Liquid chromatography–tandem mass spectrometry method for simultaneous quantification of urapidil and aripiprazole in human plasma and its application to human pharmacokinetic study

A sensitive and selective liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed and validated for simultaneous determination of urapidil and aripiprazole in human plasma. A simple liquid–liquid extraction with ethyl acetate was used for the sample preparation. Chromatographic separation was achieved on a Phenomenex C₁₈ (4.6 × 50 mm, 5 µm) column with 0.1% formic acid–acetonitrile (10:90, v/v) as the mobile phase with flow rate of 0.6 mL/min. The quantitation of the target compounds was determined in a positive ion multiple reaction monitoring mode. Calibration plots were linear over the range of 2.0–2503.95 ng/mL for urapidil and 1.0–500.19 ng/mL for aripiprazole. The lower limit of quantitation for urapidil and aripiprazole was 2.0 and 1.0 ng/mL, respectively. Mean recovery was in the range of 69.94–75.62% for both analytes and internal standards. Intra‐day and inter‐day precisions of the assay at three concentrations were 2.56–5.89% with accuracy of 92.31–97.83% for urapidil, and 3.14–6.84% with accuracy of 91.38–94.42% for aripiprazole. The method was successfully applied to human pharmacokinetic study of urapidil and aripiprazole in healthy human male volunteers. Copyright © 2013 John Wiley & Sons, Ltd.     

Cyclohexanones--Source for Selena/Thiadiazoles and Diazaphospholes

Some new heterocyclic compounds containing selenadiazole, thiadiazole and diazaphosphole fused to cyclohexanones have been prepared and characterized by spectral data.     

Influence of Comonomer Functional Groups on the Reactivity Ratios of Some Phenolic Monomers

The reactivity ratios of some halogen-substituted phenolic monomers have been determined by the linear graphical method of Kelen and Tüdöls. The nature of functional groups present in the comonomer influence the order of reactivity of p-chlorophenol, p-bromophenol, and p-iodophenol. The behavior of these monomers during copolymerization reaction has been interpreted in terms of 1) different degrees of resonance stabilization of the monomers, and 2) opposite polarization caused by the substituents present in the comonomer.     

Note High Yield Synthesis of Low Molecular Weight Poly(Vinyl Acetate) in Aqueous Acidic Media

Polymerization of vinyl acetate continues to interest workers in the field as evidenced by recent publications [1–3]. However, little information is available concerning the synthesis of low molecular weight poly(vinyl acetate) (PVAc) despite its industrial importance.     

Rapid identification of trimethyl and triethyl amines using sulphonic acidic ionic liquids: A time-of-flight secondary ion mass spectrometry study of fragmentation reactions

The time-of-flight secondary ion mass spectrometry (TOF-SIMS) has emerged as a powerful tool for the unswerving detection of biomolecules, in particular, proteins and peptides. To date, there is very little information available on the direct determination of trimethyl/triethyl amines using TOF-SIMS. One major hurdle in this regard is an ultrahigh vacuum system, usually needed in TOF-SIMS, which hampers its usability to trimethyl/triethyl amines owing to their high evaporation rate. We designed an efficient and sensitive protocol for rapid identification and sensitive determination of tertiaryalkyl amines using TOF-SIMS. The amines were derivatized by reaction with 1,4-butane sultone and sulphuric acid sequentially to afford the corresponding sulphonic acidic ionic liquids (ILs). The TOF-SIMS analysis of these task-specific ILs (TSILs) was carried out in both positive and negative polarity. The positive ion mass spectra of TSILs showed sharp fragmented peaks for tertiaryalkyl amines at typical level and up to 10 ppm. The possible mechanism for different fragmentation pathways in positive polarity was discussed.     

A validated HPLC‐PDA method for identification and quantification of two bioactive alkaloids,ephedrine and cryptolepine,in different Sida species

A simple, rapid, accurate and reproducible reverse‐phase HPLC method has been developed for the identification and quantification of two alkaloids ephedrine and cryptolepine in different extracts of Sida species using photodiode array detection. Baseline separation of the two alkaloids was achieved on a Waters RP‐18 X‐terra column (250 × 4.6 mm, 5 µm) using a solvent system consisting of a mixture of water containing 0.1% Trifluoroacetic acid (TFA) and acetonitrile in a gradient elution mode with detection at 210 and 280 nm for ephedrine and cryptolepine, respectively. The calibration curves were linear in a concentration range of 10–250 µg/mL for both the alkaloids with correlation coefficient values >0.99. The limits of detection and quantification for ephedrine and cryptolepine were 5 and 10 µg/mL and 2.5 and 5 µg/mL, respectively. Relative standard deviation values for intra‐day and inter‐day precision were 1.22 and 1.04% for ephedrine and 1.71 and 2.06% for cryptolepine, respectively. Analytical recovery ranged from 92.46 to 103.95%. The developed HPLC method was applied to identify and quantify ephedrine and cryptolepine in different extracts of Sida species. Copyright © 2013 John Wiley & Sons, Ltd.     

Clickable polyurethanes based on s‐triazine ring containing aromatic diisocyanate bearing pendent alkyne group: Synthesis and postmodification

A new s‐triazine ring containing aromatic diisocyanate bearing a pendent alkyne group, namely, 2,4‐bis(4‐isocyanatophenoxy)?6‐(prop‐2‐yn‐1‐yloxy)?1,3,5‐triazine was synthesized and reacted with various diols viz., 1,10‐decanediol, tetraethylene glycol and polyethylene glycols in the presence of dibutyltin dilaurate as the catalyst to obtain a series of linear polyurethanes. The selected polyurethanes possessing pendent alkyne groups were postmodified with chemically diverse azides viz., 1‐(azidomethyl)benzene, 1‐(azidomethyl)pyrene, and methoxy end‐caped poly(ethylene glycol) azide via copper‐catalysed azide‐alkyne Huisgen 1,3‐dipolar cycloaddition. FTIR and ¹H NMR spectra indicated quantitative click reaction. UV–vis and fluorescence spectroscopic analysis confirmed complete incorporation of pyrenyl groups indicating the formation of fluorescence active polyurethane by postmodification with 1‐(azidomethyl)pyrene. TG analysis of polyurethanes indicated two stage weight loss and their thermal stability, as judged by T ₁₀ values, was governed by weight percent of urethane linkages. The water contact angle measurements revealed improved wettability with increased content of PEG either in the backbone of polyurethanes or as grafted chains. DLS and TEM studies confirmed that certain polyurethanes possessing PEG segments displayed self‐assembly in aqueous solution, which was further supported by pyrene encapsulation studies using UV–vis spectroscopy. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 1008–1020