M. Carmen Yebra

• Professor
• University of Santiago de Compostela

An automatic on-line system is developed for the trace determination of copper and iron species in fresh waters by flame atomic absorption spectrometry using only 5 and 2 mL of sample, for copper and iron determination, respectively. This system, which includes a home-made minicolumn of commercially available resin containing aminomethylphosphonic...

A simple and rapid analytical method was developed for the determination of iron, manganese, and zinc in soluble solid samples. The method is based on continuous ultrasonic water dissolution of the sample (5-30 mg) at room temperature followed by flow injection flame atomic absorption spectrometric determination. A good precision of the whole proce...

A simple and rapid continuous manifold for sample dissolution based on ultrasound energy is evaluated for flow injection determination of calcium and magnesium in pharmaceutical tablets by flame atomic absorption spectrometry. Several parameters that could influence the dissolution process were evaluated by Plackett-Burman experimental designs. The...

The marine environment is of particular interest because is an important sink for many chemicals, some of which accumulate in the marine food chain. Heavy metals and bio accumulating toxic substances are introduced to the sea from land-based point and non-point sources, from atmospheric fallout and during marine transport of materials. Pollution of...

A simple field sampling/preconcentration strategy for determination and speciation of Cr(III) and Cr(VI) in seawater is described. Seawater was collected in-situ by pumping it through a minicolumn packed with a poly(aminophosphonic acid) chelating resin (PAPhA, 20 mesh) connected to a field flow preconcentration system (FFPS). This packing can isol...

A flow-injection system is developed for Cu, Mn and Zn partitioning in seawater by flame atomic absorption spectrometry. The first approach is where the trace metal species are fractionated in situ, but analysis is performed by using a flow injection manifold in the laboratory. This operational mode is used for the determination of the dissolved la...

A flame atomic-absorption spectrophotometric method for determining strontium in natural waters is described. The use of ethylenediamine tetraacetic acid (EDTA) to suppress interferences was studied, and ion-exchange with Amberlite IR-120 (H+) to concentrate the metal was used; strontium being eluted with 3% EDTA. The precision and reproducibility...

A simple, precise and accurate automatic method for the determination of total iodine in milk products by indirect atomic absorption spectrometry is proposed. Iodide in solutions resulting from alkaline ashing of samples is precipitated with silver ion in a precipitation-dissolution flow manifold, which allows performing on-line the retention of th...

This work deals with nickel determination in urine samples using ultrasound energy for sample preparation. It is shown that this sample digestion procedure is a fast and simple methodology based on an on-line procedure exploiting the stopped-flow mode. A minicolumn device filled with a commercial chelating resin (Chelite P) is inserted into the on-...

An efficient and fast method has been developed to determine chromium in urine. It is based on an on-line ultrasound-assisted sample digestion procedure exploiting the stopped-flow mode, followed by flow injection chromium preconcentration using a minicolumn filled with a commercially available chelating resin (Chelite Che). The precision as repeat...

A flow-injection flame atomic absorption spectrometric method using diluted nitric acid and ultrasound energy to assist metals acid leaching from welding fumes was optimised. Several variables were simultaneously studied by applying a Plackett-Burman design. Results showed that the statistically significant variables (95%) were concentration of nit...

A new sensitive and low cost flow injection method that combines acid extraction, preconcentration and flame atomic absorption spectrometric determination of nickel in food samples at μg/g levels is described. The dynamic acid extraction step was carried out by using a continuous ultrasound-assisted extraction system. The acid extract was preconcen...

A flow analysis method with on-line sample digestion/minicolumn preconcentration/flame atomic absorption spectrometry is described for the determination of trace metals in urine. First, urine sample was on-line ultrasound-assisted digested exploiting the stopped-flow mode, and then the metals were preconcentrated passing the pre-treated sample thro...

A fast and simple method for the fully automatic determination of Cr(VI) in welding fumes by flame atomic absorption spec-trometry is presented. This method is based on a dynamic alkaline ultrasound-assisted extraction coupled on-line to a flow-injection preconcentration minicolumn system. The mini-column was filled with an anionic exchange resin (...

A flow injection procedure involving continuous acid leaching for lead and cadmium determination in hair samples of persons in permanent contact with a polluted workplace environment by flame atomic absorption spectrometry is proposed. Variables such as sonication time, nature and concentration of the acid solution used as leaching solution, leachi...

A rapid and sensitive method has been proposed for the determination of chromium and cobalt in seafood samples by flame atomic absorption spectrometry combined with a dynamic ultrasound-assisted acid extraction and an on-line minicolumn preconcentration. The use of diluted nitric acid as extractant in a continuous mode at a flow rate of 3.5 mL min(...

A dynamic ultrasound-assisted extraction procedure utilizing diluted nitric acid was developed for the determination of copper, iron, manganese and zinc in human hair taken from workers in permanent contact with a polluted environment. The extraction unit of the dynamic ultrasound-assisted extraction system contains a minicolumn into which a specif...

A flow-injection flame atomic absorption spectrometric method for the determination of zinc in welding fumes has been developed. The method is based on the continuous ultrasound-assisted dissolution of the zinc oxide collected on the air filter. Variables such as sonication time, nature and concentration of the acid solution used as dissolving solu...

A simple field sampling-preconcentration method for zinc determination in seawater is described. Seawater was collected in situ by pumping it through a minicolumn packed with a chelating resin (Chelite P) connected to a field flow preconcentration system (FFPS). These packed minicolumns retain the dissolved zinc, and once are loaded with the analyt...

A new sensitive and low-cost method that combines continuous acid extraction, online preconcentration, and flame atomic absorption spectrometry for cadmium determination at microg levels in solid and semisolid milk products is described. A continuous ultrasound-assisted extraction system is used to carry out the dynamic acid extraction step. The ac...

This review focuses on the characteristics and properties of high-intensity sweeteners and bulk sweeteners. Available analytical methodologies employed for the individual or simultaneous determination of sweeteners, including liquid chromatography, gas chromatography, thin-layer chromatography and paper chromatography, capillary electrophoresis, el...

Cadmium was continuously extracted with diluted nitric acid from legumes and dried fruit samples using a simple, rapid and continuous ultrasound-assisted extraction system. A minicolumn packed with a chelating resin (Chelite P, with aminomethylphosphoric acid groups) was placed between the extraction unit and the detector for cadmium preconcentrati...

Baker's yeast (Saccharomyces cerevisiae) was used as substrate for the selective retention of Cr(III) in the presence of Cr(VI) from aqueous solutions. The experiments were performed in batch as a suitable and simple method to obtain information of chromium uptake. The effect of chemical and physical variables affecting the degree of uptake of chro...

A simple flow injection method is propose, which combines continuous acid extraction, preconcentration, and flame atomic absorption spectrometry for the determination of cadmium in meat samples. The dynamic acid extraction step was carried out by using a continuous ultrasound-assisted extraction system. The acid extract was preconcentrated on-line...

A continuous ultrasound-assisted extraction system connected to a flow injection manifold has been used for the on-line determination of zinc in meat samples by flame atomic absorption spectrometry. An experimental design was used for the optimisation of the continuous manifold. This flow injection methodology allowed a sampling frequency of ca. 80...

Copper and iron were extracted on-line from solid seafood samples by a robust, fast and simple continuous ultrasound-assisted extraction system (CUES). CUES is connected to a flow-injection manifold, which allows on-line flame atomic absorption spectrometric determination of copper and iron. Experimental designs were used to optimize the continuous...

A fully on-line flow injection method is described for the quantitative acid extraction of cadmium, preconcentration of this trace metal using a minicolumn containing a chelating resin and its determination by flame atomic absorption spectrometry (FAAS). The on-line acid extraction step was carried out using a continuous ultrasound-assisted extract...

Continuous ultrasound-assisted extraction has been coupled with preconcentration and flame atomic absorption spectrometry for the determination of cadmium and lead in mussel samples. Experimental designs were used for the optimisation of the leaching and preconcentration steps. The use of diluted nitric acid as extractant in the continuous mode at...

A simple method for the continuous field preconcentration of trace dissolved cadmium in seawater samples has been developed based on the minicolumn field sampling technique. For this purpose, minicolumns containing Chelite P (aminomethylphosphonic groups) were connected to a field flow preconcentration system (FFPS). Once in the laboratory, these m...

A review of the flow injection (FI) analytical methods used to determine citric acid (CA) is presented. These flow determinations are described and compared according to the detection technique used. In addition to the advantages involving the use of the continuous flow systems, the analytical figures of merit and interferences are also discussed.

Calcium was extracted on-line from solid seafood samples by a simple and rapid continuous ultrasound-assisted extraction system. This system is connected to a flow injection manifold, which allows the on-line flame atomic absorption spectrometric determination of calcium. This method enables the analysis of solid samples avoiding time-consuming tra...

A simple and new flow-injection manifold (CUDS) for the continuous ultrasound assisted dissolution of a soluble solid sample coupled to a flow-injection flame atomic absorption spectrometric manifold for the continuous iron determination is described. An experimental design was used for the evaluation of factors involving the CUDS. The method was a...

A flow injection system for the continuous ultrasound- assisted dissolution of solid solu- ble samples (CUDS) has been developed for the dissolution of milk powder and infant formula samples. This system is connected on-line to a flow injec- tion flame atomic absorption spectrometer for continuous zinc monitoring. This methodology allows the analys...

Iron was extracted on-line from solid meat samples by a simple and rapid continuous ultrasound-assisted extraction system (CUES). The CUES is connected to a flow injection manifold, which allows the on-line flame atomic absorption spectrometric determination of iron. A Plakett-Burman design was used for the optimisation of the CUES. The method achi...

Lead, cadmium and chromium(III) concentrations were determined in seawater from the Ría de Vigo (NW Spain) with the aim of establish the degree of pollution of this geographic area. Metal analysis were performed by flame atomic absorption spectrometry, but as the sensitivity reached by this technique is not enough for the direct determination of th...

Total chromium was extracted on-line from solid mussel samples using a simple, rapid, and continuous ultrasound-assisted extraction system (CUES). CUES is connected to a flow injection manifold, which permits the on-line flame atomic absorption spectrometric determination of chromium. The manifold for total chromium determination is the simplest po...

Manganese is extracted on-line from solid seafood samples by a simple continuous ultrasound-assisted extraction system (CUES). This system is connected to an on-line manifold, which permits the flow-injection flame atomic absorption spectrometric determination of manganese. Optimisation of the continuous leaching procedure is performed by an experi...

A flow injection analysis-flame atomic absorption spectrometric method for the determination of cadmium in seawater was developed with the aim of yielding a sensitive assay with a low detection limit. The method employs a field flow preconcentration technique involving a minicolumn containing Amberlite XAD-4 impregnated with the complexing agent 4-...

A sample-preparation procedure (extraction and saponification) using microwave energy is proposed for determination of organochlorine pesticides in oyster samples. A Plackett-Burman factorial design has been used to optimize the microwave-assisted extraction and mild saponification on a freeze dried sample spiked with a mixture of aldrin, endrin, d...

 A field flow preconcentration technique involving a minicolumn containing Amberlite XAD-4 impregnated with the complexing agent 1-(2-pyridylazo)-2-naphthol was used to preconcentrate lead from seawater. Elution of retained lead on the minicolumns was performed by a flow-injection-flame atomic absorption spectrometric system. Factorial designs have...

Iron was extracted on-line from solid mussel samples by a simple continuous ultrasound-assisted extraction system (CUES) connected to a flow injection manifold, followed by on-line flame atomic absorption spectrometric determination. An experimental design was used for the optimisation of the CUES. The method allowed a total sampling frequency of 1...

A review is presented where are shown the advantages involved in the use of flow injection (FI) analysis for the determination of lead in environmental solid samples by spectroscopic detectors. The FI methods proposed for the determination of lead in these samples are described and compared according to the detection technique used. Analytical data...

Copper was extracted on-line from solid mussel samples by a simple and rapid continuous ultrasound-assisted extraction system (CUES). The CUES is connected to a flow injection manifold, which permits the on-line flame atomic absorption spectrometric determination of copper. The manifold is simple and the copper signal was obtained for a volume of 2...

A field flow preconcentration system (FFPS) for cadmium determination in seawater is described. Seawater samples are collected and preconcentrated in situ by passing them with a peristaltic pump through a minicolumn packed with Amberlite XAD-4 impregnated with the complexing agent 1-(2-pyridylazo)-2-naphthol. Thus, cadmium is complexed, retained, a...

A Plackett–Burman 27×3/32 design for seven factors (sample pH, sample flow rate, eluent volume, eluent concentration, eluent flow rate, ethanol percentage in the eluent and mini-column diameter) was carried out in order to find the significant variables affecting the field flow pre-concentration system (FFPS) and the flow injection elution manifold...

A continuous flow procedure is proposed for the indirect determination of ascorbic acid based on its reducing properties. Chromium(VI) in acid medium was injected into a ascorbic acid stream, and the Cr(VI) was reduced to Cr(III). This Cr(III) formed was retained on-line, proportionally to the ascorbic acid concentration in the sample, on a poly(am...

An indirect flow injection method for the determination of ascorbic acid in fruit juices is proposed. Permanganate in an acid medium was injected into an ascorbic acid stream which reduced Mn(VII) to Mn(II). The Mn(II) formed was retained online, proportional to the ascorbic acid concentration in the sample, on a poly(aminophosphonic acid) chelatin...

A field flow preconcentration system for copper determination in seawater is described. Seawater samples are collected and preconcentrated in situ by passing them using a peristaltic pump through a minicolumn packed with Amberlite XAD-4 impregnated with the complexing agent 1-(2-pyridylazo)-2-naphthol. Thus, copper is preconcentrated without the in...

A minicolumn packed with poly(aminophosphonic acid) chelating resin incorporated in an on-line preconcentration system for flame atomic-absorption spectrometry was used to determine ultratrace amounts of lead in mussel samples at microg L(-1) level. The preconcentrated lead was eluted with hydrochloric acid and injected directly into the nebulizer...

A review is presented to show the advantages involved in the use of continuous flow systems for the determination of trace metals in seafood samples. The flow injection methods proposed for the determination of metals in seafood are described and compared according to the used detection technique. On-line sample dissolution and on-line separation t...

A simple field-flow preconcentration system has been developed for lead determination in seawater. Seawater samples are collected in situ by passing them with a pump through minicolumns packed with poly(aminophosphonic acid) chelating resin to retain and preconcentrate lead, and remove the saline matrix. Minicolumns loaded with lead are then return...

A flow injection (FI) on-line preconcentration method was developed for the flame atomic absorption spectrometry (FAAS) determination of trace amounts of lead in alloy samples. Lead was preconcentrated on a minicolumn packed with a poly(aminophosphonic acid) chelating resin (PAPhA), and subsequently eluted using a small volume of hydrochloric acid...

A flow injection (FI) on-line preconcentration method was developed for the flame atomic absorption spectrometry (FAAS) determination of trace amounts of lead in alloy samples. Lead was preconcentrated on a mini-column packed with a poly(aminophosphonic acid) chelating resin (PAPhA), and subsequently eluted using a small volume of hydrochloric acid...

A review is presented to show the advantages involved in the use of Flow Injection Analysis (FIA) for the determination of artificial sweeteners. The FI methods proposed for the determination of artificial sweeteners are described and compared on the basis of the detection technique used. Analytical data of interest and interferences are discussed...

A review with 44 references is presented on the development of indirect flow injection determinations of organic compounds by atomic absorption spectrometry, covering the field from the first publications to the present. The characteristics, advantages and potential of this methodology are discussed and examined. It is shown that these systems are...

A rapid, sensitive, accurate and precise flame atomic absorption method is described for the determination of cadmium in mussels. The method is based on the continuous precipitation of cadmium as an ion pair between tetraiodocadmate and quinine and dissolution of the precipitate with ethanol. The metal can be preconcentrated 32-fold using 15 ml of...

A flow injection method for the indirect determination of quinine, based on the precipitation of an ion-association species formed between the quinine and Marmé reagent (CdI42−) is reported. The precipitate is obtained by injecting the Marmé reagent into a carrier stream containing the quinine, and is then retained on a filter, the filtrate then be...

A review with 100 references is presented to show the advantages involved in the use of flow injection analysis (FIA) for the determination of ascorbic acid. The FI methods proposed for the determination of ascorbic acid are described and compared according to the used detection technique. Analytical figures of merit and interferences are also disc...

A continuous flow atomic absorption spectrometric system was used to develop an efficient on-line preconcentration-elution procedure for the determination of iodide traces. Chromium (VI) is introduced into the flow system and is reduced to chromium (III) in acid medium proportionally to the iodide present in the sample. The Cr(III) reduced by iodid...

A continuous flow procedure is proposed for the indirect determination of iodide based on its reducing properties. Chromium(VI) in acid medium was injected into an iodide stream, and Cr(VI) was reduced to Cr(III). This Cr(III) formed was retained on-line, proportionally to the iodide in the sample, on a poly(aminophosphonic acid) (PAPhA) chelating...

A continuous precipitation and filtration flow system for the separation of citric acid by precipitation with lead and indirect flame atomic absorption spectrometry is proposed. The precipitate is formed by injecting the lead solution into a carrier containing the sample and is subsequently retained on a filter. By using this reversed precipitation...

A simple and rapid acid sample digestion method by microwave heating in high pressure teflon bombs is reported for the determination of cadmium in mussels by flame atomic absorption spectrometry (FAAS) coupled on-line with a flow-injection preconcentration system. Tests concerning the digestion time, the power of the microwaves and the amount of ni...

A continuous-flow procedure is proposed for the indirect determination of sodium cyclamate by an atomic absorption spectrometric method in artificial sweeteners mixtures and soft drinks. Sulfamic group is oxidized to sulfate and it is continuously precipited with lead ion in a flow manifold. The lead sulfate formed is retained on a filter, washed w...

A flow-injection on-line system was developed for the trace determination of cobalt by flame atomic absorption spectrometry (FAAS) with separation and preconcentration on a minicolumn packed with a poly(aminophosphonic acid) chelating resin (PAPhA). This resin allows the selective separation of cobalt at pH 2 because Co(II) and Fe(III) are the only...

A continuous-flow procedure is proposed for the indirect determination of ascorbic acid, based on its reducing properties because of the oxidation of its 1,2-enediol group. Iron(III) was injected into a 1,10-phenanthroline stream, which was mixed with a sample carrier and then with a sodium picrate solution stream. In these conditions the iron(III)...

A simple method for the determination of chromium(III) and total chromium in a flow injection system comprising chelating ion-exchange and flame atomic absorption spectrometry (FAAS) was described. A minicolumn (85 mm × 1.6 mmi.d.) filled with a poly(aminophosphonic acid) chelating resin (PAPhA, 20–30 mesh) was used for speciation and preconcentrat...

An atomic absorption spectrometric method for the determination of sodium saccharin in commercially available mixtures of artificial sweeteners and pharmaceuticals by continuous precipitation with silver ion in a flow manifold is proposed. The silver saccharinate precipitate formed is retained on a filter, washed with diluted acetic acid and dissol...

An automatic continuous precipitation system for the indirect determination of tannins in foods based on the standard gravimetric method was developed as an alternative to the Official Methods of Analysis based on the Folin-Ciocalteu reagent. Tannins were precipitated by injecting the copper-acetate complex into the sample, and the unprecipitated c...

An on-line column preconcentration technique for flow-injection flame atomic absorption spectrometry has been developed for the determination of trace metals in natural waters. A minicolumn (20 mm × 2 mm i.d.) filled with a poly(aminophosphonic acid) chelating resin (PAPhA, 20–30 mesh) was used for the preconcentration procedure. For 2 ml samples,...

A continuous precipitation system for the indirect determination of reducing sugars in various types of wine based on the classical reaction with Fehling's solutions is reported. Copper(I) oxide is precipitated by injecting the Fehling's solutions into the wine carrier, which is directly aspirated. This allows reducing sugars to be determined in th...

A chelating poly(dithiocarbamate) resin with macroreticular support is shown to be effective for the preconcentration of copper, iron and zinc in natural waters. The retained ions can be eluted efficiently in 5 ml of 8M nitric acid from 1–20-cm columns of resin. This poly(dithiocarbamate) resin is used for the preconcentration and determination of...

Preliminary investigations on the application of a polystyrene macroreticular, cross-linked poly(aminophosphonic acid) resin for the concentration of trace metals from aqueous solutions are reported. The pH dependence of metal—resin chelation was determined for Mg(II), Ca(II), Fe(III), Cr(III), Ni(II), Cu(II), Pb(II), Zn(II) and Mn(II). The resin e...

A chelating poly(dithiocarbamate) resin (PDTC) with macroreticular support is characterized as effective collector for traces of manganese from natural waters. Using small PDTC columns preconcentration of manganese can be achieved even at high flow-rates (5-6 ml/min) and sample volumes (1500 ml). Accordingly, PDTC resin is used for the preconcentra...

The chelating poly(dithiocarbamate) resin with macroreticular support is shown to be effective for the preconcentration of cadmium and lead from non-saline waters. The retained ions can be eluted efficiently in 5 ml of 8 mol dm-3 nitric acid from 1-20 cm columns of resin. Poly(dithiocarbamate) resin is used for preconcentration in the determination...

A method for the spectrophotometric determination of uranium in samples of natural water is described. Ion exchange with Amberlite IR-120 (H+) to concentrate the metal was used. The absorption properties of the complex formed between uranium and the chromogenic reagent Arsenazo III, its stability over several hours, the effect of the pH on the abil...

In recent decades there has been an increase in consumption of seaweed as food, partly because of the nutritional and therapeutic benefits that these products provide 1-2 . Nevertheless, seaweed has a high metal pollution accumulation capacity. Because of this, seaweeds have been used as bio-indicators of marine environment contamination and there...