Overview
ISO 24465:2023 specifies a standardized method to determine the minimum detectability (limit of detection) of surface plasmon resonance (SPR) devices. Applicable to both white‑light illumination and laser illumination SPR systems with angle‑scanning capability, the standard defines sample preparation, instrument conditions, data acquisition and a statistical protocol to quantify the lowest reliably measurable response.
Key topics and requirements
- Scope: Method for measuring the lowest detectable SPR signal for white‑light and laser angle‑scanning devices (Kretschmann geometry).
- Measurement principle: Monitor changes in reflected light (spectral dip or resonant angle) caused by analyte‑induced changes in dielectric constant; responses recorded as a sensorgram (response units, RU) using CCD or photodetectors.
- Statistical approach: Uses the 3‑sigma rule to define the lower limit of detectability (signal-to-noise ≈ 1); series measurements across concentrations yield SD and detection limit.
- Standard sample: Recommends single neutral solutes (e.g., ethylene glycol or sucrose in DI water) to avoid complex surface chemistry; prepare multiple concentration points (minimum five) for statistical accuracy.
- Instrument conditions: Control and document optics alignment, cleanness of optics, temperature, and flow rate (typical suggested range 5 μl/min to 100 μl/min).
- Sensor chip: Use a bare metal (gold) sensor chip for absolute device characterization; typical gold film thickness is around 100 nm.
- Data recording: Detailed acquisition and recording procedures are specified to ensure reproducible RU measurements and derivation of the limit of detection.
Applications and practical value
- Characterizing and validating the sensitivity performance of SPR instruments during manufacturing, acceptance testing, or routine quality control.
- Establishing traceable limit of detection (LOD) for research labs performing label‑free biomolecular binding studies.
- Supporting procurement decisions and performance comparisons between SPR platforms (white‑light vs. laser systems).
- Providing non‑expert operators with a simple, reproducible protocol using neutral analytes for baseline device capability assessment.
Who should use this standard
- SPR instrument manufacturers and calibration labs
- Analytical chemists and surface scientists
- QA/QC personnel in biotechnology and pharmaceuticals
- Research groups deploying label‑free biosensing or surface chemical analysis
Related guidance
- Prepared by ISO/TC 201 (Surface chemical analysis). This document contains no normative references; users may consult other ISO surface chemical analysis standards and manufacturer manuals for complementary procedures.
Keywords: ISO 24465:2023, surface plasmon resonance, SPR, minimum detectability, limit of detection, 3‑sigma rule, white‑light illumination, laser illumination, Kretschmann geometry, sensor chip, response unit.
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