Due to the similarity in ionic radius,
perchlorate has been reported to inhibit the
iodide intake in the thyroid gland, which may lead to low heart rate,
weight gain, and
fatigue. In recent years, the presence of
perchlorate in
drinking water, surface water, soil, and food supplies in the United States has raised a great concern on establishing the maximum residue limit (MRL) for
perchlorate to reduce its possible adverse influence on human health. US EPA currently puts
perchlorate on the final third Contamination Candidate List (CCL3) and suggests a health reference level at 4.9 μg L⁻¹. The MRL of
perchlorate was therefore set at 5.0 μg L⁻¹ by the authors for method validation. In this study, large volume injection (up to 1-mL) and online solid phase extraction (SPE) were utilized for pre-concentrating
perchlorate ions and removing unretained matrix components prior to reversed-phase HPLC analysis using ESI-tandem MS under the negative mode. After eluting
perchlorate from online SPE, 0.1%
formic acid solution was utilized for isocratic HPLC analysis without any organic
solvent. Multiple reaction monitoring (MRM) and the internal standard, Cl₁₈O₄⁻, were utilized for quantitatively determining
perchlorate in
bottled water and bottled
tea samples. Two linear ranges, 0.05-0.50 μg L⁻¹ and 0.50-10.00 μg L⁻¹, were established to better estimate the residual amounts of
perchlorate in
bottled water samples with a method detection limit (MDL, signal-to-noise ratio of 3) of 0.01 μg L⁻¹. The linear range was 1.50-10.00 μg L⁻¹ for bottled
tea samples with a MDL of 0.5 μg L⁻¹. In addition, the proposed method was further validated based on the EU Commission Decision 2002/657/EC, including within-laboratory reproducibility, decision limit (CCα), and detection capability (CCβ) for
bottled water and bottled
tea samples. The intra-day/inter-day precision and accuracy as well as within-laboratory reproducibility were determined by calculating the relative standard deviation (RSD) at three spiked levels (0.5 MRL, 1 MRL, 1.5 MRL). The within-laboratory reproducibility (n=18) for both
bottled water and bottled
tea samples, spiked at MRL (5.0 μg L⁻¹) of ClO₄⁻, was less than 10%. The values of CCα/CCβ were reported as 5.43/5.74 μg L⁻¹ and 5.03/5.75 μg L⁻¹ for
bottled water and bottled
tea samples, respectively.