Bleasel M D, Aldous S
School of Pharmacy, University of Tasmania, Private Bag 26, Hobart, 7001 Tasmania, Australia.
Int J Cosmet Sci. 2008 Aug;30(4):259-70. doi: 10.1111/j.1468-2494.2008.00453.x.
A method for the in vitro determination of low- and high-value sun protection factors (SPF) of sunscreens using artificial substrates and a novel pseudo double beam (PDB) mode of operation of a standard double beam UV spectrophotometer is described. The method allows transmittance to be calculated from detector responses of reference and sample beams measured at different gain levels and facilitates the accurate quantification of low levels of electromagnetic radiation transmitted through highly absorbing samples. The spectrophotometer was modified to hold quartz diffusing plates on which a substrate [Transpore adhesive tape or human stratum corneum obtained from a skin surface biopsy (SSB)] and the sunscreens to be tested were applied. The PDB mode of operation increased the effective linear range of the detector response of the spectrophotometer by a factor of approximately 20000-fold, enabling the in vitro SPF determination technique to be applied to both high and low SPF value sunscreens. Eight commercial sunscreens with known SPF values ranging from 4 to 77, previously determined by in vivo methods, were tested in vitro using both test substrates and correlations between the in vivo and in vitro values were determined. SPF values determined using the in vitro method correlated well with the known in vivo results (Transpore tape, R(2) = 0.611; SSB, R(2) = 0.7928). The in vitro SPF obtained for one of the tested products differed substantially from the cited in vivo SPF value. Independent in vitro and in vivo re-evaluation of the SPF of this product matched the value predicted by the present method much more closely than the originally cited in vivo value. All determined SPFs were ordered correctly in comparison to in vivo ranking and the technique appeared to correctly identify a sunscreen that had a labelled SPF value that was significantly higher than its true SPF.
描述了一种使用人工基质和标准双光束紫外分光光度计的新型伪双光束（PDB）操作模式在体外测定防晒剂低、高值防晒系数（SPF）的方法。该方法允许根据在不同增益水平下测量的参比光束和样品光束的探测器响应来计算透过率，并有助于准确量化透过高吸收样品的低水平电磁辐射。对分光光度计进行了改装，以固定石英漫射板，在其上施加基质[透气胶带或从皮肤表面活检（SSB）获得的人体角质层]和待测试的防晒剂。PDB操作模式使分光光度计探测器响应的有效线性范围增加了约20000倍，从而使体外SPF测定技术能够应用于高和低SPF值的防晒剂。使用两种测试基质在体外测试了八种已知SPF值范围为4至77的市售防晒剂，这些值先前已通过体内方法测定，并确定了体内和体外值之间的相关性。使用体外方法测定的SPF值与已知的体内结果相关性良好（透气胶带，R(2)=0.611；SSB，R(2)=0.7928）。所测试产品之一的体外SPF与引用的体内SPF值有很大差异。对该产品的SPF进行独立的体外和体内重新评估，与本方法预测的值比最初引用的体内值更接近。与体内排名相比，所有测定的SPF都正确排序，并且该技术似乎能够正确识别一种标签SPF值明显高于其真实SPF的防晒剂。
