Magnetic Micro-Solid-Phase Extraction Using a Novel Carbon-Based Composite Coupled with HPLC–MS/MS for Steroid Multiclass Determination in Human Plasma

Abstract

A micron-sized sorbent, Magn-Humic, has been prepared by humic acids pyrolysis onto silica-coated magnetite. The material was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), thermogravimetric analysis (TGA), and Brunauer, Emmett, and Teller (BET) surface area measurements and applied for simultaneous magnetic solid-phase extraction (MSPE) of glucocorticoids, estrogens, progestogens, and androgens at ng mL−1 levels from human plasma followed by high-performance liquid chromatography coupled with mass spectrometry (HPLC–MS/MS). Due to the low affinity for proteins, steroids extraction was done with no need for proteins precipitation/centrifugation. As highlighted by a design of experiments, MSPE was performed on 250 µL plasma (after 1:4 dilution) by 50 mg Magn-Humic (reusable for eight extractions) achieving quantitative recovery and satisfying clean-up. This was improved by washing (2 mL 2% v/v formic acid) prior to analytes elution by 0.5 mL 1:1 v/v methanol-acetonitrile followed by 0.5 mL methanol; eluate reduction to 0.25 mL compensated the initial sample dilution. The accuracy was assessed in certified blank fetal bovine serum and in human plasma, gaining satisfactory recovery in the range 65–122%, detection limits in the range 0.02–0.3 ng mL−1 (0.8 ng mL−1 for 17-β-estradiol) and suitable inter-day precision (relative standard deviation (RSD) <14%, n = 3). The method was evaluated in terms of selectivity, sensitivity, matrix-effect, instrumental carry-over, and it was applied to human plasma samples.

Green and Efficient Determination of Fluoroquinolone Residues in Edible Green Fruits and Leafy Vegetables by Ultrasound-Assisted Extraction Followed by HPLC-MS/MS

“…MDLs and MQLs (ng g −1 ) were calculated from the matrix-matched calibration curves as 3.3 and 10 times the ratio between the baseline noise away from the peak tail and the regression line slope, respectively, taking into consideration the whole sample treatment [ 30 , 31 , 32 ].…”

Mikroekstrakcija čvrstom fazom – inovativni pristup u bioanalitičkim istraživanjima

“…Magn-Humic čestice pripremljene pirolizom humične kiseline na silikagel za ekstrakciju steroida iz plazme. 31 Osim što su se oba ekstrakcijska postupka pokazala iznimno jednostavnim, tim tehnikama postignute su iznimno niske LOD vrijednosti (manje od 0,8 µg l −1 ). Premda ono istiskuje nadogradnju postojeće analitičke opreme, brojne su prednosti tog načina rada, od automatizacije postupka do veće ekološke prihvatljivosti kao i manje izloženosti analitičara organskim otapalima.…”

Bar Adsorbent Microextraction with Carbon-Based Sorbent Layers for the Identification of Pharmaceutic Substances

“…Some traditional procedures, such as liquid-liquid extraction (LLE) and solid-liquid extraction (SLE), have certainly been frequently used for regular investigations with excellent results. However, there are several drawbacks, such as the usage of massive quantities of toxic organic liquids and the amount of time it takes for the extraction methods [15]. Furthermore, in LLE, achieving restricted sample preparation parameters and the likelihood of emulsion is a critical barrier to achieving the extraction accuracy and effectiveness of the assessment.…”