Post-column photolysis

Schieffer, G. W., Preliminary examination of a new post-column photolysis-molybdate reaction detection system for the determination of organophos-phorus compounds by high performance liquid chromatography, Instr. Sci. Technol., 23, 255, 1995. 

RG Luchtefeld. An HPLC detection system for phenylurea herbicides using post-column photolysis and chemical derivatization. J Chromatogr Sci 23 516-520, 1985. 

Carbamoyl oximes, car-bamothioc acids, dithiocar-bamates and phenyl urea types Vegetation HPLC with post-column photolysis for the generation of fluorophores [64]... 

L23. Liu, H., Duda, C. T., Huang, T., Aruda, W. O., and Kissinger, R T., Optimization of post-column photolysis and electrochemical detection for the liquid chromatographic determination of 3-nitro-L-tyrosine. J. Chromatogr. A 818, 69-75 (1998). 

Detector F ex 277 em 418 following post-column photolysis. The column effluent flowed through a 10 m X 0.25 mm knitted PTFE coil irradiated with a UV 254 low pressure lamp and flowed to the detector. 

Detector E, ESA Model 5100A Coulochem, model 5020 guard cell -1-950 mV, Model 5010 analytical cell + 400 mV, palladium reference electrode, following post-column photolysis. The effluent from the column flowed through a 20 m X 0.3 mm coil of PTFE tubing irradiated at 254 nm with a Sylvania GTE 8 W low-pressure lamp to the detector. 

We believe that many other classes of compounds will be shown to be suitable analytes for these approaches, and that MDLs will be, as they have been for most of the above compounds, in the low ppb ranges (1-50 ppb or below). In those Instances where particular analytes are already amenable to oxidative LCEC, without post-column photolysis, confirmative evidence for their presence can be obtained by HPLC-hv-EC. That is, the dual electrode response ratios for these compounds with and without irradiation are almost always very different, depending on the particular starting analyte. Also, the optimum working electrode potentials with and without irradiation post-column are also very different, providing further confirmation possibilities. We have demonstrated for many compounds additional confirmation via the dual electrode response ratios possible with and without irradiation, using the same electrode working potentials or different sets of these. 

Post-column photolysis to give electroactive products has been used in the measurement of trichothecene mycotoxins, such as deoxynivalenol (vomitoxin) in... 

The use of EC detection either in the form of PGE arrays or technically simpler systems in the qualitative analysis of basic drugs in urine, possibly as an adjunct to diode array or scanning UV detection, is a further topic worthy of continued investigation. An additional area where developments might be expected is in the application of post-column photolysis to generate electroactive species. 

Post-column in-line photochemical derivatization permits fluorescence detection of the common aflatoxins Bl, B2, Gl, and G2 (60). Chromatographic evidence indicates that photolysis causes the hydration of the nonfluorescent Bl and Gl components to B2a and G2a components, respectively. Analysis of naturally contaminated com samples show no interfering peaks and permits the deterrnination of 1 and 0.25 ppb for Bl and B2, respectively. 

Miles and Moye [171] have shown that several classes of nitrogen containing pesticides responded to a high performance liquid chromatography post-column reaction detector that employed ultraviolet photolysis with optional reaction with o-phthalicdicarboxaldehyde-2-mercaptoethanol followed by fluorescence detection. It was applied to the determination of jV-methylcarbamates, carbamoyl oximes, carbamethoic acids, dithiocarbamates and phenyl ureas, phenyl amides and phenyl carbamates in groundwater. See also Table 4.3. 

Bachman, W.J. Stewart, J.T. HPLC-photolysis-electrochemical detection in pharmaceutical analysis application to the determination of spironolactone and hydrochlorothiazide in tablets. J.Chromatogr.Sci., 1990, 28, 123-128 [post-column reaction electrochemical detection tablets simultaneous spironolactone]... 

There is a large volume of literature deahng with post column reactions. It can be carried out in coils, in packed bed reactors or by photolysis. The main requirement is not the completion of the reaction but the reproducibility. Reaction vessels should not produce excessive band broadening. The reagent should be delivered continuously, pulselessly, and at a constant flow rate. 

In many ways, and perhaps this is why we have Included this novel and selective detector in this review, the PCD resembles the above discussed HPLC-hv-EC approach. The HPLC-hv-EC or photoelectroanalyzer detection scheme utilizes the exact same photolysis step post-column, continuous, real-time, on-line, and then passes the newly generated anions or other photoproducts to the EC detector for measurements. 

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