The detection limits for the immobilized-enzyme test are very similar to those obtained for the solution (non-immobilized) assay. The immobilized form of the test was designed as a method for detecting particulate heroin, that is heroin that has not been metabolized; however the excellent results observed suggest that solution sample testing should also be viable. In the tests performed, a small amount of particulate heroin was placed on the surface of the test strip (see bottom of this link to review the test strip process, then use 'Back' to return here). With strips that were still dry, little or no response was seen; however, using test strips that had been moistened with 10mL of dH₂O gave strong responses. Based on a minimum density of heroin of 1.56g/cm³ and an average particle of heroin containing 137 pmol of the drug, the luminescent immobilized-enzyme assay would be sensitive to two particles.

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