differential spectrophotometry and described a method of this nature for fluoride ions. 

HF in aqueous solution in the presence of tantalum and niobium by differential spectrophotometry at 1835 m/i, using a thin Teflon cell with sapphire windows [ ]. 

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