Liquid chromatography-tandem mass spectrometric determination of propofol in rat serum and hair at attogram level after derivatization with 3-bromomethyl-propyphenazone

A Sensitive Liquid Chromatography-Mass Spectrometric Method for Determination of Bisoprolol in Rat Serum after Pre-Column Derivatization

Two derivatization regents were reacted with bisoprolol (BIS), followed by liquid-chromatography-mass spectrometric analysis. 3-Bromomethyl-propyphenazone (BMP) and dansyl-chloride (Dns-Cl) were reacted via the secondary amino group using a catalyst to accelerate the reaction progress and completeness with minimal reaction byproducts. The sensitivity and the ionization efficiency of both BIS-methyl-propyphenazone (BIS-MP) and BIS-Dns via electrospray ionization were studied. The sensitivity of BIS-MP was superior to BIS-Dns. The derivatization procedure, extraction procedure, and LC-MS method were optimized and validated to achieve the monitoring of BIS in rat serum at a picogram scale. The calibration curve showed a regression coefficient value of 0.999 within a concentration spanning a range of 10-500 pg/mL. The detection limit and quantitation were 4 and 10 pg/mL, respectively. The intraday and inter-day precision values (% relative standard deviation) ranged from 0.53 to 6.91%, whereas the accuracy values (expressed as % error) ranged from -4.20 to -0.77%. The pharmacokinetic parameters were: 15,280 pg/mL for a maximum concentration of BIS (Cmax) at the maximum time (Tmax) of 1 h. BIS's elimination half-life (t1/2) was determined to be 3 h. The value of the area under the concentration-time curve (AUC0 - t) was 34,370 pg/mL h.

Fluoride-assisted liquid chromatography-tandem mass spectrometry method for simultaneous analysis of propofol and its metabolites without derivatization in urine

The misuse of propofol for recreational purposes has become a serious social issue. Accordingly, practical and sensitive analytical methods to investigate the chronic abuse and toxicity of propofol are required. However, current propofol determination methods using liquid chromatography-mass spectrometry (LC-MS/MS) suffer from problems associated with loss in sample preparation due to its volatility and its poor ionization efficiency and collision-induced dissociation in mass spectrometry. Herein, we have developed a sensitive and accurate fluoride-assisted LC-MS/MS method combined with direct-injection for propofol determination. Ionization via fluoride-ion attachment/induced deprotonation, effected by ammonium fluoride in the mobile phase, was found to dramatically improve the sensitivity of propofol without derivatization. Furthermore, direct injection without derivatization enables the simultaneous analysis of propofol and its phase II metabolites without analyte loss. The optimal concentration of ammonium fluoride in the mobile phase was found to be 1 mM under methanol conditions. The linearity is good (R² ≥ 0.999) and the intra- and inter-day precisions for propofol determination are between 1.9 and 8.7%. The accuracies range from 87.5% to 105.4% and the limits of detection and quantitation for propofol in urine are 0.15 and 0.44 ng mL^-1, respectively. The present method was successfully applied to human urine and showed a sufficient sensitivity to determine propofol and five phase II metabolites over 48 h in human urine after administration. Consequently, the fluoride-assisted LC-MS/MS method was demonstrated to be sensitive, accurate, and practical for the determination of propofol and its metabolites.

Derivatization procedures and their analytical performances for HPLC determination in bioanalysis

Derivatization, or chemical structure modification, is often used in bioanalysis performed by liquid chromatography technique in order to enhance detectability or to improve the chromatographic performance for the target analytes. The derivatization process is discussed according to the analytical procedure used to achieve the reaction between the reagent and the target compounds (containing hydroxyl, thiol, amino, carbonyl and carboxyl as the main functional groups involved in derivatization). Important procedures for derivatization used in bioanalysis are in situ or based on extraction processes (liquid-liquid, solid-phase and related techniques) applied to the biomatrix. In the review, chiral, isotope-labeling, hydrophobicity-tailored and post-column derivatizations are also included, based on representative publications in the literature during the last two decades. Examples of derivatization reagents and brief reaction conditions are included, together with some bioanalytical applications and performances (chromatographic conditions, detection limit, stability and sample biomatrix).

Rapid determination of intraoperative blood propofol concentration in operating theatre by dopant-enhanced neutral release and negative photoionization ion mobility spectrometry

The concentration of propofol in blood is an important indicator for anesthesiologists to monitor and regulate the anesthesia depth of patients during surgery. Herein, a negative photoionization ion mobility spectrometry with acetone as the dopant was developed for rapid and direct determination of intraoperative blood propofol concentration in the operating theatre. High concentration of acetone molecules in the carrier gas was used not only to enhance neutral desorption and release free propofol molecules from the whole blood, but also to increase the intensity of reactant O₂^- and reduce the amount of non-reactive CO₃^- ions simultaneously, which allowed to measure trace propofol in less than 2 min without any tedious pretreatment. Under optimized conditions, a linear calibration curve of propofol was obtained with the range of 0.5-20 ng μL^-1 and with a limit of detection of 0.14 ng μL^-1, which met the clinical requirements and correlated well with standard HPLC methods. Finally, the method was applied to detect intraoperative blood propofol concentration in nearly 100 surgical patients, demonstrating its excellent detection capability and facilitating the study of propofol pharmacokinetics.

Propagating annotations of molecular networks using in silico fragmentation

The annotation of small molecules is one of the most challenging and important steps in untargeted mass spectrometry analysis, as most of our biological interpretations rely on structural annotations. Molecular networking has emerged as a structured way to organize and mine data from untargeted tandem mass spectrometry (MS/MS) experiments and has been widely applied to propagate annotations. However, propagation is done through manual inspection of MS/MS spectra connected in the spectral networks and is only possible when a reference library spectrum is available. One of the alternative approaches used to annotate an unknown fragmentation mass spectrum is through the use of in silico predictions. One of the challenges of in silico annotation is the uncertainty around the correct structure among the predicted candidate lists. Here we show how molecular networking can be used to improve the accuracy of in silico predictions through propagation of structural annotations, even when there is no match to a MS/MS spectrum in spectral libraries. This is accomplished through creating a network consensus of re-ranked structural candidates using the molecular network topology and structural similarity to improve in silico annotations. The Network Annotation Propagation (NAP) tool is accessible through the GNPS web-platform https://gnps.ucsd.edu/ProteoSAFe/static/gnps-theoretical.jsp.