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. Author manuscript; available in PMC: 2023 Feb 28.
Published in final edited form as: Anal Chem. 2022 Jun 27;94(27):9618–9626. doi: 10.1021/acs.analchem.2c00711

Figure 4.

Figure 4.

(A) Stability of dried urine spot containing 20 ng clenbuterol stored on hydrophilic paper, with and without xanthan gum polymer coating. The spray solvent (ethyl acetate with 0.1% formic acid) used for online extraction and paper spray contained 20 ng/mL clenbuterol-d9 internal standard (IS, transition, m/z 286 → 268 → 204). (B) Stability of dried urine spot containing 50 ng trenbolone stored on hydrophilic paper, with and without polymer coating. 1 μg/mL nandrolone (transition: m/z 275 → 145) in ethyl acetate with 0.1% formic acid was used as an internal standard (IS). All signal (A/IS) for each storage time was normalized to A/IS of day zero (0). Corresponding information pertaining to %RSD (<10%) may be found in the Supplementary Information (Table S1).