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Refractrometry

What is Refractometry?

Refractometry is an analytical method that measures a material’s refractive index (RI)—how strongly it bends light. Refractive index is a fundamental physical property that correlates with composition, concentration, purity, and temperature.
Refractometry is widely used for solution concentration control, raw material verification, and quality assurance, especially for liquids such as solvents, oils, syrups, and chemical formulations.

What Refractometry Can Help You Solve

  • Concentration measurement of solutions (e.g., % solids, sugar content, salt/acid concentration)

  • Raw material identification & verification by RI comparison to specification/standards

  • Purity screening and batch-to-batch consistency checks

  • Process monitoring for mixing, dilution, and endpoint control

  • Troubleshooting formulation shifts (wrong solvent ratio, contamination, evaporation loss)

Typical Applications

  • Food & beverage: Brix/sugar content, syrups, juices, beverages

  • Pharmaceutical & biotech: excipients, buffers, formulation concentration checks

  • Chemicals & solvents: solvent blends, monomers, reagents, cleaning solutions

  • Oils & lubricants: base oil verification, blend consistency, contamination screening

  • Coatings/inks/resins: solvent ratio control and incoming QC (project-dependent)

Measurement Options & Capabilities

Measurement Modes

  • Refractive Index (nD) at controlled temperature (typically reported at 20°C or specified temperature)

  • Brix / concentration scales (as applicable to the sample type and client requirement)

  • Temperature compensation or temperature-controlled measurement for improved comparability

What You Receive

  • Reported RI value(s) with measurement conditions (temperature, wavelength/model standard)

  • Pass/fail vs. your specification (if provided)

  • Comparison across multiple batches/suppliers (optional)

  • Notes on anomalies suggesting contamination or formulation deviation (when applicable)

Sample Requirements

  • Sample types: liquids, solutions, low-viscosity to moderate-viscosity materials

  • Typical volume: usually 0.5–5 mL (varies by method and sample handling)

  • Condition: free of bubbles and particulates when possible; filter if appropriate

  • Packaging: clean, tightly sealed vial to prevent evaporation (especially volatile solvents)

  • Information to provide: target concentration or spec range, solvent system, safety notes (SDS if available)

Workflow

  • Requirement review (RI only vs. Brix/concentration scale; reporting temperature; spec limits)

  • Sample check (homogeneity, volatility, viscosity, particulates)

  • Instrument calibration/verification (standards as needed)

  • Measurement under controlled temperature conditions

  • Reporting with clear results and comparison to spec/control

FAQs

Refractive index is the measured optical property. Brix is a derived scale commonly used for sugar solutions; the conversion depends on the solution type and assumptions.

RI alone is usually not sufficient for definitive identification, but it is excellent for verification against known specifications and detecting mixing errors or contamination. For unknown identification, we may recommend GC/MS, FTIR, or NMR.

Accuracy depends on instrument capability, calibration, and especially temperature control. We report measurement conditions to ensure comparability.

Yes. Bubbles and particulates can distort readings. We recommend gentle degassing and/or filtration when compatible with the sample.

Many viscous samples can be measured with appropriate handling. Strongly opaque or heavily particulate materials may require evaluation or a different technique.

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