Published:Journal of Chromatographic Science,
ISSN 0021-9665 Volume 45,
Number 1, January 2007, pp.50-56
Performance Characteristics of an Ion Chromatographic
Method for the Quantitation of Citrate and Phosphate in Pharmaceutical
Solutions
Dennis Jenke[1], Salma Sadain[1], Karen Nunez[1],
and Frances Byrne[2]
[1]Technology Resources Division and
[2]Medication Delivery Division, Baxter Healthcare Corporation,
Route 120 and Wilson Road, Round Lake, IL 60073
The performance of an ion chromatographic method
for measuring citrate and phosphate in pharmaceutical solutions
is evaluated. Performance characteristics examined include accuracy,
precision, specificity, response linearity, robustness, and the
ability to meet system suitability criteria. In general, the method
is found to be robust within reasonable deviations from its specified
operating conditions. Analytical accuracy is typically 100 ±
3%, and short-term precision is not more than 1.5% relative standard
deviation. The instrument response is linear over a range of 50%
to 150% of the standard preparation target concentrations (12
mg/L for phosphate and 20 mg/L for citrate), and the results obtained
using a single-point standard versus a calibration curve are essentially
equivalent. A small analytical bias is observed and ascribed to
the relative purity of the differing salts, used as raw materials
in tested finished products and as reference standards in the
analytical method. The assay is specific in that no phosphate
or citrate peaks are observed in a variety of method-related solutions
and matrix blanks (with and without autoclaving). The assay with
manual preparation of the eluents is sensitive to the composition
of the eluent in the sense that the eluent must be effectively
degassed and protected from CO2 ingress during use. In order for
the assay to perform effectively, extensive system equilibration
and conditioning is required. However, a properly conditioned
and equilibrated system can be used to test a number of samples
via chromatographic runs that include many (> 50) injections.
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