Domingo Gázquez

Optimization of chromatographic parameters for the determination of biogenic amines in wines by reversed-phase high-performance liquid chromatography.

A method suitable for the determination of eight biogenic amines (histamine, tyramine, phenylethylamine, tryptamine, cadaverine, putrescine, spermidine and spermine) in wines has been developed. The method involves derivatization of the amines by treatment with dabsyl chloride, after which the derivates were analysed by reversed-phase liquid chromatography with gradient elution and spectrophotometric detection at 446 nm. Different variables affecting separation were optimized. Validation of the method included calibration experiments, the addition of standards amines for the determination of recovery and repeatability tests. Good linearity of the responses was obtained up to 500 microg l(-1), except for putrescine (up to 2100 microg l(-1)). The detection limits ranged between 10 and 60 microg l(-1) for standard solutions. The method was successfully applied to the analysis of five Spanish wines.

Optimization of experimental variables in the dabsyl chloride derivatization of biogenic amines for their determination by RP-HPLC

SummaryIn the last few years special attention has been paid to the pre-column derivatization of biogenic amines with dabsyl chloride because proper experimental conditions for this reaction are very important. In this study, an experimental design (Doehlert design) was used to optimize the variables involved in the dabsylation of the following amines: histamine, tyramine, phenylethylamine, tryptamine, cadaverine, putrescine, spermidine, and spermine. The optimum experimental conditions for forming the dabsyl derivatives are: reagent concentration, 1.75.10−3 M; pH, 8.2; temperature, 70°C; heating time (th), 21 min. Under these conditions good chromatographic repeatability is obtained.

Multivariate optimization of solvent extraction of Cd(II), Co(II), Cr(VI), Cu(II), Ni(II), Pb(II) and Zn(II) as dibenzyldithiocarbamates and detection by AAS

A method for the simultaneous solvent extraction into IBMK from acidic medium of Cd(II), Cu(II), Co(II), Cr(VI), Ni(II), Pb(II) and Zn(II) as dibenzyldithiocarbamates and determination by AAS is proposed. Formal techniques for multidimensional optimization have been used, in particular, the response surface methodology, in order to obtain the best output variable to be optimized. The method was validated by applying it to some synthetic samples. In all cases, the trueness test indicated that the method was reliable, at least, for the samples analysed, which was confirmed by the recovery values obtained. The RSD values indicated a satisfactory precision.

Multivariate optimization of supported liquid membrane extraction of biogenic amines from wine samples prior to liquid chromatography determination as dabsyl derivatives

The application of the supported liquid membrane (SLM) technique for the extraction of biogenic amines is presented. For the extraction of these compounds, the SLM system has been applied, using di-2-ethylhexyl phosphoric acid as an anionic carrier incorporated into the membrane phase. The optimization of the extraction process, involving the composition of membrane liquid, is discussed. The simultaneous optimization of the extraction efficiencies of all the amines is achieved by a desirability function, using experimental design strategies (Doehlerts and full factorial designs). The proposed method is evaluated for the extraction of biogenic amines from wines by comparing the extraction efficiency values with those obtained for a composite amine standard solution. The results show no significant differences.

Application of Doehlert designs in the optimization of experimental variables associated with the simultaneous solvent extraction of several metals

An experimental design (Doehlert matrix design) has been carried out in this study to optimize the experimental variables for the simultaneous solvent extraction of Fe, V, Mo and Sn in isobutyl methyl ketone–tributyl phosphate with 5,5′-methylenedisalicylohydroxamic acid. Four variables were examined: pH and perchlorate, chelating reagent and synergistic agent concentrations. Two designs of two factors were performed, giving two response surfaces, one for each two factors. The plots of the analytical signalversus the experimental variables selected give two response surfaces which allow the optimum conditions to be identified for the quantitative extraction of the four metal ions. This optimization strategy is simple and quick, compared with the traditional univariate methodology.

Determination of molybdenum in various materials by normal-phase liquid chromatography using N-benzoyl-N-phenylhydroxylamine

Abstract A normal-phase liquid Chromatographie method for the selective determination of molybdenum with N-benzoyl-N-phenylhydroxylamine is described. The molybdenum(VI) complex was preconcentrated by extraction into chloroform and injected onto a nitrile column for chromatography. The mobile phase was a 0.075 M solution of reagent in chloroform (stabilized with amylene). The detection limit for molybdenum by the proposed method was 0.88 ng for a phase volume ratio of 20:1 (aqueous to organic). Molybdenum has been determined in several samples with satisfactory accuracy and precision.

Estimation of the uncertainty associated with the standard addition methodology when a matrix effect is detected

If a matrix effect is detected during the validation stage of an analytical method, the standard addition methodology must be applied. To reach a good estimation of the uncertainty associated with the determination, an adequate identification and evaluation of each uncertainty source should be done. As an example to illustrate how to calculate the uncertainty in this case, the simultaneous determination of V(V) and Mo(VI) at trace levels after precolumn chelation and extraction with N-benzoyl-N-phenylhydroxylamine, has been selected. The final results show that the main contributions to the relative overall uncertainty are those closely related with the chemical aspects of the method, i.e. liquid-liquid extraction and standard addition calibration.

Robustness study for the determination of biogenic amines by HPLC

SummaryA robustness test for the separation and LC determination of eight biogenic amines (histamine, tyramine, phenylethylamine, tryptamine, cadaverine, putrescine, spermidine and spermine) has been made in order to validate the method, which involves derivatization of the amines with dabsyl chloride, and analysis by reversed-phase liquid chromatography with gradient elution and spectrophotometric detection at 446 nm.

Spectrophotometric Determination of Lead by Extraction of the Mixed-Metal Complex Pb(II)-Ca-Purpurin (1,2,4-Trihydroxyanthraquinone)

Abstract Mixtures of Lead(II) and Ca(II) form with purpurin (P; 1,2,4-Trihydroxyanthraquinone) the mixed-metal-complex PbCaP3, which is extracted with isobutyl methyl ketone (IBMK) at pH 7.8. The molar absorptivity of the complex is 2.8 × 104 l.mol−1.cm−1 at 575 nm and its conditional extraction constant 2.5 × 1017 14.mole−4. The use of this complex for the spectrophotometric determination of lead up to 40 μg has been investigated. The proposed procedure has been successfully applied to the analysis of this metal in different samples.

Synergistic Extraction-Atomic Spectrophotometric Determination of Vanadium in Foods and Petroleum Crudes with 5,5′-Methylenedisalicylohydroxamic Acid (MEDSHA)

Abstract A method is described for the flame atomic absorption spectrometry (AAS) determination of vanadium, down to microgram level, in food samples and petroleum crudes. The procedure is based on the synergistic extraction of the V(V)-5,5′-methylene-disalicylohydroxamic acid (MEDSHA) complex with a 0.5 M tributyl phosphate (TBP) solution in isobutyl methyl ketone (IBMK). The method is highly selective and has a detection limit of 0.019 μg.ml−1 (Vorg./Vsq. = 0.2) and of 0.006 μg.ml−1 (Vorg./Vsq. = 0.05), with a relative standard deviation (RSD) not exceeding 1.5% at a level of 2 μg.ml−1 and 3% at a level of 0.4 μg.ml−1.