Table 2. MS conditions and retention times (RTs) for the four target barbiturates

Compound	Precursor ion [M-H]− (m/z)	Product ions (m/z)	Collision energy (eV)	RTs (min)
Phenobarbital	231.0	42.0a	-25	4.36
		188.0	-10
Pentobarbital	225.0	182.0a	-10	7.89
		42.0	-25
Phenobarbital	231.0	42.0a	-25	4.36
		188.0	-10
Amobarbital	225.0	182.0a	-10	7.97
		42.0	-25
Secobarbital	237.0	194.0a	-10	8.44
		42.0	-20