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Abstract(s)
A GC-FID method capable to detect 2-nitrophenol (2-NP) and the resulting intermediates from its
oxidation with H2O2 was developed and validated under the typical criteria for in-house pre-validation [1].
Linearity was demonstrated by F-test; accuracy and precision were assessed in three concentration
levels. The oxidation process under study consists on the peroxidation of 2-NP, used as target lipophilic
pollutant, in a biphasic mixture of cyclohexane(cC6)/water to simulate contaminated oily streams. The
oxidized intermediates produced by the peroxidation of 2-NP (POW = 51.3) in aqueous phase are phenol
(Ph, POW = 30.2), hydroquinone (HQ, POW = 4.4), p-benzoquinone (BQ, POW = 1.9), catechol (CTL, POW =
7.6) and carboxylic acids [1]. Those compounds can be quantified in the aqueous phase by previous
developed HPLC methods [2]. In the biphasic medium of reaction, the oxidation of cC6 can also take
place to produce cyclohexanone (cC6O, POW = 5.8) and cyclohexanol (cC6OH, POW = 21.9). The cC6-
water partition coefficient of 2-NP and the oxidized cyclic intermediates, a priori all lipophilic compounds,
were assessed by analysis of the aqueous phase before and after addition of different volumes of cC6.
HQ and CTL keep their concentration in the aqueous phase after cC6 addition and only the analysis of the
other analytes (dissolved in cC6) were done by GC-FID (Scion 436-GC, Bruker), without derivatization and
adding a little quantity of Na2SO4 to remove the moisture. The injector and detector temperatures were
set at 260 ºC and 270ºC, respectively. Separation was performed on a 50 m x 0.25 mm CP-Sil 88 column
using the following temperature program: a first isotherm step at 160 ºC, followed by a heating ramp at 5
ºC/min, then at 10 ºC/min and a final isotherm step at 220 ºC during 5, 2, 5 and 5 min, respectively. At
these conditions, the cC6, cC6O, cC6OH, BQ, 2-NP and Ph compounds show well resolved peaks, and
the method is capable to detect the compounds with maximum concentrations of 4.7, 2.3, 1.3, 1.0 and
7.1 g/L (in the same order) without overlap. The developed method, coupled with the HPLC methods,
allows to follow the evolution of all compounds in the biphasic oxidation system.
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Citation
Díaz de Tuesta, Jose Luis; Amaral, J.S.; Silva, Adrián; Faria, Joaquim; Gomes, Helder (2017). Coupling HPLC and GC-FID for the monitorization of oxidized intermediates from wet peroxide biphasic oxidation. In 10º Encontro Nacional de Cromatografia. Bragança. ISBN 978-972-745-234-7