分光光度法测定矿泉水中的铅含量全解.doc

分光光度法测定矿泉水中的铅含量 摘 要 本论文是应用分光光度法测定矿泉水中的铅含量。以二甲酚橙作为显色剂，柠檬酸三铵和硫脲为掩蔽剂，在pH值为6的醋酸-醋酸钠缓冲液中，铅离子与显色剂生成红色的络合物，在575nm处有最大吸收波长。在室温下，显色时间为30min，铅离子的浓度在0～4.0μg·mL-1范围内符合朗伯-比尔定律，铅离子的线性回归直线方程为：A0.0757C+0.0017C为铅离子浓度，单位为μg·mL-1,相关系数0.9998，摩尔吸光系数1.59×L·cm-1·mol-1。实验对15种离子进行干扰考察，发现在测定允许范围内有7种离子对测定结果存在较大干扰，分别是Co2+，Cu2+，Al3+，Fe3+，Cd2+，Sb3+，Ni2+。加入硫脲和柠檬酸三铵作为掩蔽剂，可以消除Co2+，Cu2+，Al3+，Fe3+，Cd2+，Sb3+，Ni2+的干扰，其他离子对矿泉水中的铅离子测定都在允许值的范围内。 本实验表明用分光光度法测定矿泉水中的铅含量的操作简单，时间短，不需要萃取分离，试剂用量少，加标回收率为98.3%～100%，相对标准偏差小于5%，准确度和灵敏度较高。此方法也可以用于其他样品中的铅离子测定。 关键词：分光光度法，二甲酚橙，铅，矿泉水Abstract A method for determining in lead content in mineral water with spectrophotometry is proposed in this paper. Xylenol orange is selected as the chromomeric reagent,in a acidic solution of pH6,PbⅡ reach with the above mentioned to form red complexes with the wavelength of maximum absorption at 575nm.In the room temperature ,color develop in the range of 0～4.0μg·mL-1 for lead ,it conforms lambert beer’s law. Curve linear regression equation is: A0.0757C+0.0017C：μg·mL-1,correlation coefficient is: γ0.9996,molar absorption coefficient is：1.59×104 L·cm-1·mol-1.15 kind of ions are interference studied in the experiment. Within the allowable range of 7 kind of ions on the determination there is a big disturbance that in proper order are Co2+,Cu2+,Al3+,Fe3+,Cd2+,Sb3+,Ni2+. Adding thiourea and ammonium citrate a masking agent to eliminate the interference of Co2+,Cu2+,Al3+,Fe3+,Cd2+,Sb3+,Ni2+.The experiment shows that by spectrophotometer to measure the lead simple operation, mineral real reagent consumption, recovery rate is 98.3% ～%.Satongfen relative standard deviation is less than 5%, high accuracy and sensitivity. This method can also be used for other samples of the determination of lead ions. Keyword:spectrophotometry，Xylenol orange，lead，mineral water. 1前 言 天然矿泉水物美价廉，使用方便，冰凉爽口，水质纯净，含有一定量的矿物盐，微量元素或二氧化碳气体，随着人们生活水平的提高,矿泉水成为了人们生活中不可缺少的用品。但是在加工、贮存、运输过程中如果使用了含铅器皿, 或者使用了受铅污染的水源等, 将会导致矿泉水中铅含量的增加, 甚至超过我国生活饮用水标准。天然水中的铅多来自采矿、冶金、化工、电镀等废水的污染[1]。 铅是