Carbon monoxide in blood: an improved microliter blood-sample collection system, with rapid analysis by gas chromatography.

We examined the sensitive assay for carboxyhemoglobin based on reaction with K3Fe(CN)6 and gas chromatography of the liberated CO. Our improvements included increased baseline stability, shorter analysis time, and simpler standardization. EDTA-containing Vacutainer Tubes (lavender-stoppered) increase the carboxyhemoglobin content of blood stored in them. The carboxyhemoglobin content of blood stored in capillary tubes containing solid heparin and saponin remained stable for two weeks. Using our improved procedures, we measured the carboxyhemoglobin content of blood from adults and neonates collected via venipuncture or heel or fingersticks. We observed no significant difference in carboxyhemoglobin content of blood obtained by venipuncture or heel stick for premature infants, 0.19 +/- 0.04 vs 0.18 +/- 0.03 mL of CO per 100 mL of blood, respectively (mean +/- SD). Nonsmoking adults (n = 19) had CO values (mean +/- SD) of 0.19 +/- 0.03 and 0.17 +/- 0.04 mL per 100 mL of blood, and smoking adults (n = 7) gave CO values of 0.96 +/- 0.49 and 0.91 +/- 0.49 mL/dL, for venipuncture and fingerstick, respectively.