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Browse Prior Art Database

Whole Column Resistance Detection for Focusing Methods of Separation

IP.com Disclosure Number: IPCOM000028351D
Original Publication Date: 2004-May-11
Included in the Prior Art Database: 2004-May-11
Document File: 6 page(s) / 183K

Publishing Venue

National Institute of Standards and Technology

Related People

David Ross: INVENTOR [+2]

Abstract

This disclosure describes a very simple detection scheme for use with analyte focusing methods such as electric field gradient focusing (EFGF), temperature gradient focusing (TGF), micellar affinity gradient focusing (MAGF), and isoelectric focusing (IEF). For each of these focusing methods, a high voltage is applied to the separation column to cause the analytes in the column to move towards a point of zero velocity, where each analyte is focused into a peak. Most commonly, many peaks are focused at once and each peak is detected using an external detection scheme such as laser induced fluorescence (LIF), ultra-violet (UV) absorbance, or mass spectrometry. For the detection scheme described here, the focusing method is adjusted so that only one peak is focused at a time (or so that only one peak is focused in a sensitive area at a time), and the detection simply consists of measuring the resistance of the entire separation column. In its simplest embodiment, the detection scheme described here is implemented merely by measuring the current flow that results from the application of the high voltage to the column. When a peak of analyte is focused, it locally changes the resistivity of the solution in the column resulting in a change in the total column resistance that can be easily measured. In a typical measurement with this type of detection, the focusing conditions are varied over the course of a separation so that the zero-velocity point for each analyte is scanned across the gradient focusing region, and each analyte is thus in turn, sequentially injected, focused (and detected), and then defocused and eluted from the column.

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Whole Column Resistance Detection for Focusing Methods of Separation

Inventors: David Ross (836), Constantine Maliaris (SURF student, Harvard).

Abstract

This disclosure describes a very simple detection scheme for use with analyte focusing methods such as electric field gradient focusing (EFGF), temperature gradient focusing (TGF), micellar affinity gradient focusing (MAGF), and isoelectric focusing (IEF). For each of these focusing methods, a high voltage is applied to the separation column to cause the analytes in the column to move towards a point of zero velocity, where each analyte is focused into a peak. Most commonly, many peaks are focused at once and each peak is detected using an external detection scheme such as laser induced fluorescence (LIF), ultra-violet (UV) absorbance, or mass spectrometry. For the detection scheme described here, the focusing method is adjusted so that only one peak is focused at a time (or so that only one peak is focused in a sensitive area at a time), and the detection simply consists of measuring the resistance of the entire separation column. In its simplest embodiment, the detection scheme described here is implemented merely by measuring the current flow that results from the application of the high voltage to the column. When a peak of analyte is focused, it locally changes the resistivity of the solution in the column resulting in a change in the total column resistance that can be easily measured. In a typical measurement with this type of detection, the focusing conditions are varied over the course of a separation so that the zero-velocity point for each analyte is scanned across the gradient focusing region, and each analyte is thus in turn, sequentially injected, focused (and detected), and then defocused and eluted from the column.

Purpose of Invention

The invention is a very simple detection scheme for use with high-resolution, high-performance focusing methods used for the concentration and separation of analytes in solution. Because the detection scheme is purely electronic it eliminates the need for optical access, making the focusing methods much simpler and less expensive to use. It also potentially increases the utility of the focusing methods in small, portable, chemical or biochemical analysis systems.

Introduction and Background

Two key steps in many chemical and biochemical analyses are the concentration and separation of analytes. Focusing methods combine these two steps into one operation to give a potentially very high performance analytical method. Focusing methods work by producing a velocity gradient in the separation column so that an analyte in the column moves towards a point of zero velocity where it is focused and concentrated. Separation occurs when each analyte has a zero velocity point at a different position along the length of the column. For more background on focusing see the related invention disclosures on temperature gradient focusing (TGF, U.S. patent applicati...