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    分光光度法測定礦泉水中的鉛含量 下載本文

    分光光度法測定礦泉水中的鉛含量

    摘 要

    本論文是應用分光光度法測定礦泉水中的鉛含量。以二甲酚橙作為顯色劑,檸檬酸三銨和硫脲為掩蔽劑,在pH值為6的醋酸-醋酸鈉緩沖液中,鉛離子與顯色劑生成紅色的絡合物,在575nm處有最大吸收波長。在室溫下,顯色時間為30min,鉛離子的濃度在0~4.0μg·mL-1范圍內符合朗伯-比爾定律,鉛離子的線性回歸直線方程為:A=0.0757C+0.0017(C為鉛離子濃度,單位為μg·mL-1),相關系數?=0.9998,摩爾吸光系數?=1.59×104L·cm-1·mol-1。實驗對15種離子進行干擾考察,發現在測定允許范圍內有7種離子對測定結果存在較大干擾,分別是Co2+,Cu2+,Al3+,Fe3+,Cd2+,Sb3+,Ni2+。加入硫脲和檸檬酸三銨作為掩蔽劑,可以消除Co2+,Cu2+,Al3+,Fe3+,Cd2+,Sb3+,Ni2+的干擾,其他離子對礦泉水中的鉛離子測定都在允許值的范圍內。

    本實驗表明用分光光度法測定礦泉水中的鉛含量的操作簡單,時間短,不需要萃取分離,試劑用量少,加標回收率為98.3%~100%,相對標準偏差小于5%,準確度和靈敏度較高。此方法也可以用于其他樣品中的鉛離子測定。

    關鍵詞:分光光度法,二甲酚橙,鉛,礦泉水

    I

    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,Pb(Ⅱ) 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: A=0.0757C+0.0017(C:μg·mL-1),correlation coefficient is: γ=0.9996,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% ~100%.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.

    II

    目錄

    1前言 .............................................................. 1 2實驗部分 .......................................................... 2 2.1實驗原理 ........................................................ 2 2.2儀器的結構原理 .................................................. 3 2.2.1 721B分光光度計的結構 .......................................... 3 2.2.2 721B型分光光度計外觀示意圖 .................................... 5 2.2.3 721B型分光光度計工作原理 .......................................... 6 2.2.4 721B型儀器的光學系統 .......................................... 7 2.3 儀器和試劑 ...................................................... 9 2.3.1 實驗儀器 ...................................................... 9 2.3.2 試劑和標準樣的配制 ............................................ 9 2.4 儀器的測試條件 .................................................. 10 3結果和討論 ........................................................ 10 3.1 最佳條件的選擇 .................................................. 10 3.1.1 測定波長的選擇 ................................................ 11 3.1.2 顯色劑用量的選擇 .............................................. 12 3.1.3 顯色時間的考察 ................................................ 13 3.1.4 緩沖溶液pH的考察 ............................................. 14 3.2 工作曲線的繪制 .................................................. 15 3.3干擾離子的考察 .................................................. 17

    III

    3.4干擾離子的掩蔽 .................................................. 24 3.5 樣品分析試驗 .................................................... 28 3.5.1 樣品測定及精密度考察 .......................................... 28 3.5.2 準確度的考察 .................................................. 29 4結論 ............................................................................................................................. 31 參考文獻 ........................................................................................................................ 32 致謝 ................................................................................................................................ 34

    IV





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