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171.
Nikolaos Pahimanolis Ulla Hippi Leena-Sisko Johansson Tapio Saarinen Nikolay Houbenov Janne Ruokolainen Jukka Seppälä 《Cellulose (London, England)》2011,18(5):1201-1212
In the present work, amino functionalized nanofibrillated cellulose (NFC) was prepared using click-chemistry in aqueous reaction
conditions. First, reactive azide groups were introduced on the surface of NFC by the etherification of 1-azido-2,3-epoxypropane
in alkaline water/isopropanol-mixture at ambient temperature. Then the azide groups were reacted with propargyl amine utilizing
copper catalyzed azide-alkyne cycloaddition (CuAAC), leading to pH-responsive 1,2,3-triazole-4-methanamine decorated NFC.
The reaction products were characterized using Fourier transform infrared spectroscopy, elemental analysis and X-ray photoelectron
spectroscopy. The presence of the attached azide groups was also confirmed by reacting them with 5-(dimethylamino)-N-(2-propyl)-1-naphthalenesulfonamide
by CuAAC, yielding highly fluorescent NFC. In addition, atom force microscopy and rheology studies confirmed that the original
NFC nanostructure was maintained during the synthesis. 相似文献
172.
We consider a smooth Riemannian metric tensor g on \({\mathbb{R}^n}\) and study the stochastic wave equation for the Laplace-Beltrami operator \({\partial_t^2 u - \Delta_g u = F}\) . Here, F = F(t, x, ω) is a random source that has white noise distribution supported on the boundary of some smooth compact domain \({M \subset \mathbb{R}^n}\) . We study the following formally posed inverse problem with only one measurement. Suppose that g is known only outside of a compact subset of M int and that a solution \({u(t, x, \omega_0)}\) is produced by a single realization of the source \({F(t, x, \omega_0)}\) . We ask what information regarding g can be recovered by measuring \({u(t, x, \omega_0)}\) on \({\mathbb{R}_+ \times \partial M}\) ? We prove that such measurement together with the realization of the source determine the scattering relation of the Riemannian manifold (M, g) with probability one. That is, for all geodesics passing through M, the travel times together with the entering and exit points and directions are determined. In particular, if (M, g) is a simple Riemannian manifold and g is conformally Euclidian in M, the measurement determines the metric g in M. 相似文献
173.
Pedersen CS Lauritsen FR Sysoev A Viitanen AK Mäkelä JM Adamov A Laakia J Mauriala T Kotiaho T 《Journal of the American Society for Mass Spectrometry》2008,19(9):1361-1366
Ionized acetates were used as model compounds to describe gas-phase behavior of oxygen containing compounds with respect to their formation of dimers in ion mobility spectrometry (IMS). The ions were created using corona discharge at atmospheric pressure and separated in a drift tube before analysis of the ions by mass spectrometry. At the ambient operational temperature and pressure used in our instrument, all acetates studied formed dimers. Using a homolog series of n-alkyl-acetates, we found that the collision cross section of a dimer was smaller than that of a monomer with the same reduced mass. Our experiments also showed that the reduced mobility of acetate dimers with different functional groups increased in the order n-alkyl = branched chain alkyl = cyclo alkyl < aromat. For mixed n-alkyl dimers we found that the reduced mobility of acetate dimers having the same number of carbons, for example a dimer of acetyl acetate and hexyl acetate has the same reduced mobility as a dimer composed of two butyl acetates. The fundamental behavior of acetate monomers and dimers described in this paper will assist in a better understanding of the influence of dimer formation in ion mobility spectrometry. 相似文献
174.
Ari Lehmusvuori Ulla KarhunenAntti-Heikki Tapio Urpo LamminmäkiTero Soukka 《Analytica chimica acta》2012
We introduce a switchable lanthanide luminescence reporter technology based closed-tube PCR for the detection of specific target DNA sequence. In the switchable lanthanide chelate complementation based reporter technology hybridization of two nonfluorescent oligonucleotide probes to the adjacent positions of the complementary strand leads to the formation of a highly fluorescent lanthanide chelate complex. The complex is self-assembled from a nonfluorescent lanthanide chelate and a light-harvesting antenna ligand when the reporter molecules are brought into close proximity by the oligonucleotide probes. Outstanding signal-to-background discrimination in real-time PCR assay was achieved due to the very low background fluorescence level and high specific signal generation. High sensitivity of the reporter technology allows the detection of a lower concentration of amplified DNA in the real-time PCR, resulting in detection of the target at the earlier amplification cycle compared to commonly used methods. 相似文献
175.
Kauppila TJ Talaty N Jackson AU Kotiaho T Kostiainen R Cooks RG 《Chemical communications (Cambridge, England)》2008,(23):2674-2676
Desorption electrospray ionization mass spectrometry (DESI-MS) is applied to the analysis of carbohydrates and steroids; the detection limits are significantly improved by the addition of low concentrations of salts to the spray solvent. 相似文献
176.
Laura Luosujärvi Markus Haapala Mario Thevis Ville Saarela Sami Franssila Raimo A. Ketola Risto Kostiainen Tapio Kotiaho 《Journal of the American Society for Mass Spectrometry》2010,21(2):310-316
A gas chromatography-microchip atmospheric pressure photoionization-mass spectrometric (GC-μAPPI-MS) method was developed and used for the analysis of three 2-quinolinone-derived selective androgen receptor modulators
(SARMs). SARMs were analyzed from spiked urine samples, which were hydrolyzed and derivatized with N-methyl-N-(trimethylsilyl)trifluoroacetamide before analysis. Trimethylsilyl derivatives of SARMs formed both radical cations (M+•) and protonated molecules ([M + H]+) in photoionization. Better signal-to-noise ratios (S/N) were obtained in MS/MS analysis using the M+• ions as precursor ions than using the [M + H]+ ions, and therefore the M+• ions were selected for the precursor ions in selected reaction monitoring (SRM) analysis. Limits of detection (LODs) with
the method ranged from 0.01 to 1 ng/mL, which correspond to instrumental LODs of 0.2–20 pg. Limits of quantitation ranged
from 0.03 to 3 ng/mL. The mass spectrometric response to the analytes was linear (R ≥ 0.995) from the LOQ concentration level
up to 100 ng/mL concentration, and intra-day repeatabilities were 5%–9%. In addition to the GC-μAPPI-MS study, the proof-of-principle of gas chromatography-microchip atmospheric pressure chemical ionization-Orbitrap MS
(GC-μAPCI-Orbitrap MS) was demonstrated. 相似文献
177.
Niina M. Suni Henni Aalto Tiina J. Kauppila Tapio Kotiaho Risto Kostiainen 《Journal of mass spectrometry : JMS》2012,47(5):611-619
In this article, the effect of spray solvent on the analysis of selected lipids including fatty acids, fat‐soluble vitamins, triacylglycerols, steroids, phospholipids, and sphingolipids has been studied by two different ambient mass spectrometry (MS) methods, desorption electrospray ionization‐MS (DESI‐MS) and desorption atmospheric pressure photoionization‐MS (DAPPI‐MS). The ionization of the lipids with DESI and DAPPI was strongly dependent on the spray solvent. In most cases, the lipids were detected as protonated or deprotonated molecules; however, other ions were also formed, such as adduct ions (in DESI), [M‐H]+ ions (in DESI and DAPPI), radical ions (in DAPPI), and abundant oxidation products (in DESI and DAPPI). DAPPI provided efficient desorption and ionization for neutral and less polar as well as for ionic lipids but caused extensive fragmentation for larger and more labile compounds because of a thermal desorption process. DESI was more suitable for the analysis of the large and labile lipids, but the ionization efficiency for less polar lipids was poor. Both methods were successfully applied to the direct analysis of lipids from pharmaceutical and food products. Although DESI and DAPPI provide efficient analysis of lipids, the multiple and largely unpredictable ionization reactions may set challenges for routine lipid analysis with these methods. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
178.
Jaroslav Pól Tiina J. Kauppila Sami Franssila Tapio Kotiaho Risto Kostiainen 《Rapid communications in mass spectrometry : RCM》2010,24(17):2584-2590
An ionspray microchip is introduced. The chip is based on the earlier presented nebulizer microchip that consists of glass and silicon plates bonded together. A liquid inlet channel, nebulizer gas inlet, and nozzle are etched on the silicon plate and a platinum heater is integrated on the glass plate. The nebulizer microchip has been previously used in atmospheric pressure chemical ionization, atmospheric pressure photoionization, sonic spray ionization, and thermospray ionization modes. In this work we show that the microchip can be operated also in ionspray mode by introducing high voltage to the silicon plate of the microchip. The effects of operation parameters (voltage, nebulizer gas pressure, sample solution flow rate, solvent composition, and analyte concentration) on the performance of the ion spray microchip were studied. Under optimized conditions the microchip provides efficient ionization of small and large compounds and good quantitative performance. The feasibility of the ion spray microchip in liquid chromatography/mass spectrometry (LC/MS) was demonstrated by the analysis of tryptic peptides of bovine serum albumin. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
179.
Linda L. Ahonen Markus Haapala Ville Saarela Sami Franssila Tapio Kotiaho Risto Kostiainen 《Rapid communications in mass spectrometry : RCM》2010,24(7):958-964
We examined the feasibility of capillary liquid chromatography/microchip atmospheric pressure photoionization tandem mass spectrometry (capLC/µAPPI‐MS/MS) for the analysis of anabolic steroids in human urine. The urine samples were pretreated by enzymatic hydrolysis (with β‐glucuronidase from Helix pomatia), and the compounds were liquid‐liquid extracted with diethyl ether. After separation the compounds were vaporized by microchip APPI, photoionized by a 10 eV krypton discharge lamp, and detected by selected reaction monitoring. The capLC/µAPPI‐MS/MS method showed good sensitivity with detection limits at the level of 1.0 ng mL?1, good linearity with correlation coefficients between 0.9954 and 0.9990, and good repeatability with relative standard deviations below 10%. These results demonstrate that microchip APPI combined with capLC/MS/MS provides a new potential method for analyzing non‐polar and neutral compounds in biological samples. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
180.
Sikanen T Tuomikoski S Ketola RA Kostiainen R Franssila S Kotiaho T 《Lab on a chip》2005,5(8):888-896
The characterization of SU-8 microchannels for electrokinetic microfluidic applications is reported. The electroosmotic (EO) mobility in SU-8 microchannels was determined with respect to pH and ionic strength by the current monitoring method. Extensive electroosmotic flow (EOF), equal to that for glass microchannels, was observed at pH > or =4. The highest EO mobility was detected at pH > or =7 and was of the order of 5.8 x 10(-4) cm(2) V(-1) s(-1) in 10 mM phosphate buffer. At pH < or =3 the electroosmotic flow was shown to reverse towards the anode and to reach a magnitude of 1.8 x 10(-4) cm(2) V(-1) s(-1) in 10 mM phosphate buffer (pH 2). Also the zeta-potential on the SU-8 surface was determined, employing lithographically defined SU-8 microparticles for which a similar pH dependence was observed. SU-8 microchannels were shown to perform repeateably from day to day and no aging effects were observed in long-term use. 相似文献