Determination of lapachol in the presence of other naphthoquinones using 3MPA-CdTe quantum dots fluorescent probe

3MPA-CdTe QDs in aqueous dispersion was used as a fluorescent probe for the determination of lapachol, a natural naphthoquinone found in plants of the Bignoniaceae family genus Tabebuia. Working QDs dispersions (4.5 × 10−8 mol L−1 of QDs) was prepared in aqueous media containing Tris–HCl buffer pH 7.4 and methanol (10% in volume). The excitation was made at 380 nm with signal measurement at 540 nm. To establish a relationship between fluorescence (corrected to inner filter effect) and concentration of lapachol, a Stern–Volmer model was used. The linear range obtained was from 1.0 × 10−5 to 1.0 × 10−4 mol L−1. The limit of detection (xb − 3 sb) was 8.0 × 10−6 mol L−1. The 3MPA-CdTe QDs probe was tested in the determination of lapachol in urine, previously cleansed in an acrylic polymer. The average recovery was satisfactory.

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► 3MPA-CdTe QDs as fluorescent probe to determination of lapachol.
► Intensity of probe decreases following a Stern–Volmer model.
► Excitation was made at 380 nm with signal measurement at 540 nm.
► Results were corrected to eliminate inner filter effect.
► The method can detect down to 130 ng of lapachol present in the urine samples.