Quality Assurance

For daily calculations, Pace Energy Services uses standards of known value relative to the international standards. For example, for organics, NBS-22 (light oil standard; δ 18O = -29.8‰, δD = -120‰). Below is a list of all daily standards used at Pace Energy Services. These standards are collected with samples on the gas separation vacuum line in the ratio of 1 standard:10 samples or 1 standard per work order: whichever is smaller.


Sample duplicates are collected in a ratio of 1 duplicate:10 samples. Line blanks are also determined on a regular basis.

Isotopic compositions of standards of known composition are determined at the mass spectrometer on a daily basis prior to sample collection in order to verify running conditions.

The accuracy of software calculations in the measurement and correction of isotope ratios is monitored by manual calculations.

Laboratory technicians are thoroughly trained in both the theory and application for sample preparation and isotope ratio measurement. Personnel files contain listings of approved method training and standard data where applicable.


Instrument Precision Intralab Reproducibility
2H/ 1H as H 2 0.2‰ 0.5‰
18O/ 16O as CO 2 0.01‰ 0.01‰
13C/ 12C as CO 2 0.01‰ 0.05‰
15N/ 14N as N 2 0.01‰ 0.01‰
34S/ 32S as SO 2 0.02‰ 0.01‰

The accuracy of such measurements can of course be influenced by factors other than the precision of the mass spectrometer - such as sample purity, sample size and operation technique.

Acceptable Pace Energy Services sample duplicate reproducibilities are shown below but may vary by sample type and sample size:

δD ± 3.0‰

δ 34S ± 0.3‰

δ 18O ± 0.3‰

δ 15N ± 0.3‰

δ 13C ± 0.2‰

δ 37Cl ± 0.5‰

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