Repeatability of in vitro measurements of the ultraviolet protection factor (UPF) by spectrophotometry with automatic sampling

Background/aims: Spectrophotometric assessment (in vitro) is the most estab lished method for determining the ultraviolet protection factor (UPF) of te xtiles. Apart from stringent requirements for measurement precision, practi cal methods are required for the routine determination of the UPF. We repor t here spectrophotometric measurements of textiles using a newly developed autosampler. Measurement precision was evaluated under repeatable condition s. Methods: Fifteen different textiles were spectrophotometrically assessed fo r the determination of the UPF. Sample handling inside the spectrophotomete r was performed with a computer-controlled sampling device, capable of load ing and unloading a textile sample from a magazine as well as rotating the sample perpendicular to the spectrometer beam. In order to evaluate the rep eatability of measurements, one sample of each textile was assessed eight t imes under the same conditions in the same laboratory Results. A mean percentage of the standard error of 1% [E-UPP] was calculat ed for the UPF measurements. For UPFs > 30, a significantly higher E-UPF wa s found (r=0.78; P <0.001). E-UV (3.9%) of ultraviolet A (UVA) transmission differed significantly from E-UV (1.1%) of ultraviolet B (UVB) transmissio n (P <0.05). Conclusions: Though a slight decrease of repeatability was observed for UVA transmission measurements and UPFs higher than 30, our data indicate a hig h measurement precision under repeatable conditions. In conclusion, spectro photometric measurements of textiles with the aid of the autosampler presen ted have been shown to be highly practical, time saving and precise.