Precise and Traceable ¹³C/¹²C Isotope Amount Ratios by Multicollector ICPMS

Abstract

A new method for the measurement of SI traceable carbon isotope amount ratios using a multicollector inductively coupled mass spectrometer (MC-ICPMS) is reported for the first time. Carbon (13)C/(12)C isotope amount ratios have been measured for four reference materials with carbon isotope amount ratios ranging from 0.010659 (delta(13)C(VPDB) = -46.6 per thousand) to 0.011601 (delta(13)C(VPDB) = +37 per thousand). Internal normalization by measuring boron (11)B/(10)B isotope amount ratios has been used to correct for the effects of instrumental mass bias. Absolute (13)C/(12)C ratios have been measured and corrected for instrumental mass bias and full uncertainty budgets have been calculated using the Kragten approach. Corrected (13)C/(12)C ratios for NIST RM8545 (Lithium Carbonate LSVEC), NIST RM8573 (L-Glutamic Acid USGS40), NIST RM8542 (IAEA-CH6 Sucrose) and NIST RM8574 (L-Glutamic Acid USGS41) differed from reference values by 0.06-0.20%. Excellent linear correlation (R = 0.9997) was obtained between corrected carbon isotope amount ratios and expected carbon isotope amount ratios of the four chosen NIST RMs. The method has proved to be linear within this range (from (13)C/(12)C = 0.010659 to (13)C/(12)C =0.011601), and therefore, it is suitable for the measurement of carbon isotope amount ratios within the natural range of variation of organic carbon compounds, carbonates, elemental carbon, carbon monoxide, and carbon dioxide. In addition, a CO2 gas sample previously characterized in-house by conventional dual inlet isotope ratio mass spectrometry has been analyzed and excellent agreement has been found between the carbon isotope amount ratio value measured by MC-ICPMS and the IRMS measurements. Absolute values for carbon isotope amount ratios traceable to the SI are given for each NIST RM, and the combined uncertainty budget (including instrumental error and each parameter contributing to Russell expression for mass bias correction) has been found to be< 0.1% for the four materials. The advantage of the method versus conventional gas source isotope ratio mass spectrometry measurements is that carbon isotope amount ratios are measured as C(+) instead of CO2(+), and therefore, an oxygen (17)O correction due to the presence of (12)C(17)O(16)O(+) is not required. Organic compounds in solution can be measured without previous derivatization, combustion steps, or both, thus making the process simple. The novel methodology opens new avenues for the measurement of absolute carbon isotope amount ratios in a wide range of samples.

Fractionation in position-specific isotope composition during vaporization of environmental pollutants measured with isotope ratio monitoring by 13C nuclear magnetic resonance spectrometry

“…d 13 C (‰) values were expressed relative to the international reference (Vienna-Pee Dee Belemnite, V-PDB) using the (Jancso and Van Hook, 1974). b (Schwarzenbach et al, 2003). c (Kuder et al, 2009) (Craig and Gordon, 1965 The enrichment factor ε (‰) was obtained from the isotope fractionation factor a calculated according to the common Rayleigh approach.…”

“…The bulk 13 C content, d 13 C bulk (see Table S1 for the definitions of symbols used in the paper) can be measured by several techniques on the CO 2 produced by complete combustion of the sample. These include mass spectrometry (Muccio and Jackson, 2009), high resolution absorption measurements in the near-infrared (NIR) spectral range based on cavity ring-down spectroscopy (CRDS) (Crosson et al, 2002), and multicollector inductively coupled plasma mass spectrometry (MC-ICPMS) (Malinovsky et al, 2013;Santamaria-Fernandez et al, 2008). The 13 C/ 12 C ratios of organic matter are most commonly determined by mass spectrometry, a technique correctly named irm-MS (isotope ratio monitoring by Mass Spectrometry) (B€ ottcher and Schnetger, 2004;Brand, 1996;Ellis and Fincannon, 1998;Smallwood et al, 2002).…”

Is there methane on Mars?

“…(For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) 2 HITRAN uses a 12 C/ 13 C ratio of R = 0.0112348, which is close to the PDB standard of R PDB = 0.0112372 (e.g., Santamaria-Fernandez et al, 2008). Differences from the PDB standard are conventionally expressed in the d 13 C PDB notation, which is defined by d 13 C PDB (R/R PDB À 1) Â 1000.…”

Determination of absolute 13C/12C isotope amount ratios by MC-ICPMS using calibration with synthetic isotope mixtures

“…Santamaria-Fernandez et al 10 used ultrasonic nebulisation and a membrane desolvator in order to reduce amounts of hydrogen introduced into the plasma and minimize formation of 12 C 1 H + ions. Carbon hydride ions are formed abundantly in the plasma and in the ion sampling interface because samples were introduced in the plasma as aqueous solution.…”

“…9 A current best-estimate of 13 C/ 12 C isotope amount ratio of VPDB ¼ 0.011124(45), with combined standard uncertainty in parentheses, based upon the unweighted mean of the GC-IRMS measurements is given in the review of Kaiser. 10 An important advantage of MC-ICPMS over conventional GS-IRMS for carbon isotope analysis is that singly charged positive ions, C + , are measured by MC-ICPMS instead of polyatomic CO 2 + ions, and thus a notorious correction for the 17 O isotope is not required. The need to correct for the contribution of the 17 O isotope in measured CO 2 + ions and the carryover effect for samples with non-natural isotopic composition, limiting the range of isotopic composition of carbon that can be measured, represent main challenges.…”