总离子强度缓冲体系中柠檬酸钠浓度对水氟测定的影响

Influence of sodium citrate concentration in TISAB on detection of water fluoride

目的观察总离子强度缓冲体系（TISAB）中不同柠檬酸钠浓度对水氟测定的影响，探讨0．10mol／L柠檬酸钠缓冲体系测定水氟的可行性。方法柠檬酸钠浓度为0．01、0．10和1．00mol／L的TISAB体系，在pH5．0～5．5下，分别测定0．2、0．5、1．0、2．0、5．0mg／L的氟标准系列，比较3种柠檬酸钠浓度的TISAB体系对水氟的测定结果，并对0．10mol／L柠檬酸钠的TISAB体系测定水氟的可行性进行试验，水氟测定按照《生活饮用水标准检验方法》（GB／T5750．5—2006）中氟离子选择电极法进行。结果TISAB体系中柠檬酸钠浓度为0．0l、O．10、1．00mol／L，试样氟浓度为0．2、0．5、1．0、2．0、5．0mg／L时，水氟回收率分别为96．O％、103．0％、179．5％；80．6％、97．8％、132．2％；73-3％、97．0％、103．0％；70．0％、100．0％、87．5％；66．4％、102．O％、65．4％。TISAB体系中柠檬酸钠浓度为0．01、0．10、1．00mol／L时，回归方程式为：Y=lg-1（226．4-∥47．4）、Y=lg。（226．4-E/53．4）、Y=lg。（208．1-E／36．9），相关系数（r）分别为0．9993、0．9999、0．9993。含0．10mol／L柠檬酸钠的TISAB体系，最低检出浓度、最低定量浓度分别为0．023、0．072mg／L。TISAB体系中柠檬酸钠浓度为0．10mol／L，可掩蔽铅（A13＋）100μg，铁（Fe3＋）800μg，钙（Ca2＋）1200μg，A13＋（50μg）＋Fe3＋（800μg），A13＋（50μg）4-Ca2＋（1200μg）。总平均回收率置信限（月／d）为0．99。标准溶液、水样、加标水样的总标准差〈各自浓度均数的5％。结论高浓度柠檬酸钠的缓冲体系对水氟测定的灵敏度和最低定量浓度有显著影响，rrISAB体系中0．10mol／L柠檬酸钠有理想的抗干扰能力，精密度和准确度的可信限符合要求，适合各种水源水和饮用水中氟化物的测定。

Objective To observe the influence of sodium citrate concentrations in TISAB on detection of water fluoride, and to explore the feasibility of 0.10 mol/L sodium citrate buffer system in detection of water fluoride. Methods Under pH 5.0 to 5.5, a series of fluoride standards of 0.2, 0.5, 1.0, 2.0 and 5.0 mg/L were~ measured when sodium citrate concentration was 0.01, 0.10, and 1.00 mol/L in the TISAB system. The results of water fluoride measurement were compared, recovery calculated and regression equation of the standard curve was set up. The feasibility of 0.10 mol/L sodium citrate in the TISAB system to detect water fluoride was tested, including interference test, accuracy, confidence limits, as well as precision test. Water fluoride was determined by fluoride ion selective electrode according to the ＂Standard Test Methods for Drinking Water＂ （GB/T 5750.5-2006）. Results When the sodium citrate concentrations in the TISAB system were 0.01, 0.10 and 1.00 mol/L, and the concentrations of fluoride in the sample were 0.2, 0.5, 1.0, 2.0 and 5.0 mg/L, recoveries of water fluoride were 96.0%, 103.0%, 179.5%; 80.6%, 97.8%, 132.2%; 73.3%, 97.0%, 103.0%; 70.0%, 100.0%, 87.5%; and 66.4%, 102.0%, 65.4%. The equation of linear regression was y = lg-1（226.4 - E/47.4）, y = lg-1（226.4- E/53.4） and y = lg-1（208.1 - E/36.9） ; the correlation coefficient（r） were 0.9993, 0.9999 and 0.9993. The minimum detectable concentration and limit of quantitation was 0.023 and 0.072 mg/L when sodium citrate was 0.10 mol/L in the TISAB system. Aluminum（AP＋, 100 μg）, ferrum（Fe3＋, 800 μg）, calcium（Ca2＋, 1200μg）, AP＋（50 μg） ＋ Fe3＋ （800 μg）, AP＋（50μg）＋ Ca2＋（ 1200μg） can be masked when sodium citrate was 0.10 mol/L in the TISAB system. The total average recoveries confidence limit R/d was 0.99. The total standard deviation of standard solution, water sample and spiked water sample was less than 5% of their respective mean concentration. Conclusions High concentration of sodium citrate buffer system has a significant influence on the detectionsensitivity and limit of quantification of fluoride ion in water. The capacity of anti-interference of 0.10 mol/L sodium citrate in the TISAB is strong. The confidence limits of precision and accuracy meet the requirements for fluoride determination in a variety of source water and drinking water.