Camera luminometer for use with luminescent assays
An instrument, a camera luminometer, has been developed that detects light emission from luminescent reactions using high-speed instant photographic film (ASA 20000). The luminometer simultaneously monitors light emission from 63 reaction vessels in the form of a 7 × 9 array. It also incorporates a multiple pipette, which enables luminescent reactions to be simultaneously initiated directly above the instant film. Photographic results are interpreted visually and semi-quantitative assessment is possible. This may be improved by interposing a stepped neutral density filter between each reaction vessel and the film. The application of this instrument is illustrated by an enhanced luminescent enzyme immunoassay for serum ferritin and chemiluminescent assays for Co(II), Cr(III), peroxide and luminol. The film has a limited exposure latitude and so the assays operate as threshold tests with the following detection limits: ferritin, 1 ng; Co(II), 5 pmol; Cr(III), 500 fmol; peroxide, 500 pmol; and luminol, 500 fmol.