1：Experimental Design and Method Selection:

The study employs LDI-MSI for direct and semi-quantitative analysis with minimal sample preparation, using multivariate data analysis (PLS-DA and HCA) to differentiate formulations based on spectral profiles.

2：Sample Selection and Data Sources:

Sildenafil citrate tablets from six manufacturers (one reference, four generic, one unlicensed) were purchased, with three batches per manufacturer and five replicates per tablet.

3：List of Experimental Equipment and Materials:

Includes TLC silica gel 60G plates, methanol, formic acid, PVDF membrane, MALDI LTQ-XL mass spectrometer, ESI-LTQ-XL Orbitrap Discovery mass spectrometer, and software like Image Quest, ImageJ, Mass Frontier, and MetaboAnalyst 4.

4：Experimental Procedures and Operational Workflow:

0. 4. Experimental Procedures and Operational Workflow: Tablets were smeared onto activated TLC plates and analyzed via LDI-MSI without matrix addition. HRMS analysis involved dilution in methanol, filtration, and direct infusion. Data processing included spectral analysis, semi-quantification by MSI, and statistical tests (ANOVA, PLS-DA, HCA).

5：Data Analysis Methods:

Statistical analysis included one-way ANOVA after normality check, PLS-DA for feature selection, and HCA for clustering. Semi-quantification used ImageJ for intensity measurements, and structure elucidation used Mass Frontier and PubChem.