Chemical ionization source, the reagent gas is present in large excess compared to the analyte. Electrons entering the source with energy around 200-500 eV will preferentially ionize the reagent gas. Then, the ion/molecule reactions produces more stable reagent ions and the resultant collisions with other reagent gas molecules will create an ionization plasma. Positive and negative ions of the analyte are formed by reactions with this plasma. The following reactions are possible with methane as the reagent gas. If ammonia is the reagent gas, For isobutane as the reagent gas, Self chemical ionization is possible if the reagent ion is an ionized
Negative number be combined into a single debt of greater magnitude. When adding together a mixture of positive and negative numbers, one can think of the negative numbers as positive quantities being subtracted. For example: In the first example, a credit of is combined with a debt of , which yields a total credit of . If the negative number has greater magnitude, then the result is negative: Here the credit is less than the debt, so the net result is a debt. As discussed above, it is possible for the subtraction of two non-negative numbers to yield a negative answer: In