土壤硝酸盐测定.doc

Application NoteAN 5206Date issued: 2000-03-06Last revised:DETERMINATION OF NITRATE IN 2M KCl SOIL EXTRACTS BY FIASTAR 5000使用FIASTAR 5000测定2M KCl土壤浸出样中的硝酸盐1. Scope and field of application应用范围This Application Note describes a method for determination of nitrate in soil extracts in the following range: 本简报描述方法用于测定土壤浸出液中硝酸盐，测定范围：0.1-5 mg/l NO3-N in the extract (40 ml 样品圈)，线性定标0.1-5 mg/l NO3-N ，(40 ml 样品圈), 线性定标2. Principle of the method测试原理Nitrate in the soil sample is extracted by 2M KCl. The suspension is centrifuged and filtered and can after this treatment be introduced in a flow injection system. The chemical principle for determination of nitrate is reduction to nitrite in a cadmium reductor. See AN 5201 for details. The described method gives the sum of nitrite and nitrate originally present in the extract. However, the original concentration of nitrite is in most cases negligible in comparison with the nitrate concentration. 使用2M KCl溶液浸出土壤样品中的硝酸盐。浸出悬浮液离心并过滤后可使用流动注射系统进行分析。测试硝酸盐的原理是使用镉柱（还原剂）将硝酸盐还原成亚硝酸盐，详细信息参见简报AN5201。本方法从本质上讲测试的是土壤浸出液中硝酸盐和亚硝酸盐的总和，但是，同浸出液中含有的硝酸盐量相比，所含的亚硝酸盐可忽略不计。3. Reagents试剂Before using any chemicals refer to adequate manuals or safety data sheets approved by your local authorities. If not stated otherwise, only reagents of recognized analytical grade and water according to grade 1 of ISO 3696 shall be used.在使用任何化学试剂之前，请参考当地政府颁发的准许使用手册和安全数据标准。如果没有特殊说明，本简报所允许使用的试剂为分析级，配置试剂所用的水应符合ISO3696标准的1级水。3.1 Sulphanilamide (4-aminobenzenesullfonamide), C6H8N2O2S 4-氨基苯磺酸C6H8N2O2S3.2 N-(1-naphtyl)-Ethylene Diamine Dihydrochloride , C12H14N2 x 2 HCl1-萘胺盐酸盐，C12H14N2 x 2 HCl3.3 Hydrochloric acid; HCl w=37% 盐酸, HCl 37%3.4 Sodium Nitrite, NaNO2, dried to constant mass at 150 C亚硝酸钠，NaNO2，在105C干燥至恒重3.5 Sodium Nitrate, NaNO3, dried to constant mass at 105 C硝酸钠，NaNO3，在105C干燥至恒重3.6 Ammonium Chloride, NH4Cl, dried to constant mass at 105 C 氯化铵，NH4Cl，在105C干燥至恒重3.7 Ammonia, NH4OH氨水，NH4OH3.8 Potassium Chloride, KCl氯化钾，KCl 3.9 2M Potassium chloride, KCl2M 氯化钾溶液，KClIn a suitable container, dissolve Potassium chloride in water. For preparation of this solution, see table. 采用合适的容器，将氯化钾溶解于水中配制2M的氯化钾溶液，配方如下表：VolumeKCl1 l(1升)149.1 g5 l(5升)745.5 g10 l(10升)1491 g20 l(20升)2982 g3.10 Carrier solution, 2M KCl 载液，2M KCl溶液See 3.9 见3.93.11 Ammonium Chloride buffer pH 8.5, reagent = 氯化铵缓冲液, pH 8.5，试剂=Dissolve 85 g Ammonium Chloride, NH4Cl in 500 ml of distilled water. Allow the solution to reach room temperature. Add Ammonia, NH4OH (about 12 ml) to reach a pH of 8.5. Mix and dilute to 1000 ml with distilled water.将85g氯化铵溶于500ml水中。将溶液平衡至室温。加入氨水(约12ml)，调节pH到8.5，然后将溶液充分混合，用蒸馏水稀释至1000ml3.12 Sulphanilamide reagent = 氨基苯磺酸试剂=In a volumetric flask of nominal capacity 500 ml, dissolve 5g Sulphanilamide in 250 ml distilled water. Add 25 ml concentrated Hydrochloric acid and mix carefully. Dilute to volume with distilled water. Transfer the content of the flask to the reagent bottle labelled =.This reagent is stable for several months.Note! For the preparation of this reagent 50 ml of Phosphoric acid may be used instead of Hydrochloric acid将5g氨基苯磺酸溶解在250ml蒸馏水中，加25ml浓盐酸，仔细搅拌混合后，将溶液转移至500ml的容量瓶中，用蒸馏水定容。然后将溶液转移至标号为=的试剂瓶中。此试剂可稳定保存几个月注：配制此试剂可使用50ml磷酸代替盐酸3.13 NED reagent =NED 萘胺盐酸盐试剂=In a volumetric flask of nominal capacity 500 ml, dissolve 0.5g N-(1-naphtyl)-Ethylene Diamine Dihydrochloride in approximately 250 ml of distilled water. Make up to volume with distilled water. Transfer the content to the reagent bottle labelled =.This solution should be freshly prepared every week.将0.5g1-萘胺盐酸盐C10H9N.3H2O.HCl溶于250ml蒸馏水，溶液转移至500ml容量瓶中，用蒸馏水定容。将配制的溶液转移至标号为=的试剂瓶中。此溶液应每星期新鲜配制。3.14 Stock standard solution, 1000 mg/l NO3-N 标准储备液，1000 mg/l NO3-NIn a volumetric flask of nominal capacity 1000 ml, dissolve 6.068 g Sodium Nitrate and dilute to volume with distilled water.The stock standard is stable for at least 3 months.将6.608g硝酸钠溶解于蒸馏水水中，将溶液转移至1000ml的容量瓶中，用蒸馏水定容至刻度。此储备液可稳定保存3个月。3.15 Interim stock standard 20 mg/l NO3-N临时储备液 20 mg/l NO3-NPipette 10 ml of the stock standard solution into a 500 ml volumetric flask and dilute to volume with 2 M KCl.This solution should be prepared fresh daily.取标准储备液10ml转移至500ml的容量瓶中，然后用2 M KCl溶液稀释至刻度。此溶液应每天新鲜配制3.16 Calibrating solutions 定标系列标准溶液The calibrating solutions are prepared by diluting the solution described in 3.13 with 2 M KCl. At least five calibration standards per working range are recommended使用临时储备液，根据下表用2M KCl溶液配制定标系溶液。每个工作范围至少需配制5个标准溶液。Working range 0.1-5 mg/l NO3-N工作范围0.1-5 mg/l NO3-NNO3-N concentrationmg/lNO3-N浓度mg/lVolume interim standard (3.15)ml临时储备液体积 mlFinal volumeml最终体积，ml0-1000.10.51000.52.510015100210100525100The calibrating solutions should be prepared fresh daily.定标溶液应每天新鲜配制4. Apparatus仪器和设备Usual laboratory apparatus and 常用实验室容器和4.1 FIAstar 5000 Analyzer unit. FIAstar 5000流动注射分析元4.2 Method cassette NO2/NO3 +interference filters 540 nm and 720 nm. NO2/NO3方法盒，540nm测量滤光片和720nm参比滤光片4.3 5027 Sampler (optional) 5027采样器(可选件)4.4 Prepacked reduction columns, part no. 5000 3139 预装还原Cd柱part no. 5000 31394.5 Volumetric flasks, of nominal capacity 100 ml, 500 ml and 1000 ml. 体积分别为100ml,500ml,1000ml的容量瓶4.6 Pipettes of nominal capacity 0.5-25 ml 体积为0.5-25 ml的移液器4.7 pH electrode pH电极4.8 Shaking machine 震荡器4.9 Centrifuge 离心机4.10 Filter paper, type Whatman No.1 or Munktell No.4. 滤纸，Whatman No. 1或or Munktell No. 45. Procedure操作步骤5.1 Sampling and sample preparation 采样和样品制备Weigh in 10 g air-dried soil into a 100 ml flask. Add 50 ml of 2M KCl and shake for one hour. Transfer the suspension to a centrifuge tube and centrifuge for 5 min, and/or filter the supernatant solution through Whatman No. 1 or Munktell No. 4 washed filter paper.称取10克空气干燥的土样倒入100ml三角瓶中，加入50ml 2M KCl溶液震荡一小时。然后将悬浮液转移至离心机中离心5min，并且/或采用Whatman No. 1号滤膜进行过滤，取上清液。5.2 Starting up the system 启动系统1. Turn on the FIAstar Analyzer and (if used) the 5027 Sampler.打开FIAstar分析仪主机及5027采样器电源(如果采用取样器)2. Verify that the correct method cassette and corresponding detector filters are installed 确认安装的测试盒及使用的检测器滤光片是否正确3. Start the pump/s and pump distilled water through each unit and check the flow.开启蠕动泵，将各管路接蒸馏水，检查流路连接是否正常4. Turn the PC on and start the Software.打开计算机，启动分析软件5. Start pumping the reagents. The method selector should be in the NO2 position.泵入试剂，确认测试盒指示的位置是NO2分析6. When the system is filled with liquid turn the method selector to NO2+NO3. Pump until all the air in the by-pass tube is gone. Stop the pumps and remove the by-pass tube.当系统充满液体，将测试盒指示的位置转到NO2+NO3分析。继续泵入试剂直到旁路泵管中的空气全部被赶净。将泵停止工作，取走旁路泵管。7. Install the Cadmium reductor and start the pump.在旁路泵管位置安装镉柱，继续启动泵单元8. Load the method in the software, verify that the correct sample loop is installed.将分析方法调入，确认正确的样品圈被安装9. Load the Sampler with the samples and make a Sample List in the Software.将样品置于采样器，在软件中编制样品表10. Load the calibration standard/s on the Sampler, make a few Test Injection of one of the standards to verify that the system is equilibrated. Check the efficiency of the cadmium reductor (See 5.4.1)将定标系溶液置于采样器，取一标准样品注射几次，检查流路是否平衡并检查系统是否工作正常。同时检查镉柱的工作效率(见5.4.1)。11. Make a calibration/check calibration. 制作定标并检查定标12. Start the Sample List.启动样品表Figure 1. NO2/NO3 positionFigure 2. NO2 position5.3 Closing down关闭系统Note! Since the method involves strongly concentrated liquids the closing down procedure is especially important to guarantee a good performance of the system注意！由于方法所使用的试剂浓度较高，因此关闭系统前的清洗工作十分重要，以维护系统良好的分析性能。1. Switch over to the NO2 position and pump water through the system for a few minutes. Stop the pump. Remove the cadmium reductor (See 5.4.3) and reinstall the teflon by-pass tube. Restart the pump. Switch over to NO2 + NO3 position. 将测试盒置于NO2分析位置，向分析系统泵入蒸馏水几分钟然后停止泵工作。从分析仪中取出镉柱然后重新将聚四氟乙烯旁路管连上。继续将泵启动，并将测试盒置于NO2 + NO3分析位置2. Start the Rinse cycle in the software启动软件的淋洗操作3. When the Rinse cycle is completed, disconnect all pump tubes and pump air through the units to remove the remaining water.系统淋洗完成后，将管路从蒸馏水中取出，泵入空气以去除系统中残留的水4. Turn the analyzer off.关闭分析仪电源5.4 Cadmium reductor镉柱还原剂WARNING! Cadmium is toxic. Particles cannot be released from the reductor unless broken. Handle the reductor with care.注意！金属镉为有毒试剂。不可以将镉柱填充颗粒从柱子中取出。在使用镉柱时，请妥善处理。5.4.1 Checking the efficiency of the reductor检查还原剂镉柱的效率The efficiency of the reductor must be checked regularly. Do as follows:镉柱的效率可定期进行检查，检查步骤如下：Inject a 1 mg/l NO2-N solution over the cadmium reductor.将镉柱连接于工作旁路，向系统注射浓度为1 mg/l NO2-N 的溶液Inject a 1 mg/l NO3-N solution over the cadmium reductor. The absorbance value of the NO3 solution should be 85-100 % of the NO2 solution. If efficiency is less, try activation as in section 5.4.2 然后向系统注射1 mg/l NO3-N溶液。NO3溶液的吸收值应为NO2 溶液吸收值的85-100%左右，如果低于此范围，则镉柱的工作效率不足，应将其进行活化处理，见5.4.2。5.4.2 Reductor activation镉柱还原剂的活化To activate the reductor for the first time or after a long period of without use make a few injections of 1 M HCl followed by 200 ppm NO3-N. Then make a few injections of a standard until a stable result is obtained.如果第一次使用镉柱或镉柱被长久储存再启用，应将镉柱连接于旁路，注射几次1 M HCl溶液，然后注射200 ppm NO3-N溶液。最后取一标准溶液注射几次并检查结果是否稳定5.4.3 Handling and storage of the reductor处理和储存镉柱还原剂The Cd-reductor must be kept soaked. Seal the ends with the steel stoppers provided.Avoid pumping water through the reductor as this will decrease its lifetime. Always store the reductor filled with the Ammonium Chloride buffer. This is achieved by following the above Closing down procedure.镉柱还原剂必须被浸泡保存同时其两端应使用原厂配置的钢套头。不要将镉柱接触蒸馏水，这将缩短镉柱的寿命应将镉柱浸泡在氯化铵缓冲溶液中，在分析结束后，应将镉柱取出如上描述保存。5.5 Interferences分析干扰Coloured constituents in the soil which absorb in the photometric range used will interfere. It is important that the KCl concentration in the extract is kept fairly constant, otherwise matrix effects may appear. The variation of the KCl concentration originates from the variation in water content in the soil samples. 如样品含有带颜色的成分并此成分在光度检测范围内将影响测定。保证浸出液KCl浓度的相对稳定非常重要，否则会出现基体效应。KCl浓度的变化主要来自于土壤样品中水分的变化。样品中的强氧化剂和还原剂将影响分析。含有高浓度的氯、氯化物、碘化物、腐殖酸和某些重金属将影响分析Note! Variations may occur due to temperature variations, pump tube conditions, reagent purity etc.注意 ！以上结果会出现某些波动，这是由于温度变化，泵管情况和试剂纯度等因素引起的6. Bibliography参考文献1. ISO 13395. Water quality-Determination of nitrite nitrogen and nitrate nitrogen and the sum of both by flow analysis (CFA and FIA) and spectrometric detection.2. . K. Bendschneider and R. Robinson; J.Mar.Res 11 (1952) 873. L. Anderson, Anal Chim Acta; 110 (1979) 1234. M.F. Gine, H. Bergamin Filho, E.A.G. Zagetto, & B.F. Reis; Anal Chim Acta, 114 (1980) 19.5. Methods of Seawater Analysis, K. Grasshoff, Verlag Chemie 19766. ISO 3696 Water for analytical laboratory use Specification and test methods.7. ISO 8466 Water quality - Calibration and evaluation of analytical methods and estimation of performance characteristics7. Method/cassette specifica