Measuring Method for Total Organic Carbon, Measuring Method for Total Nitrogen and Measuring Apparatus for the Methods

A method for measuring total nitrogen, comprising the steps in the order named:

• treating the sample water so that organic matter and nitrogen compounds, which may be contained in the sample water, will be decomposed into carbon dioxide and nitrous acid, respectively, through oxidation;
• removing the carbon dioxide from the sample water by bringing the sample water, whose hydrogen ion concentration has been adjusted to between pH 4 and pH 6, into contact with deionized water via a gas-permeable part;
• adjusting the hydrogen ion concentration of the sample water to pH 3 or less;
• bringing the sample water into contact with deionized measuring water via another gas-permeable part;
• and
• measuring the electric conductivity of the measuring water to determine the total nitrogen content of the sample water.

An apparatus for measuring total organic carbon comprising:

• an oxidative decomposition part for decomposing organic matter contained in sample water into carbon dioxide through oxidation;
• a first adjusting part for adjusting the hydrogen ion concentration of the sample water to between pH 4 and pH 6;
• a first gas separation part for making the carbon dioxide, which is contained in the sample water having passed through the first adjusting part and the oxidative decomposition part, permeate into deionized measuring water via a gas-permeable part;
• a first measuring part for measuring the electric conductivity of the measuring water;
• and
• an arithmetic part for determining the total organic carbon content of the sample water based on the electric conductivity measured by the first measuring part.

An apparatus for measuring total nitrogen, comprising:

• an oxidative decomposition part for decomposing organic matter and nitrogen compounds contained in sample water into carbon dioxide and nitrous acid, respectively, through oxidation;
• a first adjusting part for adjusting the hydrogen ion concentration of the sample water to between pH 4 and pH 6;
• a first gas separation part for removing the carbon dioxide from the sample water, which has passed through the first adjusting part and the oxidative decomposition part, by bringing the sample water into contact with deionized water via a gas-permeable part;
• a second adjusting part for adjusting the hydrogen ion concentration of the sample water, which has passed through the first gas separation part, to pH 3 or less;
• a second gas separation part for bringing the sample water, which has passed through the second adjusting part, into contact with second deionized measuring water via a second gas-permeable part;
• a measuring part for measuring the electric conductivity of the measuring water;
• and
• an arithmetic part for determining the total nitrogen content of the sample water based on the electric conductivity measured by the measuring part.