appac - Atmospheric Pressure Peak Area Correction for Gas Chromatography
with Standard Detectors
Corrects gas-chromatography peak areas for the influence
of ambient air pressure on standard detectors open to the
ambient atmosphere, such as the flame ionization detector,
whose pressure sensitivity was characterised by Bocek, Novak
and Janak (1969) <doi:10.1016/S0021-9673(00)99223-9>. Unlike
the pressure compensation of Ayers and Clardy (1985)
<https://patents.google.com/patent/US4512181A>, which is
combined with a calibration and valid only for a single
calibration period of a few days, per-cylinder peak areas are
decomposed by principal components into a pressure-correlated
component and per-peak drift; a common pressure-sensitivity
coefficient (kappa) is estimated with a heavy-tail-robust fit
on a drift-reduced signal, and slow drift plus a daily factor
are removed. Returns the corrected areas together with a
chi-square goodness-of-fit diagnostic. Structural-break
detection (package 'strucchange', Zeileis and others (2002)
<doi:10.18637/jss.v007.i02>) is provided for episode-level and
variance breakpoint analysis.
