PMC

Average mass spectra recorded in the positive ion mode of a lung tissue section. (A) Full mass spectrum covering the m/z range of 200-1100. (B) Full mass spectrum covering a m/z range of 200–400, showing the protonated clozapine ion (M+H)⁺ at m/z 327.1 and the protonated desmethyclozapine (DMC) ion (M+H)⁺ at m/z 313.1. (C) Full mass spectrum of control sample 984 covering the m/z range of 200–400. (D) Shown is the m/z range of 310–340, displaying the absence of clozapine and desmethylclozapine in the control.

Rat kidney and testis 0.5 h after dose. (A) Optical image of 10 μm rat testis section. (B) Corresponding DESI-MS/MS mass spectral image of clozapine for (A), represented by plotting the intensity of the characteristic fragment ion at m/z 270.1 arising from the mass-selected molecular ion at m/z 327.1 and shown in false colors in raw pixel format. (C) Optical image of 10-μm rat kidney section. (D) Corresponding DESI-MS/MS mass spectral image of clozapine for C, represented by plotting the characteristic fragment ion at m/z 270.1, arising from the mass-selected molecular ion at m/z 327.1 and shown in false colors in raw pixel format.

Optical images of a sagittal rat brain section and overlayed images of clozapine deposited onto the tissue. (A) Optical image. (B) Interpolated image of an 1 μl deposit of 20 ng/μl solution of clozapine in acetonitrile; pixel size 245 μm × 245 μm; shown with intensity scale bar. (C) Overlay of the optical image in A and the clozapine image in B, shown on the same scale. (D) Zoom (×3) of the overlayed images with 1-mm scale bar. (E) Overlay of the optical image in A and the clozapine image after a second scan. (F) Zoom (×3) of the overlayed images with 1 mm scale bar.

Optical image of a 30.6 × 16.1 mm² lung tissue section and the corresponding selected ion images, each having 132 × 70 pixels and shown in false colors in raw pixel format. (A) Optical image. (B) Image of clozapine at m/z 327.1. (C) Image of desmethylclozapine at m/z 313.1. (D) Image of sodiated (M+ Na⁺) PC 16:0/16:0 at m/z 756.4. (E) DESI-MS imaging and LC-MS/MS results of D. The signal responses in each method were normalized to the maximum response in each experiment. The normalized signal responses were then plotted against the clozapine plasma concentrations as determined by LC-MS/MS ().

Optical image of a 22 × 11 mm² sagittal rat brain section and the corresponding selected ion image. (A) Optical image of a sagittal rat brain section taken from animal 992 (0.5 h after dose). CB, cerebellum; Cbc, cerebral cortex; Cpu, caudate-putamen; Hpc, hippocampus; SNr, substantia nigra. (B) DESI mass spectral image of clozapine in the brain section recorded in MS/MS mode. The image of the fragment ion at m/z 270.1 is shown by using false colors in raw pixel format. (C) Average product ion mass spectrum of m/z 327.1 ± 2 in B. (D) Average product ion mass spectrum of m/z 327.1 ± 2 in control sample 984.