Direct spectrophotometric detection

Table 4J. Solutes for direct spectrophotometric detection in IC after ion-exchange separation...

There are certainly many other possibilities for direct spectrophotometric detection. A separation of several divalent metal ions is shown in Fig. 7.9 with 3.5 mM cupric sulfate as the eluent and indirect detection at 220 nm. 

Several analytical techniques have been described for determination of rutin. For example, direct spectrophotometric detection,9 indirect spectrophotometric methods,10 12 liquid chromatography,13 HPLC with photodiode array detection (DAD).10,14 In this paper we report the development of a fluorimetric method for rutin that is sensitive and simple. 

Pinheiro HM, Touraud E, Thomas O (2004) Aromatic amines from azo dye reduction status review with emphasis on direct UV spectrophotometric detection in textile industry waste-waters. Dyes Pigm 61 121-139... 

Following sample extraction and cleanup, tetracycline antibiotics may be separated by thin-layer or liquid chromatographic procedures, and quantified by spectrophotometric, fluorometric, or mass spectrometric detection systems. Direct spectrophotometric and capillary electrophoretic methods have also been described (Table 29.8). 

Direct spectrophotometric methods using fluorometric detection have been reported for screening of tetracycline in milk extracts (126,282), and three tetracyclines in tissues extracts (302, 310). In a different approach, Salinas et al. (212) described a fourth-derivative spectrophotometric method for the determination of oxytetracycline in honey. Although useful, these methods cannot differentiate among individual tetracycline antibiotics and are less sensitive than the screening tests used for regulatory purposes. 

The level of quinine in a soft drink can be measured either by determination of the absorbance of an extract of the soft drink after making the product alkaline with ammonia or by detecting it directly spectrophotometrically or fluori-metrically (Egan et al., 1990e). 

Process water Direct analysis Ion chromatography spectrophotometric detection (U" 6) 0.04 mg/L No data Byerley et al. 1988... 

Direct Spectrophotometric Analysis Cyclothiazide exhibits several absorption maxima in the ultraviolet range under various conditions (see Section 2.3). While this absorbance will not differentiate cyclothiazide from some starting materials, it does lend itself to the assay of formulated batches3, 14, and facilitates a means of detection for thin layer chromatographic work13 15. 

The combination of extraction with spectrophotometry is still the most popular among separation and preconcentration procedures used. Liquid-liquid and solid-phase extractions of the suitable complexes make the basis of most recently developed methods. Spectrophotometric detection of the anal)fte can be directly accomplished in the obtained extracts. Stripping of the analytes from the examined extract followed by the conversion into the complex making a basis of spectrophotometric measurement is also used. 

Detection Sample ions absorb sufficiently in the UV or visible spectral region may be detected by direct spectrophotometry. Indirect spectrophotometric detection is commonly used for ions that do not absorb. An absorptive reagent is added to the... 

An alternative sampling approach is to deploy a submersible analyser [14,15]. Water is sucked from the exterior environment by an on-board pump in order to fill the sampling loop, with excess sample directed back to the exterior. The flow system is remotely controlled and the results can be either stored in the analyser or transmitted back to the ship via a cable. In this context, a small submersible flow injection analyser, with solid-state spectrophotometric detection, was conceived for the in situ determination of nitrate (Fig. 8.2). Its performance and versatility were assessed by results from laboratory, shipboard (North Sea IMPACT Cruise) and in situ (Tamar Estuary, UK) analysis. Excellent temporal and spatial resolutions were reported and this aspect is crucial for investigating dynamic processes in estuarine, coastal and open ocean waters. 

T. Yamane, H. Ishikawa, T. Tanaka, Simple, rapid and sensitive determination of bismuth in iron and steel based on in-line preconcentration/separation directly coupled with spectrophotometric detection in a continuous flow system, ISIJ Int. 44 (2004) 698. 

It is frequently desirable to analyse for dehydroascorbic acid and l-ascorbic acid in the same solution. The former has an u.v. absorbance at 220 nm, but with a much smaller molar absorbtivity of 720. Thus any attempt at a direct spectrophotometric determination will be factor of about 20 times less sensitive than for L-ascorbic acid. We will see later that these facts have far reaching consequences in the use of chromatographic techniques for the separation and subsequent detection of L-ascorbic acid and dehydroascorbic acid. 

Whereas much of the underlying mechanisms for the effects of radiation on materials were outlined using steady state radiation sources, the advent of pulse radiolysis on the heels of flash photolysis opened a window into direct observation of the intermediates. One of the early discoveries utilizing pulse radiolysis was the spectrophotometric detection of the hydrated electron by Boag and Hart (35,36). Since then thousands of rate constants, absorption spectra, one-electron redox potentials and radical yields have been collected using the pulse radiolysis technique. The Radiation Chemistry Data Center at the University of Notre Dame accumulates this information and posts it (at www.rcdc.nd.edu/) for the scientific community to use. They cover the reactions of the primary radicals of water and many organic radicals and inorganic intermediates. 

FI manifolds for column separation and preconcentration in spectrophotometry are diverse, and there is hardly one which may be considered typical. However, the reader may refer to the manifold used in the determination of boron just mentioned (63]. Another interesting contribution by Novikov et al.[ll] combined ion-exchange column preconcentration with on-line solvent extraction followed by spectrophotometric detection. The eluate from the column preconcentration was released into an on-line liquid-liquid extraction system. An advantage of this approach is that interferences from Schlieren effects are avoided, since the eluate does not flow directly to the detector. Selectivity and sensitivity are also enhanced due to the combination of two separation procedures. The system has been used successfully for the determination of lead in alloys, soil leachates and sea water. 

Figure 11.1 Sorption of (1) Malachite Green, (2) Methylene Blue, and (3) Direct Bordeaux onto Styrosorbs 2 (a) dependence on apparent specific surface area of the polymers and (b) dependence on their swelling in water. Experimental conditions 20 mL solution of 0.3 g/L in concentration, 0.1 g dry polymer, 25°C, 24 h, spectrophotometric detection at (1) 615, (2) 665, and (3) 510nm.

Direct UV spectrophotometric detection of aromatic amines from azo dye reduction in textile industry wastewaters and electrophoretic methods for biogenic and aromatic amines have been the subject of recent reviews. In addition, environmental applications of mutagenic heterocyclic amines... 

Numerous procedures have been used to assay aminotransferase activity. Spectrophotometric methods may use an auxiliary dehydrogenase enzyme, so that the oxo acid product is reduced at the expense of NAD(P)H (e.g.. Hatch, 1973 Achituv and Bar-Akiva, 1976 Huang et al., 1976). Alternatively, one can measure the absorbance of a product directly (Kanamori and Matsumoto, 1974), or after formation of a spectrophotometrically detectable chemical derivative (Forest and Wightman, 1972a Matherton and Moore, 1973). Radiocarbon assays (e.g., Hiller and Walker, 1961 Abbadi and Shannon, 1969 Givan al., 1970 Kirk and Leech, 1972), are sometimes used in... 

Figure 5 Anaiysis of severai drugs in urine (A-C) and in a cough-coid preparation (D) (A) propranoioi (2 h after a 10 mg dose intake), determined by direct injection of a urine sampie without diiution on 0.1 moii SDS/15% propanoi/1% triethyiamine mobiie phase and fiuorimetric detection (B) propranoioi metaboiites (M1-M3) determined after a 1 25 diiution of the previous sampie (C) piretanide (2h after a 6 mg dose intake), determined after a 1 25 diiution of a urine sampie on 0.055 moii SDS/8% propanoi and fiuorimetric detection (D) pseudoephedrine (preceding peak) and dexchiorpheniramine on 0.15moi i SDS/6% pentanoi and spectrophotometric detection.

Sample ions that absorb sufficiently in the UV or visible spectral region may be detected by direct spectrophotometry. Indirect spectrophotometric detection is commonly used for ions that do not absorb. An absorptive reagent is added to the BGE, and this gives a peak in the direction of reduced absorbance when a sample ion passes through the detector. The absorbing reagent, which is sometimes called a visualization reagent, should have a mobility that matches those of the sample ions as closely as possible. Chromate is often used for the indirect detection of anions and a protonated amine cation, such as benzylamine, for detection of cations. 

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