用SPF-PA光谱测量系统评价化妆品防晒霜

在某些情况下，使用该系统计算的结果与防晒霜样本的标记值不匹配。这是由于在人体皮肤上进行紫外线照射实验的结果与使用紫外-可见分光光度计的测量结果之间的差异。皮肤测试受到受试者反应时间差异、应用的重复性、主观视觉评估的困难、测试过程中的出汗及其对紫外线照射的影响的影响。另一方面，光谱不受上述所有因素的影响。由该系统计算的SPF/PA值可能并不总是与基于直接在人体上的测试的标记值相对应。然而，光谱方法很简单，可以获得定量的SPF/PA值，并且在对人体皮肤进行测试之前，它被认为是有效的初步评估，并且在许多情况下提供了直接的相关性。Application Note130-UV-O041 2/4 Evaluation of Cosmetic Sunscreens using a Spectroscopic SPF/PA Measurement System In t ro d uc t ion Two r ati n g systems are used to assess t he protect i o n offe r ed by sunsc r eens and cosmetics： SPF (Sun Protection Factor) and PA (Protection Grade for UV-A). Both are used to indica t e the l evel of protection provided by skin care prod u cts against ski n damage from UV radiation . The SPF value represents the ratio of t ime for sunbu r n by UV with and without the protectio n of the product. For example ， i n the case of ski n irradiated by UV， using SPF25 it takes 25 times longer to obtain the same amou n t of sunburn to the skin than without using Spectrophotometer the product . On the other hand ， the PA value represents the rat i o of time f or developing a su n tan. For example， i f the PA va l ues is less than 2， “PA” is used as i ndicator . For a PA va l ue from 4 to 8， the ind i cator i s “PA++” The test methods for SPF and PA calcu l at i ons are based on two international sta n dards for in-vivo evaluation： ISO-24442and ISO-24444. These methods irradiate human sk in ， wh i c h sunscreen has been applied at 2 mg or 2 pL per 1cm²， with UV from an art i ficial sunligh t source . The min i mum t i me until redness develops is evaluated for t he areas of skin with and without the cream. However， t h ese test method s are cost l y and individ u al di f ferences can contr i bute to a su b jective variation in r esults.There f ore， JASCO h as developed an SPF/PA evaluation system based o n the ISO standards. The system is used to calcu l ate the SPF and t h e PA values f r om the t r ansmi t tance spectra of su n screens using a UV-visible spectrophotometer.A special cel l (Figure 1) has been deve l oped to r eproduce the appl i cat i on of su n scree n at a rate of 2 pL per 1 cm². Figure 1. SPF cel l . This application n ot e e va lu a te s t h e m e as u r e men t s and analysis of SPF and PF value of sunsc r een cream. Evaluation of Cosmetic Sunscreens using a Appl i cat i on Note Spect r oscopic SPF/PA Measurement System Keywords V-750，UV-Vis i ble/NIR Spectrophotometer ， Diffuse t r ansmittance， ISV-922 I n tegrating sphere， VWSP-966 SPF/PA Calculation program， Sunscreen Exper i men t al The equation below i s used to ca l culate a n SPF equ i valen t value. Th e numerical f i g ur es after t h e dec i mal points of t h e value a r e r ounded down. I f the valu e is less tha n 50， it i s us e d as i s. If the value is greater than 50， th e SPF i s def i ned as 50+. wh e r e E(入) i s the r ad iation i nte n si t y of sunlight (AS/NZA 4399：1996)， R(入) is th e CIE r e fer e nc e e r yth e ma act i o n spect ru m (CIE J.6：17-22，1987)， and T() is th e di f f u se t r ansmit t a n ce spect r um (%). T h e PA e quiva l ent valu e can be calcul a t e d using the fol l owi n g e quation： whe r e E(X) i s th e rad i at i on i n te n sity of sun li gh t (AS/NZA 4399：1996)， M(入) is minimum sustai n ed im med i ate blacken in g ac t ion spec t rum (1.00)， and T(入) i s the di ff use transmittance spectrum (%). Th e PA values are classif i ed into 5 grades according to t h eir PA equ i val e n t value a n d are label e d corres p o n ding to the i r gr ad e ： PA Less than 2 PA equivalent value PA+ From 2 to 4 PA equivalent value PA++ From 4 to 8 PA equivalent value PA+++ From 8 to 16 PA equivalent value PA++++ More than 16 PA equivalent value The f ollowing s ampl e s were measu r e d using th e p aramet e r s from t h e Measurement condi ti ons table： JASCO INC. 28600 Mary's Cour t ， E a s to n ， M D 21601US A Bandwidth 5.0nm Scan Speed 100 nm/min Response 0.96 sec Data Interval inm Data Interval 1nm Scanning Speed 125 nm/min Temperature Range 15-90°℃ Temperature Interval 5℃ R esults Depending on the nature o f the sample， the t rans m ittance may cha n ge due to sol v en t evaporat i o n . The r efore， for a sample that may exh ib it a change in tra n smitta n ce， t h e measu r ement is not made u n ti l all c h anges in transmittance had ceased . An example of this i s shown in F i gure 2. Figure 2. Examp l e of trans mi ssion spectra a f t er sa m pling . The transmissio n spectrum of each of the 6 samples i s shown in Figu r e 3 and the calculated SPF and PA results are s h own in Table 1. Figure 3. Sample transm i t tance sp e ctra. 28600 Mary's Cour t ， E a s to n ， M D 21601US A Sample Labeled Value Calculated Value SPF Value PA Value SPF Value SPF Equivalent Value PA Value PA Equivalent Value Product A (1) SPF50+ PA++++ 50+ 59.3 PA+ 3.7 Product A (2) SPF34 PA+++ 34 34.6 PA+ 3.8 Product A (3) SPF50+ PA++++ 50+ 1051.3 PA++++ 209.2 Product B SPF50+ PA++++ 50+ 174.6 PA++ 7.3 Product C SPF40 PA+++ 50+ 178.9 PA++ 6.6 Product D SPF25 PA++ 18 18.1 PA+ 2.4 Con c lu s io n In some cases， t he results calcu l at e d using th is system and la b e l ed valu e s f rom th e sunscr e en samples d i d n ot match. Th i s is due to th e di f fe r e n ces be t ween the r esults from the UV ir r adi a tio n exper i ments on h u ma n ski n and the measurements u sing a UV-visible spectrophotomete r. The skin test i s i nfluenced by t h e differences i n r eaction times in subjects， r epeatabi l i ty of application，difficu l ty of subject i ve visual evaluat i on， sweating during the test， and its in fluence on UV irrad i at i on. On the other hand， the spectroscopic i s unaffected by all of the above. The SPF/PA value calculated by th i s syste m may not always correspond wit h the l a bell i ng va lu e based o n tests direct l y on t h e human body. However， the spectroscopic m ethod i s simple and a quantitative SPF/PA value can be obtained， and i t is considered val i d for preliminary eva l uation before performing tests on human s k in and i n many cases offers a di r ect correlation. 28600 Mary's Cour t ， E a s to n ， M D 21601US A UASGO