Elementary theory of programed temperature gas chromatography

Giddings, J. Calvin

doi:10.1021/ed039p569

Cited by 33 publications

(29 citation statements)

References 6 publications

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“…This conclusion is not altered by virtue of programming; the general function of a program is simply to provide a range of conditions in proper sequence for fractionating a diverse sample (9). The prototype experimental system employed here is unable to use high rotational speeds because of the vulnerability of the special seal used to transport solvent into and out of the centrifugal basket.…”

Section: Resultsmentioning

confidence: 99%

“…For each peak (or close-lying pair of peaks), there is an ideal level of retention during migration involving a compromise between resolution, time-economy and peakheight factors (8,9). The ideal range in chromatography is generally somewhere in the region described by R = 0.2 to 0.5, where R is the retention ratio.…”

Section: Dsgz(ap)zmentioning

confidence: 99%

“…The ideal range in chromatography is generally somewhere in the region described by R = 0.2 to 0.5, where R is the retention ratio. For gas chromatography, ideal retention occurs near the boiling point (9). Effective programming, as has been shown in an analysis of programmed temperature gas chromatography, continuously alters the retention parameter of each component so that the bulk of its migration can occur in the ideal range (8,9).…”

Section: Dsgz(ap)zmentioning

confidence: 99%

“…develop integral expressions that properly sum up each small increment of migration. Similar problems exist for programmed forms of chromatography (6,8,9). In this section, we will subdivide the general programming technique into two subclasses and derive the essential integrals describing each.…”

Section: General Theory Of Programmed Retentionmentioning

confidence: 99%

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Programmed sedimentation field-flow fractionation

Yang¹,

Myers²,

Giddings³

1974

Anal. Chem.

102

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expected in an optimal system. Most importantly, the rotational velocity and the field strength must be increased to gain any significant advances. The degree to which performance might be enhanced is shown below.Under conditions of high retention, Equation 13 can be substituted into Equation 14 to yield the potential plate height H = 24h'~~(~)/D (33) With the aid of Equation 10 this expression becomes where the zone velocity in the column, R ( u ) has been written simply as u. If now Equation 8 is used to eliminate X2, we haveIf diffusion coefficient D is replaced by the Stokes-Einstein value, D = kT/3agd, where 7 is the coefficient of viscosity, we get 432If H is written as Cv, then the nonequilibrium coefficient C not only reflects the level of H achievable, but, more importantly, C can be shown to equal the minimum time in which a theoretical plate can be generated. We have 432 k T y c = -This equation shows that the efficacy of SFFF can be improved by manipulating a number of variables, including viscosity, temperature, and density. The method will, in theory, work much better with large particles than small, as reflected in the fifth power dependence on particle diameter d. However there are practical limits to this gain which will become apparent as d approaches either layer thickness 1 or surface-roughness dimensions in magnitude.Equation 37 shows that C for a given particle is inversely proportional to the square of the sedimentation field strength, G. The dependence on rotational velocity is therefore inverse fourth power. In the present study the maximum G was about 500g. If ultracentrifuges, with field strengths up to 300 times greater than this, were adapted to SFFF, C values could in theory be reduced by (300)2 = 90,000. While such gains would not be totally applicable to particles in the size range used here because of the previously mentioned restrictions on size, the above factor would be applicable to much smaller particles and to macromolecules, thus making their separation convenient also.Particle size analysis is significant in many fields of environmental control and industrial operation. The present method is promising in such analyses by virtue of its predictable dependence on simple mass and density parameters and its potential for further improvements in fractionating power. This paper describes the development of two programming systems for sedimentation field-flow fractionation (SFFF): programmed field strength SFFF and programmed solvent density SFFF. The necessity for developing programming systems in SFFF is discussed, and both general and specific theories of programming are developed. A centrifugal SFFF system was adapted to programming by the controlled variation of rotation speed and solvent density. Polystyrene latex beads with diameters from 1756 to 3117A were fractionated by this device. Agreement between theoretical and experimental retention times was within about 5%, showing that the essential features of the technique are well characterized.Sedimentation field-flow fra...

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Section: Resultsmentioning

confidence: 99%

Section: Dsgz(ap)zmentioning

confidence: 99%

Section: Dsgz(ap)zmentioning

confidence: 99%

Section: General Theory Of Programmed Retentionmentioning

confidence: 99%

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Programmed sedimentation field-flow fractionation

Yang¹,

Myers²,

Giddings³

1974

Anal. Chem.

102

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“…The existence of an optimal heating rate was w x suggested by Giddings 7,8 , who proposed several simple semiempirical formulae for evaluation of the optimal heating rate for a typical GC analysis. The formulae, however, were not based on specific optimization criteria, and, therefore, the context of their w Ž practical use was unclear.…”

Section: Introductionmentioning

confidence: 99%

Optimal heating rate in gas chromatography

Blumberg¹,

Klee

2000

J. Micro. Sep.

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Several optimization criteria for column heating rate in temperature programmed gas chromatography (GC), under different optimization constraints are identified. Applying these criteria to experimental data, it is shown that when column pressure drop is high, the optimum heating rate for n‐alkanes and pesticides in a column with a silicone stationary phase of a typical thickness is about 10°C per void time. This heating rate is recommended as a default for all temperature programs in capillary GC. © 2000 John Wiley & Sons, Inc. J Micro Sep 12: 508–514, 2000

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Programmed Temperature

and¹,

Miller²

2008

Basic Gas Chromatography

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Elementary theory of programed temperature gas chromatography

Cited by 33 publications

References 6 publications

Programmed sedimentation field-flow fractionation

Programmed sedimentation field-flow fractionation

Optimal heating rate in gas chromatography

Programmed Temperature

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