Total organic carbon meter provided with system blank function

Abstract

A total organic carbon measuring device comprises: a sample supply unit that collects and supplies sample water; an oxidative decomposition unit that is connected to the sample supply unit and oxidizes organic matter contained in the sample water supplied from the sample supply unit to carbon dioxide; a carbon dioxide separation unit that transfers carbon dioxide from the sample water that has passed through the oxidative decomposition unit to measurement water consisting of deionized water; a conductivity measuring unit that measures the conductivity of the measurement water flowing from the carbon dioxide separation unit; and an arithmetic processing unit that calculates the TOC concentration of the sample water from a measured value obtained by the conductivity measuring unit. A measured value obtained by the conductivity measuring unit when pure water subjected to aeration treatment is allowed to pass through the oxidative decomposition unit of which oxidative decomposition function is turned off and then flows through a sample water channel is defined as a system blank value.

1 . A total organic carbon measuring device comprising:
 a sample supply unit that has a system for collecting and supplying sample water and subjecting the collected sample water to aeration treatment using a gas containing no carbon dioxide;   an oxidative decomposition unit that is connected to the sample supply unit, has oxidative decomposition function that oxidizes organic matter contained in the sample water supplied from the sample supply unit to carbon dioxide, and is capable of turning on and off the oxidative decomposition function;   a carbon dioxide separation unit that includes a sample water channel through which the sample water that has passed through the oxidative decomposition unit flows, a measurement water channel through which measurement water consisting of deionized water flows, and a gas permeable membrane interposed between the sample water channel and the measurement water channel to allow carbon dioxide to be transferred therethrough;   a conductivity measuring unit that measures a conductivity of the measurement water flowing from the carbon dioxide separation unit; and   an arithmetic processing unit that includes a system blank holding section that holds, as a system blank value, a measured value obtained by the conductivity measuring unit when pure water collected in the sample supply unit and subjected to aeration treatment is allowed to pass through the oxidative decomposition unit of which oxidative decomposition function is turned off and then flows through the sample water channel, and an arithmetic section that calculates a total organic carbon concentration of the sample water from a system blank value held in the system blank holding section and a measured value obtained by the conductivity measuring unit when the sample water is allowed to pass through the oxidative decomposition unit of which oxidative decomposition function is turned on and then flows through the sample water channel.   
     
     
         2 . The total organic carbon measuring device according to  claim 1 ,
 wherein the oxidative decomposition unit includes an oxidation channel made of a UV-permeable material through which the sample water flows and an ultraviolet light source that irradiates the sample water with ultraviolet light from an outside of the oxidation channel, and   wherein the oxidative decomposition function is turned on and off by the ultraviolet light source.   
     
     
         3 . The total organic carbon measuring device according to  claim 1 ,
 wherein the oxidative decomposition unit includes an oxidation channel made of a UV-permeable material through which the sample water flows, an ultraviolet light source that irradiates the sample water with ultraviolet light from an outside of the oxidation channel, and a shutter provided between the oxidation channel and the ultraviolet light source, and   wherein the oxidative decomposition function is turned on and off by opening and closing the shutter.   
     
     
         4 . The total organic carbon measuring device according to  claim 1 ,
 wherein the arithmetic section holds calibration curve data representing a relationship between a measured value obtained by the conductivity measuring unit and a total organic carbon concentration of the sample water supplied from the sample supply unit, and   wherein the calibration curve data is corrected using a system blank value held in the system blank holding section to obtain corrected calibration curve data, and a total organic carbon concentration of the sample water is calculated from the corrected calibration curve data and a measured value obtained by the conductivity measuring unit when the sample water is measured.   
     
     
         5 . The total organic carbon measuring device according to  claim 4 ,
 wherein the corrected calibration curve data is obtained by shifting the calibration curve data obtained from a measured value so that its intercept value becomes a system blank value held in the system blank holding unit.   
     
     
         6 . The total organic carbon measuring device according to  claim 1 , wherein the sample supply unit comprises:
 a multi-port valve having at least a port connected to a channel for supplying sample water, a port connected to a channel for supplying pure water, a port connected to the oxidative decomposition unit, a port opened to the atmosphere, and a common port connected to any one of these ports by switching;   a syringe connected to the common port of the multi-port valve and collects and sends the sample water by slidably moving a piston in a cylinder in a vertical direction; and   a gas supply channel connected to a lower end portion of the cylinder at a position above the piston in a state where the piston is located at a lower end of the cylinder to supply a gas containing no carbon dioxide into the cylinder.   
     
     
         7 . The total organic carbon measuring device according to  claim 6 ,
 wherein the multi-port valve further has another port connected to an acid supply channel for supplying an acid for acidifying the sample water collected in the syringe.