Determination of acetaminophen and its main metabolites in urine by capillary electrophoresis hyphenated to mass spectrometry.

In this study, a capillary electrophoresis-tandem mass spectrometry method combining efficient separation and sensitive detection has been developed and validated, for the first time, to quantify acetaminophen and five of its metabolites in urine samples. Optimization of the method has led us to perform detection in positive ESI mode using MeOH-ammonium hydroxide (0.1%) (50:50, v/v) as sheath liquid. Moreover, optimal separation has been obtained in less than 9 min after anodic injection, using an ammonium acetate solution (40 mM, pH 10) as BGE. It was shown that the dilution solvent and the dilution factor to use for sample preparation are critical parameters to avoid peak splitting, to gain in sensitivity and then to obtain an effective analysis method. While a 200-fold factor dilution was shown to be suitable for quantitation of acetaminophen, acetaminophen mercapturate, acetaminophen sulfate and acetaminophen glucuronide, a 20-fold dilution was finally selected for methoxy-acetaminophen and 3-methylthioacetaminophen analysis, thus requiring two successive analyses to be carried out in order to quantify all metabolites. Hyphenation of CE with MS/MS versus UV permits to improve LOQ (10-20-fold factor with respect to previous works for acetaminophen, acetaminophen sulfate and acetaminophen glucuronide). Moreover, use of CE versus HPLC, permits to quantify two additional metabolites, i.e. 3-methylthio-acetaminophen and methoxy-acetaminophen. The method has been validated using the accuracy profile approach with a total error (accuracy) included in the ± 20% range. Thereby, the method allows the quantitation of acetaminophen and acetaminophen mercapturate in the range (0.1-1 mg mL-1), and of acetaminophen sulfate, methoxy-acetaminophen, acetaminophen glutathione and 3-methylthio-acetaminophen in the ranges (0.5-5 mg mL-1), (0.025-0.4 mg mL-1), (9.22-30 mg mL-1) and (0.073-0.4 mg mL-1), respectively. The method was finally applied to the analysis of urine samples of eighteen patients belonging to three different inclusion groups of the ongoing clinical trial, demonstrating that the method is suitable to highlight different metabolic profiles. This work will be subsequently extended to the analysis two hundred and seventy urine samples from patients included in a clinical trial dedicated to the study of acetaminophen metabolism changes after hepatic resection.

Chiral separation of new sulfonamide derivatives and evaluation of their enantioselective affinity for human carbonic anhydrase II by microscale thermophoresis and surface plasmon resonance.

The aim of this study was to develop a method combining chiral separation and biophysical techniques to evaluate the enantioselective affinity of original sulfonamide derivatives towards their therapeutic target, the human carbonic anhydrase II (hACII). The first step consisted in the preparation of the enantiomers by chromatographic separation. The performances of HPLC and Supercritical Fluid Chromatography (SFC) were studied at the analytical scale by optimization of various experimental conditions using adsorbed polysaccharide chiral stationary phases (amylose AD-H and cellulose OD-H). Since SFC allowed obtaining higher enantioresolutions per time unit, it was selected for the semi-preparative scale and successfully used to isolate each enantiomer with a satisfactory enantiomeric purity (>98%). Secondly, microscale thermophoresis (MST) method and surface plasmon resonance (SPR) used as reference method were developed to measure potential enantioselective affinities of these enantiomers towards the hACII. The optimizations of both methods were performed using a reference compound, i.e. acetazolamide, which affinity for hCAII has previously been demonstrated. For all compounds, KD values obtained using MST and SPR were in good agreement, leading to similar affinity scales despite both approaches totally differ (labeling for MST versus immobilization of the protein for SPR). The equilibrium dissociation constants of our original compounds for the hCAII were in the range 100-1000nM and an enantioselectivity was observed using the MST and SPR methods for the diarylpyrazole 2. Finally, by comparing the MST and SPR techniques, MST appears especially adapted for further screening of a series of sulfonamide derivatives due to the lower time required to estimate a binding constant while consuming as little hCAII as SPR.