Metrology of the vitamin-D-synthetic activity of UV lamps

Ultraviolet lamps are widely used in phototherapy, and positive health effect of UV irradiation is associated with the synthesis of vitamin D in human skin. Nevertheless, to avoid harmful effects of UV radiation a variety of commonly used broadband UV detectors have an output in erythema units. Therefore the measurement of the vitamin-D-synthetic capacity is a missing link in the metrology of UV lamps that are used for medical and/or cosmetic purposes. This paper presents original UV measuring device based on the same photoreaction in vitro by which vitamin D is synthesized in human skin via photo- and thermo- induced conversions of 7-Dehydrocholesterol (provitamin D3). Thus the targets for UV photons are provitamin D molecules embedded in specially designed UV transparent and stable matrix mimicking biological samples. Three operation modes of varying complexity are developed to follow the photoreaction course in real time