LimsPulse
Cosmetics testing

In vitro SPF analyser (UV transmittance analyser)

Measures how much ultraviolet light passes through a thin film of sunscreen spread on a roughened PMMA plate, then calculates in vitro SPF, UVA protection factor and critical wavelength from the transmittance spectrum.

  • Cosmetics & personal care
  • Sunscreen manufacturers
  • UV filter suppliers
  • Contract testing labs
  • Textiles (UV protection)
Illustration of In vitro SPF analyser (UV transmittance analyser)
Follow your site SOP
This is a typical operating sequence for learning. Your instrument model and approved SOP take precedence.
STAGE 1

Before you start

  1. 1Switch on the lamp and allow the warm-up time in the manual (often 15–30 minutes).
  2. 2Check the wavelength and transmittance verification is in date.
  3. 3Condition PMMA plates and products at room temperature (about 25 °C).
  4. 4Confirm the analytical balance used for film dosing is verified.
  • UV lamps and solar simulators can burn skin and damage eyes. Never look into the beam and keep covers closed.
STAGE 2

Reference and sample plates

  1. 1Measure a blank reference plate (glycerine or as the method states) to set the 100% transmittance baseline.
  2. 2Weigh the product onto a fresh plate as many small dots at the specified dose (for ISO 24443 typically about 1.3 mg/cm²).
  3. 3Spread quickly and evenly over the whole plate, first with light strokes and then with firmer pressure, using a pre-saturated gloved finger or an automated spreader.
  4. 4Let the film settle in the dark for the time in the method.
  • Keep spreading time and pressure consistent. Most variation in in vitro SPF comes from the film, not the instrument.
STAGE 3

Measurement

  1. 1Scan each plate at several positions (for example 4–9 spots) from 290 to 400 nm.
  2. 2Test at least three plates per product (or the number in the method).
  3. 3For UVA-PF, expose the plates to the calculated UV dose in the solar simulator and scan again.
  4. 4Run a reference sunscreen of known value with each series as a control.
  • Reject spots with visible defects, bubbles or bare patches as the method allows, and record why.
STAGE 4

Results and shutdown

  1. 1Review the spectra for unusual shapes, then calculate SPF, UVA-PF, UVA-PF/SPF ratio and critical wavelength.
  2. 2Check variability between plates against the method limit (for example a coefficient of variation or 95% confidence interval).
  3. 3Discard used plates (single use), clean the stage and switch off the lamp.
  4. 4Complete the instrument log.
In LimsPulse · Calibration Management

Keep every SPF analyser in control: usage logs, calibration and maintenance schedules, and automatic blocking of overdue instruments.

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