C. Herrero Latorre

Carbon nanotubes as solid-phase extraction sorbents prior to atomic spectrometric determination of metal species: a review.

New materials have significant impact on the development of new methods and instrumentation for chemical analysis. From the discovery of carbon nanotubes in 1991, single and multi-walled carbon nanotubes--due to their high adsorption and desorption capacities--have been employed as sorption substrates in solid-phase extraction for the preconcentration of metal species from diverse matrices. Looking for successive improvements in sensitivity and selectivity, in the past few years, carbon nanotubes have been utilized as sorbents for solid phase extraction in three different ways: like as-grown, oxidized and functionalized nanotubes. In the present paper, an overview of the recent trends in the use of carbon nanotubes for solid phase extraction of metal species in environmental, biological and food samples is presented. The determination procedures involved the adsorption of metals on the nanotube surface, their quantitative desorption and subsequent measurement by means of atomic spectrometric techniques such as flame atomic absorption spectrometry, electrothermal atomic absorption spectrometry or inductively coupled plasma atomic emission spectrometry/mass spectrometry, among others. Synthesis, purification and types of carbon nanotubes, as well as the diverse chemical and physical strategies for their functionalization are described. Based on 140 references, the performance and general properties of the applications of solid phase extraction based on carbon nanotubes for metal species atomic spectrometric determination are discussed.

Solid phase extraction for the speciation and preconcentration of inorganic selenium in water samples: a review.

Selenium is an essential element for the normal cellular function of living organisms. However, selenium is toxic at concentrations of only three to five times higher than the essential concentration. The inorganic forms (mainly selenite and selenate) present in environmental water generally exhibit higher toxicity (up to 40 times) than organic forms. Therefore, the determination of low levels of different inorganic selenium species in water is an analytical challenge. Solid-phase extraction has been used as a separation and/or preconcentration technique prior to the determination of selenium species due to the need for accurate measurements for Se species in water at extremely low levels. The present paper provides a critical review of the published methods for inorganic selenium speciation in water samples using solid phase extraction as a preconcentration procedure. On the basis of more than 75 references, the different speciation strategies used for this task have been highlighted and classified. The solid-phase extraction sorbents and the performance and analytical characteristics of the developed methods for Se speciation are also discussed.

Comparison of palladium-magnesium nitrate and ammonium dihydrogenphosphate modifiers for cadmium determination in honey samples by electrothermal atomic absorption spectrometry.

The occurrence of certain trace elements, such as cadmium, in honey bee can be considered as an indication of environmental pollution. In the present work, two methods for Cd determination in honey by electrothermal atomic absorption spectrometry, using palladium-magnesium nitrate and ammonium dihydrogenphosphate as chemical modifiers, have been developed. In none of these cases honey samples required pretreatment. Honey was diluted in water (20% w/v), and hydrogen peroxide, nitric acid, and Triton X-100 were added to minimize the matrix effect. For the first method, 21.6 microg of palladium and 4.5 microg of magnesium were added as chemical modifier; for the second method, 60 microg of ammonium dihydrogenphosphate were employed. The limits of detection obtained were 0.32 ng g(-1) for ammonium dihydrogenphosphate method and 0.54 ng g(-1) for palladium-magnesium nitrate method. The characteristic mass was 0.7 and 1.0 pg for ammonium dihydrogenphosphate and palladium-magnesium nitrate methods, respectively. The relative standard deviation (<10%) and the analytical recovery (98-105%) were comparable in both methods. The optimised methods were applied to the determination of the cadmium content in unpolluted Galician honey samples. Cd has been detected the analysed samples in the range (n.d.-4.3 ng g(-1)).Abstract The occurrence of certain trace elements, such as cadmium, in honey bee can be considered as an indication of environmental pollution. In the present work, two methods for Cd determination in honey by electrothermal atomic absorption spectrometry, using palladium–magnesium nitrate and ammonium dihydrogenphosphate as chemical modifiers, have been developed. In none of these cases honey samples required pretreatment. Honey was diluted in water (20% w/v), and hydrogen peroxide, nitric acid, and Triton X-100 were added to minimize the matrix effect. For the first method, 21.6 μg of palladium and 4.5 μg of magnesium were added as chemical modifier; for the second method, 60 μg of ammonium dihydrogenphosphate were employed. The limits of detection obtained were 0.32 ng g −1 for ammonium dihydrogenphosphate method and 0.54 ng g −1 for palladium–magnesium nitrate method. The characteristic mass was 0.7 and 1.0 pg for ammonium dihydrogenphosphate and palladium–magnesium nitrate methods, respectively. The relative standard deviation ( −1 ).

Determination of Cr and Ni in Orujo spirit samples by ETAAS using different chemical modifiers

Several analytical methods are proposed for chromium and nickel determination in Orujo spirit samples using ETAAS. Permanent chemical modifiers such as W, Ir, Ru, W-Ir and W-Ru were comparatively studied in relation to the common chemical modifier employed, Pd(NO3)2-Mg(NO3)2. Taking into account the analytical performance, the method based on the use of Ru as a permanent modifier was selected for further direct Cr determinations in Orujo samples. In the case of Ni, after comparison among the different methods developed, a method with no modifier which allows the direct interpolation in calibration graphs was chosen. Detection limits of 0.13μgL(-1) and 0.30μgL(-1) were obtained for Cr and Ni, respectively. For all methods developed, recoveries (ranged 98.6-102%) and precision (RSD<10%) were acceptable. The selected methods were applied for the determination of the Cr and Ni contents in 80 representative Orujo Galician samples. The Cr concentrations ranged from

Comparative Analysis of Explosion Vent Areas for Milk Spray Dryers According to the EN-14491 (2006) and NFPA-68 (2007) Standards

Venting systems are commonly employed to minimize damage and/or losses caused by dust explosions in spray dryers. At present, the two most commonly used vent-sizing standards are the American standard NFPA-68 (2007) and the European standard EN-14491 (2006). The work described in this paper has two main aims. The first aim is to compare the results of the venting area as required by the two aforementioned standards for conventional milk drying when dealing with three products commonly treated in the dairy industry: buttermilk, powdered milk, and full-fat milk. The vent area was calculated by taking into account the reduced pressure (Pred) and the geometry of the spray dryer (aspect ratio of the vessel length/diameter). In addition, the results obtained as per NFPA-68 were also corrected on the basis of turbulence intensity and partial volume. The second aim is to apply the two standards to the real case of a spray dryer in a dairy processing plant located in the south of the province of Lugo (NW Spain). The results showed significant differences between the two standards in that the vent areas obtained following the criteria of EN-14491 were always higher than those obtained with the American standard (except for the cases in which L/D = 1).Venting systems are commonly employed to minimize damage and/or losses caused by dust explosions in spray dryers. At present, the two most commonly used vent-sizing standards are the American standard NFPA-68 (2007) and the European standard EN-14491 (2006). The work described in this paper has two main aims. The first aim is to compare the results of the venting area as required by the two aforementioned standards for conventional milk drying when dealing with three products commonly treated in the dairy industry: buttermilk, powdered milk, and full-fat milk. The vent area was calculated by taking into account the reduced pressure (Pred) and the geometry of the spray dryer (aspect ratio of the vessel length/diameter). In addition, the results obtained as per NFPA-68 were also corrected on the basis of turbulence intensity and partial volume. The second aim is to apply the two standards to the real case of a spray dryer in a dairy processing plant located in the south of the province of Lugo (NW Spain). T...

A Simple Methodology Based on the Pittsburgh Coal Method for Assessing Specific Explosion Risks in Dust-Generated Explosive Atmospheres: A Case Study from Galicia (NW Spain)

Hazardous explosive atmospheres caused by dust may occur when powdered combustible material is present in an enclosed area. In general, dust explosions take place when high enough concentrations of combustible powdered dust particles are present in the atmosphere with another suitable gaseous medium such as oxygen. Because the manipulation of these substances in industrial activities entails a risk that could have devastating consequences (including serious injuries or loss of life, as well as significant damage in installations), the risk assessment to eliminate or control the risk of explosive atmospheres in the workplace is a challenging task. In European countries the assessment of these risks is evaluated using the ATEX Directives as per European legislation. However, using this legislation to assess the risk of explosion in powder atmospheres presents difficulties due to the variety and complexity of possible explosive atmospheres and the extremely high variety of ignition sources involved. Therefore, risk evaluation becomes a difficult and time-consuming task. In the present article, a simple empirical method for detecting and making an initial assessment of dust-generated ATEX atmospheres is presented. The force of possible explosions was estimated using the explosion index, which was obtained from other indices: explosion severity and ignition sensitivity. For a specific dust, both of these factorial indices were calculated on the basis of their explosive characteristics in relation to those of Pittsburgh coal (employed as a standard). The proposed methodology was applied to a real case study of an explosion in a milk spray dryer in Lugo (northwestern Spain). Taking into consideration the explosive characteristics of the products treated in this type of installation, the ATEX zones, the probability of the explosion, and the severity of the consequences (determined in accordance with the proposed Pittsburgh coal method), the risk assessment performed according to the methodology developed here provided results that agreed with the real accident in terms of probability and severity of the explosion as well as damages incurred.Hazardous explosive atmospheres caused by dust may occur when powdered combustible material is present in an enclosed area. In general, dust explosions take place when high enough concentrations of combustible powdered dust particles are present in the atmosphere with another suitable gaseous medium such as oxygen. Because the manipulation of these substances in industrial activities entails a risk that could have devastating consequences (including serious injuries or loss of life, as well as significant damage in installations), the risk assessment to eliminate or control the risk of explosive atmospheres in the workplace is a challenging task. In European countries the assessment of these risks is evaluated using the ATEX Directives as per European legislation. However, using this legislation to assess the risk of explosion in powder atmospheres presents difficulties due to the variety and complexity of possible explosive atmospheres and the extremely high variety of ignition sources involved. Therefor...

Spectrophotometric determination of iron with EDDHA (ethylenediamine N N bis o-hydroxyphenilacetic acid) by derivative spectroscopy

Abstract Derivative spectrometry is applied to a spectrophotometric determination of iron with EDDHA. the effect of amount of reagent, acidity, time and temperature have also been studied. the interval of application of the method is increased to 0.16–15.36 μg Fe(III) mL−1. the reproducibility, precision and potential interferents have been investigated. the interferences due to chlorate, wolframate, molybdate, permanganate, cyanide, cromate, Cu(II), Be(II), Ce(III), Al(III), Hg(II), Sn(II) and Zn(II) are reduced in this new procedure.

Rubidium determination in mineral and thermal waters by atomic-absorption spectrometry

Abstract A new procedure for rubidium determination in mineral and thermal waters using flame atomic-absorption spectrometry is described. to supress ionisation interference potassium solution was added. Rubidium can be determined in presence of Ca, Mg, Sr, Li, Cs, Fe, Al, CO2 3, F− and S2− at higher levels that levels of these elements in waters. the precision and accuracy of the method were also investigated. In 163 mineral and thermal waters analysed, the rubidium concentration range is between 0.08 to 0.84 μg mL−1.