Control process for evaporative light scattering detector

摘要

A parameter which affects nebulization is controlled to fix the response coefficient b of a detector at a value which facilitates analysis and/or increases precision and reliability. b is determined from the equation log A = b log m + log a where A is the surface of the signal measuring the intensity diffused by one component in the sample and m the mass or concentration of that component The detector contains a nebulizer connected to a nebulizing chamber into which is introduced on one hand a sample comprising a carrying liquid containing the less volatile components to be analyzed and on the other hand a nebulization gas for converting the sample into an aerosol. A heated tube forms an evaporation chamber in which the carrying liquid is evaporated to keep only the microparticles of the components to be analyzed. The residual microparticles are irradiated in a detection chamber by radiation from a polychromatic or monochromatic source and the light diffused in a direction different to that of the radiation beam is detected. The control value is near unity, or is the maximum possible. The parameter(s) influencing the nebulization conditions are: the nature of the nebulization gas, the temperature and/or flow rate of the gas, the temperature of the nebulization chamber and/or the composition of the carrying liquid. Helium is used as the nebulization gas, or air or nitrogen with a certain proportion of additive such as water vapor or an alcohol such as ethanol. Two parameters are controlled to obtain a synergy. The detector is coupled to a chromatography column and a modifying agent is added upstream of the detector to fix the response coefficient as required.