Recently, a novel analytical instrument setup was reported for automatic preconcentration and determination of organic compounds in various sample matrices based on online hollow fiber liquid-phase microextraction (HF-LPME)-high-performance liquid chromatography (HPLC). In the present work, this novel instrument has been developed for extraction and determination of phthalate esters samples located in the polyethylene (PET) bottles. By using an automated syringe pump for loading supported liquid membrane (SLM) and acceptor solvents, a platform lift for moving sample vial, and a sampling loop for online injection of extract to HPLC, along with an electronic board with AVR microcontroller for storage of data and instrument programs, an automated sample preparation-HPLC analysis was developed. Optimization of extraction parameters was carried out by Box-Behnken design (BBD) which required a minimum of 29 experiments; the entire set of experiments was performed completely automatically and consecutively without any human intervention. The limits of detection (three times the S/N) ranged from 0.3 to 0.5 mu g L-1. Effective preconcentration of the analytes was also achieved (between 153 and 335). The method is highly precise, with relative standard deviations varying between 5.1 and 6.4 % and also accurate (recovery percentages >94.6 %). The main advantages of the developed method are high sensitivity, selectivity, and reliability of results, minimum sample manipulation, full automation, suitable extraction time, low solvent consumption, and ease of use. The applicability of the online automated HF-LPME/HPLC-UV instrument was validated for quantitative extraction and determination of phthalate esters in aqueous samples located inside the PET bottles.