Control of continuous microwave digestion process.

摘要

A controlled process and suitable apparatus are described for controlled continuous microwave digestion of samples of materials to prepare them for subsequent analyses or other chemical operations. The material to be analyzed, in finely divided form and mixed with digesting liquid, which is usually a strong acid, is charged as a slug into a flowing liquid carrier stream, usually water, which stream, containing the slug, is passed in a tube through a zone in which the tube and contents are subjected to microwave radiation, to heat the digesting liquid and the material to be digested to promote the digestion. The process and apparatus are like those of U.S. patent 5,215,715, modified by inclusion of detecting and controlling steps and corresponding apparatus components to detect a condition of the flowing liquid without physically contacting it, as by determining the dielectric constant of contents of the tube, or a related property of such contents at one or more locations of the tube, usually outside the microwave zone, and controlling operations of the process and apparatus accordingly. Such controlled or controllable operations include charging of subsequent slugs to the system, feeding digested slugs or portions thereof to autosampler means, and backwashing of a filter, and in such operations the controlling means is preferably microprocessor or computer means that is activated by signals from the detection means and automatically operates appropriate valves, pumps and autosampling means. Also within the invention is a procedure for converting a manual process, such as that described in U.S. patent 5,215,715, to an automatic one.