Density-viscosity product of small-volume ionic liquid samples using quartz crystal impedance analysis
Density-viscosity product of small-volume ionic liquid samples using quartz crystal impedance analysis
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DOI：
10.1021/ac800490q
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发表时间：
2008-08-01
影响因子：
7.4
通讯作者：
Newton, Michael I.
中科院分区：
文献类型：
--
作者：
McHale, Glen;Hardacre, Chris;Newton, Michael I.
石英晶体阻抗分析已被开发作为一种技术，以评估是否室温离子液体是牛顿流体，并作为一个小体积的方法，用于确定其粘度密度产品，ρ η的值。水溶性室温离子液体1-丁基-3-甲基咪唑引起的5 MHz基频石英晶体阻抗谱的变化。三氟甲基磺酸盐（[C（4）mim][OTf]）。从耦合的频率偏移和带宽随着浓度从0变化到100%离子液体的变化，确定该液体提供牛顿响应。测试了第二种与水不混溶的离子液体，1-丁基-3-甲基咪唑鎓双（三氟甲磺酰基）酰亚胺[C（4）mim][NTf 2]，其浓度使用甲醇变化，并且也发现其提供牛顿响应。在这两种情况下，从小体积石英晶体技术推导出的粘度-密度乘积的平方根的值与使用粘度计和密度计测量的值一致。发现晶体的三次谐波提供了两种测量方法之间最接近的一致性;纯离子液体具有接近10%的最大差异。此外，测试了18种纯离子液体，其中11种获得了高质量的频移和带宽数据;这12种都具有牛顿响应。三次谐波的频移与纯离子液体的粘度-密度乘积的平方根呈线性关系，其均方根（rho eta）值约为18 kg m（-2）s（-1/2），但斜率比金泽和Gordon方程预测的小10%。设想石英晶体技术可用于高通量微流体系统中用于表征离子液体。
Quartz crystal impedance analysis has been developed as a technique to assess whether room-temperature ionic liquids are Newtonian fluids and as a small-volume method for determining the values of their viscosity-density product, rho eta. Changes in the impedance spectrum of a 5-MHz fundamental frequency quartz crystal induced by a water-miscible room-temperature ionic liquid, 1-butyl-3-methylimidazolium. trifluoromethylsulfonate ([C(4)mim][OTf]), were measured. From coupled frequency shift and bandwidth changes as the concentration was varied from 0 to 100% ionic liquid, it was determined that this liquid provided a Newtonian response. A second water-immiscible ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [C(4)mim][NTf2], with concentration varied using methanol, was tested and also found to provide a Newtonian response. In both cases, the values of the square root of the viscosity-density product deduced from the small-volume quartz crystal technique were consistent with those measured using a viscometer and density meter. The third harmonic of the crystal was found to provide the closest agreement between the two measurement methods; the pure ionic liquids had the largest difference of similar to 10%. In addition, 18 pure ionic liquids were tested, and for 11 of these, good-quality frequency shift and bandwidth data were obtained; these 12 all had a Newtonian response. The frequency shift of the third harmonic was found to vary linearly with square root of viscosity-density product of the pure ionic liquids up to a value of root(rho eta) approximate to 18 kg m(-2) s(-1/2), but with a slope 10% smaller than that predicted by the Kanazawa and Gordon equation. It is envisaged that the quartz crystal technique could be used in a high-throughput microfluidic system for characterizing ionic liquids.