M. Masar et al., Determination of organic acids and inorganic anions in wine by isotachophoresis on a planar chip, J CHROMAT A, 916(1-2), 2001, pp. 167-174
Isotachophoretic (ITP) separation and determination of a group of 13 organi
c and inorganic acids, currently present in wines, on a poly(methyl methacr
ylate) chip provided with on-column conductivity detection was a subject of
a detailed study performed in this work. Experiments with the ITP electrol
yte systems proposed to the separation of anionic constituents present in w
ine revealed that their separation at a low pH (2.9) provides the best resu
lts in terms of the resolution. Using a 94 mm long separation channel of th
e chip, the acids could be resolved within 10-15 min also in instances when
their concentrations corresponded to those at which they typically occur i
n wines. A procedure suitable to the ITP determination of organic acids res
ponsible for some important organoleptic characteristics of wines (tartaric
, lactic, malic and citric acids) was developed. Concentrations of 2-10 mg/
l of these acids represented their Limits of quantitation for a 0.9 mul vol
ume sample loop on the chip. A maximum sample load on the chip, under the p
referred separating conditions, was set by the resolution of malate and cit
rate. A complete resolution of these constituents in wine samples was reach
ed when their molar concentration ratio was 20:1 or less. ITP analyses of a
large series of model and wine samples on the chip showed that qualitative
indices [RSH (relative step height) values] of the acids, based on the res
ponse of the conductivity detector, reproduced with RSD better than 2% whil
e reproducibilities of the determination of the acids of our interest chara
cterized RSD values better than 3.5%. (C) 2001 Elsevier Science B.V. All ri
ghts reserved.