Selective, rapid and simultaneous determination of ergosterol and ergocalciferol in mushrooms by UPLC-Q-TOF-MS.

An ultra-performance liquid chromatography coupled to atmospheric pressure chemical ionization-quadrupole time-of-flight mass spectrometry method has been optimized and validated for the determination of ergosterol and ergocalciferol in mushroom samples, using cholecalciferol as surrogate standard. The separation was carried out with a Synergi Hydro-RP column (100 mm x 3.00 mm i.d, 2.5 µm particle size), (Phenomenex, CA, USA) column, thermostated at 35 °C. The mobile phase was 0.1 % formic acid aqueous solution and methanol in gradient elution mode and it was achieved in 5 min approximately. Detection was achieved by atmospheric pressure chemical ionization in positive mode and quadrupole time-of-flight mass spectrometry. Desolvation and interface temperatures were set at 500 °C and 150 °C, respectively. The recoveries obtained were within 92-105 % for ergosterol, 77-81 % for ergocalciferol and 83-87 % for cholecalciferol. Method limits of detection were 0.4 and 0.5 µg g-1 for ergosterol and ergocalciferol, respectively, and method limits of quantitation were 1.2 and 1.3 µg g-1 for ergosterol and ergocalciferol, respectively. A rapid and simple extraction procedure using small amount of sample (100 mg) with hexane was optimized and the method was applied to the determination of ergosterol and ergocalciferol in white button mushrooms (Agaricus bisporus var. bisporus) exposed to UV irradiation. Results were compared to the corresponding non-irradiated mushrooms.

Hollow fiber liquid-phase microextraction and determination of nonsteroidal anti-inflammatories by capillary electrophoresis and sulfonamides by HPLC in human urine.

In this paper two applications of three-phase HF-LPME for the determination of pharmaceuticals in human urine are proposed: a capillary electrophoresis with a photodiode array detection method for the analysis of seven nonsteroidal anti-inflammatory drugs (NSAIDs) and a high-performance liquid chromatographic with photo diode array and fluorescence detection method for the determination of four sulfonamides and their corresponding N(4)-acetyl-metabolites. Q3/2 Accurel® polypropylene hollow fibers were used for both procedures. Dihexyl ether was used as the supported liquid membrane for the determination of anti-inflammatories and 1-octanol for sulfonamides. An aqueous solution (pH 12) was used in both procedures as the acceptor phase and as the donor phase an aqueous solution (pH 2), and a 2 M Na(2)SO(4) aqueous solution (pH 4) was used for the determination of the anti-inflammatories and sulfonamides. The detection limits obtained were between 0.25 (naproxen) and 0.86 ng/mL (aceclofenac) for the determination of anti-inflammatories and 7 × 10(-4) (sulfamethoxazole) and 0.048 ng/mL (N(4)-acetyl-sulfamethazine) for sulfonamides. The method was successfully applied to the determination of the analytes in human urine.

Urea as new stabilizing agent for imipenem determination: electrochemical study and determination of imipenem and its primary metabolite in human urine.

Imipenem shows a fast chemical conversion to a more stable imin form (identical to that of biochemical dehydropeptidase degradation) in aqueous solutions and stabilizing agents used avoid its electrochemical study and determination. The aim of this work is the proposal of urea as stabilizing agent which allows the electrochemical study of imipenem and the proposal of electrochemical methods for the determination of imipenem and its primary metabolite (M1) in human urine samples. Electrochemical studies were realized in phosphate buffer solutions over pH range 1.5-8.0 using differential-pulse polarography, DC-tast polarography, cyclic voltammetry and adsorptive stripping voltammetry. In acidic media, a non-reversible diffusion-controlled reduction involving a two steps mechanism which involves one electron and one proton in the first step and two electrons and two protons in the second step occurs and the mechanism for the reduction was suggested. A differential-pulse polarographic method for the determination of imipenem in the concentration range 3.2x10(-6) to 2x10(-5)M (0.95-3.4 mg/L) and its primary metabolite in the concentration range 1.4x10(-6) to 10(-4)M (0.43-26.1 mg/L) with detection limits of 9.6x10(-7)M (0.28 microg/L imipenem) and 4.3x10(-7)M (0.14 microg/L M1) was proposed. Also, a method based on controlled adsorptive pre-concentration of imipenem on the hanging mercury drop electrode followed by voltammetric measure, allows imipenem determination in the concentration range 1.8x10(-8) to 1.2x10(-6)M (5.42-347 microg/L) with a detection limit of 5.4x10(-9)M (1.63 microg/L). The proposed methods have been used for the direct determination of the analytes in a pharmaceutical formulation and human urine.