NMR‐based analysis of the chemical composition of Japanese persimmon aqueous extracts

Japanese persimmon (Diospyros kaki L.) is recognized as an outstanding source of biologically active compounds relating to many health benefits. In the present study, NMR spectroscopy provided a comprehensive metabolic overview of Japanese persimmon juice. Detailed signal assignments of Japanese persimmon juice were carried out using various 2D NMR techniques incorporated with broadband water suppression enhanced through T₁ effects (BB‐WET) or WET sequences, and 26 components, including minor components, were identified. In addition, most components were quantitatively evaluated by the integration of signals using conventional ¹H NMR and BB‐WET NMR. This is the first detailed analysis combined with quantitative characterization of chemical components using NMR for Japanese persimmon. Copyright © 2015 John Wiley & Sons, Ltd.     

Detection challenges in quantitative polymer analysis by liquid chromatography

Accurate quantification of polymer distributions is one of the main challenges in polymer analysis by liquid chromatography. The response of contemporary detectors is typically influenced by compositional features such as molecular weight, chain composition, end groups, and branching. This renders the accurate quantification of complex polymers of which there are no standards available, extremely challenging. Moreover, any (programmed) change in mobile‐phase composition may further limit the applicability of detection techniques. Current methods often rely on refractive index detection, which is not accurate when dealing with complex samples as the refractive‐index increment is often unknown. We review current and emerging detection methods in liquid chromatography with the aim of identifying detectors, which can be applied to the quantitative analysis of complex polymers.     

Development of a method for quantitative determination of the cytotoxic agent piplartine (piperlongumine) in multiple skin layers

This study reports the development of a simple and reproducible method, with high rates of recovery, to extract the cytotoxic agent piplartine from skin layers, and a sensitive and rapid UV‐HPLC method for its quantification. Considering the potential of piplartine for topical treatment of skin cancer, this method may find application for formulation development and pharmacokinetics studies to assess cutaneous bioavailability. Porcine skin was employed as a model for human tissue. Piplartine was extracted from the stratum corneum (SC) and remaining viable skin layers (VS) using methanol, vortex homogenization and bath sonication, and subsequently assayed by HPLC using a C₁₈ column, and 1:1 (v/v) acetonitrile–water (adjusted to pH 4.0 with acetic acid 0.1%) as mobile phase. The quantification limit of piplartine was 0.2 μg/mL (0.6 μm ), and the assay was linear up to 5 μg/mL (15.8 μm ), with within‐day and between‐days assay coefficients of variation and relative errors <15%. Piplartine recovery from SC and VS varied from 86 to 96%. The method was suitable to assay samples from skin penetration studies, enabling detection of differences in cutaneous delivery in different skin compartments resulting from treatment with various formulations and time periods.     

Differential isotope dansylation labeling combined with liquid chromatography mass spectrometry for quantification of intact and N-terminal truncated proteins

The N-terminal amino acids of proteins are important structure units for maintaining the biological function, localization, and interaction networks of proteins. Under different biological conditions, one or several N-terminal amino acids could be cleaved from an intact protein due to processes, such as proteolysis, resulting in the change of protein properties. Thus, the ability to quantify the N-terminal truncated forms of proteins is of great importance, particularly in the area of development and production of protein-based drugs where the relative quantity of the intact protein and its truncated form needs to be monitored. In this work, we describe a rapid method for absolute quantification of protein mixtures containing intact and N-terminal truncated proteins. This method is based on dansylation labeling of the N-terminal amino acids of proteins, followed by microwave-assisted acid hydrolysis of the proteins into amino acids. It is shown that dansyl labeled amino acids are stable in acidic conditions and can be quantified by liquid chromatography mass spectrometry (LC–MS) with the use of isotope analog standards.     

Development and assessment of an intrusive polynomial chaos expansion-based continuous adjoint method for shape optimization under uncertainties

This article contributes to the development of methods for shape optimization under uncertainties, associated with the flow conditions, based on intrusive Polynomial Chaos Expansion (iPCE) and continuous adjoint. The iPCE to the Navier–Stokes equations for laminar flows of incompressible fluids is developed to compute statistical moments of the Quantity of Interest which are, then, compared with those obtained through the Monte Carlo method. The optimization is carried out using a continuous adjoint-enabled, gradient-based loop. Two different formulations for the continuous adjoint to the iPCE PDEs are derived, programmed, and verified. Intrusive PCE methods for the computation of the statistical moments require mathematical development, derivation of a new system of governing equations and their numerical solution. The development is presented for a chaos order of two and two uncertain variables and can be used as a guide to those willing to extend this development to a different set of uncertain variables or chaos order. The developed method and software, programmed in OpenFOAM, is applied to two optimization problems pertaining to the flow around isolated airfoils with uncertain farfield conditions.     

Development and validation of an LC‐MS/MS method for simultaneous quantitative analysis of free and conjugated bisphenol A in human urine

Bisphenol A (BPA) is an environmental endocrine‐disrupting chemicals that is widely used in common consumer products. There is an increasing concern regarding human exposure to BPA owing to the potential adverse effects associated with its estrogenic activity. For assessing environmental exposure to BPA, it is essential to have a sensitive, accurate and selective analytical method, especially one that can detect low BPA levels in complex sample matrices. In this study, we developed and validated an accurate, sensitive, and robust liquid chromatography–tandem mass spectrometry method for simultaneous quantification of free BPA and BPA β‐d ‐glucuronide (BPA‐gluc) concentrations in human urine with only a single injection. Calibration curves were linear over a concentration range of 1–100 ng/mL for BPA and 10–1000 ng/mL for BPA‐gluc. The levels of the analytes were determined quantitatively with HPLC/ESI‐MS/MS by using negative electrospray ionization in the select ion monitoring mode and a pentaflouraphenyl propyl column. The validated method was applied to the analysis of spot urine specimens collected from randomly selected healthy human subjects. Copyright © 2013 John Wiley & Sons, Ltd.     

Application of Anodic Stripping Differential Alternative Pulses Voltammetry for Simultaneous Species Quantification

The second order voltammetric technique Differential Alternative Pulses Voltammetry (DAPV) was applied in anodic stripping mode for simultaneous quantification of traces of species having close E_1/2. The potential‐time waveform and the signal processing allowing the DAPV application in stripping mode are presented. The pulses widths and amplitudes were optimized to obtain maximal sensitivity and resolution at traces of In³⁺ and Cd²⁺ (having E_1/2 difference of 45 mV) simultaneous quantification in presence of excess of Pb²⁺. Precise results for both species concentrations were obtained up to In³⁺ to Cd²⁺ concentration ratio as high as 1 to 10 without any sample pre‐treatment in purified industrial waste waters using 0.1 mol L⁻¹ HCl as supporting electrolyte.     

Simultaneous quantification of 11 isoquinoline alkaloids in Corydalis impatiens (Pall.) Fisch by HPLC

Isoquinoline alkaloids are the primary active ingredients of Corydalis, but an analytical method for quality assessment of the active ingredients in Corydalis impatiens (Pall). Fisch has not been reported. A new, simple, and multiple‐component quantification method was developed for the simultaneous quantification of 11 isoquinoline alkaloids including capnoidine, chelianthifoline, bicuculline, protopine, isoapocavidine, apocavidine, cavidine, tetrahydroepiberberine, ochotensimine, tetrahydrocoptisine, and tetrahydrocorysamine in C. impatiens. Separation of the isoquinoline alkaloids was performed on a RP C₁₈ column (150 × 4.6 mm, 5 μm) with potassium dihydrogen phosphate buffer (pH 2.5, adjusted by phosphoric acid)/acetonitrile (53:47, v/v) containing 0.3% sodium dodecyl sulfonate. The flow rate and detection wavelength were set at 1 mL/min and 295 nm, respectively. Full validation of the assay was carried out including linearity, precision, accuracy, stability, LOD, and limit of quantitation. All calibration curves showed a good linear relationship (r > 0.999) in test range. The results demonstrated that the developed method was reliable, rapid, and specific. Six batches of C. impatiens samples from different sources were determined using the established method. The contents of alkaloids ranged from 11.68 to 351.83 μg/g. This method can be applied for quality evaluation and control of C. impatiens. Eleven isoquinoline alkaloids were first reported on simultaneous determination with HPLC.     

Ultra high performance liquid chromatography-quadrupole-time of flight analysis for the identification and the determination of resveratrol and its metabolites in mouse plasma

Resveratrol is a polyphenol that has numerous interesting biological properties, but, per os, it is quickly metabolized. Some of its metabolites are more concentrated than resveratrol, may have greater biological activities, and may act as a kind of store for resveratrol. Thus, to understand the biological impact of resveratrol on a physiological system, it is crucial to simultaneously analyze resveratrol and its metabolites in plasma. This study presents an analytical method based on UHPLC-Q-TOF mass spectrometry for the quantification of resveratrol and of its most common hydrophilic metabolites. The use of ¹³C- and D-labeled standards specific to each molecule led to a linear calibration curve on a larger concentration range than described previously. The use of high resolution mass spectrometry in the full scan mode enabled simultaneous identification and quantification of some hydrophilic metabolites not previously described in mice. In addition, UHPLC separation, allowing run times lower than 10 min, can be used in studies that requiring analysis of many samples.     

Simultaneous derivatization and air-assisted liquid–liquid microextraction of some aliphatic amines in different aqueous samples followed by gas chromatography-flame ionization detection

The paper presents a new method based on simultaneous derivatization and air-assisted liquid–liquid microextraction (AALLME) for the extraction and preconcentration of some aliphatic amines prior to gas chromatography-flame ionization detection (GC-FID). Primary aliphatic amines are derivatized and extracted simultaneously by a fast reaction with butylchloroformate (derivatization agent/extraction solvent) under mild conditions. The mixture of butylchloroformate and aqueous sample solution is rapidly sucked into a 10-mL glass syringe and then is injected into a test tube with conical bottom and the procedure is repeated seven times. After centrifuging the resulted cloudy solution, the derivatized analytes in the sedimented phase are determined by GC-FID. The influence of main factors on the efficiency of derivatization/extraction procedure is studied. Under the optimal conditions, the enrichment factors (EFs) for aliphatic amines are obtained in the range of 248–360 and limits of detection (LODs) are between 0.30 and 2.6 μg L⁻¹. The obtained extraction recoveries ranged from 50 to 72% and the relative standard deviation (RSD) was less than 4.8% for intra-day (n = 6) and inter-days (n = 4) precision. The method is successfully applied to determine some aliphatic amines in environmental water samples.