Ionspray microchip

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.     

Analysis of lipids with desorption atmospheric pressure photoionization‐mass spectrometry (DAPPI‐MS) and desorption electrospray ionization‐mass spectrometry (DESI‐MS)

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.     

Rapid LC-UV Analysis of Iohexol in Canine Plasma for Glomerular Filtration Rate Determination

A rapid high-performance liquid chromatography UV method and a simple sample preparation for analyzing iohexol in canine plasma, for evaluating glomerular filtration rate (GFR) and intestinal permeability, were developed and validated. Trifluoroacetic acid (TFA) was used for protein precipitation and iohexol extraction from plasma, followed by vortex mixing and centrifugation. As an internal standard, 4-aminobenzoic acid (para-aminobenzoic acid, PABA) was added. The supernatant (5 μL) was injected into a Zorbax SB-C18 LC column maintained at 50 °C. The mobile phase of the LC method was a water–methanol gradient at pH 3.0 adjusted with TFA. Fast LC measurement was achieved by using a rapid-resolution LC technique. Total run time was 13 min, and UV wavelength was set at 246 nm. Precision of the method was 0.2–9.0%, depending on the iohexol concentration in plasma. Recovery of iohexol from plasma was over 90%, and recovery of the internal standard 99.1 ± 1.4%. The calibration curve was linear (r = 0.9997) over iohexol concentrations of 2.5–150 μg mL^?1 (n = 5). This method is fast, simple, reliable and applicable in clinical settings.     

Modification of polypropylene surfaces with micropits and hierarchical micropits/nanodepressions

Micropit surfaces and hierarchically structured micropit/nanodepression surfaces were fabricated in polypropylene by injection moulding. The first step in the process was the microstructuring of aluminium foils with a micro-working robot to obtain a pattern of micropits. Dimensions of the micropits could be controlled by adjusting the working parameters of the robot. The microstructured faces of some of the foils were anodized to aluminium oxide giving a surface in which both micropits and the smooth areas between were covered with nanopores. Mould inserts for the injection moulding were obtained by cold mounting of an epoxy resin mixture on the foils. After the epoxy resin had hardened, the foils were etched away. Dimensions of the micropillars and micropillars/nanobumps on the epoxy related to the dimensions of the structures on the foils. Finally, structures were replicated in polypropylene as micropits and hierarchical micropits/nanodepressions by injection moulding. The dimensions of these hollow structures corresponded well with those of the epoxy pillars and the original micropits.Static and dynamic contact angles on the micropit-structured polypropylene surfaces were elevated from the slightly hydrophobic values of smooth polypropylene. With hierarchical micropit/nanodepression structures, the contact angles approached the superhydrophobic limit of 150°. The work demonstrates an inexpensive and reproducible technique to fabricate hollow structures of various dimensions and scales on polypropylene and modify the surface properties of the polymer.     

Determination of triacylglycerols in donkey milk by using high performance liquid chromatography coupled with atmospheric pressure chemical ionization mass spectrometry

The separation and determination of triacylglycerols (TAGs), which are the main components of naturally occurring fats and oils, in milk fat is a challenging task due to the very complex nature of this matrix. In the present study the TAG fraction of donkey milk lipids has been characterized by using high performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (HPLC-APCI-MS). HPLC in reversed phase mode has been used for TAG separation and silver ion (Ag+) HPLC has been used as a second dimension to clarify and confirm the identification. The RP-HPLC eluate was fractionated and the fractions of interest were injected onto the Ag+-HPLC column. In both cases peak assignment was carried out by combining retention data with APCI-MS spectra information. In total, 55 TAGs in donkey milk fat were identified (without considering the positional isomers) and quantified on the basis of percentage peak areas in the RP-HPLC chromatogram (without the use of correction factors). Amongst the identified triacylglycerols, POLn, POO, PPO, CaPO, POL, and PPoO proved to be the main components of the TAG fraction of donkey milk.     

Use of bioluminescent bacterial sensors as an alternative method for measuring heavy metals in soil extracts

The luminescence based bacterial sensor strains Pseudomonas fluorescens OS8 (pTPT11) for mercury detection and Pseudomonas fluorescens OS8 (pTPT31) for arsenite detection were used in testing their application in detecting heavy metals in soil extracts. Three different soil types (humus, mineral and clay) were spiked with 1, 100 or 500 μg g⁻¹ Hg²⁺ or As³⁺. Samples were taken 1, 14 and 30 days and extracted with water, ammonium acetate, hydrogen peroxide and nitric acid to represent water soluble, bioavailable, organic matter bound and residual fractions, respectively. The lowest mercury-concentration measured using biosensor (0.003 μg kg⁻¹) was considerably lower than by chemical method (0.05 μg kg⁻¹). The sensor strain with pTPT31 appeared to have a useful detection range similar to that of chemical methods. Concentration results with chemical and biosensor analysis were very similar in the case of mercury-spiked samples. Although some of the arsenite samples showed higher variation between methods, it is concluded that the bacteria can be used as an alternative traditional methods for different types of samples.     

Total synthesis of (±)-tangutorine and chiral HPLC separation of enantiomers

The first total synthesis of racemic tangutorine, a novel indole alkaloid, was performed in 7 steps. The key reactions, dithionite reduction and acidic cyclization provided easy access with good yields to the tangutorine skeleton. Comprehensive NMR spectroscopic data of new compounds are given. Chiral HPLC separation of enantiomers is reported.     

Expected energy spectrum of cosmic ray protons and helium below4 PeV measured by LHAASO

The Large High Altitude Air Shower Observatory(LHAASO) is a composite cosmic ray observatory consisting of three detector arrays: kilometer square array(KM2 A), which includes the electromagnetic detector array and muon detector array, water Cherenkov detector array(WCDA) and wide field-of-view Cherenkov telescope array(WFCTA). One of the main scientific objectives of LHAASO is to precisely measure the cosmic rays energy spectrum of individual components from 10~(14) eV to 10~(18) eV. The hybrid observation will be employed by the LHAASO experiment, in which the lateral and longitudinal distributions of extensive air shower can be observed simultaneously. Thus, many kinds of parameters can be used for primary nuclei identification. In this paper, high purity cosmic ray simulation samples of the light nuclei component are obtained using multi-variable analysis. The apertures of 1/4 LHAASO array for pure proton and mixed proton and helium(HHe) samples are 900 m~2 Sr and1800 m~2 Sr, respectively. Prospect of obtaining proton and HHe spectra from 100 TeV to 4 PeV is discussed.     

Characterization of SU-8 for electrokinetic microfluidic applications

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.     

Rapid analysis of metabolites and drugs of abuse from urine samples by desorption electrospray ionization-mass spectrometry

Urine samples obtained from drug abusers were screened for drugs of abuse and their metabolites using DESI-MS and the results obtained were compared to results obtained from GC-MS experiments. The detected analyte classes included amphetamines, opiates, cannabinoids and benzodiazepines. The compounds detected were codeine, morphine, oxymorphone, 11-nor-9-carboxy-Delta(9)-tetrahydrocannabinol, Delta(9)-tetrahydrocannabinol, alprazolam, temazepam, oxazepam, N-desmethyldiazepam (nordiazepam) and hydroxytemazepam. Identities of all the analytes were confirmed by tandem mass spectrometry, matching MS/MS spectra with authentic standard compounds. The concentrations of the analytes in the samples were obtained from semi-quantitative GC-MS studies and were in the range of 270-22,000 ng mL(-1). The analytes could be detected by DESI even after a hundred-fold dilution indicating that the sensitivity of DESI was more than adequate for this study. Selectivity in the DESI-MS measurements for different kinds of analytes could be increased further by optimizing the spray solvent composition: the use of an entirely aqueous solvent enhanced the signal of polar analytes, such as the benzodiazepines, whereas the use of a spray solvent with a high organic content increased the signal of less polar analytes, such as codeine and morphine.