In a large field study, the in-situ calibration of the Chemcatcher (R) passive sampler - styrenedivinylbenzene (SDB) covered by a polyether sulfone (PES) membrane - was evaluated for 322 polar organic micropollutants. Five rivers with different agricultural and urban influences were monitored from March to July 2012 with two methods i) two-week time-proportional composite water samples and ii) two-week passive sampler deployment. All substances - from different substance classes with logK(ow) -3 to 5, and neutral, anionic, cationic, and zwitterionic species - were analyzed by liquid-chromatography high-resolution tandem mass spectrometry. This study showed that SDB passive samplers are well-suited for the qualitative screening of polar micropollutants because the number of detected substances was similar (204 for SDB samples vs. 207 for composite water samples), limits of quantification were comparable (median: 1.3 ng/L vs. 1.6 ng/L), and the handling in the field and laboratory is fast and easy. The determination of in-situ calibrated sampling rates (field R-s) was possible for 88 compounds where the R-2 from the regression (water concentration vs. sampled mass on SDB disk) was >0.75. Substances with moderately fluctuating river concentrations such as pharmaceuticals showed much better correlations than substances with highly fluctuating concentrations such as pesticides (R-2 > 0.75 for 93% and 60% of the investigated substances, respectively). Flow velocity (0.05-0.8 m/s) and temperature (5 -20 degrees C) did not have an evident effect on the field R-s. It was observed that ionic species had significantly lower field R-s than neutral species. Due to the complexity of the different transport processes, a correlation between determined field R-s and logD(ow) could only predict R-s with large uncertainties. We conclude that only substances with relatively constant river concentrations can be quantified accurately in the field by passive sampling if substance-specific R-s are determined. For that purpose, the proposed in-situ calibration is a very robust method and the substance specific R-s can be used in future monitoring studies in rivers with similar environmental conditions (i.e., flow velocity, temperature, pH). (C) 2014 Elsevier Ltd. All rights reserved.