(19)

(11)

EP 0 458 869 A1

(12)

(43) Date of publication: 04.12.1991 Bulletin 1991/49 (21) Application number: 90903617.0 (22) Date of filing: 13.02.1990

(51) International Patent Classification (IPC):  G01N 15/ 02( . ) G01N 9/ 00( . ) (86) International application number: PCT/GB1990/000225 (87) International publication number: WO 1990/009573 (23.08.1990 Gazette 1990/20)

(84) Designated Contracting States: CH DE FR GB LI (30) Priority: 14.02.1989 GB 19890003320 (71) Applicant: NATIONAL RESEARCH DEVELOPMENT CORPORATION London SE1 6BU (GB)	(72) Inventors: MAHGEREFTEH, Haroun London NW9 8TG (GB) BRISCOE, Brian Middx HA5 5NQ (GB) (74) Representative: Charlton, Peter John, et al  Elkington and Fife Prospect House 8 Pembroke Road Sevenoaks, Kent TN13 1XR Sevenoaks, Kent TN13 1XR (GB)