Optimization of Sensitivity

  • Kevin D. Altria
Part of the Methods in Molecular Biology book series (MIMB, volume 52)

Abstract

The injection volumes involved in CE are very small (in the order of 1–10 nL). In addition, the area of capillary employed for on-column detection may be only 50 × 200 µm. Both these factors influence the detector sensitivity to a large extent. CE is less sensitive when directly compared to HPLC with typical injections of 10–50 µL and 1-cm detector cells. The difference may be up to an order of magnitude (2) when comparing at the same UV wavelength. Several strategies may be employed (Table 1) to maximize the sensitivity in CE. These include use of low UV wavelengths, increased capillary bore, and optimized sampling procedure.
Table 1

Summary of Approaches Available for Increasing Sensitivity

Action to improved sensivity

Drawback(s) to consider

Employ low-UV wavelength

Increased background noise—determine wavelength to give optimum signal-to-noise ratio

Increase capillary bore

Increased current, reduced EOF giving possible alteration in selectivity

Increased injection time

Reduction in separation efficiency; excessive time will result in run failure

Appropriate use of electrokinetic injection

Sampling bias for more mobile ions, sample matrix effects on injection amount

Increased electrolyte strength

Increased current and associated noise

Optimize electrolyte composition

Effects on selectivity and current

Decrease operating voltage

Increase in analysis time

Decrease temperature

Increase in analysis time

Capillary modifications

Reduction in separation efficiency and resolution, increased cost

Sample derivatization

Additional sampling handling

Indirect detection

Extra method development considerations

Wide-bore capillaries

EOF profile disturbed, adjustments to rinse and injection times, siphoning effects more pronounced

Increased detector slit width

Reduction in separation efficiency and resolution

Keywords

Sugar Cellulose HPLC Glycerol EDTA 

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Copyright information

© Humana Press Inc., Totowa, NJ 1996

Authors and Affiliations

  • Kevin D. Altria
    • 1
  1. 1.Glaxo Research and DevelopmentWare, HertfordshireUK

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