A synthetic standard for the analysis of carbon isotopes of carbon in silicates, and the observation of a significant water-associated matrix effect

House, Christopher H.

doi:10.1186/s12932-015-0029-x

Table 2 Carbon isotope analyses by ion microprobe of possible synthetic standards

From: A synthetic standard for the analysis of carbon isotopes of carbon in silicates, and the observation of a significant water-associated matrix effect

Sample material	Primary Cs⁺ intensity	Pre sputter (s)	C₂ ⁻ intensity (cps)	Observed δ¹³C ± σ	PPRG #215-1 Instrument mass fractionation factor α	Corrected δ¹³C	True δ¹³C	Observed matrix effect
905	6.7E−10	15	1.7E+05	−33.1 ± 1.1	1.0006 (0.6 ‰)	−33.7	−27.9	−6.0
905	6.7E−10	15	3.4E+05	−34.5 ± 0.7	1.0006 (0.6 ‰)	−35.1	−27.9	−7.4
905	2.2E−10	15	3.7E+05	−35.9 ± 0.7	1.0006 (0.6 ‰)	−36.5	−27.9	−8.9
905	2.2E−10	45	2.6E+05	−35.5 ± 0.7	1.0006 (0.6 ‰)	−36.1	−27.9	−8.4
905	2.2E−10	45	2.3E+05	−35.4 ± 1.1	1.0006 (0.6 ‰)	−36.0	−27.9	−8.4
					Weighted mean	−35.7		−8.0
					Weighted standard deviation	1.0
526N	8.30E−11	45	1.3E+05	−41.9 ± 0.7	1.0006 (0.6 ‰)	−41.9	−27.7	−14.7
526N	8.40E−11	45	7.6E+05	−40.0 ± 1.1	1.0006 (0.6 ‰)	−40.0	−27.7	−12.7
					Weighted mean	−40.4		−13.1
					Weighted standard deviation	1.4

Sample material	Primary Cs⁺ intensity	PrE−sputter (s)	C₂ ⁻ intensity (cps)	Observed δ¹³C ± σ	PPRG #215-1 Instrument mass fractionation factor α	Corrected δ¹³C	True δ¹³C	Observed matrix effect
905	7.5E−11	60	1.2E+05	−24.9 ± 1.4	1.0046 (4.6 ‰)	−29.4	−27.9	−1.6
905	1.1E−10	60	2.6E+05	−22.9 ± 0.8	1.0046 (4.6 ‰)	−27.4	−27.9	0.5
905	5E−11	60	1.4E+05	−24.0 ± 1.2	1.0046 (4.6 ‰)	−28.5	−27.9	−0.7
905	5.2E−11	60	1.6E+05	−24.4 ± 1.0	1.0046 (4.6 ‰)	−29.0	−27.9	−1.1
905	4.1E−11	60	1.4E+05	−22.5 ± 1.4	1.0046 (4.6 ‰)	−27.0	−27.9	0.9
905	5E−11	60	1.6E+05	−22.9 ± 0.8	1.0046 (4.6 ‰)	−27.4	−27.9	0.5
905	1E−10	60	2.1 E+05	−26.0 ± 0.8	1.0046 (4.6 ‰)	−30.5	−27.9	−2.7
905	1E−10	60	2.0E+05	−24.1 ± 1.1	1.0046 (4.6 ‰)	−28.6	−27.9	−0.7
905	1.6E−10	60	2.4E+05	−24.4 ± 1.1	1.0046 (4.6 ‰)	−28.9	−27.9	−1.0
905	1.6E−10	60	3.0E+05	−22.9 ± 0.8	1.0046 (4.6 ‰)	−27.4	−27.9	0.5
					Weighted mean	−28.4		−0.5
					Weighted standard deviation	1.1
526N	9.5E−10	60	1.2E+05	−32.8 ± 2.0	1.0046 (4.6 ‰)	−37.2	−27.7	−9.8
526N	3.6E−10	60	3.9E+04	−35.2 ± 3.5	1.0046 (4.6 ‰)	−39.7	−27.7	−12.4
526N	9.4E−10	60+	2.7E+05	−25.4 ± 1.2	1.0046 (4.6 ‰)	−29.9	−27.7	−2.3
526N	3.6E−10	60+	6.2E+04	−28.4 ± 2.1	1.0046 (4.6 ‰)	−32.9	−27.7	−5.4
					Weighted mean	−32.5		−4.9
					Weighted standard deviation	4.5
CN703	3.1E−11	60	4.5E+05	−17.5 ± 1.1	1.0046 (4.6 ‰)	−22.1	0.0	6.7
CN703	3.1E−11	60	2.5E+05	−15.9 ± 1.2	1.0046 (4.6 ‰)	−20.5	0.0	8.3
					Weighted mean	−21.3		7.4
					Weighted standard deviation	1.1

Instrument mass factionation (IMF) factor α = (δ¹³C_obs + 1000)/(δ¹³C_Exp + 1000)
IMF in ‰ = 1000 * Ln (α). Corrected δ¹³C = ((δ¹³C_obs + 1000/α) − 1000
True δ¹³C is that measured by conventional elemental analyzer-isotope ratio mass spectrometry (EA-IRMS). apparent matrix effect (AS) = Corrected δ¹³C − True δ¹³C
The last two 526N samples add the following additional pre-sputter respectively: 20 seconds of an ~2 nA beam and 60 s of an ~0.4 nA beam; 20 s of an ~2 nA beam

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ISSN: 1467-4866

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