CHEMILUMINESCENCE ANALYSIS OF NITRIC-OXIDE IN SMALL-VOLUME SAMPLES BY A MODIFIED INJECTION METHOD

To detect NO in samples of the headspace of static cores, a sample-mixing unit was developed which made it possible to detect NO in small-volume samples (50 mu l to 10 ml) by a continuous flow chemiluminescence NO analyzer. The sample-mixing unit enables the detector of the NO analyzer to reach a steady-state response. The detection limit was 3.5 pmol NO in a sample, which is equivalent to 8.5 ppbv NO in a 10-ml sample or 85 ppbv NO in a 1-ml sample at room temperature. The coefficient of variation between replicates varied between 6.4% at low NO levels and 0.60% at high NO levels. The linear response was good, the R(2) value was above 0.99 even in the lowest detection range. The sample-mixing unit in combination with an NO analyzer provides a sensitive, reliable, easy to use method for the detection of NO in incubation systems with small headspace volumes such as static cores.