Daniel Sancho

Determination of nickel and cobalt in refined beet sugar by adsorptive cathodic stripping voltammetry without sample pretreatment

Abstract Nickel and cobalt have been analysed in refined beet sugar at the μg kg −1 level by adsorptive cathodic stripping voltammetry in the differential-pulse mode (DPCSV) at the hanging mercury drop electrode (HMDE) as their dimethylglyoxime complexes, M(DMG) 2 . Measurements were directly carried out on untreated sugar solutions. The performance of the procedure was compared with electrothermal atomic absorption spectrometry (ETAAS) applied to digested sugar samples, and showed in general better accuracy. The procedure was applied to the determination of these toxic elements in refined beet sugar samples, and concentrations below 50 μg kg −1 nickel and 10 μg kg −1 cobalt were found, which are much lower than the toxic levels of these elements.

Determination of copper and arsenic in refined beet sugar by stripping voltammetry without sample pretreatment.

Copper and arsenic have been analysed in refined beet sugar at the microgram kg-1 level by anodic stripping voltammetry (copper) and cathodic stripping voltammetry (arsenic) in the differential-pulse mode (DPASV and DPCSV) at a hanging mercury drop electrode (HMDE). DPCSV measurements of arsenic are based on its accumulation onto the HMDE as an intermetallic Cu-As compound followed by the reduction of As0 to arsine in hydrochloric acid medium. Measurements were directly carried out on untreated sugar solutions. The performance of the procedures was compared with electrothermal atomic absorption spectrometry and stripping voltammetry applied to digested sugar samples, and showed in general better accuracy. The procedures were applied to the determination of these toxic elements in commercial beet sugar samples of concentrations below 50 micrograms kg-1 copper and 15 micrograms kg-1 arsenic were found, which are much lower that those allowed by the current regulations.

Determination of Zinc, Cadmium and Lead in Untreated Sugar Samples by Anodic Stripping Voltammetry

Trace amounts of zinc, cadmium and lead were determined in refined beet sugar by differential-pulse anodic stripping voltammetry (DPASV) at a hanging mercury drop electrode. Measurements were performed on samples without previous treatment. The optimised procedure allowed the direct determination of metals at the m g kg-1 level. The performance of the procedure was compared with electrothermal atomic absorption spectrometry and DPASV applied to digested samples, and showed better accuracy. The procedure was applied to the determination of toxic elements in commercial beet sugar samples and levels of metals below 35 m g kg-1 Pb, 80 m g kg-1 Zn and 10 m g kg-1 Cd were found.

Determination of mercury in refined beet sugar by anodic stripping voltammetry without sample pretreatment

Abstract Total mercury has been analysed in refined beet sugar at the μg kg−1 level by differential-pulse anodic stripping voltammetry (DPASV) at a rotating gold disk electrode (RGDE). DPASV measurements of mercury are based on its accumulation onto the RGDE as a Hg–Au amalgam and followed by the reoxidation of Hg(0) to Hg(II). Measurements were directly made on untreated sugar solutions. The DPASV procedure was compared with cold-vapour atomic absorption spectrometry carried out at a flow-injection mercury system when applied to digested sugar samples. The DPASV method has been demonstrated to perform conveniently for metal determination in beet sugar of good quality (low metal concentration) produced by Spanish sugar refineries. Mercury concentrations below 5 μg kg−1 were found in all commercial beet sugar samples analysed, which are much lower that the maximum permissible contents derived from the provisional tolerable weekly intake recommended by the World Health Organization.

New trends in beer flavour compound analysis

As the beer market is steadily expanding, it is important for the brewing industry to offer consumers a product with the best organoleptic characteristics, flavour being one of the key characteristics of beer. New trends in instrumental methods of beer flavour analysis are described. In addition to successfully applied methods in beer analysis such as chromatography, spectroscopy, nuclear magnetic resonance, mass spectrometry or electronic nose and tongue techniques, among others, sample extraction and preparation such as derivatization or microextraction methods are also reviewed.

Electrochemical determination of the effect of lead(II) on the photochemical degradation of the pesticide metamitron

The complexation of the pesticide Metamitron by lead(II) was investigated by polarography and stripping voltammetry. The influence of the pH on the complexation was determined and a maximum value for the conditional stability constant of the lead‐metamitron complex (logβ’ = 3.1) was obtained at pH 5.6. An investigation into the photochemical degradation of the pesticide demonstrated that lead decreases the degradation rate of metamitron by 13% within the first 30 days, due to stabilisation by complexation.

Free iron in pale, dark and alcohol-free commercial lager beers

BACKGROUND A highly sensitive, selective, rapid, reliable and inexpensive method has been developed for the direct analysis of free iron in 40 samples of bottled lager beer. RESULTS A differential pulse adsorptive stripping voltammetry technique at a hanging mercury drop electrode without any sample digestion was performed. The iron content in the analysed samples was in the range of 41 to 165 ppb. CONCLUSIONS The results point out that dark beers keep the highest free iron concentrations, which may be related to the highest amounts of minor ingredients in dark beers. Meanwhile, alcohol-free beers present the lowest free iron concentrations. Some discussion is presented regarding the basis of the free and complexed iron in beer and its participation as an essential element in the human diet.

Determination of saponin in sugar juices from sugar refining processes by stripping voltammetry

Abstract Saponins were determined as oleanolic acid in refined sugar and sugar juices from beet sugar refining processes by differential‐pulse cathodic stripping voltammetry (DPCSV) at the hanging mercury drop electrode (HMDE) after acidic hydrolysis of the saponin. Measurements were performed on diluted samples at the mg/1 level without further pretreatment. The optimised procedure allowed the determination of saponin at the mg/kg level. The DPCSV method showed a precision and accuracy adequate for the determination of low levels of saponin in sugar and sugar juices. The perfonnance of the procedure is compared with the HPLC method currently in use in many sugar refineries.

Direct determination of dextran in sugar juices from sugar refining processes by stripping voltammetry

Abstract Dextran has been determined in sugar juices from beet sugar refining processes by differential‐pulse cathodic stripping voltammetry (DPCSV) at the hanging mercury drop electrode (HMDE). Measurements were performed on diluted samples without previous treatment. The optimised procedure allowed the direct determination of dextran at the mg‐kg‐1 level. The performance of the procedure is compared with the Roberts copper method.