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. Author manuscript; available in PMC: 2012 Feb 11.
Published in final edited form as: J Chromatogr A. 2010 Nov 16;1218(6):763–777. doi: 10.1016/j.chroma.2010.11.009

Table 3.

The Cation Exchange Capacity of the HC-COOH and HC-C8 Phases

Stationary phases Void volume (ml) Total amount of K+ eluted from column (mmol) Cation-exchange capacity (mmol/m2)a
pH = 4.0 pH = 5.0 pH = 6.0 pH = 4.0 pH = 5.0 pH = 6.0
HC-COOHb,c 0.608 58.96 77.95 130.95 0.42 0.57 1.00
HC-C8b,d 0.572 52.69 57.70 62.73 0.38 0.42 0.46
[-COOH]=L(HC-COOH)-L(HC-C8)e 6.27 20.25 68.21 0.05 0.16 0.54
-SO3-HC-C8b,f 0.476 11.99 0.11
a

The cation exchange capacity was calculated based on Eq. (1) assuming that each column was packed with 0.5 g of particles.

b

Phase designation is the same as in Table 1.

c

For HC-COOH phase, Λ(HC – COOH) = Λ(–SiOH) + Λ(–COOH).

d

For HC-C8 phase, Λ(HC – C8) = Λ(–SiOH).

e

The number of ionized carboxylic groups on the HC-COOH at different pH.

f

The data was obtained from reference [49]. The cation exchange capacity of the -SO3-HC-C8 was measured in 50/50 ACN/water containing 0.1% formic acid (pH=2.8).