| 1. |
- Ek, Patrik, et al.
(författare)
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Electrospray Ionization from an Adjustable Gap between two Silicon Chips
- 2009
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 44:2, s. 171-181
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Hartmann, Michael, et al.
(författare)
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Non-contact protein microarray fabrication using a procedure based on liquid bridge formation
- 2009
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 393:2, s. 591-598
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Tidskriftsartikel (refereegranskat)abstract
- Contemporary microarrayers of contact or noncontact format used in protein microarray fabrication still suffer from a number of problems, e. g. generation of satellite spots, inhomogeneous spots, misplaced or even absent spots, and sample carryover. In this paper, a new concept of non-contact sample deposition that reduces such problems is introduced. To show the potential and robustness of this pressure-assisted deposition technique, different sample solutions known to cause severe problems or to be even impossible to print with conventional microarrayers were accurately printed. The samples included 200 mg mL(-1) human serum albumin, highly concentrated sticky cell adhesion proteins, pure high-salt cell-lysis buffer, pure DMSO, and a suspension of 5-mu m polystyrene beads. Additionally, a water-immiscible liquid fluorocarbon, which was shown not to affect the functionality of the capture molecules, was employed as a lid to reduce evaporation during microarray printing. The fluorocarbon liquid lid was shown to circumvent hydrolysis of water-sensitive activated surfaces during long-term deposition procedures.
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| 3. |
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| 4. |
- Bonn, Jonas, et al.
(författare)
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Electrostatic Sample Nebulization for Improved Sample Vaporization in the Split/Splitless Gas Chromatography Inlet
- 2009
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 81:13, s. 5327-5332
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Tidskriftsartikel (refereegranskat)abstract
- The split/splitless inlet system has basically the same fundamental drawbacks it had when it was introduced: poor repeatability of the injected amount of sample and discrimination of high-boiling analytes. Hot needle injection improves the repeatability of the sample transfer but suffers from in-needle discrimination. Injection with a fast autosampler, resulting in minimal heating of the needle, solves this problem but usually requires a glass wool packing in the inlet liner to assist in vaporization of the sample. As glass wool has been reported to cause degradation of labile analytes, it cannot be applied as a general remedy for improving incomplete vaporization. In this paper, a novel concept, based on electrostatic nebulization of the injected sample, is presented. The resulting fine droplets promote a more effective heat transfer and a rapid vaporization. Evaluation of the electrospray inlet in the split mode, using a straight, empty glass liner and a cold needle, showed an improvement in peak area repeatability by about 1 order of magnitude, compared with the results obtained when no electrostatic field was applied, Splitless injection of a series of hydrocarbons up to C-28 in the electrospray inlet with an empty, tapered liner, using a cold needle, showed no measurable analyte discrimination. The relative standard deviation in terms of area count for the largest hydrocarbon (C-28) was < 1.5%, compared to similar to 30% for injections where no high voltage was applied.
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| 5. |
- Bonn, Jonas, et al.
(författare)
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Mixed sorbent phases for thick film open tubular traps
- 2009
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Ingår i: Journal of Chromatographic Science. - : Oxford University Press (OUP). - 0021-9665 .- 1945-239X. ; 47:4, s. 297-303
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we present a technique for the preparation of tailor-made sorbent phases for thick film open tubular traps. Solid or liquid polymers are dispersed in a polydimethylsiloxane (PDMS) pre-polymer, which is cross-linked in situ after coating. The technique is evaluated by preparing thick film open tubular traps with PDMS containing solid or liquid poly(ethylene glycol) (PEG). A significant increase in retention for polar analytes is observed, even when only 7.5% PEG is present. The increase in retention for 3-chloro-1,2-propanediol is more than tenfold. The preparation method is simple and no solvents are required. Also, the concept provides great flexibility in terms of phase composition.
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| 6. |
- Chilo, José, 1960-, et al.
(författare)
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A flexible electronic nose for odor discrimination using different methods of classification
- 2009
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Ingår i: 2009 16th IEEE-NPSS Real Time Conference - Conference Record. - New York : IEEE. - 9781424444557 ; , s. 317-320, s. 317-320
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Konferensbidrag (refereegranskat)abstract
- Ovarian cancer is one of the leading causes of death from cancer in women. The lifetime risk is around 1.5%, which makes it the second most common gynecologic malignancy (the first one being breast cancer). To have a definitive diagnose, a surgical procedure is generally required and suspicious areas (samples) will be removed and sent for microscopic and other analysis. This paper describes the result of a pilot study in which an electronic nose is used to "smell" the aforementioned samples, analyze the multi-sensor signals and have a close to real-time answer on the detection of cancer. Besides being fast, the detection method is inexpensive and simple. Experimental analysis using real ovarian carcinoma samples shows that the use of proper algorithms for analysis of the multi-sensor data from the electronic nose yielded surprisingly good results with more than 77% classification rate. The electronic nose used in this pilot study was originally developed to be used as a "bomb dog" and can distinguish between e.g. TNT, Dynamex, Prillit. However, it was constructed to be a flexible multi-sensor device and the individual (16) sensors can easily be replaced/exchanged. This is suggestive for further investigations to obtain even better results with new, specific sensors. In another pilot experiment, headspace of an ovarian carcinoma sample and a control sample were analyzed using gas chromatography-mass spectrometry. Significant differences in chemical composition and compound levels were recorded, which would explain the different response obtained with the electronic nose.
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| 7. |
- Ek, Patrik, et al.
(författare)
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Electrospray Ionization from a Gap with Adjustable Width
- 2006
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Ingår i: Rapid Communications in Mass Spectrometry. - : Wiley. - 0951-4198 .- 1097-0231. ; 20:21, s. 3176-3182
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present a new concept for electrospray ionization mass spectrometry, where the sample is applied in a gap which is formed between the edges of two triangular-shaped tips. The size of the spray orifice can be changed by varying the gap width. The tips were fabricated from polyethylene terephthalate film with a thickness of 36 μm. To improve the wetting of the gap and sample confinement, the edges of the tips forming the gap were hydrophilized by means of silicon dioxide deposition. Electrospray was performed with gap widths between 1 and 36 μm and flow rates down to 75 nL/min. The gap width could be adjusted in situ during the mass spectrometry experiments and nozzle clogging could be managed by simply widening the gap. Using angiotensin I as analyte, the signal-to-noise ratio increased as the gap width was decreased, and a shift towards higher charge states was observed. The detection limit for angiotensin I was in the low nM range.
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| 8. |
- Hamberg, Anders, et al.
(författare)
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C-terminal ladder sequencing of peptides using an alternative nucleophile in carboxypeptidase Y digests
- 2006
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Ingår i: Analytical Biochemistry. - : Elsevier BV. - 0003-2697 .- 1096-0309. ; 357:2, s. 167-172
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Tidskriftsartikel (refereegranskat)abstract
- A method for improved sequence coverage in C-terminal sequencing of peptides, based on carboxypeptidase digestion, is described. In conventional carboxypeptidase digestions, the peptide substrate is usually extensively degraded and a full amino acid sequence cannot be obtained due to the lack of a complete peptide ladder. In the presented method, a protecting group is introduced at the C terminus of a fraction of the peptide fragments formed in the digest, and thereby further degradation of the C-terminally modified peptides are slowed down. The protecting group was attached to the C-terminal amino acid through a carboxypeptidase-catalyzed reaction with an alternative nucleophile, 2-pyridylmethylamine, added to the aqueous digestion buffer. Six peptides were digested by carboxypeptidase Y with and without 2-pyridylmethylamine present in the digest buffer, and the resulting fragments subsequently were analyzed with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Comparison of the two digestion methods showed that the probability of successful ladder sequencing increased, by more than 50% using 2-pyridylmethylamine as a competing nucleophile in carboxypeptidase Y digests.
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| 9. |
- Kempka, Martin, et al.
(författare)
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Improved method for peak picking in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry
- 2004
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Ingår i: Rapid Communications in Mass Spectrometry. - : Wiley. - 0951-4198 .- 1097-0231. ; 18:11, s. 1208-1212
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Tidskriftsartikel (refereegranskat)abstract
- A method for peak picking for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) is described. The method is based on the assumption that two sets of ions are formed during the ionization stage, which have Gaussian distributions but different velocity profiles. This gives rise to a certain degree of peak skewness. Our algorithm deconvolutes the peak and utilizes the fast velocity, bulk ion distribution for peak picking. Evaluation of the performance of the new method was conducted using peptide peaks from a bovine serum albumin (BSA) digest, and compared with the commercial peak-picking algorithms Centroid and SNAP. When using the new two-Gaussian algorithm, for strong signals the mass accuracy was equal to or marginally better than the results obtained from the commercial algorithms. However, for weak, distorted peaks, considerable improvement in both mass accuracy and precision was obtained. This improvement should be particularly useful in proteomics, where a lack of signal strength is often encountered when dealing with weakly expressed proteins. Finally, since the new peak-picking method uses information from the entire signal, no adjustments of parameters related to peak height have to be made, which simplifies its practical use.
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| 10. |
- Kloskowski, Adam, et al.
(författare)
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Thick film traps with an irregular film : Preparation and evaluation
- 2004
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1035:2, s. 159-165
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Tidskriftsartikel (refereegranskat)abstract
- A new method for preparation of sorbent-based ultra-thick film traps for concentration of trace volatile components from gaseous matrices is described. The procedure is based on blowing a prepolymer (polydimethylsiloxane) through a capillary tube, forming an irregular film of stationary phase. Subsequently, the prepolymer is immobilized in a few seconds by heating to 200 °C. Evaluation of the performance of the new traps showed that the loss of efficiency, compared to regular smooth film traps is only on the order of 20–30%. In terms of breakthrough volume, this loss in performance is rather insignificant. The technology is extremely simple and allows a rapid and cheap production of a large number of ultra-thick film traps, even in non-specialized laboratories. The method can be applied to any type of cross-linkable stationary phase, thereby expanding the scope of sorbent-based trapping and preconcentration concept. Many applications are anticipated in trace and ultra-trace analysis in a wide range of fields, such as environmental chemistry, polymers, food and process analysis.
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