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Report No: DOT/FAA/AM-98/21

Title and Subtitle: Preparation of Carboxyhemoglobin Standards and Calculation of Spectrophotometric Quantitation Constants

Report Date: August 1998

Authors: Canfield, D.V., Smith, M.D., Ritter, R.M., and Chaturvedi, A.K.

Abstract: The Toxicology and Accident Research Laboratory of the Federal Aviation Administration is required to analyze specimens from all pilots involved in fatal aircraft accidents for the presence of carbon monoxide poisoning to determine if carbon monoxide caused pilot incapacitation leading to the accident. Therefore, reliable and stable carbon monoxide controls are needed to assure the accuracy of the analysis of carbon monoxide. A method was developed for the preparation of carboxyhemoglobin standards, which were stable for more then 4 months with the prepared control remaining within acceptable limits during this time.

A mathematical equation was developed to more accurately determine the constants A and B used in the equation COHB% = 100[(C-B)/(A-B)], where B = 0% COHB peak ratio at 540nm and 579nm; A = 100% COHB peak ratio at 540nm and 579nm; and C = the peak ratio at 540nm and 579nm for the blood being analyzed. The following equations were developed to calculate A and B: B = Pavg - (P)[(Pavg - Navg)/(P - N)]; A = B + (Pavg - Navg)/(P - N), Pavg = average peak ratio 540/579 for the positive standard run on the spectrophotometer; P = average decimal concentration measured on the CO-OXIMETER for the positive standard; Navg = average peak ratio 540/579 for the negative standard; N = average decimal concentration measured on the CO-OXIMETER for the negative standard. The new equations provided results consistent with those obtained from a CO-OXIMETER.

Key Words: Carboxyhemoglobin, Analysis, Standards

No. of Pages: 11