Quenched flow has both advantages and disadvantages with respect to stopped flow. On the one hand, chemical analysis makes it clear what process is being measured, whereas it may not always be obvious what process a spectroscopic signal represents. On the other hand, quenched flow is much more laborious, as each point along the time course must be determined separately. The image at left for catalysis by nitrogenase from Klebsiella pneumoniae illustrates both of these points: the agreement in half times indicates that the absorbance at 420 nm measured the release of Pi, but the quenched-flow experiment required 11 data points.
