以硫代乙酰胺/凹凸棒石复合物为载体的钙离子选择性电极

A New Calcium Electrode Based on the Composite Thioacetamide/attapulgite as Ionophore

报道了以硫代乙酰胺/凹凸棒石有机无机复合物为载体的新型钙离子选择性电极的研制.探讨了该有机无机复合物中硫代乙酰胺与凹凸棒石的组成比例、增塑剂用量、被测溶液pH等因素对钙电极性能的影响.结果表明新制钙电极对溶液中的钙离子有较好的近能斯特响应,响应斜率为15.2 mV decade-1,最低检出下限为1.0×10-6mol L-1.新制钙电极具有很好的稳定性,其可应用在溶液pH=6.0～10.0范围内.新电极对常见阳离子表现出好的抗干扰性.利用红外、紫外、相关电导率实验等方法研究了有机无机复合物型电活性物质的结构及所制钙电极的工作机理.

A kind of novel organic/inorganic composites as ionophore in the membrane of calcium ion selective electrode,which were made of thioacetamide and attapulgite,had been prepared.Thioacetamide is a type of small organic molecule with functional groups including amino groups and carbon-sulfur double bonds.Attapulgite has been characterized by a high negative charge at its surface,a large specific surface area,and a large micropore volume due to the existence of intercrystalline cavities.Thioacetamide molecules can carry positive charges when their amino groups get protons from hydroxyl groups of attapulgite.So thioacetamide molecules with positive charges can be adsorbed on the negative surface of attapulgite by electrostatic interaction as well as hydrogen-bonding,to form a super-molecular host-guest structure.Considering the stagger arranged pores on the outer surface of attapulgite,we inferred that adsorbed thioacetamide molecules should be around the edge of pore mouth of the attapulgite.Experiments proved that the organic/inorganic complex structure promoted the ability of attapulgite adsorbing more calcium ions from the solution.Based on the attapulgite/thioacetamide composite as ionophore,the calcium ion selective electrodes were prepared using 7.0 wt% of ionophore,43.0 wt% of polyvinyl chloride,and 50.0 wt% of dibutyl phthalate.The influence of the weight amount ratio of attapulgite to thioacetamide in the organic/inorganic composite on the calcium electrode performance had been investigated in our experiment.The experimental results showed that the prepared calcium electrode had a proximate Nernst response in the concentration range of 1.0×10-1～1.0×10-6 mol L-1.When the mATT∶mTAA was 0.315 in the ionophore,the prepared electrode showed a Nernstian slope of 15.2 mV decade-1and a detection limit as 1.0×10-6mol L-1.Moreover,the usable pH range of the prepared electrode was from 6.0 to 10.0,and the electrode also exhibited a favorable stability with time.IR,UV and conductivity experiments etc.have been used to research the structure of the composite made of attapulgite and thioacetamide,and the working mechanism of the prepared electrode.