请问：TOC（total organic carbon）在没有专门仪器下，能不能测定?There are two types of TOC measurement methods, one is the differential method and the other is the direct method.In the differential method both TC (Total Carbon) and IC (Inorganic Carbon) may be determined by separately measuring them and TOC (Total Organic Carbon) may be calculated by subtracting IC from TC. This method is suitable for samples in which IC is less than TOC, or at least of similar size.In the direct method the first IC is removed from a sample by purging the acidified sample with a purified gas, and then TOC may be determined by means of TC measuring method as TC equal TOC. This method is also called as NPOC (Non-purgeable Organic Carbon) due to the fact that POC (Purgeable Organic Carbon) such as benzene, toluene, cyclohexane and chloroform may be partly removed from a sample by gas stripping. The direct method is suitable for surface water, ground water and drinking water because of, in most cases, less TOC comparing with IC and negligible amount of POC in these samples.(1) Combustion / NDIR MethodTC is measured by injecting a portion, tens or hundreds microliter, of the sample into a heated combustion tube packed with an oxidation catalyst. The water is vaporized and TC, the organic carbon and the inorganic carbon, is converted to carbon dioxide (CO2). The carbon dioxide is carried with the carrier gas stream from the combustion tube to a NDIR ( non-dispersive infrared gas analyzer) and concentration of carbon dioxide is measured. The TC concentration of the sample is obtained by using the calibration curve prepared with standard solutions.IC is measured by injecting a portion of the sample into an IC reaction chamber filled with phosphoric acid solution. All IC is converted to carbon dioxide and concentration of carbon dioxide is measured with a NDIR.TOC may be obtained as the difference of TC and ICIn the direct method the sample from which IC was removed previously, injected into the combustion tube and TOC (NPOC) is measured directly.The combustion / NDIR method is applicable to a wide variety of samples such as surface water, ground water, drinking water and waste water including intake water and discharged water for a waste water treatment facility. The strong points of this method are quick operation and strong oxidation capability for any kind of organic substance including suspended particulate organic substance. The weak point is a lack of sensitivity needed to apply to pure water analysis for semiconductor, pharmaceutical and power-generation industries except some TOC analyzer which has a capability of measuring down to 0.01 mg / L.(2) Persulfate oxidation / NDIR MethodThere are two types of method, persulfate oxidation supported with UV (Ultraviolet) irradiation activation and heated persulfate oxidation.TC is converted to carbon dioxide in an oxidation chamber by being acidified with phosphoric acid and reacting with persulfate in the irradiation of UV light if provided. The carbon dioxide produced in the oxidation chamber is carried with the carrier gas stream to a NDIR and concentration of carbon dioxide is measured. IC , TOC and NPOC are measured by the same manner with the combustion / NDIR method mentioned above.The persulfate oxidation / NDIR method is a rapid, precise method for the measurement of lower levels of TOC in purified water used mainly in semiconductor, pharmaceutical and power-generation industries. But since this method has some restrictions about samples which contain difficult oxidizable organic substances, suspended organic particles and salts, it is necessary to check the operational performance of the TOC analyzer beforehand when the TOC analyzer which employs this method is apply to domestic and industrial wastes, surface and saline waters and ground water. Check efficiency of oxidation with selected model compounds representative of the sample matrix as mentioned in U.S. Standard methods 5310 C or with samples containing particulates as mentioned in EPA method 9060. (3) UV oxidation / conductivity methodOxidation of organic carbon in a sample to carbon dioxide is carried out by UV radiation with oxidation catalyst or persulfate. Conductivity change of water in conductivity detection cell separated from the sample with a gas permeable membrane or a gas-liquid separator is measured.The application of these methods is restricted to low polluted waters that have no suspended particles by the reason mentioned above article.更多见：http://www.gec.jp/CTT_DATA/WMON/CHAP_4/html/Wmon-089.html，查看更多
第1天
关注盖德视界
添加小助手
