Development of a Straightforward and Robust Technique to Implement Hadamard Encoded Multiplexing to High-Performance Liquid Chromatography

Abstract

High-performance liquid chromatography (HPLC) is an indispensable technique to separate, quantify, and identify a broad range of compounds. Recent advances in HPLC technology led to the development of ultrahigh-performance instruments that allow rapid sample analysis with high efficiency. Nevertheless, there is still the opportunity to increase the sample throughput and to improve the signal-to-noise ratio by the application of multiplexing, where the injected samples are encoded with defined sequences. The obtained signal is then deconvoluted to give conventional chromatograms. In this work we present a method and technique which can be easily implemented in commercially available HPLC instruments to perform multiplexing analysis. Using our approach, multiplexing can be performed on standard laboratory equipment by software control and offers an inherent advantage in sensitivity and minimization of analysis time, demonstrated for the analysis of highly diluted polynuclear aromatic hydrocarbon (PAH) samples in water.

Implementation of Hadamard encoding for rapid multisample analysis in liquid chromatography

“…We implemented Hadamard encoding in HPLC by software modification of standard instrumentation. The macro and algorithm used therefore are described in reference . If the same sample is injected repeatedly according to a Hadamard modulation sequence significant gain in S/N can be found.…”

“…Binary modulation sequences were applied to the auto sampler using a macro that can be read by ChemStation. For a detailed description of the macro see reference . To start a multiplexing run the macro containing information about sample positions, injection order, injection intervals, and run time was executed using a prerun command.…”

“…By employing this technique extraordinarily high sample‐throughputs of up to 453 samples/h can be achieved in GC separations. Recently, we demonstrated the implementation of Hadamard encoding in HPLC . Multiplexing could be performed on standard HPLC devices by a simple software modification.…”

Fourier transformation liquid chromatography: increasing sensitivity by a factor of 50

“…[8][9][10][11][12][13][14][15][16][17][18][19] Methods with multiple random injections have been applied to liquid and gas chromatography where the chromatogram is evaluated using cross-correlation or Hadamard transformation to increase the S/N and for process control. [8][9][10][14][15][16][17][18] However, continuous sinusoidal "injections" have only been established in rare cases for gas chromatography for process control purposes. [11][12][13] To date, none of these modified injection methods have been used extensively or fully developed.…”

“…In subsequent publications, both methods have been further investigated. 8–19 Methods with multiple random injections have been applied to liquid and gas chromatography where the chromatogram is evaluated using cross-correlation or Hadamard transformation to increase the S/N and for process control. 8–10,14–18 However, continuous sinusoidal “injections” have only been established in rare cases for gas chromatography for process control purposes.…”