(19)

(11)

EP 0 293 448 A1

(12)

(43) Date of publication: 07.12.1988 Bulletin 1988/49 (21) Application number: 88900329.0 (22) Date of filing: 08.12.1987

(51) International Patent Classification (IPC):  G01N 33/ 497( . ) G01N 1/ 24( . ) (86) International application number: PCT/US1987/003253 (87) International publication number: WO 1988/004419 (16.06.1988 Gazette 1988/13)

(84) Designated Contracting States: AT BE CH DE FR GB IT LI LU NL SE (30) Priority: 09.12.1986 US 19860939926 (71) Applicant: NATIONAL PATENT ANALYTICAL SYSTEMS, INC. Roslyn, NY 11577 (US)	(72) Inventor: MARTIN, Peter, G. Mercer Island, WA 98040 (US) (74) Representative: Bannerman, David Gardner, et al  Withers & Rogers 4 Dyer's Buildings Holborn London, EC1N 2JT London, EC1N 2JT (GB)