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Inverse gas chromatography standard solutions, device and method

This technology is to make inverse gas chromatography (IGC) standard mixtures; improving accuracy of surface energy analysis; and shortening experiment running time of surface analysis.


Inverse gas chromatography (IGC) is simple, fast and accurate techniques for characterizing the surface properties of solids in any form [1].
These chromatographic systems have been designed in order to obtain measurements of high precision.
However, random errors can be minimized but not eliminated [2]. The tolerances of the equipment used for the control of the temperature and flow rate, user error, and sampling procedure cause variations of column temperature and carrier gas flow rate which, in turn, causes significant changes in the measured retention times [3, 4].
The retention times also change with variation in column performance or column overloading with sample [5].
These potential variations in retention times of a probe or probes will deviate the calculated surface properties from their accurate values.


For surface energy measurement, it is recommended to use a series of four alkanes [6].
Five n-alkanes are essential to validate the IGC experiment accuracy and to estimate the accurate value of the surface free energy from its measured value [7].
Researchers’ criterion to judge the accuracy of IGC measurements for the retention times is the linearity of the n-alkane line, which must be ≥ 0.9995 [8].
New criteria, which depend on the measured dispersive retention factor, verify the accuracy of the measured retention times and so the calculated surface data [7].
The fixed partial pressure injection method is traditionally utilized by standard IGC systems, i.e., similar amounts of n-alkanes’ molecules are separately injected through the solids. With the introduction of Surface Energy Analyser (SEA), the probe injection approach has been altered to depend on the target fractional surface coverage, i.e., amounts of n-alkanes covering similar surface areas of the analysed solid are separately injected through the solids [9].


Therefore, injecting four or five n-alkanes separately through a column full with an investigated material is the used method to determine the surface components. Moreover, usually, these injections are repeated to get retention times with acceptable accuracy.
This makes IGC experiments time-consuming.


Our invention is to make the analysis of surface properties using IGC or SEA much faster and more accurate.
Moreover, it can be used to valid the accuracy of IGC and SEA systems. These advantages of our invention occur through preparing IGC standard mixtures.
These standard mixtures enable IGC and SEA systems to probe the tested materials with the same target fractional surface coverage of each probe simultaneously at infinite regions and finite concentrations. Also, this invention is to design a “One injection IGC” device to prepare the standard IGC mixtures and to be fitted within the IGC and SEA systems.


References


[1] S. Mohammadi-Jam, K.E. Waters, Inverse gas chromatography applications: a review, Adv. Colloid Interface Sci. 212 (2014) 21-44.

[2] J.N. Miller, J.C. Miller, Statistics and Chemometrics for Analytical Chemistry, fifth ed., Pearson Education Limited, Harlow, 2005.

[3] T. Perl, B. Bödeker, M. Jünger, J. Nolte, W. Vautz, Alignment of retention time obtained from multicapillary column gas chromatography used for VOC analysis with ion mobility spectrometry, Anal. Bioanal. Chem. 397 (2010) 2385-2394.

[4] A. Barcaru, A. Anroedh-Sampat, H.G. Janssen, G. Vivó-Truyols, Retention time prediction in temperature-programmed, comprehensive two-dimensional gas chromatography: Modeling and error assessment, J. Chromatogr. A 1368 (2014) 190-198.

[5] Y. Koh, K.K. Pasikanti, C.W. Yap, E.C. Chan, Comparative evaluation of software for retention time alignment of gas chromatography/time-of-flight mass spectrometry-based metabonomic data, J. Chromatogr. A 1217 (2010) 8308-8316.

[6] iGC SEA Quick Start Guide, page 22, Version 1.1, October 2012 Surface Measurement Systems, Ltd., 5 Wharfside, Rosemont Road, Alperton, Middlesex HA0 4PE, United Kingdom.

[7] M.A. Mohammad, Accuracy verification of surface energy components measured by inverse gas chromatography, J. Chromatogr. A 1399 (2015) 88-93.

[8] J.R. Conder, C.L. Young, Physicochemical Measurement by Gas Chromatography, Wiley-Interscience Publication, Chichester, 1979.

[9] J.F. Gamble, M. Leane, D. Olusanmi, M. Tobyn, E. Supuk, J. Khoo, M. Naderi, Surface energy analysis as a tool to probe the surface energy characteristics of micronized materials—A comparison with inverse gas chromatography. Int. J. Pharm. 422 (2012) 238– 244.

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