Determination of δ¹³C of Trace Hydrocarbons in Natural Gas Using Syringe Solid Phase Extraction (SSPE) Coupled with Gas Chromatography/Isotope Ratio Mass Spectrometry (GC/IRMS)

Table 4

δ¹³C ratios of standard sample at different temperatures (°C) and times (min).

Compound	Adsorption temperature (°C)						Desorption temperature (°C)										Adsorption time (min)										Desorption time (min)
	-20	0	20	40	60	80	50	100	150	200	250	300	350	400	450	500	1	2	3	4	5	6	7	8	9	10	0.5	1	1.5	2	3	4	5	6	7	8
CH4	-44	-42	-42	-41	-42	-43	-41	-41	-41	-41	-42	-41	-42	-41	-42	-43	-42	-41	-41	-42	-42	-41	-42	-42	-42	-41	-45	-42	-42	-42	-42	-42	-42	-41	-42	-41
C2H6	-31	-31	-30.0	-31	-31	-31	-30	-30	-30	-30	-30	-30	-30	-30	-30	-28	-30	-30	-30	-30	-30	-30	-30	-31	-30	-30	-32	-30	-29	-29	-30	-30	-30	-29	-29	-30
C3H8	-27	-27	-27	-28	-27	-27	-28	-27	-28	-28	-28	-27	-28	-28	-28	-27	-28	-28	-27	-27	-26	-26	-27	-27	-27	-27	-28	-28	-29	-27	-28	-28	-28	-28	-28	-28
i-C4H10	-25	-26	-26	-26	-25	-26	—	—	-26	-27	-27	-27	-27	-27	-26	-26	-27	-27	-27	-27	-27	-27	-27	-27	-27	-27	-27	-27	-27	-27	-27	-27	-27	-27	-27	-27
n-C4H10	-24.7	-25.0	-25.8	-26.4	-24.4	-26.0	—	-26.4	-26.0	-27.0	-26.9	-26.1	-27.0	-26.9	-27.1	-26.3	-25.5	-25.4	-26.2	-25.5	-25.0	-25.8	-25.2	-25.4	-25.9	-26.1	-25.1	-25.4	-25.8	-25.1	-25.5	-25.1	-25.3	-25.1	-25.5	-25.7
i-C5H12	-27	-22	-24	-25	-27	-24	—	—	—	-25	-25	-25	-25	-24	-24	-24	-25	-25	-25	-25	-25	-25	-25	-26	-26	-26	—	—	-25	-25	-25	-26	-26	-25	-25	-25
n-C5H12	-22.4	-23.8	-23.5	-22.8	-21.1	-24.0	—	—	—	-24.9	-24.6	-23.1	-24.6	-24.6	-24.3	-22.8	-24.0	-23.9	-23.6	-23.3	-23.2	-23.2	-23.5	-23.5	-23.3	-23.2	—	—	-24.1	-24.9	-23.5	-24.9	-25.2	-24.8	-25.1	-24.5

ATe: adsorption temperature; DTe: desorption temperature; ATi: adsorption time; DTi: desorption time.