“…The sorbent can be coated as a thin lm on the inner surface of the needle [18][19][20] or packed (as particles or monolith) inside it. [21][22][23] In both cases, the technique allows the sample to ow through the needle boosting the interaction with the target analytes. The miniaturized size of the needles requires little solvent for the elution, even when high sample volumes are processed, which is particularly interesting for an efficient preconcentration.…”