Micro Ion Extractor for Single Drop Whole Blood Analysis

A micro ion extractor (MIE) was developed for trace anion determination by ion chromatography-mass spectrometry from a single drop (25 μL) of whole blood without pretreatment. Target analytes were iodide and thiocyanate, which play key roles in thyroid hormone production. Whole blood (25 μL) was pipetted from an earlobe or finger prick and placed in the 16 μL cavity of the device. A reproducible fraction of iodide and thiocyanate was transferred through a membrane to an acceptor solution layer by electromigration for 60 s. An isolator solution layer and a cation exchange membrane is provided between the acceptor and the anode to prevent gas formation or redox processes in the acceptor. The acceptor contents are transferred online to the ion chromatograph. Isolator solution composition and applied voltage were optimized. Recoveries from samples from 16 different volunteers of both sexes and differing ages were the same within ±10% relative standard deviation. Dietary effects on blood iodide and thiocyanate levels are reported. The very low sample requirement permitted multiple sample collections per day. The MIE device is expected to be useful for clinical studies that require several/many temporally spaced blood samples by keeping the invasive nature of blood collection as minimal as possible.