(19)

(11)

EP 0 496 804 A1

(12)

(43) Date of publication: 05.08.1992 Bulletin 1992/32 (21) Application number: 90916126.0 (22) Date of filing: 27.09.1990

(51) International Patent Classification (IPC):  G01N 33/ 53( . ) G01N 33/ 543( . ) (86) International application number: PCT/US1990/005424 (87) International publication number: WO 1991/005259 (18.04.1991 Gazette 1991/09)

(84) Designated Contracting States: AT BE CH DE DK ES FR GB IT LI NL SE (30) Priority: 06.10.1989 US 19890418403 (71) Applicant: E.I. DU PONT DE NEMOURS AND COMPANY Wilmington Delaware 19898 (US)	(72) Inventor: STRAHAN, Johanne, C. Wilmington, DE 19806 (US) (74) Representative: Hildyard, Edward Martin, et al  Frank B. Dehn & Co. Imperial House 15-19 Kingsway London WC2B 6UZ London WC2B 6UZ (GB)