The response of the Intox EC/IR II to isopropanol and isopropanol/ethanol mixtures

Abstract The Intox EC/IR II was tested with isopropyl alcohol (IPA) solutions, and IPA and ethanol (EtOH) mixtures, at various concentrations to determine whether IPA contributes to, or produces, an apparent ethanol concentration (AEC). Two test modes were used – Subject Test, which has the interfering substance (IS) detection mechanism enabled and reports truncated results; and Quick Test, which reports untruncated results and does not detect IS. When testing IPA solutions alone, concentrations of 40 mg/dL (mg%) and above produced the IS status message while concentrations below 40 mg% produced numerical results in the Subject Test mode. With IPA alone, the IPA contribution to AEC was approximately half of the target IPA concentration. When IPA + EtOH mixtures were tested, all mixtures except one generated the IS status message. The one IPA + EtOH mixture, with 10 mg% IPA and 150 mg% target apparent EtOH, consistently produced numerical results in the Subject Test mode; however, the 10 mg% IPA in the mixture did not contribute to the AEC. This study showed that with the IS detection mechanism activated on the Intox EC/IR II, Subject Tests were aborted in instances where IPA would have contributed to the AEC and the AEC was 20 mg% or above.