Manuel Aboal-Somoza

Slurry sampling for the determination of lead in marine sediments by electrothermal atomic absorption spectrometry using palladium–magnesium nitrate as a chemical modifier

A method for the determination of lead in slurries of marine sediment using palladium–magnesium nitrate as a chemical modifier has been optimized. To stabilize the marine sediment slurry, different thickening agents were studied. The grinding time and the particle size were also studied. To achieve complete pyrolysis of the slurry sample, two charring steps were used: the first one at a low temperature, 480 °C, and the second at 900 °C. The precision of the method was studied as within-run and within-batch precision; the relative standard deviations obtained in both cases were less than 3%. The relative standard deviation for the repeatability of the over-all procedure was 5.0%. The accuracy of the method was studied using a Certified Reference Material PACS-1 (Marine Sediment) from the National Research Council of Canada, which has a certified lead content of 404 ± 20 mg kg–1; the result obtained was 418 ± 11 mg kg–1. The detection limit for lead was 0.22 µg l–1. Calibrations using aqueous standards and the reference material were compared. This method has been applied to the determination of lead in marine sediment samples from the Galicia Coast and the results were compared with a sample digestion method using nitric and hydrochloric acids in a high pressure poly(tetrafluoroethylene) bomb and microwave energy. No significant differences were found between the two procedures.

Palladium–magnesium nitrate as a chemical modifier for the determination of lead in mussel slurries by electrothermal atomic absorption spectrometry

A method for the determination of lead in mussel slurries by atomic absorption spectrometry with electrothermal atomization using Pd–Mg(NO3)2 as a chemical modifier is proposed. The drying, ashing and atomization temperatures were optimized. Calibration and standard additions graphs, sensitivity, precision, accuracy and the effects of different slurry stabilization agents were also studied. The method was applied to the determination of lead in mussel samples from the Galician coast and the results obtained were compared with those achieved by means of a wet digestion procedure.

Indirect atomic absorption spectrometry (IAAS) as a tool for the determination of iodide in infant formulas by precipitation of AgI and redissolution with cyanide

Abstract A method to determine iodide in infant formula samples by indirect atomic absorption spectrometry (IAAS) was developed. The iodide in solution resulting from an alkaline digestion (Na 2 CO 3 –NaOH) of the sample is precipitated with silver; the precipitate is redissolved by adding cyanide solution, and this solution is subjected to GF-AAS. Temperatures of 1000 and 2100°C were selected for the ashing and atomization steps, respectively, using a mixture of Pd and Mg(NO 3 ) 2 as a matrix modifier (at concentrations of 36 and 16 μg ml −1 , respectively). The sensitivity, LOD, LOQ and characteristic mass obtained were, respectively, 1.12×10 −2 l μg −1 , 3.1 μg g −1 and 10.4 μg g −1 and 7.3 pg, referred to sample. The linear interval of concentrations extends up to 10 μg l −1 of iodide, with no need to use the standard addition method; the mean R.S.D. of data within this range is 3.4%, with 2.9% over the whole procedure. No interfering effects were observed among the foreign ions studied, and 100.0% was the mean analytical recovery achieved within the linear range of concentrations. The application of the method to seven real samples gave a mean content of 12.8 μg g −1 of iodide, as well as less than 3.1 μg g −1 in eight other samples.

Atomic absorption spectrometry as an alternate technique for iodine determination (1968–1998)

1 Introduction 2 Discussion 2.1 Iodine species and optical details 2.2 Atomization and procedure 2.2.1 Solvent extraction methods 2.2.2 Precipitation methods 2.2.3 Complexation methods 2.3 Analytical figures of merit 2.4 Interferences and samples 3 Conclusions

Application of High Resolution-Continuum Source Flame Atomic Absorption Spectrometry (HR-CS FAAS): determination of trace elements in tea and tisanes.

A new application of HR-CS FAAS (High Resolution-Continuum Source Flame Atomic Absorption Spectrometry) has been developed for the determination of several trace elements (Ca, Co, Cu, Fe, Mn, Ni, Na and Zn) in infusions made from tea, rooibos and tea with seaweed samples. The proposed methods are fast, inexpensive and show good performances: the mean analytical recovery was approximately 100%. The mean limit of detection was 29.4 μg/l, and the mean limit of quantification was 98.0 μg/l (both limits refer to the brewed samples). Due to the matrix effect observed, the standard addition method had to be applied. Preliminary classification (based on metal contents) using chemometric techniques such as PCA (Principal Component Analysis) and CA (Cluster Analysis), was successful for infusions made from rooibos and tea with seaweed, but inconclusive for black and green teas.

Contribution to the Development of Indirect Atomic Absorption Methods: Application of the Ion Pair 1,10-phenanthroline-mercury(II)-iodide to Iodide Determination in Water and Infant Formulae Samples

Abstract A method to determine iodide is developed, based on the formation of an ion pair between 1, 10-phenanthroline, mercury(II) and iodide that can be selectively extracted into IBMK. When the IBMK layer is analyzed by electrothermal atomic absorption spectrometry (ETAAS) for mercury, iodide can be quantified too. Parameters related to the preparation of the ion pair and to the measuring process are studied. Thus, 7.2–7.4 reveals to be the best pH interval to carry out the extraction, and 250 and 1000 °C, respectively, the mineralization and atomization temperatures for mercury determination by ETAAS. The procedure is applied to drinking tap water and commercial infant formulae milk samples. The accuracy of the method has been investigated by means of the analytical recovery for water samples (mean analytical recovery obtained at different concentration levels 98.1%) and by using the certified reference material BCR CRM No 151 Skim Milk Powder (Spiked) for the infant formulae (results within certification interval). The repeatability of the measurements at different concentration levels gave a RSD lower than 10% for both types of samples and the repeatability of the whole procedure for infant formulae shows a RSD of 1.33%. In addition, the limits of detection and quantification were 2.5 μg/L and 8.5 μg/L, respectively, for drinking water and 1.1 μg/g and 3.8 μg/g, respectively, for infant formulae.

Determination of arsenic in mussels by slurry sampling and electrothermal atomic absorption spectrometry (ETAAS)

A method for the determination of arsenic in slurries of mussel tissue using palladium-magnesium nitrate as modifier was optimized. The slurry was stabilized by a 0.015% (v/v) of Triton X-100. To achieve complete mineralization the slurries were ashed at 480 °C for 10s in an air flow (50 ml/min) and at 1200 °C for 15s in an argon flow (300 ml/min) in the presence of Pd—Mg(NO3)2 as modifier. The optimum atomization temperature was 2200 °C. The precision and accuracy of the method were studied using the Reference Material BCR n ° 278 Mussel Tissue (Mytilus edulis). The detection limit (LOD) of the final slurry solution was 1 μg/l of arsenic corresponding to an arsenic level in the mussel of 1.3 μg/g, for a 0.5% (m/v) slurry. Results of calibration using aqueous standards and the standard additions method were compared. The method was applied to the determination of arsenic in mussels from the Galician coast. The levels found lie between 2 and 9.3 μg/g of arsenic.

Studies on solvent extraction to determine iodide indirectly by electrothermal atomic absorption spectrometry

Preliminary studies addressed to the determination of iodine, as iodide, by indirect ETAAS and applying solvent extraction are described. The work was carried out to achieve a selective quantification of the iodide contained in the complex formed with mercury(II) in acid medium, but selectivity problems were found. The formation of an ion association complex between mercury(II), iodide and 2,2′-dipyridyl was studied. Several parameters were optimized related to the extraction process: the optimal pH interval, 6.8–7.6; volume of extractant, 2 ml; and shaking time 30 s are proposed. Regarding the performance of the measurements, the optimized graphite furnace temperature programme was also studied, yielding 200 and 1000 °C as the best temperatures for the mineralization and atomization steps, respectively. The standard calibration and the standard additions methods were performed. The RSDs of the procedure were between 4.9 and 8.0%, for the standard calibration and from 3.2 to 15.6% for the standard additions method.

Indirect determination of iodide, as an HgxIy complex, by electrothermal atomic absorption spectrometry

A method for the indirect determination of trace amounts of iodide by electrothermal atomic absorption spectrometry through the measurement of the mercury signal generated when small amounts of iodide and mercury are heated in a graphite furnace is described. The measured absorbances are related to the values of the signals from an iodide–mercury complex. The pH required for the formation of the HgxIy complex as well as other parameters involved in measurement of the signals are also determined. The limits of detection and quantification obtained were 3.0 and 10.1 µg l–1 of iodide, respectively, and the characteristic mass was 38.8 pg of iodide. The relative standard deviations obtained were from 5.1–8.9%(n= 7), depending on concentration. In the range 5–20 µg l–1 recoveries were 94.8–104.4%. The method has been applied to a range of tap waters.

Preliminary results of a quick, simple method of detecting antimony in water samples

Preliminary results of development of a direct and fast method of determination of antimony in samples of tap water using GFAAS are presented. The found levels of antimony were lower than permitted for human consumption. A mixture of Pd and Mg(NO3)2 (concentrations in the injected solution: 8.6 μg mL−1 and 5.8 μg mL−1 respectively) was used as the chemical modifier. The pyrolysis and atomization temperatures were 1000 and 1700°C, respectively and the mean analytical recovery 98.2%.