tetradecanol) are separated and detected, quantitation is
hindered by poor solubility and the formation of micelles.
Since a prerequisite for PAD reactivity is
adsorption of the analyte, the presence of other surface-ad-
sorbable substances, as well as electroactive compounds, can
act as interferences. Therefore, general selectivity is achieved
via chromatographic separation prior to PAD. This conclusion
does not preclude additional selectivity from control of de-
The assay for alcohols was applied to several matrices to
illustrate the analytical utility of the procedure. Separation
on an ion-exclusion column with direct detection is illustrated
in Figure 8 for various aliphatic alcohols and polyalcohols in
toothpaste (A), liquid cold formula (B), brandy (C), and wine
cooler (D). The selectivity for alcohols in acidic media at a
Pt electrode contributes to decreased time for sample prep-
aration and simplified chromatograms.
The versatility of separations on mixed-mode ion-exchange
columns with selective detection is illustrated in Figure 9 by
the simultaneous detection of ionic and neutral species in a
pharmaceutical preparation. This experiment utilizes a UV
detector and PAD in series after a PCX-500 column. Under
acidic conditions, the cephalosporin antibacterial consists of
a cation (i.e., cefazolin) and neutral and anionic compounds
(i.e., lB-hexanediol, 1,4-cyclohexanediol, and p-toluenesulfonic
acid). The neutral and anionic compounds are separated by
the reversed-phase character of the column, while the cationic
compound is separated by a combination of cation exchange
and reversed-phase mechanism. Figure 9 shows that the
p-toluenesulfonic acid and the cefazolin are both detected by
UV at 254 nm (A), and the two diols, which do not have a
chromophore, are easily detected by PAD (B). In addition,
the cefazolin has a PAD signal, which has a higher limit of
detection than UV, but may be utilized for added selectivity.
Kisslnger, P. T. In
Klssinger, P. T., Heineman, W.
Eds.; Marcel Dekker: New
Bard, A. J., Ed.; Marcel
Dekker: New York,
B.; Little, C. J. J.
W.; Poppe. H.
Anal. Chim. Acta
Meschi, P. L.; Johnson, D. C.
Anal. Chim. Acta
Johnson, D. C.; Lacourse, W. R.
Budna. K. W. J.
Beden, B.; Cetin,
Takky, D.; Lamy, C. J.
Ocon, P.; Alonso, C.; Celdran, R.; Gonzalez-Velasco, J. J.
Rey, M. J.
1880, 73(1), 107.