A simple, fast, sensitive and accurate methodology based on a LLE followed by liquid chromatography-tandem mass spectrometry for simultaneous determination of four regioisomers (8-iso prostaglandin F-2 alpha, 8-iso-15(R)-prostaglandin F-2 alpha, 11 beta-prostaglandin F-2 alpha, 15(R)-prostaglandin F-2 alpha) in routine analysis of human plasma samples was developed. Isoprostanes are stable products of arachidonic acid peroxidation and are regarded as the most reliable markers of oxidative stress in vivo. Validation of method was performed by evaluation of the key analytical parameters such as: matrix effect, analytical curve, trueness, precision, limits of detection and limits of quantification. As a homoscedasticity was not met for analytical data, weighted linear regression was applied in order to improve the accuracy at the lower end points of calibration curve. The detection limits (LODs) ranged from 1.0 to 2.1 pg/mL. For plasma samples spiked with the isoprostanes at the level of 50 pg/mL, intra-and interday repeatability ranged from 2.1 to 3.5% and 0.1 to 5.1%, respectively. The applicability of the proposed approach has been verified by monitoring of isoprostane isomers level in plasma samples collected from young patients (n = 8) subjected to hyperbaric hyperoxia (100% oxygen at 280 kPa(a) for 30 min) in a multiplace hyperbaric chamber. (C) 2017 Elsevier B.V. All rights reserved.