Use of floating electrodes in transient isotachophoresis to increase the sensitivity of detection.

We report a protocol for on-chip electrophoretic sample loading and sample component separation in which each operation requires simultaneous control of the potential of only two electrodes: during the sample-loading phase, the potentials at the ends of the separation channel are electrically floating; during electrophoresis of the sample mixture down the separation channel, the potentials at the ends of the sample-introduction channel are floating. This method, which we call "floating-stacking," avoids the dispersion/distortion of the sample plug that is commonly associated with simultaneous electrical control of only two electrodes in a crossed-channel or offset-double-tee injection system. Further, when this floating loading/separation is done in the presence of back-transient-isotachophoresis, sample loss from the plug of material being injected is minimal and a significant concentration increase--up to 13x--of the sample components in the separated bands occurs relative to the commonly used "pinch-and-pull-back" technique (which requires simultaneous electrical control of four electrodes).

Rotation algorithm for determining cycle thresholds in Real-Time Polymerase Chain Reactions.

The Real Time-Polymerase Chain Reaction (RT-PCR) is a methodology that is widely used to amplify and quantify specific sections of nucleic acid strands. A key aspect of RT-PCR is to determine the reaction cycle that produces a positive PCR signal. This cycle is proportional to the relative concentration of nucleic acid and produces a linear curve when plotted vs. the log of the sample concentration. The cycle that produces a positive PCR signal is called the elbow or more precisely the Cycle Threshold (Ct) value. This paper describes a novel Rotation Algorithm that determines the Ct value and is less susceptible to signal interferences.