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Springer, V., Jacksén, J., Ek, P., Lista, A. G. & Emmer, Å. (2015). Capillary Electrophoretic Determination of Fluoroquinolones in Bovine Milk Followed by Off-Line MALDI-TOF-MS Analysis. Chromatographia, 78(3-4), 285-290
Open this publication in new window or tab >>Capillary Electrophoretic Determination of Fluoroquinolones in Bovine Milk Followed by Off-Line MALDI-TOF-MS Analysis
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2015 (English)In: Chromatographia, ISSN 0009-5893, E-ISSN 1612-1112, Vol. 78, no 3-4, p. 285-290Article in journal (Refereed) Published
Abstract [en]

A novel appro ach for the determination of ciprofloxacin, norfloxacin and ofloxacin by capillary electrophoresis and off-line capillary electrophoresis-matrix-assisted laser desorption/ionization-time of flight-mass spectrometry coupling for the confirmation of analyte identities is presented. A polymer capillary coating was proposed with the aim to minimize suppression of the MS signal caused by the CE solution components. The fluoroquinolones were successfully separated and determined by CE-UV followed by fractionation onto a MALDI plate and off-line MS characterization. Full-cream and low-fat milk samples were used to illustrate that the proposed method represents an efficient alternative for fluoroquinolone antibiotics determination in milk.

Keywords
Capillary electrophoresis, Matrix-assisted laser desorption/ionization mass spectrometry, Fluoroquinolones, Off-line integration
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-161110 (URN)10.1007/s10337-014-2823-5 (DOI)000348976900016 ()2-s2.0-84925487438 (Scopus ID)
Note

QC 20150323

Available from: 2015-03-23 Created: 2015-03-09 Last updated: 2017-12-04Bibliographically approved
Rokhas, M. K., Mikkonen, S., Beyer, J., Jacksén, J. & Emmer, Å. (2014). CE analysis of single wood cells performing hydrolysis and preconcentration in open microchannels. Electrophoresis, 35(2-3), 450-457
Open this publication in new window or tab >>CE analysis of single wood cells performing hydrolysis and preconcentration in open microchannels
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2014 (English)In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 35, no 2-3, p. 450-457Article in journal (Refereed) Published
Abstract [en]

In the present work, monosaccharides from pulp samples and single wood fibers were analyzed with CE, using indirect detection due to the lack of chromophores on the monosaccharides. The hydrolysis degradation of cellulose and hemicellulose into monosaccharides was performed using TFA, either in bulk scale or in microscale. In the microscale, one single wood fiber was hydrolyzed in an open microchannel manufactured on a silicon microchip with the dimensions 50 μm × 50 μm (length 1 or 3 cm). The low monosaccharide amounts derived from a single fiber implied that a preconcentration step was necessary to increase the detectability. Thus, an electromigration preconcentration of the hydrolyzed samples was performed within the microchannel, which resulted in a significantly enhanced signal intensity of the monosaccharides. In addition to the experimental study, computer simulations were performed regarding the preconcentration step of monosaccharides. The results from these simulations correlated well with the experimental results.

Keywords
Capillary electrophoresis, Open microchannels, Preconcentration, Wood cells
National Category
Other Chemistry Topics Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:kth:diva-143085 (URN)10.1002/elps.201300408 (DOI)000331899400028 ()2-s2.0-84892478458 (Scopus ID)
Funder
Swedish Research Council, 621-2009-4095
Note

QC 20140317

Available from: 2014-03-17 Created: 2014-03-17 Last updated: 2017-12-05Bibliographically approved
Springer, V., Jacksén, J., Ek, P., Lista, A. G. & Emmer, Å. (2014). Determination of fluoroquinolones in bovine milk samples using a pipette-tip SPE step based on multiwalled carbon nanotubes prior to CE separation. Journal of Separation Science, 37(1-2), 158-164
Open this publication in new window or tab >>Determination of fluoroquinolones in bovine milk samples using a pipette-tip SPE step based on multiwalled carbon nanotubes prior to CE separation
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2014 (English)In: Journal of Separation Science, ISSN 1615-9306, E-ISSN 1615-9314, Vol. 37, no 1-2, p. 158-164Article in journal (Refereed) Published
Abstract [en]

A simple CE-UV method was developed for the simultaneous determination of ciprofloxacin, norfloxacin, and ofloxacin in milk samples. The optimum separation was obtained using a 20 mM ammonium dihydrogenphosphate solution with 2 mM cetyltrimethylammonium bromide at pH 3.0 as the BGE. Satisfactory resolution for structurally very similar analytes, like norfloxacin and ciprofloxacin, was achieved without including any organic solvent. Milk samples were prepared using a simple/extraction procedure based on acidic protein precipitation followed by an SPE step using only 5 mg of multiwalled carbon nanotubes as the sorbent material. The LODs for the three compounds were between 7.5 and 11.6 g/L and the RSDs for the peak areas were between 2.6 and 4.9%. The complete method was applied to spiked real milk samples with satisfactory recoveries for all analytes (84-106%).

Keywords
CE, Fluoroquinolones, Multiwalled carbon nanotubes, SPE
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:kth:diva-140664 (URN)10.1002/jssc.201300980 (DOI)000329478100023 ()
Note

QC 20140131

Available from: 2014-01-31 Created: 2014-01-30 Last updated: 2017-12-06Bibliographically approved
Mikkonen, S., Jacksén, J. & Emmer, Å. (2014). Mass spectrometric analysis of nanoscale sample volumes extracted from open microchannels after sample preconcentration applied on amyloid beta peptides. Analytical and Bioanalytical Chemistry, 406(14), 3521-3524
Open this publication in new window or tab >>Mass spectrometric analysis of nanoscale sample volumes extracted from open microchannels after sample preconcentration applied on amyloid beta peptides
2014 (English)In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 406, no 14, p. 3521-3524Article in journal (Refereed) Published
Abstract [en]

A new instrumental concept for extraction of nanovolumes from open microchannels (dimensions 150 mu m x 50 mu m, length 10 mm) manufactured on silicon microchips has been used in combination with a previously developed method for preconcentrating proteins and peptides in the open channels through electromigration. The extracted nanovolumes were further analyzed using nanoelectrospray ionization (nESI) or matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) directly or with subsequent enzymatic protein digestion in a nanodroplet prior to the MS analysis. Preconcentration of the samples resulted in a 15-fold sensitivity increase in nESI for a neurotensin solution, and using MALDI-MS, amyloid beta (A beta) peptides could be detected in concentrations down to 1 nM. The method was also successfully applied for detection of cell culture A beta.

Keywords
Mass spectrometry, Microchannel, Preconcentration, Amyloid beta, MALDI, Nano-ESI
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:kth:diva-147047 (URN)10.1007/s00216-014-7781-0 (DOI)000336261800030 ()2-s2.0-84901603229 (Scopus ID)
Funder
Swedish Research Council, 621-2009-4095
Note

QC 20140624

Available from: 2014-06-24 Created: 2014-06-23 Last updated: 2017-12-05Bibliographically approved
Hedberg, Y., Lundin, M., Jacksén, J., Emmer, Å., Blomberg, E. & Wallinder, I. O. (2012). Chromium-protein complexation studies by adsorptive cathodic stripping voltammetry and MALDI-TOF-MS. Journal of Applied Electrochemistry, 42(5), 349-358
Open this publication in new window or tab >>Chromium-protein complexation studies by adsorptive cathodic stripping voltammetry and MALDI-TOF-MS
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2012 (English)In: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 42, no 5, p. 349-358Article in journal (Refereed) Published
Abstract [en]

A methodology using stripping voltammetry has been elaborated to enable sensitive and reliable protein-chromium complexation measurements. Disturbing effects caused by adsorption of proteins on the mercury electrode were addressed. At low concentrations of proteins (< 60-85 nM), chromium-protein complexation measurements were possible. Chromium(VI) complexation was quantitatively determined using differently sized, charged, and structured proteins: serum albumin (human and bovine), lysozyme, and mucin. Generated results showed a strong relation between complexation and protein size, concentration, and the number of amino acids per protein mass. Complexation increased nonlinearly with increasing protein concentrations. The nature of this complexation was based on weak interactions judged from combined results with MALDI-TOF-MS and adsorptive cathodic stripping voltammetry.

Keywords
Chromium, Complexation, Lysozyme, Serum albumin, Mucin, Stripping voltammetry
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-93903 (URN)10.1007/s10800-012-0404-6 (DOI)000302410900009 ()
Funder
Swedish Research Council
Note
QC 20120504Available from: 2012-05-04 Created: 2012-05-03 Last updated: 2017-12-07Bibliographically approved
Jacksén, J. & Emmer, Å. (2012). Evaluation of 2,6-dihydroxyacetophenone as matrix-assisted laser desorption/ionization matrix for analysis of hydrophobic proteins and peptides. Analytical Biochemistry, 425(1), 18-20
Open this publication in new window or tab >>Evaluation of 2,6-dihydroxyacetophenone as matrix-assisted laser desorption/ionization matrix for analysis of hydrophobic proteins and peptides
2012 (English)In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 425, no 1, p. 18-20Article in journal (Refereed) Published
Abstract [en]

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is widely used for analysis of macromolecules like peptides and proteins. The analysis procedure is generally simple but must be adapted to the characteristics of the analytes. Therefore, specific matrices suitable for, e.g., hydrophobic proteins and peptides that are difficult to analyze would be preferable in order to optimize the outcome. In the present work, 2,6-dihydroxyacetophenone (DHAP) was shown to be beneficial in comparison to DHB for intact bacteriorhodopsin (BR) as well as for chemically digested BR.

Keywords
DHAP, Hydrophobic protein/peptides, MALDI-MS, Matrix
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:kth:diva-96183 (URN)10.1016/j.ab.2012.02.039 (DOI)000303950100004 ()2-s2.0-84859323545 (Scopus ID)
Funder
Swedish Research Council, 621-2009-4095
Note
QC 20120531Available from: 2012-05-31 Created: 2012-05-31 Last updated: 2017-12-07Bibliographically approved
Mikkonen, S., Rokhas, M. K., Jacksén, J. & Emmer, Å. (2012). Sample preconcentration in open microchannels combined with MALDI-MS. Electrophoresis, 33(22), 3343-3350
Open this publication in new window or tab >>Sample preconcentration in open microchannels combined with MALDI-MS
2012 (English)In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 33, no 22, p. 3343-3350Article in journal (Refereed) Published
Abstract [en]

In this work, a method for preconcentrating samples in 1 cm long, 50-150 μm wide open microchannels is presented. Platinum electrodes were positioned at the channel ends, voltage was applied, and charged analyte was preconcentrated at the oppositely charged side during continuous supply of sample. The preconcentration was initially studied in a closed system, where an influence on the analyte position from a pH gradient, generated by water electrolysis, was observed. In the open channel, the analyte distribution after preconcentration was evaluated using MALDI-MS with the channel as MALDI target. MALDI matrix was applied with an airbrush or by electrospray matrix deposition and by using the latter technique higher degrees of crystallization in the channels were obtained. After preconcentrating a 1 nM cytochrome c solution for 5 min, corresponding to a supplied amount of 1.25 fmol, a signal on the cathodic channel end could be detected. When a solution of cytochrome c trypsin digest was supplied, the peptides were preconcentrated at different positions along the channel depending on their charge.

Keywords
Electrospray deposition, MALDI-MS, Preconcentration, Silicon microchip
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:kth:diva-108041 (URN)10.1002/elps.201200129 (DOI)000311303100013 ()2-s2.0-84869782576 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20121220

Available from: 2012-12-20 Created: 2012-12-19 Last updated: 2017-12-06Bibliographically approved
Jacksén, J. (2011). Improved techniques for CE and MALDI-MS including microfluidic hyphenations foranalysis of biomolecules. (Doctoral dissertation). Stockholm: KTH
Open this publication in new window or tab >>Improved techniques for CE and MALDI-MS including microfluidic hyphenations foranalysis of biomolecules
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, improved techniques for biomolecule analysis using capillary electrophoresis (CE) and matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) and hyphenations between those have been presented.A pre-concentration method which is possible to apply in both techniques, has also been investigated.

In this work the off-line MS mode has been used either in the form of fractionation (Paper I) or by incorporating the MALDI target in the CE separation system (Paper II).In Paper I, a protocol for CE-MALDI analysis of cyanogen bromide digested bacteriorhodopsin (BR) peptides as model integral membrane protein peptides were established. Also, an improved protocol for partially automated manufacturing of a concentration MALDI-target plate is presented. The design of the targets was suitable for the fractions from the CE.

A novel technique for the integration of CE to MALDI-MS using a closed-open-closed system is presented in Paper II, where the open part is a micro canal functioning as a MALDI target window. A protein separation was obtained and detected with MALDI-MS analysis in the micro canal.

A method has been developed for detection of monosaccharides originating from hydrolysis of a single wood fiber performed in a micro channel, with an incorporated electromigration pre-concentration step preceding CE analysis in Paper III. The pre-concentration showed to be highly complex due to the fact that several parameters are included that affecting each other.

In Paper IV a protocol using enzymatic digestion, MALDI-TOF-MS and CE with laser induced fluorescence (LIF) detection for the investigation of the degree of substitution of fluorescein isothiocyanate (FITC) to bovine serum albumin (BSA), as a contact allergen model system for protein-hapten binding in the skin, is presented. The intention of a further CE-MALDI hyphenation has been considered during the work.

In Paper V 2,6-dihydroxyacetophenone (DHAP) was investigated, showing promising MALDI-MS matrix properties for hydrophobic proteins and peptides. 2,5-dihydroxybenzoic acid (DHB) was undoubtedly the better matrix for the hydrophilic proteins, but its performance for the larger and hydrophobic peptides was not optimal. Consequently, DHAP can be used as a compliment matrix for improved analysis of hydrophobic analytes.

Place, publisher, year, edition, pages
Stockholm: KTH, 2011. p. Xii, 85
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2011.1
Keywords
Capillary electrophoresis, Hydrophobic peptides/proteins, Matrix-Assisted Laser Desorption Ionization Mass Spectrometry, Prestructured target, Off-line interface, Silicon micro canal, Matrix, Peptide-fluorescein isothiocyanate adducts, Bovine serum albumin, DHAP, Hyphenations, Hydrophobicity, Single wood fiber analysis, Pre-concentration, Concentration platform
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:kth:diva-27342 (URN)978-91-7415-808-3 (ISBN)
Public defence
2011-01-21, F3, Lindstedtsvägen 26, Stockholm, 10:00 (Swedish)
Opponent
Supervisors
Note
QC 20101214Available from: 2010-12-14 Created: 2010-12-10 Last updated: 2011-02-02Bibliographically approved
Jacksén, J., Dahl, K., Karlberg, A.-T., Redeby, T. & Emmer, Å. (2010). Capillary electrophoresis separation and matrix-assisted laser desorption/ionization mass spectrometry characterization of bovine serum albumin fluorescein isothiocyanate conjugates. Journal of chromatography. B, 878(15-16), 1125-1134
Open this publication in new window or tab >>Capillary electrophoresis separation and matrix-assisted laser desorption/ionization mass spectrometry characterization of bovine serum albumin fluorescein isothiocyanate conjugates
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2010 (English)In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 878, no 15-16, p. 1125-1134Article in journal (Refereed) Published
Abstract [en]

A protocol using enzymatic digestion, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and capillary electrophoresis with laser induced fluorescence detection (CE-LIF) for the investigation of the binding of the fluorescent contact allergen fluorescein isothiocyanate (FITC) to the 66 kDa large protein bovine serum albumin (BSA), as a model system for protein-hapten binding in the skin, is presented. Mass spectra of BSA-FITC digestions, using trypsin and chymotrypsin, respectively, provided sequence coverage of 97%. To investigate the number of FITC-bound peptides using CE-LIF separation, three different buffer salts at four different pH levels were evaluated. The use of 20 mM sodium citrate pH 6.5 as well as 20 mM sodium phosphate pH 6.5 or pH 7.5 as background electrolyte revealed high numbers of peptides with at least one bound FITC. The effect of the electrolyte counter ion on MALDI-MS was investigated and was found to have effect on the MALDI spectra signal-to-noise (S/N) at 50 mM but not at 10 m M. Of the 60 theoretical FITC-binding sites in BSA this MALDI-MS protocol presents 30 defined. 28 possible and 2 non-binding sites for FITC. (C) 2010 Elsevier B.V. All rights reserved.

Keywords
Capillary electrophoresis, MALDI-TOF-MS, Contact allergy, Peptide-fluorescein isothiocyanate adducts, Bovine serum albumin
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:kth:diva-27396 (URN)10.1016/j.jchromb.2010.03.024 (DOI)000277672000014 ()
Note
QC 20101213Available from: 2010-12-13 Created: 2010-12-13 Last updated: 2017-12-11Bibliographically approved
Ek, P., Schönberg, T., Sjödahl, J., Jacksén, J., Vieider, C., Emmer, Å. & Roeraade, J. (2009). Electrospray Ionization from an Adjustable Gap between two Silicon Chips. Journal of Mass Spectrometry, 44(2), 171-181
Open this publication in new window or tab >>Electrospray Ionization from an Adjustable Gap between two Silicon Chips
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2009 (English)In: Journal of Mass Spectrometry, ISSN 1076-5174, E-ISSN 1096-9888, Vol. 44, no 2, p. 171-181Article in journal (Refereed) Published
Abstract [en]

In this paper, a silicon chip - based electrospray emitter with a variable orifice size is presented. The device consists of two chips, with a thin beam elevating from the center of each of the chips. The chips are individually mounted to form an open gap of a narrow, uniform width between the top areas of the beams. The electrospray is generated at the endpoint of the gap, where the spray point is formed by the very sharp intersection between the crystal planes of the < 100 > silicon chips. Sample solution is applied to the rear end of the gap from a capillary via a liquid bridge, and capillary forces ensure a spontaneous imbibition of the gap. The sample solution is confined to the gap by means of a hydrophobic treatment of the surfaces surrounding the gap, as well as the geometrical boundaries formed by the edges of the gap walls. The gap width could be adjusted between 1 and 25 μm during electrospray experiments without suffering from any interruption of the electrospray process. Using a peptide sample solution, a shift toward higher charge states and increased signal-to-noise ratios was observed when the gap width was decreased. The limit of detection for the peptide insulin (chain B, oxidized) was approximately 4 nM. We also show a successful interfacing of the electrospray setup with capillary electrophoresis.

Keywords
Adjustable gap, Chip, Electrospray ionization, Emitter, Mass spectrometry, Nozzle
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:kth:diva-8438 (URN)10.1002/jms.1478 (DOI)000264013300002 ()18946877 (PubMedID)2-s2.0-59949093565 (Scopus ID)
Note
QC 20100913. Uppdaterad från Manuskript till Artikel (20100913)Available from: 2008-05-13 Created: 2008-05-13 Last updated: 2017-12-14Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-3548-217X

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