Electrophoretic separation

Patents Electrophoretic separation Tile t e c h n i q u e of e l e c t r o p h o r e s l s - - using a polential difference a c r o s s a m e m b r a n e or gel layer to separate some macromolecules from o t h e r s m a n e l e c t r o l y t e s o l u t i o n a c c o r d i n g to th e i r s u r f a c e electric c h a r g e - - is a p p l i e d wideli¢ in biological a n d pharmaceutical separations. T h e r e ls a p o s s i b i l i t y t h a t th e m e m b r a n e u s e d in t h i s p r o c e s s will b e c o m e clogged, p a r t i c u l a r l y w h e n tile p o l a r i t y of th e electric field is c o n s t a n t a n d w h e n the s u s p e n s i o n to be s e p a r a t e d c o n t a i n s ver\ high-molecular-weight molecules. Tile t e c h n i q u e of p e r i o d i c a l l y r e v e r s i n g the electric field in or de r to d r a w a w a y s u c h m o l e c u l e s is a p p l i e d in this p a t e n t o r i g i n a t i n g from A u s t r a l i a , to the s e p a r a t i o n p r o c e s s . The p o l a r i t y r e v e r s a l n e c e s s a r i l y h a s to e n s u r e a n ow'rall m o v e m e n t of th e d e s i r e d molecules towards the m e m b r a n e , a n d ls t h e r e f o r e c o n d u c t e d li~. s h o r t b u r s t s , to give a f o r w a r d : r e v e r s e r a t i o of 1:2 to 1:4. For b e t t e r effect, the m e m b r a n e p o r e l e n g t h or t h e m e a n p a t h t h r o u g h th e gel layer a r e at l e a s t 10 0 0 0 to 20 0 0 0 t h n e s t h e eflective m o l e c u l a r d i a m e t e r . It is also e n v i s a g e d t h a t s e v e r a l m e m b r a n e s cau] be a r r a n g e d as a s e r i e s of cells, w h e r e a c r o s s t h e set of cells e a c h membrane has a progressively d e c r e a s i n g p o r e size, a k i n to a set of sieves, t h o u g h this is m o s t l y a f e a t u r e of t h e prior art. The t i m i n g of tile f o r w a r d a n d r e v e r s e a l t e r n a t i o n s of t h e field is d e s i g n e d to allow s o m e m o l e c u l e s of the d e s i r e d c o i n p o u n d to migrate through the m e m b r a n e before a n y o t h e r m a c r o m o l e c u l e s c a n d o so. O n c e tlle d e s i r e d m o l e c u l e s are c a p t u r e d b y t h e e l e c t r o l y t e s o l u t i o n at th e far stde of t he m e m b r a n e , t h e y a r e t r a n s p o r t e d for f u r t h e r p r o c e s s i n g . The t i m i n g of t h e r e v e r s e field is sufficient to c a u s e all th e m a c r o m o l e c u l e s , of w h a t e v e r type, to m i g r a t e b a c k i n t o th e first e le c t ro l y t e s o l u t i o n c o m p a r t m e n t .

Membrane

T e c h n o l o g y No. 6 2

Tile a n a l o g y u s e d by t h e A u s t r a l i a n I n v e n t o r is t h a t of a fun-run which has male and f e m a l e c o m p e t i t o r s . It is e x p e c t e d , by t h e inventor, that on a v e r a g e m a l e r u n n e r s are f a s t e r t h a n f e m a l e r u n n e r s , so a c e r t a i n n u m b e r of m a l e r u n n e r s will finish before t h e first female r u n n e r . Th e f u n - r u n is p u r p o s e l y s t o p p e d j u s t before m]y f e m a l e r u n n e r c r o s s e s the line. a n d all t h e r u n n e r s w h o did n o t c r o s s t h e line a r e s e n t b a c k to the start for a n o t h e r race. The f u n - r u n r a c e s c a n be r e p e a t e d u n t i l a d e s i r e d p r o p o r t i o n of the m a l e r u n n e r s h a v e b e e n s e p a r a t e d from the felnale r u n n e r s .

Patelzt number: WO 9 4 2 2 9 0 4 Date: 13 O c t o b e r 1994 Inventor: J Margolis Applicaot: G r a d i p o r e I,td

Hollow fibre assembly; rectifying manufacturing faults In tins p a t e n t , t h e e x i s t e n c e of m a n u f a c t u r i n g f a u l t s in a s m a l l p r o p o r t i o n of hollow fibre m e m b r a n e s is a c k n o w l e d g e d and circumvented. Rather than introduce extensive quality c o n t r o l s a n d c h e c k s , t h e 'pile it high, sell it c h e a p ' s t r a t e g y is e m p l o y e d . B u n d l e s of fibres are a s s e m b l e d a n d held vertically m a c h a m b e r , a n d tile cut e n d s are d i p p e d into a liquid w h i c h is n o n - p e r m e a b l e . Tile cu t e n d s ar e n e x t d i p p e d into a liquid w h i c h c a n act as a sealmlt, a n d the p r e s s u r e In tile c h a m b e r is r e d u c e d slightly. The I m p er f ect fibres will allow m u c h m o r e of t h e n o n - p e r m e a b l e fluid t h r o u g h t h e f a u l t s in t h ei r w a l ls t h a n will t h e s o u n d fibres, so t h e s e a l a n t c o m p o u n d will rise f u r t h e r in t h e faulty fibres. W h e n th e s e a l a n t h a s solidified, tile fibres a r e cu t far e n o u g h up their l e n g t h t h a t t h e m a j o r i t y of fibres will be left with o p e n en d s. Only t h e lailed ones, in w h i c h the

s e a l a n t r o s e fllrther, will still be b l o c k e d . Th e s e p a r a t i o n c a p a c i t y of s u c h a b u n d l e will b e l e s s t h a n t h a t of o n e In w h i c h all t he fibres ar e s o u n d , b u t If t h e failure r a t e is low t h e n t h e slight r e d u c t i o n in c a p a c i t y m a y be tolerable, p a r t i c u l a r l y if t h e p e r c e n t a g e i n c r e a s e d cost of a p e r f e c t b u n d l e ( i n c l u d i n g the cost of t e s t i n g e a c h fibre) is g r e a t e r tlaan the p e r c e n t a g e r e d u c t i o n In capacity.

P a t e n t number: EP 6 2 7 5 5 5 Date: 7 D e c e m b e r 1994 Inventor: S S a g u e e . D Golub, H Cohen. M Azarlah

Application: R o t e m I n d u s t r i e s , Ltd

Chlorine dioxide generation D r i n k i n g w a t e r t r e a t m e n t by adding chemical c o m p o u n d s can be u n p r e d i c t a b l e : large u n p l a n n e d e x c u r s i o n s from t h e i n t e n d e d r a t e of a d d i t i o n c a n l e a d to a l a r m in tile tmblic, h e a l t h a n d safety investigations, and even c r i m i n a l p r o s e c u t i o n , to s a y n o t h i n g of long- term liability if it c a n be s h o w n t h a t tile c u s t o m e r s ' h e a l t h h a s b e e n affected. W h e n the c o m p o u n d is a s toxic a n d r e a c t i v e as c h l o r i n e dioxide, t h e n a c o n t i n u o u s p r o c e s s for m a k i n g s m a l l q u a n t i t i e s is v e r y m u c h to b e p r e f e r r e d to a d o s i n g plant. In tills p r o c e s s , t h e c h l o r i n e dioxide is p r e p a r e d by the e l e c t r o c h e m i c a l o x i d a t i o n of a s o d i u m chlorite s o l u t i o n , a n d is e x t r a c t e d from ,~olution a n d p u r i f i e d b y its p a s s a g e a c r o s s a h y d r o p h o b l c m e m b r a n e . Unlike previous memb:rane-based p r o c e s s e s for clflorine dioxide m a n u f a c t u r e , the electrochemical cell ls o p e r a t e d so that all t he s o d l m n c h l o r i t e ls c o n v e r t e d Into sodium hydroxide.

P a t e n t number: WO 9 4 2 6 6 7 0 Date: 24 N o v e m b e r 1994 Inventors: G Cowley, M Llpsatzin, G J Ranger

Applicant: S t e r l i n g Pulp Chemicals. lad

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