Detection spectrophotometric

The light source for the spectrophotometric detectors is either the deuterium lamp or the wolfram lamp. Selection of an appropriate wavelength is performed by a monochromator. 

The deuterium lamp can be used at/ffom 190 nm into the visible part of the spectrum (about 600 nm). The wolfram lamp is used only for the visible sector (up to 950 nm), and has a much lower price and a longer lifetime than the deuterium lamp. 

Unlike the filter photometric detector, which is limited to one or a few wavelengths, the spectrophotometers can choose the wavelength that is closest to an absorption maximum of the analyte(s) in order to obtain the highest sensitivity. 

Separations of metal cations with ionic eluents has been limited mostly to the alkali metals, ammonium, magnesium(II), calcium(Il), strontium(ll) and barium(ll). Separations of other metal cations are usually performed with eluents that complex the sample cations to varying degrees (see Section 7.4). Some organic cations have also been separated with ionic eluents, although this appears to be an under-utilized area of cation chromatography. 

The eluent amines listed in Table 7.2 form 1-h cations with the exception of the ami-nopyridines which can form 2+ cations. A t5rpical separation of alkali metal cations employs approximately -0.1 mM protonated phenylethylamine or 4-methylbenzyla-mine. A higher concentration (approximately -10 mM) is used for separation of the divalent magnesium and alkaline earth cations. 

The equivalent conductances of the aromatic bases listed in Table 7.2 are low enough for non-suppressed conductivity detection. However, the detection limits are generally lower with indirect UV detection and the resolution is often better also. In Fig. 7.8 chromatograms of the alkali metal cations are compared with direct conductivity and indirect UV absorption detection. With the aromatic base eluents Li elutes 

Conditons 3,5 mM Cupric Sulfate. Isocratic. Ambient. 2mL/min. Indirect UV 220 nm. 

Either suppressed- or non-suppressed-conductivity detection is generally satisfactory for these separations. However, under carefully controlled conditions, indirect spectrophotometric detection may sometimes be used to advantage. Haddad 

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In Scheme 111, AX is the acetylating agent, N is A-methylimidazole, and 1 is an intermediate formed by the reaction of N with AX the extra piece of information in this case was the spectrophotometric detection of We can describe the rate constants in this way ... 

F. Alternative methods of detecting the end point. In addition to the visual and spectrophotometric detection of end points in EDTA titrations with the aid of metal ion indicators, the following methods are also available for end point detection. 

Sutin et a/. have found iron(If) to catalyse the aquation of the iron(III) ions, FeCl (refs. 1,2) and FeNCS (ref. 3), in perchlorate media. A flow technique, with spectrophotometric detection at 336 m.fi (disappearance of FeCl ) and 460 m/f (disappearance of FeNCS " ), was used to obtain rate data. The rate law... 

Halpern et al, from data recorded using a stopped flow technique with spectrophotometric detection, have obtained values of and 2X2 for each of the above-mentioned anions. 

Use of 10 pm LiChrosorb RP18 column and binary eluent of methanol and aqueous 0.1 M phosphate buffer (pH 4.0) according to suitable gradient elution program in less than 20-min run time with satisfactory precision sensitivity of spectrophotometric detection optimized, achieving for all additives considered detection limits ranging from 0.1 to 3.0 mg/1, below maximum permitted levels Simultaneous separation (20 min) of 14 synthetic colors using uncoated fused silica capillary column operated at 25 kV and elution with 18% acetonitrile and 82% 0.05 M sodium deoxycholate in borate-phosphate buffer (pH 7.8), recovery of all colors better than 82%... 

The identification and quantification of potentially cytotoxic carbonyl compounds (e.g. aldehydes such as pentanal, hexanal, traw-2-octenal and 4-hydroxy-/mAW-2-nonenal, and ketones such as propan- and hexan-2-ones) also serves as a useful marker of the oxidative deterioration of PUFAs in isolated biological samples and chemical model systems. One method developed utilizes HPLC coupled with spectrophotometric detection and involves precolumn derivatization of peroxidized PUFA-derived aldehydes and alternative carbonyl compounds with 2,4-DNPH followed by separation of the resulting chromophoric 2,4-dinitrophenylhydrazones on a reversed-phase column and spectrophotometric detection at a wavelength of378 nm. This method has a relatively high level of sensitivity, and has been successfully applied to the analysis of such products in rat hepatocytes and rat liver microsomal suspensions stimulated with carbon tetrachloride or ADP-iron complexes (Poli etui., 1985). 

All previous discussion has focused on sample preparation, i.e., removal of the targeted analyte(s) from the sample matrix, isolation of the analyte(s) from other co-extracted, undesirable sample components, and transfer of the analytes into a solvent suitable for final analysis. Over the years, numerous types of analytical instruments have been employed for this final analysis step as noted in the preceding text and Tables 3 and 4. Overall, GC and LC are the most often used analytical techniques, and modern GC and LC instrumentation coupled with mass spectrometry (MS) and tandem mass spectrometry (MS/MS) detection systems are currently the analytical techniques of choice. Methods relying on spectrophotometric detection and thin-layer chromatography (TLC) are now rarely employed, except perhaps for qualitative purposes. 

Irth, H., De Jong, G. J., Brinkman, U. A. Th., and Frei, R. W., Determination of disulfiram and two of its metabolites in urine by reversed-phase liquid chromatography and spectrophotometric detection after post-column com-plexation, /. Chromatogr., 424, 95, 1988. 

Gagliardi et al. [72] developed a simple high performance liquid chromatographic method for the determination of miconazole and other antimycotics in cosmetic antidandruff formulations. This high performance liquid chromatographic method was carried out on a Discovery RP Amide Ci6 column and spectrophotometric detection was performed at 220 nm. The initial mobile phase was a mixture of acetonitrile and aqueous 0.001 M sodium perchlorate (pH 3) in the ratio of 15 85 (v/ v) then a linear gradient less than 46% acetonitrile in 70 min, and less than 50% in 80 min. The extraction procedure was validated by analyzing samples of shampoo... 

Three anticonvulsant drugs including valproic acid were determined using different dyes as ion-pair reagents. Gentian violet was used for the spectrophotometric detection at 588 nm and acridine orange for the fluorimetric detection at 470 nm after excitation at 297 nm. Calibration graphs were linear for 5-50 pg/mL 2.5 0.50 pg/mL for the spectrophotometric and fluorimetric methods, respectively [15]. 

For the last several years, mass spectrometry with atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) have determined the trends in the analysis of dyes. Since 1987, various variants of ESI have been used in which droplet formation was assisted by compressed air,[1,2] temperature (e.g. Turbo Ion Spray ) or ultrasound, and they were able to handle flow rates up to 1 2 ml min This made a combination of analytical RPLC and ESI easily and widely used. The reason why it often was (and is) used instead of a traditional UV-Vis detector is the better sensitivity and selectivity of MS in comparison with spectrophotometric detection. Apart from these advantages, MS offers easily interpretable structural information. However, various... 

RPLC separation with spectrophotometric detection is often applied to the identification of the anthraquinone colour components of cochineal, lac dye and madder. [28,40,41,50 53] In particular the latter, containing many colourants, is the object of many research studies. Due to the large number of anthraquinones isolated from plants of the Rubiaceae family, their unambiguous identification solely by UV-Vis detection is not always possible,... 

Indigo is considered as one of the most important dyes. Its preparations are usually analysed by HPLC with UV-Vis [46,60] or APCI MS detection. [61,62] Separation of the colouring components of indigo extracted with DMSO is usually performed with the use of a Cl 8 column. Spectrophotometric detection of blue indigotin is performed at 617 nm, red indirubin at 540 nm, and brown isoindigo at 365 and 490 nm. As mobile phases, mixtures of methanol or acetonitrile and water with the addition of TFA or formic acid are used to ensure compatibility with the requirements of the APCI source. 

Recknagel, R.O. and Glende, E.A. (1984). Spectrophotometric detection of lipid conjugated dienes. Methods in Enzymology 105 331-337. 

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... 

Traces of boron in seawater have been determined by flow injection analysis with spectrophotometric detection at 415 nm using G 30 methine H. The linear range was 1 -10 mg/1 boron with a detection limit of 0.017 mg/1 [3]. 

The kinetics of proton transfer from protonated 1,8-bis(dimethyl-amino)-2,7-dimethoxynaphthalene to substituted phenolate ions (69) were studied in 70% (v/v) Me2SO—H20 using the temperature-jump technique with spectrophotometric detection to follow reactions with half-lives in the range 1-100 ms (Hibbert and Robbins, 1978). A limited... 

Water None FIA spectrophotometric detection (free cyanide) 20 ng/mL 88-107 Ma and Liu 1992... 

Water Sample shaken in presence of quinoline and benzoyl chloride at pH 7 HPLC with spectrophotometric detection (free CN) 26 pg/mL No data Madungwe et al. 1991... 

Waste water None FIA with spectrophotometric detection 3 ng/mL 98 Kuban 1992... 

Modifications of the Bratton-Marshall method mentioned in Section IV.D.3.g can be used for sensitive spectrophotometric detection and determination of primary aromatic and heterocyclic amines. Thus, a simple spectrophotometric determination of the cardioprotective agent acadesine (142) was developed, to measure concentrations of the drug in plasma during intravenous infusion to patients undergoing coronary artery bypass graft surgery336. 

Flow injection analysis is based on the injection of a liquid sample into a continuously flowing liquid carrier stream, where it is usually made to react to give reaction products that may be detected. FIA offers the possibility in an on-line manifold of sample handling including separation, preconcentration, masking and color reaction, and even microwave dissolution, all of which can be readily automated. The most common advantages of FIA include reduced manpower cost of laboratory operations, increased sample throughput, improved precision of results, reduced sample volumes, and the elimination of many interferences. Fully automated flow injection analysers are based on spectrophotometric detection but are readily adapted as sample preparation units for atomic spectrometric techniques. Flow injection as a sample introduction technique has been discussed previously, whereas here its full potential is briefly surveyed. In addition to a few books on FIA [168,169], several critical reviews of FIA methods for FAAS, GF AAS, and ICP-AES methods have been published [170,171]. 

Chung, Y. S., Determination of total phenols in environmental waters by capillary-HPLC with USEPA classified eleven priority pollutant phenols after nitrosation and their visible spectrophotometric detection, Bulletin of the Korean Chemical Society 26(2), 297-302, 2005. 

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