Ionic liquids (ILs) are salts that are liquid at low temperatures, usually including the region around room temperature. They are under intense investigation, especially as replacement solvents for reactions and separations, since they exhibit negligible vapor pressure and would not, therefore, contribute to air pollution. Clearly, basic thermophysical properties are vital for design and evaluation for these applications. We present density as a function of temperature, melting temperatures, glass-transition temperatures, decomposition temperatures, and heat capacities as a function of temperature for a series of 13 of the popular imidazolium-based ILs. The ionic liquids investigated here are 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium dicyanamide, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium tris(trifluoromethylsulfonyl)methide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium bis-(trifluoromethylsulfonyl)imide, 2,3-dimethyl-1-ethylimidazolium bis(trifluoromethylsulfonyl)imide, 2,3dimethyl-1-propylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-2,3-dimethylimidazolium tetrafluoroborate, and 1-butyl-2,3-dimethylimidazolium hexafluorophosphate. The properties follow quite reasonable trends. For instance, density decreases as the length of the alkyl chain on the cation increases. For a given cation, the density increases as the molecular weight of the anion increases for the anions studied here. Many of the ILs tend to subcool easily, forming glasses at very low temperatures rather than exhibiting crystallization or melting transitions. The thermal stability increases with increasing anion size, and heat capacities increase with temperature and increasing number of atoms in the IL.

The reference human genome provides an adequate basis for biological researchers to study the relationship between genotype and the associated phenotypes, but a large push is underway to sequence many more genomes to determine the role of various specificities among different individuals that control these relationships and to enable the use of human genome data for personalized and preventative healthcare. The current electrophoretic methodology for sequencing an entire mammalian genome, which includes standard molecular biology techniques for genomic sample preparation and the separation of DNA fragments using capillary array electrophoresis, remains far too expensive ($5 million) to make genome sequencing ubiquitous. The National Human Genome Research Institute has put forth goals to reduce the cost of human genome sequencing to $100,000 in the short term and $1000 in the long term to spur the innovative development of technologies that will permit the routine sequencing of human genomes for use as a diagnostic tool for disease. Since the announcement of these goals, several companies have developed and released new, non-electrophoresis-based sequencing instruments that enable massive throughput in the gathering of genomic information. In this review, we discuss the advantages and limitations of these new, massively parallel sequencers and compare them with the currently developing next generation of electrophoresis-based genetic analysis platforms, specifically microchip electrophoresis devices, in the context of three distinct types of genetic analysis.

To realize the immense potential of large-scale genomic sequencing after the completion of the second human genome (Venter's), the costs for the complete sequencing of additional genomes must be dramatically reduced. Among the technologies being developed to reduce sequencing costs, microchip electrophoresis is the only new technology ready to produce the long reads most suitable for the de novo sequencing and assembly of large and complex genomes. Compared with the current paradigm of capillary electrophoresis, microchip systems promise to reduce sequencing costs dramatically by increasing throughput, reducing reagent consumption, and integrating the many steps of the sequencing pipeline onto a single platform. Although capillary-based systems require Ϸ70 min to deliver Ϸ650 bases of contiguous sequence, we report sequencing up to 600 bases in just 6.5 min by microchip electrophoresis with a unique polymer matrix/adsorbed polymer wall coating combination. This represents a two-thirds reduction in sequencing time over any previously published chip sequencing result, with comparable read length and sequence quality. We hypothesize that these ultrafast long reads on chips can be achieved because the combined polymer system engenders a recently discovered ''hybrid'' mechanism of DNA electromigration, in which DNA molecules alternate rapidly between reptating through the intact polymer network and disrupting network entanglements to drag polymers through the solution, similar to dsDNA dynamics we observe in single-molecule DNA imaging studies. Most importantly, these results reveal the surprisingly powerful ability of microchip electrophoresis to provide ultrafast Sanger sequencing, which will translate to increased system throughput and reduced costs.DNA separation mechanism ͉ microchip electrophoresis ͉ entangled polymer solution ͉ DNA imaging

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Although a finished human genome reference sequence is now available, the ability to sequence large, complex genomes remains critically important for researchers in the biological sciences, and in particular, continued human genomic sequence determination will ultimately help to realize the promise of medical care tailored to an individual's unique genetic identity. Many new technologies are being developed to decrease the costs and to dramatically increase the data acquisition rate of such sequencing projects. These new sequencing approaches include Sanger reaction-based technologies that have electrophoresis as the final separation step as well as those that use completely novel, nonelectrophoretic methods to generate sequence data. In this review, we discuss the various advances in sequencing technologies and evaluate the current limitations of novel methods that currently preclude their complete acceptance in large-scale sequencing projects. Our primary goal is to analyze and predict the continuing role of electrophoresis in large-scale DNA sequencing, both in the near and longer term.