SCOPE AND LIMITATIONS. ( i) P h a se 2 t es t i n g sep a r a t es t es t c h e m ic a l s i n t o t hr ee co n ve n ie n t c a t ego r ies: ‘‘ P h o t o- l a bile’’, ‘‘p h o t oi n e r t ’’, a n d t h ose c h e m i- c a l s h a vi n g s un lig h t h a lf- lives i n r o un d t u bes i n t h e r a n ge of 1 h o ur t o 50 d a y s. Ch e m ic a l s i n t h e fi r s t t wo c a t ego r ies fa ll o u t s ide t h e p r a c t ic a l li m i t s of t h e t es t , a n d c a nn o t be u sed i n P h a se 3. All o t h e r c h e m ic a l s a r e s u i t a ble fo r P h a se 3 t es t i n g. ( ii) T h e t es t p r oced ur e i s s i m ple a n d i n expe n s ive, b u t does r eq u i r e t h a t t h e c h e m ic a l dissolve i n w a t e r a t s ufficie n t co n ce n t r a t io n s t o be m e a s ur ed b y so m e a n a l y t ic a l t ec hn iq u e b u t n o t h a ve a p- p r eci a ble a bso r b a n ce i n t h e r a n ge 290 t o 825 n m . P h a se 2 t es t s s h o u ld be do n e d ur i n g a cle a r - s k y pe r iod t o ob t a i n t h e bes t r es u l t s. T es t i n g will be less a cc u- r a t e fo r c h e m ic a l s wi t h h a lf- lives of less t h a n 1 d a y bec a u se d r a m a t ic fl u c- t u a t io n s i n s un lig h t i n t e n s i t y c a n a r i se f r o m t r a n sie n t we a t h e r co n di t io n s a n d t h e diffic u l t y of a ssig n i n g eq u iv a le n t r e a c t io n t i m es. No r m a l di urn a l v a r i- a t io n s a l so affec t t h e p h o t ol y s i s r a t e co n s t a n t . P h a se 3 t es t s s h o u ld be s t a r t - ed a s soo n a s possible af t e r t h e P h a se 2 t es t s t o e n s ur e t h a t t h e ( kp)SHW es t i- m a t e r e m a i n s v a lid.
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Sources: Testing Consent Agreements and Test Rules, Testing Consent Agreements and Test Rules
SCOPE AND LIMITATIONS. ( i) P h a se 2 t es t i n g sep a r a t es t es t c h e m ic a l s i n t o t hr ee co n ve n ie n t c a t ego r ies: ‘‘ P h o t o- l a bile’’, ‘‘p h o t oi n e r t ’’, a n d t h ose c h e m i- c a l s h a vi n g s un lig h t h a lf- lives i n r o un d t u bes i n t h e r a n ge of 1 h o ur t o 50 d a y s. Ch e m ic a l s i n t h e fi r s t t wo c a t ego r ies fa ll o u t s ide t h e p r a c t ic a l li m i t s of t h e t es t , a n d c a nn o t be u sed i n P h a se 3. All o t h e r c h e m ic a l s a r e s u i t a ble fo r P h a se 3 t es t i n g.
( ii) T h e t es t p r oced ur e i s s i m ple a n d i n expe n s ive, b u t does r eq u i r e t h a t t h e c h e m ic a l dissolve i n w a t e r a t s ufficie n t co n ce n t r a t io n s t o be m e a s ur ed b y so m e a n a l y t ic a l t ec hn iq u e b u t n o t h a ve a p- p r eci a ble a bso r b a n ce i n t h e r a n ge 290 t o 825 n m . P h a se 2 t es t s s h o u ld be do n e d ▇ ▇ ▇ ur i n g a ▇ ▇ ▇ ▇ cle a r - s k y pe r iod t o ob t a i n t h e bes t r es u l t s. T es t i n g will be less a cc u- r a t e fo r c h e m ic a l s wi t h h a lf- lives of less t h a n 1 d a y bec a u se d r a m a t ic fl u c- t u a t io n s i n s un lig h t i n t e n s i t y c a n a r i se f r o m t r a n sie n t we a t h e r co n di t io n s a n d t h e diffic u l t y of a ssig n i n g eq u iv a le n t r e a c t io n t i m es. No r m a l di urn a l v a r i- a t io n s a l so affec t t h e p h o t ol y s i s r a t e co n s t a n t . P h a se 3 t es t s s h o u ld be s t a r t - ed a s soo n a s possible af t e r t h e P h a se 2 t es t s t o e n s ur e t h a t t h e ( kp)SHW es t i- m a t e r e m a i n s v a lid.
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