A biomarker panel of secondary hypertension is simultaneously quantified by coupling of magnetic solid-phase extraction and liquid chromatography-tandem mass spectrometry.

RATIONALE: Secondary hypertension is often caused by activation of complex multi-organ endocrine systems, while renin activity indicated by angiotensins (Angs), aldosterone (ALD) and cortisol (COR) in such systems are generally accepted as its diagnostic markers. As antibody-based methods cannot offer comparable quantification for these biomarkers, a liquid chromatography (LC)-tandem mass spectrometry (MS/MS)-based approach was developed to quantify them simultaneously and accurately. METHODS: Five different beads for magnetic solid-phase extraction (MSPE) were evaluated towards their enrichment efficiency for these biomarkers. An LC system with optimized elution gradient and a triple-quadrupole MS with tuned parameters were coupled to quantitatively monitor the extracted analytes. The method performance was further examined such as linearity, precision, stability, recovery rate and matrix effect. Based on the developed method, the abundance of Ang II, ALD and COR in plasma was measured and the quantification was compared with that derived from commercial ELISA kits. RESULTS: As compared with other MSPEs, Angs, ALD and COR were highly enriched by the HLB magnetic beads with satisfactory recoveries. These analytes were simultaneously quantified by LC/MS/MS and all the method parameters for quantification were well matched with the requirements of clinical testing. Comparison of the quantitative results derived from ELISA and LC/MS/MS exhibited that the two methods offered basically comparable values with Pearson r values at 0.896, 0.895 and 0.835, respectively. The stability test for plasma Angs at room temperature indicated that the abundance of Ang II was relatively stable within 3 h, whereas that of Ang I and Ang 1-7 was time-dependently changed. CONCLUSIONS: Coupling of HLB beads and LC/MS/MS thus enables simultaneous quantification of a set of biomarkers related to secondary hypertension.

Validation of a HILIC Method for the Analysis of Ergothioneine in Fermentation Broth.

A hydrophilic interaction liquid chromatography method has been established for the quantification of ergothioneine (EGT) in fermentation broth. Chromatographic separation was conducted on a Venusil hydrophilic interaction liquid chromatography (HILIC) column (250 × 4.6 mm, 5 µm) at an elution rate of 1.0 mL/min with an isocratic mobile phase consisting of acetonitrile/20 mmol/L ammonium acetate solution (85 : 15, v/v) adjusted to pH 6.0 with acetic acid. Analytes were detected at 254 nm using a UV-VIS detector. The injection volume was 10 µL, and the column temperature was 40°C. The limits of detection and limits of quantification were 63 and 21 µg/L, respectively. Excellent linearity [correlation coefficient (R(2)) = 0.9999] was achieved for EGT quantification in the range of 5-400 mg/L. The relative standard deviations of repeatability, intermediate precision and stability were 1.47, 1.03 and 1.66%, respectively, and EGT recoveries were within 99.2-100.8%. The chromatographic peak corresponding to EGT in the HILIC spectrum was confirmed using ESI-MS. In general, the method developed here is simple, reliable, accurate, and stable and may be useful for routine analyses in EGT biosynthesis research.

An Optimized High Throughput Clean-Up Method Using Mixed-Mode SPE Plate for the Analysis of Free Arachidonic Acid in Plasma by LC-MS/MS.

A high throughput sample preparation method was developed utilizing mixed-mode solid phase extraction (SPE) in 96-well plate format for the determination of free arachidonic acid in plasma by LC-MS/MS. Plasma was mixed with 3% aqueous ammonia and loaded into each well of 96-well plate. After washing with water and methanol sequentially, 3% of formic acid in acetonitrile was used to elute arachidonic acid. The collected fraction was injected onto a reversed phase column at 30°C with mobile phase of acetonitrile/water (70 : 30, v/v) and detected by LC-MS/MS coupled with electrospray ionization (ESI) in multiple reaction monitoring (MRM) mode. The calibration curve ranged from 10 to 2500 ng/mL with sufficient linearity (r (2) = 0.9999). The recoveries were in the range of 99.38% to 103.21% with RSD less than 6%. The limit of detection is 3 ng/mL.

High-throughput GC/MS and HPLC/MS/MS techniques for the multiclass, multiresidue determination of 653 pesticides and chemical pollutants in tea.

An efficient and sensitive method has been established for simultaneous determination of 653 pesticides in teas by GC/MS and HPLC/MS/MS. The method involved extraction with acetonitrile followed by cleanup using Cleanert-TPT SPE and subsequent identification and quantitation of 490 pesticides by GC/MS and 448 pesticides by HPLC/MS/ MS. The LODs for pesticides determined by GC/MS were between 1.0 and 500 microg/kg, and those determined by HPLC/MS/MS were between 0.03 and 4820 microg/kg. At the low fortification levels of 0.01-100 microg/kg, the average recoveries of 94% of the pesticides determined by GC/MS were between 60 and 120%, 77% of which had an RSD below 20%. For 91% of pesticides determined by HPLC/MS/MS, the average recoveries were between 60 and 120%, 76% of which had an RSD below 20%. The paper also reports a novel SPE column, Cleanert TPT, which comprised graphitized carbon black (PestiCarb), polyamine silica, and amide polystyrene for purifying the tea samples. The results indicated good repeatiblity and reproducibility.