No abstract

The aim of this study was to assess the interlaboratory reproducibility of ultra‐high performance supercritical fluid chromatography coupled with tandem mass spectrometry method for routine antidoping analyses. To do so, a set of 21 doping agents, spiked in urine and analyzed after dilute and shoot treatment, was used to assess the variability of their retention times between four different laboratories, all equipped with the same chromatographic system and with the same ultra‐high performance supercritical fluid chromatography stationary phase chemistry. The average relative standard deviations (RSD%) demonstrated a good reproducibility of the retention times for 19 out of 21 analytes, with RSD% values below 3.0%. Only for two substances, namely fenbutrazate and niketamide, the retention was not repeatable between laboratories, with RSD% of approximately 15% in both cases. This behaviour was associated with (a) the low organic modifier percentage (around 2‐4%) in the mobile phase at the corresponding retention times, and (b) the influence of the system volume on poorly retained analytes. An analysis on seven “blind” urines was subsequently carried out in the same four laboratories. In these blind samples, either one, two, or none of the 21 doping agents previously analyzed were present at an unknown concentration. Each laboratory had to perform the identification of the compounds in the samples and estimate their concentrations. All laboratories assigned all target analytes correctly in all blind urine samples and provide a comparable estimation of their concentrations.

The aim of this paper is to investigate the interactions between industrial-grade polycarboxylate ether (PCE) polymers and ordinary Portland cement to assess whether it is possible to draw structure/performance relations for impure, yet fully characterized, poly-mers. To this end, thirteen PCE polymers were synthesised in industrial fashion, deeply ana-lyzed and tested in cement paste. Chemical stability and adsorption behaviour have been evaluated through gel permeation chromatography technique, leading to insights regarding the plasticization timing and the adsorption control. All the results were interpreted and criti-cally discussed by invoking the characteristics of initial dispersers and workability retainers; furthermore a comprehensive description has been attempted through the Gay and Raphaël conformation plot, based on the establishment of which molecular feature affects each step of the PCE’s working mechanism. The results confirm many of the findings despite the imper-fect nature of the chosen polymers and show that common impurities, such as unreacted side chains, do not noticeably interact with the binder. In particular it is clear that the limiting stage of the entire action lies on adsorption rate and occurrence, which seems to be ruled by the absolute value of charge per chain and by the conformation regime