Sensitivity of the IL 282 Co-oximeter to low hemoglobin concentration and high proportions of methemoglobin.

dard to those of the chromatographic standard (25 mg of HPPH and 50 mg of hexobarbital, dissolved in 1 L of methanol). Free HPPH was also measured by comparison to the chromatographic standard after serum protein precipitation with acetonitrile containing the internal standard (1). Table 2 presents these results. We believe that these concentrations are sufficient to increase the EMIT phenytomn values. We conclude that phenytoin values obtained by EMIT assay for patients with impaired renal function should be cautiously interpreted. We thank the technologists of the Special Chemistry Section for their assistance in performing the assays, and Dr. Andrew Wilson of Presbyterian Hospital for his clinical investigation.