Chromatographic detection

B. Langfoid, I. H. Stice, L. Latimei, and R. E. Walsh, Ttetermination of Hydrogen by Impulse Furnace Fusion Employing Chromatographic Detection, Teledyne Wab Chang Corp., Albany, Oieg., 1974. 

Fodor-Csorba K, Dutka F. 1986. Selectivity and sensitivity of some thin-layer chromatographic detection systems. J Chromatogr 365 309-314. 

Farinotti, R., Siard, Ph., Bourson, J., Kirkiacharian, S., Valeur, B., and Mahuzier, G., 4-bromomethyl-6, 7-dimethoxycoumarin as a fluorescent label for carboxylic acids in chromatographic detection, /. Chromatogr., 269, 81, 1983. 

Drushel [58] and others [31,59] have described the needs of the chromatographer in the area of detectors. Specific texts concern detection in quantitative GC [54], diode-array detection in HPLC [48], selective detectors [39] and element-specific chromatographic detection by AES [60], electrochemical detectors [61] and laser detectors [62]. 

Post-chromatographic detection in TLC usually proceeds according to one of three procedures (i) fluorescence detection (many organic substances exhibit natural fluorescence or can be derivatised to form fluorescent compounds) [399] (ii) UV absorption and (iii) visually (many chemical procedures - reagent spray, derivati-sation - render the spots on the TLC plate visible). There is no difficulty in detecting coloured substances... 

P.C. Uden (ed.), Element-Specific Chromatographic Detection by Atomic Emission Spectroscopy, ACS Symposium Series, Vol. 479, American Chemical Society, Washington, DC (1992). 

This chapter also deals in particular with chromatographic detection by atomic plasma spectrometry and plasma mass spectrometry (AED, MIP, ICP). With the application of such detectors, metal-specific signals can be obtained - thus the information content of a separation increases significantly. The major objectives of interfaced chromatography-atomic plasma source emission spectrometry (C-APES) are ... 

Four types of atomic spectrometry have been interfaced for chromatographic detection, namely AAS, FES, AFS and APES. Ebdon et al. [178] have discussed coupling of HPLC with AAS. HPLC-FAAS is relatively insensitive. Application of HPLC-GFAAS or... 

HPLC-QFAAS is also problematical. Most development of atomic plasma emission in HPLC detection has been with the ICP and to some extent the DCP, in contrast with the dominance of the microwave-induced plasmas as element-selective GC detectors. An integrated GC-MIP system has been introduced commercially. Significant polymer/additive analysis applications are not abundant for GC and SFC hyphenations. Wider adoption of plasma spectral chromatographic detection for trace analysis and elemental speciation will depend on the introduction of standardised commercial instrumentation to permit interlaboratory comparison of data and the development of standard methods of analysis which can be widely used. 

Evaporative LC-FTIR is rapidly gaining industrial acceptance as a useful tool in low-MW additive analysis. HPLC has also been coupled with various element-selective detectors. There is significant demand for speciation information for many elements, and the separation ability of chromatography coupled to ICP-MS offers the analyst a versatile tool for such studies. It is apparent that ICP-MS is increasingly being employed for chromatographic detection. Several modes of GC, SFC, LC and CE have been hyphenated with ICP-MS for improved detection limits compared to other traditional methods of detection such as UV-VIS spectroscopy. Inorganic speciation deserves more attention. 

AAS = atomic absorption spectroscopy CdS04 = cadmium sulfate GC/ECD = electrochemical gas chromatographic detection GC/FPD = gas chromatography with flame photometric detection HC1 = hydrochloric acid H2S = hydrogen sulfide NaOH = sodium hydroxide NR = not reported PAS = photoacoustic spectroscopy... 

Stetter JR, Sedlak JM, Blurton KF. 1977. Electrochemical gas chromatographic detection of hydrogen sulfide at PPM and PPB levels. J Chromatogr Sci 15 125-128. 

If the detector baseline is allowed to stabilize after the experiments, the noise level can be measured and the chromatographic detection limit at optimum detection potential can be estimated. 

Photoionization a gas chromatographic detection system that uti-hzes an ultraviolet lamp as an ionization source for analyte detection. It is usually used as a selective detector by changing the photon energy of the ionization source. 

Colgan ST, Krull IS, Dorschel C, et al. 1986. Derivatization of ethylene dibromide with silica-supported silver picrate for improved high-performance liquid chromatographic detection. Anal Chem 58 2366-2372. 

M. Zheng, C. Fu and H. Xu, High-performance liquid chromatographic detection of trace N-nitrosoamines by precolumn derivatization with 4-(2-phthalimidyl)benzoyl chloride. Analyst, 1993,118(3), 269-271. 

E.L. Inman and E.C. Rickard, Chromatographic detection limits in pharmaceutical method development. Journal of Chromatography, 447 (1988) 1-12. 

Solid-phase extraction columns offer a rough cleanup of the crude extract, which might nevertheless not be sufficient for some detection systems such as mass spectrometry. Some authors have proposed a combination of solid-phase extraction and liquid chromatography columns for extract cleanup (440). Other methods appeal to liquid chromatography on Cig columns with automated fraction collection. Fractions containing the analyte of interest were evaporated to dryness, yielding a residue that in most cases was suitable for gas chromatographic detection after suitable derivatization (445, 437). 

Ultraviolet spectrophotometers have been used as gas chromatographic detection systems mainly after condensation of the chromatographic effluent. Systems are capable of detecting naphthalene at 10 8g by scanning every 20 sec from 165 to 220 nm. Use of a monochrometer permits selectivity. Reactions producing chemiluminescence are known. 

Voltammetry experiments are not often performed in flow cells for analytical purposes. One reason for this is the special problem of ohmic potential losses (iR drops) at an electrode in a confined stream. Another reason is the problem of precisely pumping solution at a carefully controlled velocity. In general, rotating electrodes are more easily controlled and do not involve serious plumbing problems. On the other hand, flow cells operated at a fixed potential (i.e., at one point along the steady-state voltammetric curve) are eminently useful for electrosynthesis, chromatographic detection, and automated analysis systems. These features will be described in later chapters. 

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