(19)

(11)

EP 0 228 441 A1

(12)

(43) Date of publication: 15.07.1987 Bulletin 1987/29 (21) Application number: 86904284.0 (22) Date of filing: 11.07.1986

(51) International Patent Classification (IPC):  G01N 21/ 95( . ) G01N 21/ 892( . ) (86) International application number: PCT/GB1986/000399 (87) International publication number: WO 1987/000629 (29.01.1987 Gazette 1987/03)

(84) Designated Contracting States: AT BE DE FR GB IT NL SE (30) Priority: 15.07.1985 GB 19850017834 (71) Applicant: SIRA LIMITED Chislehurst Kent BR7 5EH (GB)	(72) Inventors: CLARIDGE, John, Frederick Chislehurst Kent (GB) WEST, Robert, Noel Chislehurst Kent (GB) ATKINSON, Richard, Mark Orpington Kent (GB) (74) Representative: Wright, Hugh Ronald, et al  Brookes & Martin 52/54 High Holborn London WC1V 6SE London WC1V 6SE (GB)