石墨炉原子吸收光谱法用于重金属离子的富集和分析
摘要
本论文研究的主要内容是开发用于重金属萃取和富集的新方法的，并利用石墨炉原子吸收光谱法(GFAAS)对重金属离子进行了定量分析。利用浊点萃取和固相萃取作为样品预处理技术，成功的实现了对镍、镉和铅的萃取和预富集。
我们设计了一个利用浊点萃取(CPE)技术对镍离子的分离和预富集，并利用石墨炉原子吸收光谱法检测的新方法。8-羟基喹啉作为螯合剂能和镍离子形成疏水性的化合物。曲拉通X-100可以将这个疏水化合物包覆在胶束中，胶束再由小体积的表面活性剂富集相萃取。最后通过在表面活性剂的浊点温度下加热胶束溶液实现相分离。此操作同时实现了对样品溶液中镍离子的萃取和预富集。我们研究并优化了影响浊点萃取和石墨炉原子吸收光谱法的实验条件，如酸度、螯合剂浓度、表面活性剂浓度、加热时间以及分解温度、原子化温度、离心速度和时间等等。我们也研究了不同无机盐的加入对浊点温度的影响。加入氯化钠可以降低浊点温度，从而提高实验操作的效率和方便性。通过对各种实验参数的优化有实现了对痕量镍离子的检测，其检出限达到12ng/L，富集因子为25。我们利用所建立的方法用于检测水样以及国家标准样品中的镍离子，回收率在95-103%之间，结果令人满意。
在第二部分实验中，我们利用浊点萃取成功的分离和萃取了镉离子。首先，镉离子和2-巯基烟酸形成疏水化合物。然后该疏水化合物被吐温80萃取进入胶束相。以上操作在pH为5的条件下，萃取效率最高。研究并优化了对镉离子萃取和分析有影响的实验条件，例如酸度、螯合剂浓度、表面活性剂浓度、加热时间等。在本实验中，我们在胶束相中加入了氟化钠，从而使相分离在比较低的浊点温度下进行。本方法对检测镉离子具有检出限低（60ng/L）、精度高（R.S.D2.5%）的优点。利用本方法对国家标准样品和水样中镉离子的检测结果令人满意。
最后我们合成了一种新型的铅离子印迹型的超顺磁的介孔二氧化硅吸附材料(SPMS)，并利用各种技术手段对这一材料进行了表征，利用这一材料实现了对沉积物中的铅离子高选择性的吸附。巯基官能化的SPMS对铅具有快速动力学响应，在pH8.0的条件下，在20分钟内即可达到吸附平衡。通过对吸附等温线的测定研究，确定吸附模式为Langmuir吸附模式，最大吸附容量为377.36mgg-1。选择性研究表明印迹型吸附剂在铋离子共存条件下对铅离子的吸附比非印迹型吸附剂高3.05倍。我们利用这个印迹型吸附剂实现了对铅离子的固相萃取，并通过石墨炉原子吸收光谱法进行测定，并对各测定参数进行了研究和优化。铅离子的线性检测范围是50-900ngL-1，检出限为15ngL-1。通过利用印迹型吸附剂对两种国家标准样品中的铅离子进行了萃取和检测，结果令人满意。这说明铅离子印迹型的超顺磁的介孔二氧化硅吸附剂可以用作复杂基体中的铅离子的吸附剂。
我们还合成并表征了一种新型的吸附剂用来固相萃取Cu(Ⅱ)和Co(Ⅱ)。通过通过氧化处理巯基修饰的磁性多孔二氧化硅（MMS）制备出磺酸修饰的MMS。我们将这种新合成的吸附剂应用于Cu(Ⅱ)和Co(Ⅱ)的固相萃取,然后进行GFAAS分析。这种新材料具有快速吸附动力学，并且吸附平衡很好的符合Langmuir,Freundlich以及Temkin等温吸附方程式。这种吸附剂对Cu(Ⅱ)和Co(Ⅱ)的最大吸附容量分别为132mg/g和99.1mg/g。对Cu(Ⅱ)和Co(Ⅱ)的工作线性范围分别为70-400ng/L和85-350ng/L，其相应的检测线分别为20ng/L and27ng/L。
This dissertation is focused on the development of new methods for heavymetals extraction and enrichment and their subsequent quantitative analysis via graphitefurnace atomic absorption spectrometry (GFAAS). Cloud point and solid phaseextraction were utilized as sample pretreatment techniques. Nickel, cadmium and leadwere extracted and preconcentrated using these strategies.
A new method based on the cloud point extraction (CPE) for separationand preconcentration of nickel (Ⅱ) and its determination by GFAAS was designed.8-hydroxyquinoline was used as chelating agent to form a hydrophobic complexwith nickel(Ⅱ). The micelles of Triton X-100entrapped the resulting hydrophobiccomplex which was extracted into the small volume surfactant rich phase. The phaseseparation was achieved by heating the miceller solution above cloud point temperature(CPT) of the surfactant. This step simultaneously extracted and preconcentrated the traceamounts of nickel(Ⅱ) present in the sample solution. The factors which affect the cloudpoint extraction and GFAAS analysis i.e. pH, ligand concentration, surfactantconcentration, incubation time, pyrolysis and atomization temperature, centrifugation rateand time were thoroughly investigated and optimized. The effect of different inorganicsalts on the cloud point temperature was also explored. The addition of sodium chlorideresulted in the depreciation of cloud point temperature, rendering it to be advantageous interms of time and economy of the experiment. The optimized set of parameters facilitatedthe determination of trace amounts of nickel and the detection limit was calculated to be 12ng/L. The enrichment factor was found to be25. Besides analysis of differentwater samples, the proposed method was also successfully applied to determine nickel(Ⅱ)in certified reference material with satisfactory recoveries in the range of95-103%.
In another experiment, Cd(Ⅱ) was successfully separated and enriched viacloud point extraction. The metal was allowed to make a hydrophobic complex with2-mercaptonicotinic acid which was later extracted into a miceller phase of Tween80.The pH was maintained at5to achieve high efficiency. The other parameters affectingthe extraction and analysis of Cd(Ⅱ) such as pH, ligand concentration,surfactant concentration, and the incubation time were also comprehensively studied andoptimized. In this experiment, the phase separation was achieved at rather lowertemperature due to the addition of NaF in miceller media. This method offered a very lowdetection limit (60ng/L) with a high precision (R.S. D2.5%) for cadmium. Theapplicability of this method was confirmed by analyzing certified reference material andwater samples with satisfactory results.
For a highly selective removal of Pb(Ⅱ) from sediments, a new Pb(Ⅱ)-imprinted superparamagnetic mesoporous silica (SPMS) sorbent was synthesized andcharacterized by different techniques. The thiol functionalized SPMS offered a fastadsorption kinetics for Pb(Ⅱ) and equilibrium was achieved in just20min at pH8.0. Theadsorption isotherm data fits Langmuir model well with a maximum adsorption capacityof377.36mg g-1. The selectivity co-efficients of imprinted adsorbent for Pb(Ⅱ)/Bi(ⅡI)were3.05times higher than that of non-imprinted adsorbent. The imprinted adsorbentwas employed for the solid phase extraction of Pb(Ⅱ) and its detection by graphitefurnace atomic absorption spectrometry (GFAAS). The parameters affecting the determination of Pb(Ⅱ) were also well investigated and optimized. A linear relationshipbetween the Pb(Ⅱ) concentration and the absorbance was found in the range of50-900ng/L with a detection limit of15ng/L. The imprinted adsorbent was applied to thedetermination of Pb(Ⅱ) in two certified sediment samples with satisfactory results, whichindicates that Pb(Ⅱ)-imprinted superparamagnetic mesoporous silica adsorbent possesspromising features of a viable adsorbent for the preconcentration of Pb(Ⅱ) ions incomplex matrices.
A new sorbent for solid phase extraction of Cu(Ⅱ) and Co(Ⅱ) was also synthesizedand characterized. Sulphonic acid functionalized magnetic mesoporous silica (MMS)was prepared by oxidation of thiol functionalized MMS. The newly synthesized sorbentwas applied for the solid phase extraction of Cu(Ⅱ) and Co(Ⅱ) prior to their analysis byGFAAS. The new material offered fast adsorption kinetics and the equilibrium data fittedwell to the Langmuir, Freundlich and Temkin adsorption isotherms. The experimentalmaximum adsorption capacity for Cu(Ⅱ) and Co(Ⅱ) was found to be132mg/g and99.1mg/g respectively. The linear working range for Cu(Ⅱ) and Co(Ⅱ) were found tobe70-400ng/L and85-350ng/L respectively with corresponding detection limits of20ng/L and27ng/L.
我们设计了一个利用浊点萃取(CPE)技术对镍离子的分离和预富集，并利用石墨炉原子吸收光谱法检测的新方法。8-羟基喹啉作为螯合剂能和镍离子形成疏水性的化合物。曲拉通X-100可以将这个疏水化合物包覆在胶束中，胶束再由小体积的表面活性剂富集相萃取。最后通过在表面活性剂的浊点温度下加热胶束溶液实现相分离。此操作同时实现了对样品溶液中镍离子的萃取和预富集。我们研究并优化了影响浊点萃取和石墨炉原子吸收光谱法的实验条件，如酸度、螯合剂浓度、表面活性剂浓度、加热时间以及分解温度、原子化温度、离心速度和时间等等。我们也研究了不同无机盐的加入对浊点温度的影响。加入氯化钠可以降低浊点温度，从而提高实验操作的效率和方便性。通过对各种实验参数的优化有实现了对痕量镍离子的检测，其检出限达到12ng/L，富集因子为25。我们利用所建立的方法用于检测水样以及国家标准样品中的镍离子，回收率在95-103%之间，结果令人满意。
在第二部分实验中，我们利用浊点萃取成功的分离和萃取了镉离子。首先，镉离子和2-巯基烟酸形成疏水化合物。然后该疏水化合物被吐温80萃取进入胶束相。以上操作在pH为5的条件下，萃取效率最高。研究并优化了对镉离子萃取和分析有影响的实验条件，例如酸度、螯合剂浓度、表面活性剂浓度、加热时间等。在本实验中，我们在胶束相中加入了氟化钠，从而使相分离在比较低的浊点温度下进行。本方法对检测镉离子具有检出限低（60ng/L）、精度高（R.S.D2.5%）的优点。利用本方法对国家标准样品和水样中镉离子的检测结果令人满意。
最后我们合成了一种新型的铅离子印迹型的超顺磁的介孔二氧化硅吸附材料(SPMS)，并利用各种技术手段对这一材料进行了表征，利用这一材料实现了对沉积物中的铅离子高选择性的吸附。巯基官能化的SPMS对铅具有快速动力学响应，在pH8.0的条件下，在20分钟内即可达到吸附平衡。通过对吸附等温线的测定研究，确定吸附模式为Langmuir吸附模式，最大吸附容量为377.36mgg-1。选择性研究表明印迹型吸附剂在铋离子共存条件下对铅离子的吸附比非印迹型吸附剂高3.05倍。我们利用这个印迹型吸附剂实现了对铅离子的固相萃取，并通过石墨炉原子吸收光谱法进行测定，并对各测定参数进行了研究和优化。铅离子的线性检测范围是50-900ngL-1，检出限为15ngL-1。通过利用印迹型吸附剂对两种国家标准样品中的铅离子进行了萃取和检测，结果令人满意。这说明铅离子印迹型的超顺磁的介孔二氧化硅吸附剂可以用作复杂基体中的铅离子的吸附剂。
我们还合成并表征了一种新型的吸附剂用来固相萃取Cu(Ⅱ)和Co(Ⅱ)。通过通过氧化处理巯基修饰的磁性多孔二氧化硅（MMS）制备出磺酸修饰的MMS。我们将这种新合成的吸附剂应用于Cu(Ⅱ)和Co(Ⅱ)的固相萃取,然后进行GFAAS分析。这种新材料具有快速吸附动力学，并且吸附平衡很好的符合Langmuir,Freundlich以及Temkin等温吸附方程式。这种吸附剂对Cu(Ⅱ)和Co(Ⅱ)的最大吸附容量分别为132mg/g和99.1mg/g。对Cu(Ⅱ)和Co(Ⅱ)的工作线性范围分别为70-400ng/L和85-350ng/L，其相应的检测线分别为20ng/L and27ng/L。
This dissertation is focused on the development of new methods for heavymetals extraction and enrichment and their subsequent quantitative analysis via graphitefurnace atomic absorption spectrometry (GFAAS). Cloud point and solid phaseextraction were utilized as sample pretreatment techniques. Nickel, cadmium and leadwere extracted and preconcentrated using these strategies.
A new method based on the cloud point extraction (CPE) for separationand preconcentration of nickel (Ⅱ) and its determination by GFAAS was designed.8-hydroxyquinoline was used as chelating agent to form a hydrophobic complexwith nickel(Ⅱ). The micelles of Triton X-100entrapped the resulting hydrophobiccomplex which was extracted into the small volume surfactant rich phase. The phaseseparation was achieved by heating the miceller solution above cloud point temperature(CPT) of the surfactant. This step simultaneously extracted and preconcentrated the traceamounts of nickel(Ⅱ) present in the sample solution. The factors which affect the cloudpoint extraction and GFAAS analysis i.e. pH, ligand concentration, surfactantconcentration, incubation time, pyrolysis and atomization temperature, centrifugation rateand time were thoroughly investigated and optimized. The effect of different inorganicsalts on the cloud point temperature was also explored. The addition of sodium chlorideresulted in the depreciation of cloud point temperature, rendering it to be advantageous interms of time and economy of the experiment. The optimized set of parameters facilitatedthe determination of trace amounts of nickel and the detection limit was calculated to be 12ng/L. The enrichment factor was found to be25. Besides analysis of differentwater samples, the proposed method was also successfully applied to determine nickel(Ⅱ)in certified reference material with satisfactory recoveries in the range of95-103%.
In another experiment, Cd(Ⅱ) was successfully separated and enriched viacloud point extraction. The metal was allowed to make a hydrophobic complex with2-mercaptonicotinic acid which was later extracted into a miceller phase of Tween80.The pH was maintained at5to achieve high efficiency. The other parameters affectingthe extraction and analysis of Cd(Ⅱ) such as pH, ligand concentration,surfactant concentration, and the incubation time were also comprehensively studied andoptimized. In this experiment, the phase separation was achieved at rather lowertemperature due to the addition of NaF in miceller media. This method offered a very lowdetection limit (60ng/L) with a high precision (R.S. D2.5%) for cadmium. Theapplicability of this method was confirmed by analyzing certified reference material andwater samples with satisfactory results.
For a highly selective removal of Pb(Ⅱ) from sediments, a new Pb(Ⅱ)-imprinted superparamagnetic mesoporous silica (SPMS) sorbent was synthesized andcharacterized by different techniques. The thiol functionalized SPMS offered a fastadsorption kinetics for Pb(Ⅱ) and equilibrium was achieved in just20min at pH8.0. Theadsorption isotherm data fits Langmuir model well with a maximum adsorption capacityof377.36mg g-1. The selectivity co-efficients of imprinted adsorbent for Pb(Ⅱ)/Bi(ⅡI)were3.05times higher than that of non-imprinted adsorbent. The imprinted adsorbentwas employed for the solid phase extraction of Pb(Ⅱ) and its detection by graphitefurnace atomic absorption spectrometry (GFAAS). The parameters affecting the determination of Pb(Ⅱ) were also well investigated and optimized. A linear relationshipbetween the Pb(Ⅱ) concentration and the absorbance was found in the range of50-900ng/L with a detection limit of15ng/L. The imprinted adsorbent was applied to thedetermination of Pb(Ⅱ) in two certified sediment samples with satisfactory results, whichindicates that Pb(Ⅱ)-imprinted superparamagnetic mesoporous silica adsorbent possesspromising features of a viable adsorbent for the preconcentration of Pb(Ⅱ) ions incomplex matrices.
A new sorbent for solid phase extraction of Cu(Ⅱ) and Co(Ⅱ) was also synthesizedand characterized. Sulphonic acid functionalized magnetic mesoporous silica (MMS)was prepared by oxidation of thiol functionalized MMS. The newly synthesized sorbentwas applied for the solid phase extraction of Cu(Ⅱ) and Co(Ⅱ) prior to their analysis byGFAAS. The new material offered fast adsorption kinetics and the equilibrium data fittedwell to the Langmuir, Freundlich and Temkin adsorption isotherms. The experimentalmaximum adsorption capacity for Cu(Ⅱ) and Co(Ⅱ) was found to be132mg/g and99.1mg/g respectively. The linear working range for Cu(Ⅱ) and Co(Ⅱ) were found tobe70-400ng/L and85-350ng/L respectively with corresponding detection limits of20ng/L and27ng/L.
引文
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