Chapter 26: Q39P (page 749)

(a) A particular solution in a particular capillary has an electroosmotic mobility of $1.3 \times 10^{- 8} m^{2} / (V \times s) atpH 2$ and 8.1 $10^{- 8} m^{2} / (V \times s)$ . How long will it take a neutral solute to travel 52 cm from the injector to the detector if 27 kV is applied across the 62-cm-long capillary tube at pH 2? At pH 12?(b) An analyte anion has an electrophoretic mobility of $- 1.6 \times 10^{- 8} m^{2} / (V \times s)$ How long will it take to reach the detector at pH 2?At pH 12?

Short Answer

Expert verified

a)A neutral solute to travel at pH=2 and pH=12 is $t = 9.2 \times 10^{2} s$ and $t = 1.47 \times 10^{2} s$ .

b)An analyte anion to reach the detector at pH=2 and pH=12 is $μ_{app} = - 0.3 \times 10^{- 8} m^{2} / Vs$ and $t = 1.84 \times 10^{2} s$

Step by step solution

A neutral solute to travel at pH=2 and pH=12

a)At pH=2 use the following requations

$u = μ_{eo} E u = (1.3 \times 10^{- 8} m^{2} / Vs) \times (\frac{27 \times 10^{3} V}{0.62 m}) u = 5.66 \times 10^{- 4} m / s t = s / u t = 0.52 m / (5.66 \times 10^{- 4} m / s) t = 9.2 \times 10^{2} s$

b)At pH=12 use the following requations

$u = μ_{eo} E u = (1.3 \times 10^{- 8} m^{2} / Vs) \times (\frac{27 \times 10^{3} V}{0.62 m}) u = 3.53 \times 10^{- 3} m / s t = s . u t = 0.52 m / (3.53 \times 10^{- 3} m / s) t = 1.47 \times 10^{2} s$

An analyte anion to reach the detector at pH=2 and pH=12

a)At pH=2 use the following requations

$μ_{app} = μ_{ap} + μ_{eo} μ_{app} = (- 1.6 \times 10^{- 8} m^{2} / Vs) + (1.3 \times 10^{- 8} m^{2} / Vs) μ_{app} = - 0.3 \times 10^{- 8} m^{2} / Vs$

Anion wouldn’t migrate towards the detector.

b)At pH=12 use the following requations

$u = μ_{a p p} E u = (6.5 \times 10^{- 8} m^{2} / Vs) \times (\frac{27 \times 10^{3} V}{0.62 m}) u = 2.83 \times 10^{- 3} m / s t = s / u t = 0.52 m / (2.83 \times 10^{- 3} m / s) t = 1.84 \times 10^{2} s$

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Short Answer

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A neutral solute to travel at pH=2 and pH=12

An analyte anion to reach the detector at pH=2 and pH=12

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