The analysis of amino acids and peptides by isotachophoresis

Holloway, C. J.; Pingoud, Vera

doi:10.1002/elps.1150020302

Cited by 19 publications

(3 citation statements)

References 17 publications

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“…77 The effect of bicarbonate, carbonate, and carbamates as background ions can be especially important in displacement type assays such as isotachophoresis. 78 An example visualization of carbonate and carbamate zones, their effect on isotachopherograms, and the mitigation of these effects with barium hydroxide is discussed by Khurana and Santiago. 72 Khurana and Santiago introduced Ba(OH) 2 at 5 mM concentrations into a 250 mM glycine buffer.…”

Section: Carbon Dioxide and Buffer Phmentioning

confidence: 99%

Basic principles of electrolyte chemistry for microfluidic electrokinetics. Part I: Acid–base equilibria and pH buffers

2009

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We review fundamental and applied acid-base equilibrium chemistry useful to microfluidic electrokinetics. We present elements of acid-base equilibrium reactions and derive rules for pH calculation for simple buffers. We also present a general formulation to calculate pH of more complex, arbitrary mixtures of electrolytes, and discuss the effects of ionic strength and temperature on pH calculation. More practically, we offer advice on buffer preparation and on buffer reporting. We also discuss "real world" buffers and likely contamination sources. In particular, we discuss the effects of atmospheric carbon dioxide on buffer systems, namely, the increase in ionic strength and acidification of typical electrokinetic device buffers. In Part II of this two-paper series, we discuss the coupling of acid-base equilibria with electrolyte dynamics and electrochemistry in typical microfluidic electrokinetic systems.

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Section: Carbon Dioxide and Buffer Phmentioning

confidence: 99%

Basic principles of electrolyte chemistry for microfluidic electrokinetics. Part I: Acid–base equilibria and pH buffers

2009

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“…Barium hydroxide is for this effect commonly added to TE. 52,53 We present our control experiments, with and without barium hydroxide in the TE in the spatiotemporal plots in Fig. 4a-d.…”

Section: Validation Of Presence Of Carbonate and Carbamate: Control E...mentioning

confidence: 99%

Effects of carbon dioxide on peak mode isotachophoresis: Simultaneous preconcentration and separation

Khurana

Santiago

2009

Lab Chip

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We present a method that achieves simultaneous preconcentration and separation of analytes using peak-mode isotachophoresis with a single step injection in simple, off-the-shelf microchannels or capillaries. We leverage ions resulting from dissolved atmospheric carbon dioxide to weakly disrupt isotachophoretic preconcentration and induce separation of analyte species. We experimentally study the region between the leading and trailing electrolytes, and individually identify the carbonate and carbamate zones that result from the hydration and carbamation reaction of dissolved atmospheric carbon dioxide, respectively. The width of these zones and the gradient regions between them grow with time and create an electric field gradient that causes analytes to separate. Using this assay, we achieve focusing and separation of a 25 bp DNA ladder in a straight, 34 microm wide microchannel in a single loading step. As a demonstration of the fractionation capabilities of the assay, we show simultaneous preconcentration and separation of a DNA ladder from two proteins, GFP and allophycocyanin.

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“…The analysis of amino acids using ITP has been implemented using both transient ITP (tITP) for on-line preconcentration, and column ITP (cITP) using ad hoc ITP devices or standard capillary electrophoresis (CE) equipment [4,5]. tITP-CE analysis of amino acids has been implemented for on-line preconcentration in several studies involving sets of up to 11 different amino acids [6,7].…”

Section: Introductionmentioning

confidence: 99%

Non-aqueous electrolytes for isotachophoresis of weak bases and its application to the comprehensive preconcentration of the 20 proteinogenic amino acids in column-coupling ITP/CE–MS

Kler

Hühn

2014

Anal Bioanal Chem

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Isotachophoresis (ITP) has long been used alone but also as a preconcentration technique for capillary electrophoresis (CE). Unfortunately, up to now, its application is restricted to relatively strong acids and bases as either the degree of (de)protonation is too low or the water dissociation is too high, evoking zone electrophoresis. With the comprehensive ITP analysis of all 20 proteinogenic amino acids as model analytes, we, here, show that non-aqueous ITP using dimethylsulfoxide as a solvent solves this ITP shortcoming. Dimethylsulfoxide changes the pH regime of analytes and electrolytes but, more importantly, strongly reduces the proton mobility by prohibiting hydrogen bonds and thus, the so-called Zundel-Eigen-Zundel electrical conduction mechanism of flipping hydrogen bonds. The effects are demonstrated in an electrolyte system with taurine or H(+) as terminator, and imidazole as leader together with strong acids such as oxalic and even trifluoroacetic acid as counterions, both impossible to use in aqueous solution. Mass spectrometric as well as capacitively coupled contactless conductivity detection (C(4)D) are used to follow the ITP processes. To demonstrate the preconcentration capabilities of ITP in a two-dimensional set-up, we, here, also demonstrate that our non-aqueous ITP method can be combined with capillary electrophoresis-mass spectrometry in a column-coupling system using a hybrid approach of capillaries coupled to a microfluidic interface. For this, C(4)D was optimized for on-chip detection with the electrodes aligned on top of a thin glass lid of the microfluidic chip.

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The analysis of amino acids and peptides by isotachophoresis

Cited by 19 publications

References 17 publications

Basic principles of electrolyte chemistry for microfluidic electrokinetics. Part I: Acid–base equilibria and pH buffers

Basic principles of electrolyte chemistry for microfluidic electrokinetics. Part I: Acid–base equilibria and pH buffers

Effects of carbon dioxide on peak mode isotachophoresis: Simultaneous preconcentration and separation

Non-aqueous electrolytes for isotachophoresis of weak bases and its application to the comprehensive preconcentration of the 20 proteinogenic amino acids in column-coupling ITP/CE–MS

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