Grob test

Figure 15.11 (a) Total ion clnomatogram of a Grob test mixture obtained on an Rtx-1701 column, and (b) re-injection of the entire clnomatogram on to an Rtx-5 column. Peak identification is as follows a, 2,3-butanediol b, decane c, undecane d, 1-octanol e, nonanal f, 2,6-dimethylphenol g, 2-ethylhexanoic acid h, 2,6-dimethylaniline i, decanoic acid methyl ester ], dicyclohexylamine k, undecanoic acid, methyl ester 1, dodecanoic acid, methyl ester. Adapted from Journal of High Resolution Chromatography, 21, M. J. Tomlinson and C. L. Wilkins, Evaluation of a semi-automated multidimensional gas chromatography-infrared-mass specti ometry system for initant analysis , pp. 347-354, 1998, with permission from Wiley-VCH. 

STANDARD EXPERIMENTAL CONDITIONS FOR PERFORMING THE GROB TEST... 

Figura 2.9 Dse of th Grob test Mixture to compare tbe activity of various glass surfaces coated with ov-ioi. Surface types A > Untreated pyrex glass, B pyrex glass deactivated by thermal degradation of Ceurbowax 20M, C < SCOT column, prepared with Silanox 101, D pyrex glass column coated with a layer of barium carbonate and deactivated as in (B), and E - untreated fused silica. Components are identified in Table 2.7 with ac - 2-ethylhexanoic acid. (Reproduced with permission from ref. 152. Copyright Elsevier Scientific Publishing Co.)...

A good way to test the operation of the GC and the GC-MS interface is to run a standard sample. For this purpose the so-called Grob test mixture [226] is suitable. 

Figure 15.11 (a) Total ion chromatogram of a Grob test mixture obtained on an Rtx-1701... 

Figure 8.7. Grob test mixture run on 30 m DB-5 OT column. Courtesy of J W Scientific.

The following capillary GC tests were performed with the Grob Test Mixture (7 ), listed in "Table IV". It represents a combination of constituents of varickble polarity and reflects quite well the real world of industrial problems. 

In "Figure 5" a compcurison is made between isothermal and temperature programmed capillary GC with equal retention times for the last eluting component of the Grob Test Mixture. In order... 

Figure 12" represents the temperature dependence of the Ko-vats indices for the substances F, G and H from the Grob Test Mixture. "Table V" summarizes the values of the prominent components of the Grob Test Mixture for OV-1, SE-54, OV-1701 and PEG 40M. 

Fig. 3.9. Gas chromatograms (FID) of test mixtures on AR-glass capillary columns. (1) Grob test mixture on OV-21S. Initial temperature 70°C, programmed at 5°C/min. Peaks Cn = undecane ol = octanol P = 2.6-dimethylphenol s = 2-ethylhexanoic acid al = nonanal A = 2,6-dimelhylaniline am = dicyclohexylamine E,o, E, and E,j = C,q, C, and C,2-acid methyl esters. (2) Nitrophenol test on SE-52. Initial temperature 100°C, programmed at 7°C/min. Peak assignment o, m, p = oriho,meta,para-nilTophenol , 2,4, 2,6 = 2,4-dinitrophenol and 2,6-dinitrophenol. (3) Diamine test on SE-30. Initial temperature 60°C, programmed at 7°C/min. Peaks dh = 1,6-diaminohexane do = 1,8-diaminooctane. Reproduced from [lOS].

Grob test provides quantitative information about four important aspects of column quality separation efficiency, adsorptive activity, acidity/basicity and the stationary phase film thickness. The experimental conditions are optimized for columns of low polarity with a medium range of film thickness (0.08-0.4 p,m) and column internal diameters of 0.25-0.35 mm. The composition of the Grob test mixture and experimental conditions for the test is summarized in Table 2.16. The individual standard solutions are stable almost indefinitely and the test mixture for several months when stored in a refrigerator. Reaction between nonanal and 2,6-dimethylaniline to form a Schiff base derivative occurs on prolonged storage resulting in reduced peak areas for these two compounds [362]. The test mixture is injected to allow ca. 2 ng of each substance to enter the column (e.g. 1 xl with a split ratio of 1 20 to 1 50). 

Test mixture composition and optimum experimental conditions for the Grob test. 

Figure 2.16. Example of column deterioration due to aging. The 0.25 mm I. D. fused silica columns are 15 m (A) and 30 m (B) coated with 1.0 xm DB-5 stationary phase. Column activity is determined using the Grob test method (Table 2.16). Column (A) is an old column exhibiting strong activity. Column (B) is a new column. The reduced peak heights of nonanal and 2,6-dimethylaniline on both columns also indicate change in relative composition of the test mixture due to storage time.

A computer program for the optimisation of ID GC separations [30] has been modified to include the additional variables required for GCxGC [31]. The estimation is also based on Equation (6), but the use of the distribution constant K instead of the retention factor k allows the extension of its application to different column geometries and to mixed stationary phases. The compounds in the Grob test mixture were used in the validation. The retention times of these compounds, obtained using two different temperature programs were the only experimental data required. Results were good except for the retention of a few compounds in the D column. 

Figure 6 Typical results of the standardized Grob test, for determination of column quality. Mixture contents (and mass in the split method-injected solution, in mg ml ) are (1) 2,3-butanediol (0.95) (2) />decane (0.43) (3) 1-octanol (0.555) (4) nonanal (0.625) (5) 2,6-dimethylphenol (0.485) (6) 2-ethylhexanoic acid (0.605) (7) 2,6-dimethylaniline (0.513) (8) n-dodecane (0.44) (9) methyl decanoate (0.605) (10) dicyclohexyl amine (0.51) (11) methyl undecanoate (0.59) and (12) methyl dodecanoate (0.578). The dotted line represents the expected peak maxima when each solute exhibits complete recovery, and excellent chromatographic behavior. (From Jennings W (1987) Analytical Gas Chromatography, p. 234. Orlando Academic Press.)...

Fig. 3 Chromatogram of the Grob test mixture on Column 1. Temperature programmed from 120°C to 160°C at 4°C/min. Peaks 1, n-decane 2, n-undecane 3, n-dodecane 4, n-octanol 5, 2,3-butanediol 6, naphthalene 7, n-tridecane 8, 2,6-dimethylaniline 9, n-tetradecane 10, 2,6-...

Testing the properties and quality of a GC column can be done by the Grob test that includes the injection of a mixture of G10-G12 fatty add methyl esters, C10-C12 n-alkanes, 1-octanol, 2,3-butanediol, 2,6-dimethylaniline, 2,6-dimethyl-phenol, dicyclohexylamine, and 2-hexylhexanoic add. 

The Grob test provides quantitative information on four important aspeds of column quality separation efficiency, adsorptive activity, acidity/basidty, and stationary phase thickness. This test is now widely used by column manufacturers. 

More about the Grob test can be found in Refs [2,3]. 

The use of dendronized silica as a stationary phase in capillary gas chromatography was pioneered in 2001 by Newkome et al.," who used the triply branched dendrons prepared in solution and immobilized on fused silica inside the capillary column. The dendritic architecture provides unique selectivity in separation of a Grob test mixture of compounds. The same dendron-silica hybrids were used by the authors for solventless capillary microextraction (CME) and preconcentration in chemical analysis. 

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