Hollow polymer nanospheres (HPSs) were prepared based on the feeble acid–base interaction-induced assembly in hydrothermal conditions. It was first used as a sorbent in microextraction by packed sorbent method for the separation of the major biomarkers of BTEXs in urine samples. Fourier-transform infrared spectroscopy, X-ray diffraction, scanning, and transmission electron microscopy were employed to assess the morphological and dimensional structures of the products. All parameters affecting the adsorption of the analytes by the sorbent, including sorbent amount, sample volume, washing, and elution solutions, extraction cycles, pH, and temperature of the sample solution, were investigated. Good linear ranges (e.g., 5–1000 µg/mL for MA, r2 > 0.98) and good limits of detection (e.g., 0.01 µg/mL for tt-MA) were obtained as well. The values of inter- and intra-day relative standard deviations were in the range of 2.09–3.41 and 5.74–7.12%, respectively. The HPS-MEPS technique coupled with HPLC–UV detection was successfully applied to determine tt-MA, HA, MA, and m-MHA in the urine with the extraction recoveries of 104.9, 105.5, 102.6, and 81.8%, respectively. Based on the results, HPS as a durable and reusable adsorbent (more than 100 times) with MEPS was excellent for the facile and rapid determination of HA, MA, and tt-MA from urine samples in the shortest time and without using complicated processes. It can also be suggested as an alternative method for earlier procedures in the biomonitoring of BTEX compounds.
