Time scans of the chemiluminescent emission at 545 nm from (a) 40 μM CHS-1, (b) 40 μM CHS-2, or (c) 40 μM CHS-3 and 0, 5, 10, 20, 40, 80, 100, 150, 200 μM Na2S in 20 mM HEPES buffer (pH 7.4) containing 20% Emerald II Enhancer. Insets are chemiluminescence spectra of (a) 40 μM CHS-1, (b) 40 μM CHS-2, and (c) 40 μM CHS-3 and 200 μM Na2S, acquired immediately after adding probes.