Evaluation of cosmetic sunscreens using a spectroscopic SPF/PA measurement system

The optical design employs ‘true double beam optics’ with a chopper providing timed sample, reference and dark current measurements.A high sensitivity PMT (photomultiplier tube) provides accurate and reproducible measurements of both low (and high) concentration samples. By controlling the high voltage applied to the PMT, the dynode feedback circuit allows a wider dynamic range. It also provides excellent sensitivity for diffuse reflectance or transmittance of solid and liquid samples using an integrating sphere. The spectral bandwidth can be set as narrow as 0.1 nm for high resolution measurements, such as gas and vapor phase spectroscopy. Special low stray light slit settings which optimize the light image on the monochromator provide increased linearity of up to 5 absorbance units. With a comprehensive range of sampling accessories, the V-750 is well suited to measurement of samples in the UV and visible regions, with temperature control for biological samples and a number of transmittance and reflectance accessories for materials analysis.