Formamide as an organic modifier in MEKC with SDS

Téllez, A S Claudio; Kenndler, Ernst

doi:10.1002/elps.200800329

Cited by 9 publications

(5 citation statements)

References 23 publications

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“…Values of the cmc for NR 4 + DS – in buffered solutions have not been reported. We determined these values for Na + DS – and NR 4 + DS – in Tris-Gly buffer with established methods using fluorescent probes (pyrene and 8-anilinonapthalenesulfonate) − or UV-absorbing probes (e.g., 2-naphthalenecarbinol) in CE experiments. , CE was also useful for characterizing the electrophoretic mobility of micelles of Na + DS – and NR 4 + DS – . The method used to analyze the partitioning of UV-absorbing probes into micelles is described in the Supporting Information.…”

Section: Experimental Designmentioning

confidence: 99%

Denaturation of Proteins by SDS and Tetraalkylammonium Dodecyl Sulfates

et al. 2011

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This paper describes the use of capillary electrophoresis (CE) to examine the influence of different cations (C+; C+ = Na+ and tetra-n-alkylammonium, NR4 +, where R = Me, Et, Pr, Bu) on the rates of denaturation of bovine carbonic anhydrase II (BCA) in the presence of the anionic surfactant dodecylsulfate (DS−). Analysis of the denaturation of BCA in solutions of Na+DS− and NR4 +DS− (in Tris-Gly buffer) indicated that the rates of formation of complexes of denatured BCA with DS− (BCAD-DS−n,sat) are indistinguishable and independent of the cation below the critical micellar concentration (cmc), and independent of the total concentration of DS− above the cmc. At concentrations of C+DS− above the cmc, BCA denatured with rates that depended on the cation; the rates decreased by a factor > 104, in the order Na+ ~ NMe4 + > NEt4 + > NPr4 + > NBu4 + – the same order as the values of cmc (which decrease from 4.0 mM for Na+DS− to 0.9 mM for NBu4 +DS− in Tris-Gly buffer). The relationship between values of cmc and rates of formation of BCAD-DS−n,sat suggested that the kinetics of denaturation of BCA involve the association of this protein with monomeric DS−, rather than with micelles of (C+DS−)n. A less-detailed survey of seven other proteins (α-lactalbumin, β-lactoglobulin A, β-lactoglobulin B, carboxypeptidase B, creatine phosphokinase, myoglobin, and ubiquitin) showed that the difference between Na+DS− and NR4 +DS− observed with BCA was not general. Instead, the influence of NR4 + on the association of DS− with these proteins depended on the protein. The selection of cation contributed to the properties (including composition, electrophoretic mobility, and partitioning behavior in aqueous two-phase systems) of aggregates of denatured protein and DS−. These results suggest that variation in the behavior of NR4 +DS− with changes in R may be exploited in methods for analyzing and separating mixtures of proteins.

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Section: Experimental Designmentioning

confidence: 99%

Denaturation of Proteins by SDS and Tetraalkylammonium Dodecyl Sulfates

et al. 2011

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“…It is important to point out that this restriction on the SDS concentration, although may be undesirable, is not as debilitating as it may seem. Several MCE separations of practical interest, for example, have been realized with buffers containing this surfactant at 10 mM concentration or lower levels. − Moreover, it is possible to apply the reported approach toward analyzing liquid samples prepared in matrices with higher SDS concentrations by simply diluting the specimens to bring down the surfactant level in them below the 10 mM mark. Although this strategy would somewhat compromise the detectability of the analytes, the overall detection limit for the assay is expected to be still substantially better than that realized without employing any SDS cleanup procedures.…”

Section: Discussionmentioning

confidence: 99%

Electrophoretic Extraction of Low Molecular Weight Cationic Analytes from Sodium Dodecyl Sulfate Containing Sample Matrices for Their Direct Electrospray Ionization Mass Spectrometry

2015

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While the use of sodium dodecyl sulfate (SDS) in separation buffers allows efficient analysis of complex mixtures, its presence in the sample matrix is known to severely interfere with the mass-spectrometric characterization of analyte molecules. In this article, we report a microfluidic device that addresses this analytical challenge by enabling inline electrospray ionization mass spectrometry (ESI-MS) of low molecular weight cationic samples prepared in SDS containing matrices. The functionality of this device relies on the continuous extraction of analyte molecules into an SDS-free solvent stream based on the free-flow zone electrophoresis (FFZE) technique prior to their ESI-MS analysis. The reported extraction was accomplished in our current work in a glass channel with microelectrodes fabricated along its sidewalls to realize the desired electric field. Our experiments show that a key challenge to successfully operating such a device is to suppress the electroosmotically driven fluid circulations generated in its extraction channel that otherwise tend to vigorously mix the liquid streams flowing through this duct. A new coating medium, N-(2-triethoxysilylpropyl) formamide, recently demonstrated by our laboratory to nearly eliminate electroosmotic flow in glass microchannels was employed to address this issue. Applying this surface modifier, we were able to efficiently extract two different peptides, human angiotensin I and MRFA, individually from an SDS containing matrix using the FFZE method and detect them at concentrations down to 3.7 and 6.3 µg/mL, respectively, in samples containing as much as 10 mM SDS. Notice that in addition to greatly reducing the amount of SDS entering the MS instrument, the reported approach allows rapid solvent exchange for facilitating efficient analyte ionization desired in ESI-MS analysis.

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“…Other classes of the organic modifiers can target the PSP through direct interaction with micelles (depression of the CMC and decreased micelle surface polarity) and were used at much lower concentrations than the former. In this context, Tellez and Kenndler 65 studied the effect of formamide, as an organic modifier, on the retention of a series of alkylphenones in SDS‐MEKC. As expected, the CMC of SDS decreased as organic modifier concentrations increased in electrolyte‐free formamide–water systems because the micelles were destabilized; however, in the presence of an electrolyte such as borate buffer (pH 9.23) with 50 mM ionic strength, the CMC increased and changes in the migration sequence of the analytes were observed.…”

Section: Approaches For Improving Resolutionmentioning

confidence: 99%

Micellar electrokinetic chromatography: A practical overview of current methodological and instrumental advances

Silva

2010

Electrophoresis

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This review highlights recent methodological and instrumental advances in MEKC focused on the improvement of this CE technique in routine analyses. As in the previous reviews, the present one deals with the last 2 years' most relevant methodological contributions for improving sensitivity and resolution in MEKC as well as instrumental research related to MS and LIF detection. The most widespread approaches are discussed in detail, including enhancements in sensitivity arising from the use of on-line sample concentration (stacking, sweeping, and a combination of both of these protocols) and improvements in resolution, obtained by changing the composition of the BGE (e.g. with additives to the aqueous phase or employing alternative micellar phases to classical SDS) and using 2-D separation systems. The advantages and restrictions in MS and LIF detection as applied to MEKC analysis are also examined, especially in the direct coupling of MEKC and MS detection. Finally, some thoughts on potential future directions are also considered.

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Formamide as an organic modifier in MEKC with SDS

Cited by 9 publications

References 23 publications

Denaturation of Proteins by SDS and Tetraalkylammonium Dodecyl Sulfates

Denaturation of Proteins by SDS and Tetraalkylammonium Dodecyl Sulfates

Electrophoretic Extraction of Low Molecular Weight Cationic Analytes from Sodium Dodecyl Sulfate Containing Sample Matrices for Their Direct Electrospray Ionization Mass Spectrometry

Micellar electrokinetic chromatography: A practical overview of current methodological and instrumental advances

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