A comparative study of analytical methods to determine postmortem changes in carbon monoxide concentration

Area of Science:

• Forensic Toxicology
• Analytical Chemistry
• Biochemistry

Background:

• Accurate postmortem carboxyhemoglobin (COHb) measurement is crucial for determining cause of death.
• Blood sample degradation during storage can compromise analytical results.
• Understanding COHb stability in autopsy samples is vital for reliable forensic interpretation.

Purpose of the Study:

• To evaluate the stability of carboxyhemoglobin (COHb) and carbon monoxide (CO) in autopsy blood samples.
• To assess the impact of storage duration (30 and 150 days) on COHb and CO quantification.
• To compare COHb and CO measurement accuracy using spectrophotometric and gas chromatographic methods.

Main Methods:

• Analysis of 21 autopsy blood samples stored for 30 and 150 days.
• Spectrophotometric measurement of COHb at absorbance ratios of 540 nm/555 nm and 540 nm/579 nm.
• Gas chromatographic determination of carbon monoxide (CO) using combining capacity and calculation based on hemoglobin and iron content.

Main Results:

• Spectrophotometric COHb measurements showed average losses of 8% (30 days) and 35% (150 days) at 540 nm/555 nm, and 7% (30 days) and 34% (150 days) at 540 nm/579 nm.
• Gas chromatographic CO determination revealed average losses of 15% (30 days) and 37% (150 days).
• Calculated CO based on hemoglobin and iron content also demonstrated significant average losses, up to 40% and 37% respectively after 150 days. Wavelength shifts and spectral distortions were noted at 150 days.

Conclusions:

• Autopsy blood samples exhibit significant degradation of carboxyhemoglobin and carbon monoxide over extended storage periods.
• Both spectrophotometric and gas chromatographic methods are susceptible to COHb and CO loss, affecting accuracy.
• Forensic toxicologists must consider sample storage duration and potential degradation when interpreting COHb and CO results from autopsy blood.