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Chromatographia

, Volume 35, Issue 1–2, pp 73–84 | Cite as

Determination of gas-liquid partition coefficients by automatic equilibrium headspace-gas chromatography utilizing the phase ratio variation method

  • L. S. Ettre
  • C. Welter
  • B. Kolb
Originals

Summary

The new phase ratio variation method is described which represents a convenient way for the determination of gas-liquid partition coefficients for practical purposes, utilizing equilibrium headspace-gas chromatography (EHS-GC). This method is based on the relationship between reciprocal peak area and the phase ratio in the vial containing the sample solution; it involves regression analysis of the EHS-GC measurements of a number of sample vials containing the same sample solution but with a wide variation of phase ratios. Examples are given for both aqueous systems and systems consisting of a stationary (liquid) phase used as the solvent; comparison of the measured values with results obtained by other methods shows satisfactory agreement. A critical discussion of the conditions influencing the accuracy of the analytical results is given.

Key Words

Gas chromatography Equilibrium headspace sampling Partition coefficient determination Theory of chromatography 

Acronyms and Symbols

EHS

equilibrium headspace (sampling)

GC

gas chromatography

GLPC

gas-liquid partition chromatography

HS

headspace (sampling)

MHE

multiple headspace extraction

VPC

vapor-phase calibration method for determination of the partition coefficient (EHS-GC)

a

intercept of Eq. (20)

a′

intercept of Eq. (27)

a″

intercept of Eq. (30)

A

peak area obtained when analyzing an aliquot of the gas phase (headspace) of the sample vial, in equilibrium with the sample (EHS-GC)

A1, A2

peak area obtained in EHS-GC measurements corresponding to vials with respective phase ratios of β1 and β2

b

slope of Eq. (20)

b′

slope of Eq. (27)

b″

slope of Eq. (30)

cG*

concentration of the analyte in the gas phase (headspace) of vial, at equilibrium (EHS)

cL*

concentration of the analyte in the stationary (liquid) phase, at equilibrium

cM*

concentration of the analyte in the mobile phase, at equilibrium

cS

concentration of the analyte in the original sample (solution) in the sample vial (EHS)

cS*

concentration of the analyte in the sample phase (solution) in the sample vial, at equilibrium (EHS)

fi

proportionality factor

j

carrier gas compressibility correction factor (GC)

k

retention factor (capacity ratio) of the analyte

K

partition coefficient (distribution constant) of the analyte

mL*

amount of analyte present in the stationary (liquid) phase, at equilibrium

mM*

amount of analyte present in the mobile phase, at equilibrium

r

correlation coefficient of linear regression calculation

rc

inner radius of the chromatographic column

tM

hold-up time (retention time of a non-retained compound)

tR

retention time of the analyte

tR

adjusted retention time of the analyte

T

absolute temperature

VG

volume of the gas phase in the column (GC); volume of the gas phase (the headspace) in the sample vial (EHS)

VL

volume of the stationary (liquid) phase in the chromatographic column

VM

volume of the mobile phase in a chromatographic column in general; gas hold-up volume (retention volume of a non-retained compound) in GC)

VR

retention volume of the analyte

VR

adjusted retention volume of the analyte

VS

volume of the sample solution introduced into the vial (EHS)

VV

total volume of the vial (EHS)

WL

amount of the stationary (liquid) phase in the column

β

phase ratio of the chromatographic column (GC, LC); phase ratio of the sample vial (EHS)

β1, β1

maximum and minimum phase ratio values of a series of sample vials containing the same sample solution but in different volumes (EHS-GC)

πL

density of the stationary (liquid) phase at column temperature

ΦS

sample phase fraction in the headspace vial (EHS)

*

asterisk refers to equilibrium conditions

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References

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Copyright information

© Friedr. Vieweg & Sohn Verlagsgesellschaft mbH 1993

Authors and Affiliations

  • L. S. Ettre
    • 1
  • C. Welter
    • 2
  • B. Kolb
    • 2
  1. 1.Department of Chemical EngineeringYale UniversityNew HavenUSA
  2. 2.Bodenseewerk Perkin-Elmer GmbHÜberlingenGermany

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