Simultaneous determination of both

The quantitative solution of the problem, i.e. simultaneous determination of both the sequence of surface chemical steps and the ratios of the rate constants of adsorption-desorption processes to the rate constants of surface reactions from experimental kinetic data, is extraordinarily difficult. The attempt made by Smith and Prater 82) in a study of cyclohexane-cyclohexene-benzene interconversion, using elegant mathematic procedures based on the previous theoretical treatment 28), has met with only partial success. Nevertheless, their work is an example of how a sophisticated approach to the quantitative solution of a coupled heterogeneous catalytic system should be employed if the system is studied as a whole. 

Simultaneous determination of both cations and anions in acid rain has been achieved using a portable conductimetric ion-exclusion cation-exchange chromatographic analyzer.14 This system utilized the poly(meth-ylmethacrylate)-based weak acid cation exchange resin TSK-Gel OA-PAK-A, (Tosoh , Tokyo, Japan) with an eluent of tartaric acid-methanol-water. All of the desired species, 3 anions and 5 cations, were separated in less than 30 minutes detection limits were on the order of 10 ppb. Simultaneous determination of nitrate, phosphate, and ammonium ions in wastewater has been reported utilizing isocratic IEC followed by sequential flow injection analysis.9 The ammonium cations were detected by colorimetry, while the anions were measured by conductivity. These determinations could be done with a single injection and the run time was under 9 minutes. 

Stability is the need for simultaneous determinations of both the heat and momentum fluxes. Another approach is to deflne a quantity similar to Eq. (7.1) called the gradient Richardson number R ... 

The simultaneous determination of both the position and momentum of a particle each has an inherent uncertainty, the product of these being not less than a known constant. 

Several papers have reported use of a weak acid/crown ether eluent in ion-exclusion/cation exchange chromatography with conductimetric detection on a weakly acidic cation-exchange column to effect the simultaneous determination of both cations and anions. Resolution was significantly improved when 18-crown-6 was present in the eluent. Detector response was positive for anions and negative for cations. [76-80] A sample chromatogram is shown in Figure 9. 

Manousek and Zuman (90) have described a direct polarographic determination of pyridoxal in the presence of pyridoxal 5-phosphate. The simultaneous determination of both compounds is possible only when the concentrations are comparable. The same authors also have reported the polarography of pyridoxine and several analogues in buffered solutions. A 2-electron wave was observed which corresponds to a diffusion-controlled reduction of the activated C-OH bond in position 4. 

Specificity The method is specific and permits simultaneous determination of both compounds. Even a 10-fold excess of one compound does not impair the results. 

A mobile capillary micromanometer that can be set at various levels of the foam column, thus allowing pressure measurements at different points, can be used to evaluate the dependence of the radius of border curvature on the coordinates of either gravitational field or pressure gradient [51,68]. For a simultaneous determination of both the pressure and the radius of border curvature at non-steady state flow (for example, gravitational drainage) a system of a number of micromanometers can be used. 

Decarboxylation of L-3,4-dihydroxyphenylalanine to dopamine, and of 5-hydroxytryptophan to serotonin, is catalyzed by aromatic L-amino acid decarboxylase. A single enzyme may be responsible for both activities. This assay permits simultaneous determination of both activities. 

Atmospheric pressure ionization LC/MS has several distinct advantages over other more established quantitative approaches for these biochemical markers. The HPLC/fluorescence methods that have been reported require involved sample preparation, analyte extraction, and long chromatographic run times and are prone to interferences. The reported enzyme assays are less selective in that they cannot differentiate between the two compounds in a single run. Pyridinoline must therefore be quantified by difference. The API LC/MS/MS approach has allowed for a decrease in chromatographic run time, a streamlining of the sample preparation approach (dilute/inject as opposed to extraction), and a decrease in the analytical run time, while allowing simultaneous determination of both components. 

The method based on iron catalysed oxidation of o-phenylenediamine with H2O2 has been developed for speciation of iron in river and tap waters [11]. Xylenol Orange was applied to simultaneous determination of iron and nickel in alloys and industrial waste water [12]. The chelate complexes of Fe and Co with PAR made a basis of simultaneous determination of both metals by the second derivative spectrophotometry [13]. 

Biquinoline and 2,9-diinethyl-l,10-phenanthroline are very specific reagents for copper but lack sensitivity (B17) nevertheless the latter has been used successfully for the determination of copper in certain foodstuffs (J5). 4,7-Diphenyl-1,10-phenanthroline and bathocuproine are more sensitive the latter is specific for copper to such an extent that it can be used for the simultaneous determination of both copper and iron in serum (Zl). 

Figure 4.67. Manifolds designed for speciation analysis of Cr(VI) and Cr(III) by reversed FI A, both species being determined spectrophotometrically by a single detector, (a) Asynchronous merging zones mode for simultaneous determination of both species, (b) Sequential method for this speciation by use of a selecting valve for determination of Cr(VI) (channel 1) or overall chromium (channel 2). (From Ref. 968, by permission of Springer Verlag.)...

Analytical Methods. Historically, the copolymer composition of cationic acrylic polymers has been measured by conductiometric (28), silver nitrate (29), or colloid titration (52, 53). Chromatographic methods have been reported for acrylamide monomer (54-56) however, no such methods have been employed for quaternary ammonium monomers. In this chapter, a new HPLC method (Nalco) is described for the simultaneous determination of both comonomers. Colloid titration is described in the next paragraph and was used only for comparison purposes. 

In this case, an intercalibration study served not only to test the ability of the various laboratories to perform an analysis, it also pointed out the steps in the determination which required further research. The high temperature catalytic oxidation (HTCO) technique has become much more common in this field, with several companies now supplying suitable instrumentation. This technique is not only simpler to run than the older wet oxidation methods, it also allows almost-real-time analyses at sea. The problem of the production of a proper blank, and therefore of a proper reference material for the DOC analysis, has yet to be solved at this time it is being patched by the use of low DOC deep water as a blank, or of water which has passed through the combustion chamber of the analyzer and subsequently condensed. Placing DOC and total nitrogen (TN) detectors in-line has made simultaneous determinations of both quantities on the same sample a routine procedure [53]. 

Infrared spectroscopy is a powerful method that allows the direct determination of the Bronsted centers. When pyridine (py) is adsorbed on the catalyst simultaneous determination of both types of center is possible, since it is bound to Bronsted centers in the form of a pyridinium ion through a hydrogen bond (Eq. 5-63), whereas on Lewis acid centers, adsorption occurs by a coordinative acid-base interaction (Eq. 5-64). 

Ambroxol and doxycycline First derivative of ratio sp>ectra method was applied for simultaneous determination of both analytes in pharmaceutical formulations and in laboratory-made mixtures. 28... 

Tramadol and ibuprofen The first-derivative method was proposed for simultaneous determination of both compounds. The measurements of amplitude was done at 230.5 and 280 nm for tramadol (Trama) and ibuprofen (Ibu), respectively. The linearity was obeyed in the rage 5-50 pg mL-i for Trama and 5-100 pg mL-1 for Ibu. 29... 

This sampling and analytical procedure is very similar to the method recommended by NIOSH for aaolein. Some changes in the NIOSH methodology were necessary to permit the simultaneous determination of both aldehydes and also to accommodate OSHA laboratory equipment and analytical techniques. 

Another important practical result from these speciation studies with NTA and EDTA is a new very sensitive voltammetric procedure for the simultaneous determination of both ligands, down to trace levels in natural water[75]. The method is based on a voltammetric titration with Bi(III). 

The inline conversion of nitrate to nitrite and subsequent spectrophotometric determination after diazotization and coupling reactions is the basis of an important set of analytical methods for the simultaneous determination of both ions. Either homogeneous (titanium(III) chloride, hydrazinium sulfate, etc.) or heterogeneous (zinc, cadmium, amalgamated cadmium, copperized cadmium, etc.) reduction agents, photochemical or enzymatic reactions have been used [157]. The nitrite so produced is determined through spectrophotometric detection of the reddish purple azo dye formed as a result of the modihed Griess chemistry. 

The determination of mixtures of />-nitrotoluene and p-aminobenzaldehyde is possible in 0 1 N acetic acid containing 10 per cent ethanol.< ) The waves of /)-nitrotoluene (—0 46 V) and of /)-aminobenzaldehyde (—1 18 V) are well separated and allow the simultaneous determination of both components. 

Vitamin analyses in elemental diets are frequently required for process and quality control. Van der Horst et al. developed reversed phase methodology to determine the water-soluble vitamins, including PN, in total parenteral nutrition solutions (103). Iwase described a HPLC method to analyze the aqueous extract from an elemental pediatric diet for PN and nicotinamide (104). Chromatography involved a two-column, double-UV detector system to allow simultaneous determination of both PN and nicotinamide (104). 

An integrated method for the simultaneous determination of both alkyl and alk-1-enyl moieties of... 

Biopolymer Characterization Electrospray loniz ation Mass Spectrometry (ESI-MS) has become a popular method in biophysical and biochemical communities as new high-resolution techniques have been developed to detect a wide range of physiologically relevant noncovalent protein complexes [50, 51]. Thus, Painter et al. [50] used Nano-ESI-MS approach for monitoring reactions of protein complexes in real time, allowing simultaneous determination of both structural and dynamical properties of the proteins studied. 

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