METHOD OF MEASURING TOTAL QUANTITY OF ORGANIC SUBSTANCES IN ULTRAPURE WATER AND ULTRAPURE WATER TREATING SYSTEM UTILIZING SAID METHOD IN PREPARATION OF ULTRAPURE WATER

摘要

This invention relates to a method of measuring the total quantity of organic substances in ultrapure water and an ultrapure water treating system utilizing said method, and also provides a method capable of simple and accurate on-line measurement of TOC quantity in ultrapure water with one set of sensor and an on-line ultrapure water treating system capable of stably supplying ultrapure water containing an extremely small quantity of TOC. The method comprises applying ultraviolet rays to ultrapure water whose specific resistance value has been set to a known constant one by ion exchange treatment, finding decreases by subtracting specific resistance values of ultrapure water measured continuously at different points from the abovesaid constant specific resistance value, and measuring a quantity of TOC on the basis of correlation of the decreases with the quantity of generated CO2 and so on converted into the total content of organic substances in ultrapure water. The system is composed of ion exchange means (13); ultraviolet treating means (14) for decomposing organic substances by exposing ultrapure water, which is supplied from the ion exchange means (13); to ultraviolet rays; means (15) for measuring a specific resistance value of ultrapure water subjected to the above treatment; ion exchange means (16) for restoring a specific resistance value above a predetermined one; a valve (17) capable of changing over the flow direction; a reflux pipe (18) to form a circulation passage connected between one of the outlets of the valve (17) and the upstream side of said ion exchange means (13); and monitor means (20) for finding a total content of organic carbon in ultrapure water on the basis of the correlation of a TOC quantity in ultrapure water with the difference between a measured specific resistance value of ultrapure water and a pre-fixed constant one.