Time filter

Source Type

North Logan, UT, United States

Barrow D.A.,University of Cardiff | Castell O.K.,University of Cardiff | Sykes N.,University of Cardiff | Myers P.,University of Liverpool | Ritchie H.,ThermoFisher Scientific Inc.
Journal of Chromatography A | Year: 2011

We report the first development of a novel, planar, microfluidic, graphitic carbon separations column utilizing an array of graphitic micropillars of diamond cross-section as the chromatographic stationary phase. 795nm femtosecond laser ablation was employed to subtractively machine fluidic architectures and a micropillared array in a planar, graphitic substrate as a monolithic structure. A sample injector was integrated on-chip, together with fluid-flow distribution architectures to minimize band-broadening and ensure sample equi-distribution across the micro-pillared column width. The separations chip was interfaced directly to the ESI probe of a Thermofisher Surveyor mass spectrometer, enabling the detection of test-mixture analytes following their differential retention on the micro-pillared graphitic column, thus demonstrating the exciting potential of this novel separations format. Importantly, unlike porous, graphitic microspheres, the temperature and pressure resilience of the microfluidic device potentially enables use in subcritical H 2O chromatography. © 2010 Elsevier B.V. Source

Audronis M.,Gencoa Ltd | Hinder S.J.,University of Surrey | MacK P.,ThermoFisher Scientific Inc. | Bellido-Gonzalez V.,Gencoa Ltd | And 3 more authors.
Thin Solid Films | Year: 2011

Abstract PET web samples have been treated by magnetically enhanced glow discharges powered using either medium frequency pulse direct current (p-DC) or low frequency high power pulse (HIPIMS) sources. The plasma pre-treatment processes were carried out in an Ar-O2 atmosphere using either Cu or Ti sputter targets. XPS, AFM and sessile drop water contact angle measurements have been employed to examine changes in surface chemistry and morphology for different pre-treatment process parameters. Deposition of metal oxide onto the PET surface is observed as a result of the sputter magnetron-based glow discharge web treatment. Using the Cu target, both the p-DC and HIPIMS processes result in the formation of a thin CuO layer (with a thickness between 1 and 11 nm) being deposited onto the PET surface. Employing the Ti target, both p-DC and HIPIMS processes give rise to a much lower concentration of Ti (< 5 at.%), in the form of TiO2 on the PET treated surface. The TiO2 is probably distributed as an island-like distribution covering the PET surface. Presence of Cu and Ti oxide constituents on the treated PET is beneficial in aiding the adhesion but alone (i.e. without oxygen plasma activation) is not enough to provide very high levels of hydrophilicity as is clear from sessile drop water contact angle measurements on aged samples. Exposure to the plasma treatments leads to a small amount of roughening of the substrate surface, but the average surface roughness in all cases is below 2.5 nm. The PET structure at the interface with a coating is mostly or wholly preserved. The oxygen plasma treatment, metal oxide deposition and surface roughening resulting from the HIPIMS and p-DC treatments will promote adhesion to any subsequent thin film that is deposited immediately following the plasma treatment. © 2011 Elsevier B.V. Source

Pan J.,Charles River Laboratories | Pan J.,Primera Analytical Solution Corporation | Fair S.J.,Charles River Laboratories | Fair S.J.,ThermoFisher Scientific Inc. | Mao D.,Maxxam Analytics
Bioanalysis | Year: 2011

Background: The skeletal symmetric structure of chlorhexidine predicts that each doubly charged molecular ion may generate two para-chlorbenzenguanidines daughter ions through bond cleavage at two protonation sites, thus generating better sensitivity in MRM transition than that involving singly charged molecular ions. This unique nature can be used to improve sensitivity of a LC-MS/MS method. Results: High-throughput LC-MS/MS was developed and validated to quantify chlorhexidine in rat plasma as low as 0.500 ng/ml. In the method, a unique chromatographic method on a narrow bore column reduced run time to 2.5 min and successfully minimized high background from accumulation of endogenous compounds in matrix on the column. Conclusion: This method was proved to be robust and suitable to support rat dermal toxicology studies. © 2011 Future Science Ltd. Source

Yang Y.,Zhejiang University | He J.,Zhejiang University | Huang Z.,Zhejiang University | Zhong N.,ThermoFisher Scientific Inc. | And 6 more authors.
Journal of Chromatography A | Year: 2013

An ion chromatography (IC) system with on-line sample pretreatment using valve-switching technique was developed for the determination of hexavalent chromium (Cr(VI)) in Colla corii asini. Colla corii asini is a complicated sample with organics as main matrix. In this work, a polymer-based reversed-phase column was used as a pretreatment column. Via valve-switching technique, sample solution with target ions were eluted from a collection loop to analytical columns, with matrix eliminated on-line. Under the optimized separation conditions, the method showed good linearity (r= 0.9998) in the range of 0.004-1.0. mg/L and satisfactory repeatability (RSD < 3%, n= 6). The limit of detection (LOD) was 1.4 μg/L (S/N = 3). The average spiked recoveries of Cr(VI) were 93.4-102.0%. The result showed that the on-line sample pretreatment IC system was convenient and practical for the determination of trace Cr(VI) in Colla corii asini samples. © 2013 Elsevier B.V. Source

Long Z.,ThermoFisher Scientific Inc. | Guo Z.,CAS Dalian Institute of Chemical Physics | Acworth I.N.,ThermoFisher Scientific Inc. | Liu X.,ThermoFisher Scientific Inc. | And 3 more authors.
Talanta | Year: 2016

A non-derivative method was developed for the qualitative and quantitative analysis of isosteroidal alkaloids from Fritillaria thunbergii. During method development the performance of two universal detectors, the charged aerosol detector (CAD) and evaporative light scattering detector (ELSD), were evaluated. The CAD was found to be 30 to 55 times more sensitive than ELSD enabling the measurement of low levels of reference compound impurities that could not be detected by ELSD. The peak area percent of the reference compound, peimisine, obtained by CAD was 50.10%, but 91.66% by ELSD showing that CAD is suitable to estimate the presence of impurities. The CAD showed good reproducibility with overall intra- and inter-day peak area RSD values of less than 1.8% and 2.7%, respectively and had a linear dynamic range of up to 4 orders of magnitude (0.06-44 mg/L) for peimine and peiminine. The optimized method was used for the quantitative analysis of peimine and peiminine from F. thunbergii. © 2016 Published by Elsevier B.V. Source

Discover hidden collaborations