TY - JOUR
T1 - Measurement of 13C and 15N isotopic composition on nanomolar quantities of C and N
AU - Polissar, Pratigya J.
AU - Fulton, James M.
AU - Junium, Christopher K.
AU - Turich, Courtney C.
AU - Freeman, Katherine H.
PY - 2009/1/15
Y1 - 2009/1/15
N2 - We describe a trapping and chromatography system that cryogenically removes CO 2 and N 2 generated from sample combustion in an elemental analyzer (EA) and introduces these gases into a low-flow helium carrier stream for isotopic analysis. The sample size required for measurement by this system (termed nano-EA/ IRMS) is almost 3 orders of magnitude less than conventional EA analyses and fills an important niche in the range of analytical isotopic methods. Only 25 nmol of N and 41 nmol of C are needed to achieve 1.0 % precision (2σ) from a single measurement while larger samples and replicate measurements provide better precision. Analyses of standards demonstrate that nano-EA measurements are both accurate and precise, even on nanomolar quantities of C and N. Conventional and nano-EA measurements on international and laboratory standards are indistinguishable within analytical precision. Likewise, nano-EA values for international standards do not differ statistically from their consensus values. Both observations indicate the nano-EA measurements are comparable to conventional EA analyses and accurately reproduce the VPDB and AIR isotopic scales. Critical to the success of the nano-EA system is the procedure for removing the blank contribution to the measured values. Statistical treatment of uncertainties for this procedure yields an accurate method for calculating internal and external precision.
AB - We describe a trapping and chromatography system that cryogenically removes CO 2 and N 2 generated from sample combustion in an elemental analyzer (EA) and introduces these gases into a low-flow helium carrier stream for isotopic analysis. The sample size required for measurement by this system (termed nano-EA/ IRMS) is almost 3 orders of magnitude less than conventional EA analyses and fills an important niche in the range of analytical isotopic methods. Only 25 nmol of N and 41 nmol of C are needed to achieve 1.0 % precision (2σ) from a single measurement while larger samples and replicate measurements provide better precision. Analyses of standards demonstrate that nano-EA measurements are both accurate and precise, even on nanomolar quantities of C and N. Conventional and nano-EA measurements on international and laboratory standards are indistinguishable within analytical precision. Likewise, nano-EA values for international standards do not differ statistically from their consensus values. Both observations indicate the nano-EA measurements are comparable to conventional EA analyses and accurately reproduce the VPDB and AIR isotopic scales. Critical to the success of the nano-EA system is the procedure for removing the blank contribution to the measured values. Statistical treatment of uncertainties for this procedure yields an accurate method for calculating internal and external precision.
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U2 - 10.1021/ac801370c
DO - 10.1021/ac801370c
M3 - Article
C2 - 19072032
AN - SCOPUS:64349111326
SN - 0003-2700
VL - 81
SP - 755
EP - 763
JO - Analytical Chemistry
JF - Analytical Chemistry
IS - 2
ER -