Centrifugation Assisted Two‐Phase Hollow‐Fiber Liquid‐Phase Microextraction Coupled With Direct Fluorimetry for Precise Thiamine Detection

ABSTRACT To address the poor reproducibility associated with manual acceptor phase collection in two‐phase hollow‐fiber liquid‐phase microextraction, we introduce a novel centrifugal collection technique for the first time. Thiamine, selected as a model analyte, was oxidized into fluorescent thiochrome and extracted via hollow‐fiber liquid‐phase microextraction. Following extraction, centrifugation at 7000 rpm quantitatively transferred 15.7 ± 0.4 µL (relative standard deviation [RSD] 2.55%) of the acceptor phase, accounting for over 80% recovery, from the hollow fiber into a glass capillary for direct fluorescence detection. This procedure enhanced collection efficiency nearly 7‐fold and reduced RSD to 2.55%, compared with 2.3 ± 0.5 µL and 21.74% for the conventional syringe‐based method. Optimal extraction conditions were established as follows: n ‐heptanol as the acceptor phase, a 20 min extraction time, 400 rpm orbital shaking, 15% NaCl, and 8 min for acceptor phase loading. Under these optimal conditions, a good linear relationship was established for thiamine across the concentration range of 0.05–3.0 µg/mL ( R 2 = 0.9996), with recoveries exceeding 91.0% and a limit of detection (LOD) of 1.112 × 10 −2 µg/mL. The intra‐day and inter‐day RSD ( n = 7) were below 1.7%. The proposed centrifugal collection method is simple, highly reproducible, and efficient, offering a generic strategy to enhance reliability and throughput for the hollow‐fiber liquid‐phase microextraction technique.