The development of an efficient mass balance approach for the purity assignment of organic calibration standards.
The purity determination of organic calibration standards using the traditional mass balance approach is described. Demonstrated examples highlight the potential for bias in each measurement and the need to implement an approach that provides a cross-check for each result, affording fit for purpose purity values in a timely and cost-effective manner. Chromatographic techniques such as gas chromatography with flame ionisation detection (GC-FID) and high-performance liquid chromatography with UV detection (HPLC-UV), combined with mass and NMR spectroscopy, provide a detailed impurity profile allowing an efficient conversion of chromatographic peak areas into relative mass fractions, generally avoiding the need to calibrate each impurity present. For samples analysed by GC-FID, a conservative measurement uncertainty budget is described, including a component to cover potential variations in the response of each unidentified impurity. An alternative approach is also detailed in which extensive purification eliminates the detector response factor issue, facilitating the certification of a super-pure calibration standard which can be used to quantify the main component in less-pure candidate materials. This latter approach is particularly useful when applying HPLC analysis with UV detection. Key to the success of this approach is the application of both qualitative and quantitative (1)H NMR spectroscopy.
Chemical Reference Materials, National Measurement Institute, P.O. Box 138, North Ryde, New South Wales, 1670, Australia. Stephen.Davies@measurement.gov.au.
Stephen R
SR
Davies
Chemical Reference Materials, National Measurement Institute, P.O. Box 138, North Ryde, New South Wales, 1670, Australia.
Mahiuddin
M
Alamgir
Chemical Reference Materials, National Measurement Institute, P.O. Box 138, North Ryde, New South Wales, 1670, Australia.
Benjamin K H
BK
Chan
Chemical Reference Materials, National Measurement Institute, P.O. Box 138, North Ryde, New South Wales, 1670, Australia.
Thao
T
Dang
Chemical Reference Materials, National Measurement Institute, P.O. Box 138, North Ryde, New South Wales, 1670, Australia.
Kai
K
Jones
Chemical Reference Materials, National Measurement Institute, P.O. Box 138, North Ryde, New South Wales, 1670, Australia.
Maya
M
Krishnaswami
Chemical Reference Materials, National Measurement Institute, P.O. Box 138, North Ryde, New South Wales, 1670, Australia.
Yawen
Y
Luo
Chemical Reference Materials, National Measurement Institute, P.O. Box 138, North Ryde, New South Wales, 1670, Australia.
Peter S R
PS
Mitchell
Chemical Reference Materials, National Measurement Institute, P.O. Box 138, North Ryde, New South Wales, 1670, Australia.
Michael
M
Moawad
Chemical Reference Materials, National Measurement Institute, P.O. Box 138, North Ryde, New South Wales, 1670, Australia.
Hilton
H
Swan
Chemical Reference Materials, National Measurement Institute, P.O. Box 138, North Ryde, New South Wales, 1670, Australia.
Greg J
GJ
Tarrant
Bias; Certified reference materials; Mass balance method; Organic calibration standards; Purity assessment