(19)

(11)

EP 0 497 856 A1

(12)

(43) Date of publication: 12.08.1992 Bulletin 1992/33 (21) Application number: 90916339.0 (22) Date of filing: 26.10.1990

(51) International Patent Classification (IPC):  G01N 33/ 53( . ) G01N 33/ 569( . ) G01N 33/ 564( . ) (86) International application number: PCT/GB1990/001649 (87) International publication number: WO 1991/006856 (16.05.1991 Gazette 1991/11)

(84) Designated Contracting States: AT BE CH DE DK ES FR GB GR IT LI LU NL SE (30) Priority: 26.10.1989 GB 19890024112 (71) Applicant: 3i RESEARCH EXPLOITATION LIMITED London SE1 8XP (GB)	(72) Inventor: STEVENSON, Freda, Kathryn Southampton SO1 7AD (GB) (74) Representative: March, Gary Clifford  Batchellor, Kirk & Co. 2 Pear Tree Court Farringdon Road London EC1R 0DS London EC1R 0DS (GB)