Free mycophenolic acid determination in human plasma ultrafiltrate by a validated liquid chromatography–tandem mass spectrometry method

The aim of this study was to develop and validate fully the liquid chromatography–tandem mass spectrometry method for free mycophenolic acid (MPA) concentration measurements in plasma ultrafiltrate that will be reliable and simple in preparation with deuterated MPA (MPA‐d3) chosen as an internal standard. The chromatographic separation was made with Zorbax Eclipse XDB‐C18 column (4.6 × 150 mm) using a gradient of two solutions as a mobile phase: (A) water and (B) methanol, each containing 0.1% formic acid and 2.5 mm ammonium acetate. Satisfactory repeatability of retention times was achieved with average values of 7.54 ± 0.20 min and 7.50 ± 0.19 min for MPA and MPA‐d3, respectively. The method was selective, with no carry‐over or matrix effect observed. The analytical range was proven for MPA ultrafiltrate concentrations of 1–500 ng/mL. The accuracy and precision fell within the acceptance criteria for intraday (accuracy: 100.63–110.46%, imprecision: 6.23–7.76%), as well as interday assay (accuracy: 98.81–110.63%; imprecision: 5.36–10.22%). The method was used for free MPA determination in plasma samples from patients treated with mycophenolate mofetil. To the best of our knowledge this is the first liquid chromatography–tandem mass spectrometry method for free MPA monitoring using MPA‐d3 that allows to measure plasma ultrafiltrate concentrations as low as 1 ng/mL.     

Novel rapid liquid chromatography tandem masspectrometry method for vemurafenib and metabolites in human plasma,including metabolite concentrations at steady state

A novel, rapid and sensitive liquid chromatography tandem–mass spectrometry method for quantification of vemurafenib in human plasma, that also for the first time allows for metabolite semi‐quantification, was developed and validated to support clinical trials and therapeutic drug monitoring. Vemurafenib was analysed by precipitation with methanol followed by a 1.9 min isocratic liquid chromatography tandem masspectrometry analysis using an Acquity BEH C₁₈ column with methanol and formic acid using isotope labelled internal standards. Analytes were detected in multireaction monitoring mode on a Xevo TQ. Semi‐quantification of vemurafenib metabolites was performed using the same analytical system and sample preparation with gradient elution. The vemurafenib method was successfully validated in the range 0.5–100 μg/mL according to international guidelines. The metabolite method was partially validated owing to the lack of commercially available reference materials. For the first time concentration levels at steady state for melanoma patients treated with vemurafenib is presented. The low abundance of vemurafenib metabolites suggests that they lack clinical significance. Copyright © 2016 John Wiley & Sons, Ltd.     

Simultaneous analysis of 35 specific antihypertensive adulterants in dietary supplements using LC/MS/MS

A sensitive and specific LC/MS/MS method was developed for the simultaneous analysis of 35 compounds used for treating hypertension as adulterants in dietary supplements. The method was validated for specificity, linearity, accuracy, precision, limit of detection, limit of quantitation, stability and recovery. The limit of detection and limit of quantitation ranged from 0.20 to 20.0 and 0.50 to 60.0 ng/g, respectively. The linearity was good (r ² > 0.999), with intra‐ and interday precision levels of 0.43–7.87% and 0.65–9.95% and the intra‐ and interday accuracies of 84.36–115.82% and 83.78–118.69%, respectively. The stability (relative standard deviation) was <14.75%. The mean recovery was 80.81–117.86% (relative standard deviation <10.00%). Ninety‐seven commercial dietary supplements available in South Korea were analyzed. While none contained detectable amounts of the 35 antihypertensive compounds, the developed LC/MS/MS procedure can be used for routine analysis to monitor illegal adulteration in various forms of dietary supplements.     

LR12‐peptide quantitation in whole blood by RP‐HPLC and intrinsic fluorescence detection: Validation and pharmacokinetic study

A simple, sensitive, selective and robust HPLC method based on intrinsic fluorescence detection was developed for the quantitation of a dodecapeptide (designated as LR12), inhibitor of Triggering Receptor Expressed on Myeloid cells‐1, in rat whole blood. Sample treatment was optimized using protein precipitation and solid‐phase extraction. Chromatographic separation was carried out in a gradient mode using a core–shell C₁₈ column (150 × 4.6 mm, 3.6 μm) with mobile phases of acetonitrile and water containing trifluoroacetic acid at 1.0 mL/min. The method was validated using methodology described by the US Food and Drug Administration guidelines for bioanalytical methods. Linearity was demonstrated within the 50–500 ng/mL range and the lower limit of quantitation was 50 ng/mL. Finally, a preliminary pharmacokinetic study after intraperitoneal injection of LR12 in rats was conducted to evaluate both LR12 monomer and its corresponding disulfide dimer, the main product of degradation. Beyond the fact that this paper describes the first fully validated method for LR12 analysis in blood samples, the approach followed here to optimize pre‐analytical steps could be beneficial to develop HPLC and/or MS methods for other pharmaceutical peptides.     

Validation and clinical application of an LC‐ESI‐MS/MS method for simultaneous determination of tolmetin and MED5, the metabolites of amtolmetin guacil in human plasma

A highly sensitive, rapid assay method has been developed and validated for the simultaneous estimation of tolmetin (TMT) and MED5 in human plasma with liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the positive‐ion mode. A simple solid‐phase extraction process was used to extract TMT and MED5 along with mycophenolic acid (internal standard, IS) from human plasma. Chromatographic separation was achieved with 0.2% formic acid–acetonitrile (25:75, v/v) at a flow rate of 0.50 mL/min on an X‐Terra RP₁₈ column with a total run time of 2.5 min. The MS/MS ion transitions monitored were 258.1 → 119.0 for TMT, 315.1 → 119.0 for MED5 and 321.2 → 207.0 for IS. Method validation and clinical sample analysis were performed as per FDA guidelines and the results met the acceptance criteria. The lower limit of quantitation achieved was 20 ng/mL and the linearity was observed from 20 to 2000 ng/mL, for both the anlaytes. The intra‐day and inter‐day precisions were in the range 3.27–4.50 and 5.32–8.18%, respectively for TMT and 4.27–5.68 and 5.32–8.85%, respectively for MED5. This novel method has been applied to a clinical pharmacokinetic study. Copyright © 2010 John Wiley & Sons, Ltd.     

A microscopic pedestrian-simulation model and its application to intersecting flows

We develop a microscopic pedestrian-simulation model in which pedestrian positions are updated at discrete time steps. At each time step, each pedestrian probabilistically selects a direction of movement from a predetermined set according to a logit-type function that considers the dynamics of other pedestrians around, and then selects a step size that satisfies a certain distribution. We perform a number of field experiments on real intersecting pedestrian flows with four different angles. We then validate and calibrate the model using sample data on the deviation angles, step velocities, and velocity–density relations obtained from the experiments.     

Phase equilibria and excess properties for binary systems in reactive distillation processes Part I. Methyl acetate synthesis

Isothermal vapor–liquid equilibrium (VLE) and excess enthalpy (H^E) data were measured for binary systems required for the design of reactive distillation processes for the methyl acetate production. The isothermal P–x data were measured with the help of a computer-operated static apparatus. A commercial isothermal flow calorimeter was used for the determination of the heats of mixing. Temperature-dependent interaction parameters for the UNIQUAC model were fitted simultaneously to the experimental data from this work and other authors.     

Segmentation of synthetic aperture radar image using multiscale information measure-based spectral clustering

A multiscale information measure （MIM）, calculable from per-pixel wavelet coefficients, but relying on global statistics of synthetic aperture radar （SAR） image, is proposed. It fully exploits the variations in speckle pattern when the image resolution varies from course to fine, thus it can capture the intrinsic texture of the scene backscatter and the texture due to speckle simultaneously. Graph spectral segmen- tation methods based on MIM and the usual similarity measure are carried out on two real SAR images. Experimental results show that MIM can characterize texture information of SAR image more effectively than the commonly used similarity measure.     

Copyright protection in digital museum based on digital holography and discrete wavelet transform

A new method to protect the copyright of digital museum based on digital holography is proposed. The Fresnel hologram of watermark image is embedded in the object to be protected through discrete wavelet transform （DWT）. After the watermark detection, the copyright information appears in the reconstructed hologram. With the higher redundancy feature in the hologram, the proposed technique can actually survive several kinds of image processing. Experimental results prove that the presented method has good robustness in image protection.     

A novel pose and illumination robust face recognition with a single training image per person algorithm

In the real-world application of face recognition system, owing to the difficulties of collecting samples or storage space of systems, only one sample image per person is stored in the system, which is so-called one sample per person problem. Moreover, pose and illumination have impact on recognition performance. We propose a novel pose and illumination robust algorithm for face recognition with a single training image per person to solve the above limitations. Experimental results show that the proposed algorithm is an efficient and practical approach for face recognition.