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Separation and determination of inorganic cations in beverages by capillary electrophoresis with indirect UV detection

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Gao J., Fan H., Yang W., Sun X., Li C., Mao X., Wang J., Wang R., Jia Z.

Open Chemistry

2008

vol. 6

issue 4

617-621

A rapid, simple and reliable capillary electrophoresis method for the separation and quantitation of inorganic cations with indirect UV detection at 214 nm was developed. The electrolyte was: 12 mM imidazole as background absorbance provider; 5 mM malic acid and 1.0 mM 18-crown-6 ether as complexing agents; and 20% D2O (v/v) to improve ion mobility. The pH was 4.25. The applied voltage was 22 kV at 22°C. Nine ions were completely separated and determined with correlation coefficients of 0.9979-0.9992. The relative standard deviations (RSD) were less than 0.5% for migration time and less than 5.2% for peak area (n=8). The detection limits (S/N=3) were from 0.08 mg L−1 (for Na+) to 0.51 mg L−1 (for Cu2+). To assess the reliability atomic absorption (AA) was also used to determine the same samples. Satisfactory results were obtained for real samples of jasmine tea drink and coconut milk. [...]

Comparison of biosensors based on gold and nanocomposite electrodes for monitoring of malic acid in wine

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Monošík R., Streďanský M., Greif G., Šturdík E.

Open Chemistry

2012

vol. 10

issue 1

157-164

Amperometric biosensors based on a gold planar electrode and on two types of nanocomposite electrodes consisting of multi-walled carbon nanotubes for the determination of L-malic acid designed for wine-makers were developed. The biosensors designed for wine-makers were constructed by immobilization of L-malate dehydrogenase and diaphorase within chitosan layers on the surface of the electrodes. The coenzyme NAD+ and the electrochemical mediator ferricyanide were present in the measuring solution. The current resulting from re-oxidation of produced ferrocyanide was measured at a working potential of +300 mV against an Ag/AgCl reference electrode. The biosensor based on a gold electrode showed linearity over the range 10–520 µM with a detection limit of 5.41 µM. Calibration curves for biosensors utilizing nanocomposites were obtained both with the linear range of 10 to 610 µM. The detection limits were 1.57 and 1.77 µM, respectively. The biosensors showed satisfactory operational stability (no loss of sensitivity after 30 consecutive measurements) and storage stability (90% of the initial sensitivity after one year of storage at room temperature). The results obtained from measurements of wine samples were in a good correlation with the standard HPLC method. Satisfactory biosensor sensitivity, specificity and stability allowed their successful commercialization.

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2 Open Chemistry

1 2012

1 2008

1 Fan H.

1 Gao J.

1 Greif G.

1 Jia Z.

1 Li C.

1 Mao X.

1 Monošík R.

1 Streďanský M.

1 Sun X.

1 Wang J.

1 Wang R.

1 Yang W.

1 Šturdík E.

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Separation and determination of inorganic cations in beverages by capillary electrophoresis with indirect UV detection

Comparison of biosensors based on gold and nanocomposite electrodes for monitoring of malic acid in wine