Purpose: Blanking Total Transmittance Readings  

Why is Blanking Required?

• It corrects for the absorption of the cuvette and the solvent or carrier liquid.
• Ensures that only the sample's properties are measured, removing background interference.

Blanking Method:

• Use a matched cuvette filled with pure solvent as the blank. Place in the instrument during standardization.

Example Use Cases:

• Aromatic & Aliphatic Hydrocarbons (blank with hexane, toluene, or isopropanol).
• Ethanol or Methanol-Based Solutions (blank with the same alcohol).
• Edible Oils & Lipids (blank with neutral, colorless oil).

Typical Equipment:

• HunterLab spectrophotometer with TTRAN mode (Total Transmittance).
• Quartz or borosilicate absorption cells (cuvettes).

Haze & Clarity Measurements (ASTM D1003, Transparency Analysis)

Why is Blanking Required?

• Ensures light scattering and stray light are accounted for without the sample.
• Corrects for minor variations in optical path and instrument response.

 Blanking Method:

• Use an empty glass cell as the blank before measuring hazy liquids.
• For oil-based samples, use a matching, clear oil standard as the blank.
• Place in the instrument during standardization.

 Example Use Cases:

• Industrial Fluids & Lubricants (ASTM D1003 haze measurement).
• Beer, Wine, & Soft Drinks (clarity and transparency evaluation).
• Biological Fluids (protein aggregation and turbidity measurements).

 Typical Equipment:

• HunterLab spectrophotometer with TTRAN mode (Total Transmittance).
• Optical glass absorption cells.
• Plastic absorption cells may also be used, if appropriate.

Colorimetric Measurements (APHA, Pt-Co, Saybolt, Gardner Color)

Why is Blanking Required?

• Blanking corrects for instrument drift and background absorption from the carrier liquid.
• Ensures that color differences are measured relative to a standard.
• Place in the instrument during standardization.

Blanking Method Examples:

• Use a colorless reference liquid (e.g., distilled water or a known standard).
• In Pt-Co (APHA) color measurements, blank with ultra-pure water.
• In oil-based color tests, Saybolt uses Dodecane.
• For liquid standards in oils, varnishes, fatty acids, and resins, use Gardner and blank with air or water, depending upon your SOP.
• Fuel & Diesel Color Testing following ASTM D1500 & Saybolt Color use Dodecane.
• Vegetable Oils & Fats use the Lovibond scale.
• Pharmaceutical & Cosmetic Liquids (yellowness index, whiteness index).

Typical Equipment:

• HunterLab Vista spectrophotometer
• Glass or quartz colorimetric sample cells.
• Plastic absorption cells may also be used, if appropriate.

pH & Chemical Reaction-Based Measurements (UV-Vis & Fluorometry)

Why is Blanking Required?

• Ensures that background fluorescence or absorbance from buffers does not interfere with results.
• Normalizes pH-sensitive solutions against their unreacted blank.

Blanking Method:

• Use a buffer-only blank for pH-sensitive reactions.
• For fluorescent measurements, use a solvent blank that matches the sample medium.
• Place in the instrument during standardization.

Example Use Cases:

• Protein Assays (Bradford, Lowry, BCA protein assays).
• Enzyme Kinetics (fluorescent or colorimetric enzyme activity tests).
• Dye & Indicator-Based pH Studies (phenol red, bromothymol blue).

Typical Equipment:

• HunterLab UltraScan PRO, UV-Vis spectrophotometers.
• Quartz cuvettes for fluorescence and borosilicate cells for colorimetric pH tests. Plastic cuvettes may be used as appropriate. 

Test Type	Key Measurement Scale	Blanking/Calibration Method	Typical Standards Used
Transmittance & Absorbance (UV-Vis/NIR)	%T, Absorbance (A)	Solvent blanking	NIST-traceable neutral density filters
Haze & Clarity (ASTM D1003)	Haze %, Clarity Index	Empty cuvette calibration	ASTM D1003 reference haze materials
Colorimetric (APHA, Saybolt, Gardner)	APHA, Saybolt, and Gardner color scales	Certified liquid color standards	ASTM D1209, D156, D1544
pH & Enzymatic Reactions	Absorbance shifts (pH, protein assays)	Buffer-only blanking	pH buffers, protein standards
Refractive Index & Turbidity	RI (Brix, nD20), NTU, FTU	RI liquid standards, Formazan calibration	Cargile RI liquids, & ISO 7027 turbidity standards

Do you need more information? Submit a ticket and a support team member will reach out to you soon!