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Improve Pass Rates for Residual Solvents by
USP <467> With New Rxi®-624Sil MS
GC Columns
By Rick Lake, Pharmaceutical Market Development Manager and Amanda Rigdon, Innovations Chemist
It has been over a year since the revised USP <467> Residual
Solvents general chapter became effective. Since then, many
labs have experienced difficulty implementing this more expan-
sive procedure. Most of the problems encountered relate to the
selectivity and sensitivity needed to meet system suitability
requirements in Procedure A. Finding an instrument setup that
adequately resolves acetonitrile and dichloromethane in the
Class 2 Mixture A standard, while also maintaining carbon tetra-
chloride sensitivity in the Class 1 solution, can prove difficult. Since increasing system
suitability pass rates directly increases lab productivity, Restek has developed a new
G43 capillary column that better meets USP <467> requirements.
Greater Resolution Improves Pass Rates
The Class 2 Mixture A solution contains the most difficult selectivity requirement of the
method: the resolution between acetonitrile and dichloromethane must be greater
than 1. This is often difficult to achieve on conventional G43 columns, which only give
marginal selectivity for this pair. Poor selectivity can result in lower overall pass rates,
and, thus, decreased sample throughput. In contrast, the Rxi®-624Sil MS column incor-
porates a distinctive bonding chemistry that results in resolution values consistently
greater than 3 (Figure 1). The greater resolution routinely achieved on the Rxi®-624Sil MS
column results in more consistent system suitability pass rates, and thus greater lab
productivity.
Higher Inertness Gives Increased Sensitivity
Rxi®-624Sil MS columns are manufactured using proprietary Rxi® technology, which
produces extremely inert and stable columns. The high thermal stability of the
Rxi®-624Sil MS column produces a very stable baseline, which leads to accurate and
consistent integration. For example, carbon tetrachloride in the Class 1 system
suitability solution, the most difficult sensitivity requirement in the method, can be
easily and consistently integrated, reliably providing the necessary sensitivity. Another
significant advantage of the Rxi®-624Sil MS column for the Class 1 solution is the
complete resolution of benzene and 1,2-dichloroethane (Figure 2). Complete resolution
of these analytes is often not achieved on other columns, making the Rxi®-624Sil MS
column particularly beneficial for testing programs using USP <467>.
Conclusion
Not all G43 columns are equivalent for residual solvent testing, and the new Rxi®-624Sil MS
column offers best-in-class performance advantages for all aspects of USP <467> system
suitability testing. These columns reliably produce improved resolution and sensitivity,
increasing system suitability pass rates and ensuring more productive laboratory time.
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• Greatest resolution of acetonitrile and dichloromethane
of any G43 column.
• Stable baseline for improved sensitivity of carbon
tetrachloride.
• Exceptional column-to-column reproducibility.
ID df (µm) temp. limits length* cat. #
0.18mm 1.00 -20 to 300/320°C 20 13865
0.25mm 1.40 -20 to 300/320°C 30 13868
0.32mm 1.80 -20 to 300/320°C 30 13870
0.32mm 1.80 -20 to 300/320°C 60 13872
0.53mm 3.00 -20 to 280/300°C 30 13871
*Length in meters.
Rxi®-624Sil MS Columns (fused silica)
(mid polarity Crossbond® silarylene phase; equivalent to
6% cyanopropylphenyl/94% dimethyl polysiloxane)
pharmaceutical
USP-equivalent residual solvent
Class 1 & 2 mixes & singles.
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for a complete selection
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For more information
on USP <467>
analysis, download
PHFL1018A at
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