### Abstract

The variance is generally used as a measure of dispersion of
zones in capillary zone electrophoresis (CZE). It is a quantitative
measure of the separation power of a system and different causes of
dispersion can be rated by their partial variances, which can be summed
up to total variance. However, the additivity is only valid for
independent dispersion sources, a fact that often seems to be ignored.
The ubiquitous dispersion source diffusion is taken into consideration
by the Einstein term 2*Dt*. Other sources of dispersion are, *e.g.*,
injection, detection, thermal gradients, adsorption, and hydrodynamic
flow. For each of these sources various variance expressions have been
derived. The origin of the term 2*Dt* and its relation to the
variance is explained and the calculation of variance in general is
discussed. The equivalence of the diffusion variance and the term 2*Dt*
is verified with some simple initial forms of sample zone and the
additivity of variances in ideal zone electrophoresis is demonstrated.
The change of conductivity in zones results in asymmetrical zone forms
which is an indication of nonideality of a system. It is shown that in
such cases the term 2*Dt* is no longer valid and its use as an
additive variance component leads to an erroneous total variance.
Because in zone electrophoresis conductivity in a zone always changes
more or less, the additivity of variances is never perfectly valid.
However, in many cases the nonideality may be so small that the
additivity in practice is still applicable. A generally valid way to
calculate theroretically the total variance of a zone is to derive a
functional representation of the distribution and then calculate the
variance from it. This is possible only in the simplest cases. Usually
the distribution must be calculated by numerical methods.

Original language | English |
---|---|

Pages (from-to) | 1266 - 1270 |

Number of pages | 5 |

Journal | Electrophoresis |

Volume | 14 |

Issue number | 1 |

DOIs | |

Publication status | Published - 1993 |

MoE publication type | A1 Journal article-refereed |

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### Cite this

*Dt*in capillary zone electrophoresis.

*Electrophoresis*,

*14*(1), 1266 - 1270. https://doi.org/10.1002/elps.11501401193

}

*Dt*in capillary zone electrophoresis',

*Electrophoresis*, vol. 14, no. 1, pp. 1266 - 1270. https://doi.org/10.1002/elps.11501401193

**The variance and the quantity 2 Dt in capillary zone electrophoresis.** / Virtanen, Rauno.

Research output: Contribution to journal › Article › Scientific › peer-review

TY - JOUR

T1 - The variance and the quantity 2Dt in capillary zone electrophoresis

AU - Virtanen, Rauno

N1 - Project code: KEM3015

PY - 1993

Y1 - 1993

N2 - The variance is generally used as a measure of dispersion of zones in capillary zone electrophoresis (CZE). It is a quantitative measure of the separation power of a system and different causes of dispersion can be rated by their partial variances, which can be summed up to total variance. However, the additivity is only valid for independent dispersion sources, a fact that often seems to be ignored. The ubiquitous dispersion source diffusion is taken into consideration by the Einstein term 2Dt. Other sources of dispersion are, e.g., injection, detection, thermal gradients, adsorption, and hydrodynamic flow. For each of these sources various variance expressions have been derived. The origin of the term 2Dt and its relation to the variance is explained and the calculation of variance in general is discussed. The equivalence of the diffusion variance and the term 2Dt is verified with some simple initial forms of sample zone and the additivity of variances in ideal zone electrophoresis is demonstrated. The change of conductivity in zones results in asymmetrical zone forms which is an indication of nonideality of a system. It is shown that in such cases the term 2Dt is no longer valid and its use as an additive variance component leads to an erroneous total variance. Because in zone electrophoresis conductivity in a zone always changes more or less, the additivity of variances is never perfectly valid. However, in many cases the nonideality may be so small that the additivity in practice is still applicable. A generally valid way to calculate theroretically the total variance of a zone is to derive a functional representation of the distribution and then calculate the variance from it. This is possible only in the simplest cases. Usually the distribution must be calculated by numerical methods.

AB - The variance is generally used as a measure of dispersion of zones in capillary zone electrophoresis (CZE). It is a quantitative measure of the separation power of a system and different causes of dispersion can be rated by their partial variances, which can be summed up to total variance. However, the additivity is only valid for independent dispersion sources, a fact that often seems to be ignored. The ubiquitous dispersion source diffusion is taken into consideration by the Einstein term 2Dt. Other sources of dispersion are, e.g., injection, detection, thermal gradients, adsorption, and hydrodynamic flow. For each of these sources various variance expressions have been derived. The origin of the term 2Dt and its relation to the variance is explained and the calculation of variance in general is discussed. The equivalence of the diffusion variance and the term 2Dt is verified with some simple initial forms of sample zone and the additivity of variances in ideal zone electrophoresis is demonstrated. The change of conductivity in zones results in asymmetrical zone forms which is an indication of nonideality of a system. It is shown that in such cases the term 2Dt is no longer valid and its use as an additive variance component leads to an erroneous total variance. Because in zone electrophoresis conductivity in a zone always changes more or less, the additivity of variances is never perfectly valid. However, in many cases the nonideality may be so small that the additivity in practice is still applicable. A generally valid way to calculate theroretically the total variance of a zone is to derive a functional representation of the distribution and then calculate the variance from it. This is possible only in the simplest cases. Usually the distribution must be calculated by numerical methods.

U2 - 10.1002/elps.11501401193

DO - 10.1002/elps.11501401193

M3 - Article

VL - 14

SP - 1266

EP - 1270

JO - Electrophoresis

JF - Electrophoresis

SN - 0173-0835

IS - 1

ER -

*Dt*in capillary zone electrophoresis. Electrophoresis. 1993;14(1):1266 - 1270. https://doi.org/10.1002/elps.11501401193