环境水中有机物综合指标检测方案

智能文字提取功能测试中

analytikjena analytikjena Determination of TOC in Sea Water Samples General The concentration of TOC in sea water is rather low (in the lower ppm range down to ppb) incomparison to the salt content of this matrix. The mean concentration of salts (mainly chlorides and sulfates) is approx. 3，5%. The Baltic Sea differs in its salt concentration between 0，2 and 2%whereas the Dead Sea contains up to 28% of salts. Common high temperature TOC analyzers are capable for TOC determination in sea water but anearlier exhaust of the combustion tube filling material (catalyst and protective materials) isexpected in comparison to water samples with lower salt concentrations. A more cost-effective alternative without the necessity to exchange filling materials is representedby the wet chemical TOC analyzer multi N/C UV HS for TOC determination in sea watersamples. The multi N/CUV HS combines wet-chemical digestion with persulfate and the presence of hardUV radiation (254 and 185 nm) inside a high power UV-reactor.The special reactor in combinationwith a robust and highly sensitive wide range NDIR detection system makes the multi N/C UV HSespecially well-suited for TOC determination in the ultra low concentration range beside very highsalt concentrations at extremely low operating costs. Sea water 1000g 口Water 965 g■ Salt 35 g 口 Chloride 19，25 g 口l Sodium 10，7 g 口 Sulfate 2.7 g口Magnesium 1，3 gl Calcium 0，42 g 口l Potassium 0，39 g Minor Constituents 0，25 g Measurements with the multi N/CUV HS A synthetic sea water sample containing 32 g/l sodium chloride and 4 g/l sodium sulfate wasprepared and spiked with different TOC concentrations ( potassium hydrogen phthalate) in arange from 0，2 to5 mg/ITOC. All samples were diluted 1：10 with distilled water to reduce thechloride concentration to a value <5 g/l which is the limit concentration for a complete oxidation oforganic compounds. All samples were acidified afterwards with 0，5 ml of 2 N H2SO4 per 100 ml ofsample. TOC measurement was performed according to the direct method (NPOC mode) becausein native sea water samples the expected TIC content is higher than the TOC value and for thisreason a TOC measurement by the difference method should not be applied. All samples were analyzed using the "high content mode”-a combination of UV-light andpersulfate digestion. This mode is particularly suitable even for very high salt concentrations notonly of sea water samples but also for electrolytic bath solutions， concentrated acids etc. Theconcentration of the oxidation reagent were doubled to 160 g/l sodium peroxidisulfate.Following method settings were used： Sample volume： 5 ml Rinse volume： 5 ml NPOC purge time ： 600 sec Max.integration time： 600 sec Results obtained with the multi N/C UV HS TOC concentation [mg/] The different levels of TOC concentration from 0，2 up to 5 mg/l could be recovered at the 100 %level in all synthetic sea water samples compared to the common TOC standards. For better comparability the recovery rates for each TOC concentration level are shown for thesynthetic sea water samples and the corresponding TOC standard samples without salt matrix. Limit of detection and limit ofauantificationwere calculated by an independentsoftwareaccording to DIN 32645 which yieldedfollowing results：LOD： 0，018 mg/ILOQ： 0，103mg/l Conclusion Sea water samples can be measured with a very good reproducibility and sensitivity with the TOCanalyzer multi N/C UV HS. The running costs of wet chemical TOC analyzers are rather low in comparison to hightemperature combustion systems due to the less aggressive digestion. No need to exchangepermanently consumables like combustion tubes， catalyst filling etc. Extremely low running costs can be achieved with the multi N/C@UV HS thanks to the long servicelife of the UV lamp and the robust and at the same time highly sensitive NDIR detection system.This predestines the multi N/C UV HS for the preferred solution for many TOC applications notonly for low polluted samples but especially for samples containing high salt concentrations， likee.g. sea water samples. Printout and further use permitted with a reference to the source. C 2010 Analytik Jena AG Publisher： Analytik Jena AG Konrad-Zuse-StraBe 1 07745 Jena Telephone +49 (0) 3641/77-70Fax +49 364177-9279 Determination of TOC in Sea Water Samples. Reference：SP TOC e|AKF/