ESR measurement of dissolved oxygen in 4-day chick embryo blood

The magnetic interactions between dissolved oxygen molecules and nitroxide radical spin probes lead to broadening of electron spin resonance (ESR) lines. Based on this property we described an ESR methodology to measure PO2 values in 4-day chick embryo and adult human blood. The total blood volume required for the measurement was only 9 microliter. Using this method PO2 for adult human mixed venous blood was found to be 36.7 mmHg. This is within the established clinical range of 25-40 mmHg for mixed venous blood PO2. The range of mean PO2 values for 4-day chick embryo blood was 27.3- 35.0 mmHg. This is the first time that PO2 values have been reported for individual chick embryos at such an early stage.