Lefevere, et al³² used a photochemical reactor with a 200 W xenon - mercury high-pressure lamp, operated at 6.2 A with air cooling and supplementary water cooling of the reactor coil, which acts at the same time as a filter for the radiation spectrum produced by the lamp.  The reaction coils were PTFE tubing of 1/16 inch o.d. and 0.42, and 1.07 mm. i.d., with varying length to adjust reaction time.  They observed that the fluorescence of Vitamin K and its metabolites and photoproducts was greatly affected by the temperature of the reactor coil.  Cooling of the reactor coil with water instead of air, doubled the optimal reaction time and resulted in a two fold increase in sensitivity.  In the latter case, the absorption of the residual IR radiation of the xenon - mercury lamp probably plays a role.  With only air cooling of this high intensity, hot bulb, a rapid decrease in fluorescence intensity was observed, once the optimal reaction time was exceeded.  This is caused by the formation of polymeric reaction products, which decrease the fluorescence by light absorption, scattering and quenching effects.  This is why they actually developed the supplementary water cooling.

     Bachman and Stewart³³ used a home-made on-line post column photochemical reactor for the EC determination of clofibric acid in human serum.  According to the lamp manufacturer, UVP, Inc., this model 15 W lamp emits 5.4 mW/cm² at 254 nm. with minor emissions at 185 and 365 nm. The manufacturer's reported typical body ("skin") temperature of the lamp with the described power supply is 48° C, which is the temperature the Teflon tube would constantly be exposed to without active cooling .  However, with higher lamp currents, the typical lamp "skin" temperature will reach 64° C.  Bachman and Stewart provided air cooling in their apparatus with a 3 inch diameter fan.  A "Teflon" tube (0.3 mm. i.d.; 7.9 meters long), cylindrically crocheted to fit directly onto the surface of the lamp in a sleeve - like manner was used with a 42% methanol - 58% 0.1 M phosphate buffer (pH 7.0) and no tubing leakage was reported.

     Wolf and Schmid³⁴ used a commercial photochemical reactor with a tubular 8 W low pressure mercury lamp.  They claim that "because of the low heat production of the light source, no active cooling was necessary".  They used a PTFE tube (0.01 inch ( 0.25 mm.) i.d.; 1/16 inch o.d.; 25 meters long) in a cylindrically crocheted configuration, with a mobile phase of  30% acetonitrile - 70% 15 mM phosphate buffer, pH 7.0.  They did not report tubing leakage under these conditions.


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