SpectralBench
Side-by-side spectral comparison with five visualization modes
Comparing spectra is essential for QA/QC batch consistency checks, identifying unknowns against reference materials, monitoring chemical reactions, and verifying formulations. Traditionally this requires expensive desktop software — packages like OPUS, GRAMS, or LabSolutions that can cost thousands of dollars per seat and lock data inside proprietary workflows.
SpectralBench brings spectral comparison to the browser. Load two or more spectra, choose a visualization mode, and interpret both visual and quantitative results without installing anything. All processing is client-side — your data never leaves your machine. When you need to prepare your spectra first, the Spectral File Viewer lets you inspect individual files, and the Preprocessing tool handles baseline correction and normalization before comparison.
Upload two or more spectral files by dragging them onto the workbench or clicking the upload area. SpectralBench displays them simultaneously with automatic color coding so each trace is immediately distinguishable. No manual configuration is needed — file format detection and axis alignment happen automatically.
Select from five comparison modes to suit your analysis goal. Overlay superimposes spectra directly on a shared axis so you can spot peak shifts and intensity differences at a glance. Stack offsets spectra vertically, preserving individual trace shape while avoiding visual overlap — ideal when comparing many spectra in a series. Difference subtracts one spectrum from another point by point, isolating components that vary between the two samples.
Mirror mode flips the reference spectrum below the sample on the same axis, creating a symmetric view that makes peak alignment immediately obvious — a classic technique in pharmaceutical and forensic comparison workflows. Split mode shows two spectra in side-by-side panels with synchronized zoom so panning or zooming one panel updates the other simultaneously. Throughout all modes, the HQI similarity score provides a single quantitative measure of how closely the two spectra match.
Spectral comparison is one of the most common tasks in analytical chemistry, yet its purpose varies widely depending on the application. In QA/QC, overlaying a sample spectrum against a reference standard is a fast, objective test for batch consistency — a significant peak shift or intensity change flags a potential problem before a product reaches the next stage of production.
For unknown identification, comparing a measured spectrum against a library of reference spectra allows you to narrow down candidate compounds. The HQI score ranks candidates objectively, removing the subjectivity of visual inspection. In reaction monitoring, overlaying spectra taken at different time points reveals how functional groups evolve as a reaction proceeds — the appearance of a carbonyl peak or the disappearance of an alkene band tells the story of a transformation.
Formulation verification relies on comparison to confirm that a finished product contains the correct active ingredients and excipients at the expected ratios. In all of these workflows, preprocessing the spectra before comparison significantly improves results. Baseline correction removes instrumental drift that would otherwise inflate or distort differences, while normalization puts both spectra on the same intensity scale so HQI scores reflect genuine compositional similarity rather than measurement artifacts. Use the Spectral Preprocessing tool to prepare your spectra before loading them here.
The Hit Quality Index (HQI) is a quantitative measure of spectral similarity computed by calculating the correlation between two spectral vectors after optional preprocessing. The result is expressed on a scale from 0 to 100, where 0 indicates no spectral similarity and 100 indicates mathematically identical spectra.
In practice, a score above 90 is considered a strong match and typically confirms that two samples share the same compound identity or formulation. Scores in the 70–90 range suggest structural similarity — the samples may share a common chemical class or backbone while differing in substituents or concentration. Scores below 70 indicate significant spectral differences, pointing to distinct compounds, degradation products, or contamination.
HQI is the standard metric used in spectral library searching and forensic analysis precisely because it condenses a complex multi-point comparison into a single interpretable number. When screening a large batch of samples against a reference, HQI lets you quickly triage results — samples scoring below a threshold are flagged for further investigation while high-scoring samples are confirmed automatically.
Load both FTIR files into SpectralBench by dragging them onto the workbench. Select overlay mode to superimpose the spectra with color-coded traces, or use difference mode to subtract one from the other. The HQI similarity score gives you a quantitative measure of how closely the two spectra match.
HQI stands for Hit Quality Index, a quantitative measure of spectral similarity on a scale from 0 to 100. A score above 90 typically indicates a very good match between two spectra. Lower scores suggest significant spectral differences. HQI is widely used in QA/QC, forensic analysis, and library searching to rank candidate matches.
Yes, but for the best results you should preprocess the spectra first. Use SpectralBench's preprocessing tools to apply baseline correction and normalization before comparing. This removes instrumental artifacts and puts both spectra on the same scale, giving you a more meaningful comparison.
A difference spectrum is the result of subtracting one spectrum from another, point by point. It highlights changes between two samples — for example, identifying a contaminant in a batch QA check, monitoring a chemical reaction over time, or detecting subtle compositional differences between formulations. Peaks in the difference spectrum correspond to components present in one sample but not the other.