Hollow cathode This is due to the fact that the ESI is a soft ion source, therefore thermally labile molecules like NG are not severely fragmented . The generation of a large amount of NO3 -as reagent ions is also aided by the ambient conditions for ESI. The synergistic effect of the soft ESI ion source and the abundance of the NO3 -ion under ambient conditions aided the formation of the adduct ion for NG, ([NG+NO3] -, m/z 289), resulting in it gaining prominence as a major ion with improved sensitivity. Using ac-APCI, detected the adduct ion of NG with the NO3 -, ([NG+NO3] -, m/z 289), as a minor ion signal with NO3 -(m/z 62) as a major background ion . Because of the abundance of NO3 -ions formed by APCI under ambient conditions, it is expected that it will provide the adduct ion ([NG+NO3] -, m/z 289) as a major ion. Because the ESI, APCI, and/or DBDI have different ionization methods, the mass spectra may show differences in ion signals. Due to the fragile nature of NG molecules, even temperatures as low as 60-70 °C might trigger thermal degradation. The deposited NG on a metal substrate was almost degraded at 100 °C in our preliminary experiment .