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Sanchez R.,Nutrition and Food science | Sanchez C.,Nutrition and Food science | Lienemann C.-P.,French Institute of Petroleum | Todoli J.-L.,Nutrition and Food science
Journal of Analytical Atomic Spectrometry | Year: 2015

Biofuel quality control involves the determination of metal and metalloid content. These species play a very important role because they may modify the efficiency of biofuel production as well as the stability of these products. Furthermore, some metals are toxic and generate environmental concerns whereas others are used as additives. Normally, products such as biodiesel and bioethanol are mixed with conventional fossil fuels (diesel and gasoline, respectively). Therefore, metals come from the raw product employed for biofuel production (seeds, sugars...) as well as from the production and storage process or even from the added fuels. The determination of the final metal and metalloid concentration in biofuels is a challenging subject because of several reasons. On the one hand, their content is usually low (i.e., from several μg L-1 to mg L-1) and, hence, sensitive techniques should be used. Besides all these, calibration with organic complex matrices becomes more difficult and degrades the accuracy of the determination. Several approaches have been evaluated to carry out this kind of analysis going from spectrochemical to electroanalytical techniques. Within the first group, Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) and Mass Spectrometry (ICP-MS) are often employed together with atomic absorption methods. The different procedures applied will be discussed in the present review emphasizing the most widely employed ones. On this subject, fundamental as well as applied studies related to the biofuel analysis through ICP-OES and ICP-MS will be shown to illustrate the current difficulties associated with these determinations. Comments regarding the possible solutions proposed to overcome the drawbacks encountered will be made. This journal is © The Royal Society of Chemistry.


Sanchez R.,Nutrition and Food science | Todoli J.L.,Nutrition and Food science | Lienemann C.-P.,French Institute of Petroleum | Mermet J.-M.,Spectroscopy Forever
Journal of Analytical Atomic Spectrometry | Year: 2012

The benefits of using a 350 °C heated single pass spray chamber following a segmented flow injection methodology were demonstrated for the analysis of petroleum products through inductively coupled plasma atomic emission spectrometry (ICP-OES). The present work shows that a small sample volume (i.e., 5 μl or less) can be precisely injected into the system following a manual procedure. Two different sample introduction systems were employed: a Cyclonic spray chamber and a single pass spray chamber (a modified version of the Torch Integrated Sample Introduction System, TISIS) equipped with a heating brass hollow cylinder. First the effect of temperature on the peak shape and sensitivity has been studied for a set of nineteen different organic products (gasoline, superethanol, diesel and biodiesel diluted in xylene). The results have proved that the higher the chamber walls temperature, the higher the sensitivity. As a result limits of detection decreased below 7 μg l -1 for elements such as manganese, vanadium and silicon. Furthermore, memory effects were less severe as the temperature raised. Another benefit of increasing the TISIS chamber walls temperature is that matrix effects became less pronounced as compared to a Cyclonic chamber. Thus, at 350 °C non-spectral interferences are eliminated likely because the analyte transport efficiency to the plasma is close to 100% irrespective of the sample analyzed. This has two important consequences: (i) it is possible to obtain a calibration line by merely modifying the injected solution volume and (ii) a single xylene based solution can be used as a universal standard. The developed procedure was applied to the analysis of nineteen spiked petroleum derivatives with recoveries for manganese, silicon, vanadium and copper in the range 95-106%. © 2012 The Royal Society of Chemistry.


Sanchez R.,Nutrition and Food science | Sanchez R.,European Commission | Sanchez C.,Nutrition and Food science | Todoli J.L.,Nutrition and Food science | And 2 more authors.
Journal of Analytical Atomic Spectrometry | Year: 2014

A heated Torch Integrated Sample Introduction System (hTISIS) has been applied to the analysis of petroleum products and biofuels through Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Three elements have been determined because of their importance in the petroleum industry: V, Ni and Mn. Sample injection has been accomplished by means of the introduction of a low sample volume (2.5 μl) into an air carrier stream. A peak has been thus obtained. Two sets of samples have been selected: five solvents (xylene, kerosene, nonane, undecane and hexadecane) and five real samples (biodiesel, diesel, kerosene, superethanol and gasoline). The chamber temperature has been varied when introducing either solvents or real samples. In both cases it has been found that sensitivity peaked at 110 °C heating temperature. However, non-spectral interferences caused by differences in the matrix composition became less severe as this variable was increased and they were virtually eliminated at temperatures of 150 °C (alkanes) and 200 °C (real samples). When comparing with a default spray chamber (i.e., conical chamber with an impact bead) 3 to 6 times lower LODs were obtained. At 150 °C, this parameter has taken values of approximately 80 ng l-1 for V and Ni to 140 ng l -1 for Mn. At 200 °C heating temperature it has been possible to carry out accurate ICP-MS determinations by applying external calibration. Additional advantages of the present approach were that no oxygen was required to avoid soot deposition at the sampler cone and that nickel, instead of platinum cones, was used. © 2014 The Royal Society of Chemistry.


Sanchez R.,Nutrition and Food science | Todoli J.L.,Nutrition and Food science | Lienemann C.-P.,French Institute of Petroleum | Mermet J.-M.,Spectroscopy Forever
Journal of Analytical Atomic Spectrometry | Year: 2010

A method based on the use of a high temperature single pass spray chamber and the injection of a sample plug into an air carrier gas stream was developed to mitigate non spectral interferences caused by organic samples and petroleum products and to reduce plasma loading in Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). The studied solvents were eleven alkanes (hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane), xylene, kerosene and tetralin. As regards to the real samples two gasolines, a kerosene and a diesel sample were taken. The evaluated sample introduction systems were a 12 cm3 inner volume single pass spray chamber (also called Torch Integrated Sample Introduction System, TISIS) with and without heating and a 40 cm3 inner volume cyclonic spray chamber that was taken as a reference device. A characterization of the matrix effect in continuous aspiration mode at a 30 μl min -1 flow rate was initially performed. Drop size distributions were measured for the aerosols generated by the nebulizer (primary aerosols) and those leaving the spray chamber (tertiary aerosols). The results proved that the median of the aerosol volume drop size distribution (D50) for primary aerosols took values from 13.2 to 15.3 μm. Meanwhile, tertiary ones changed more significantly as a function of both the solvent nature and the chamber temperature. They went from 2 to 4 μm for the TISIS at room temperature, whereas at 100 °C D50 was included within the 0.7 to 3.1 μm range. The analyte mass transported towards the plasma was also measured and it was confirmed that this parameter was directly related to the solvent volatility. Thus, at room temperature, efficiencies went from 20 to 60% for hexadecane and octane, respectively. ICP-AES sensitivities changed significantly as a function of the solvent. For real samples, heating of the chamber walls mitigated the interferences, thus, while at room temperature, gasoline samples provided more than one order of magnitude higher signals than diesel samples, at 100 °C this signal improvement factor was only of five. All these problems were mostly overcome when the segmented injection of a 5 μl sample plug was performed. It was concluded that, for all the solutions at 200 °C heating temperature the injected sample volume (c.a., 5 μl) evaporated completely before its further introduction into the plasma. Therefore, differences in analyte mass transported as a function of the solution matrix were mitigated. © 2010 The Royal Society of Chemistry.


Sanchez R.,Nutrition and Food science | Todoli J.L.,Nutrition and Food science | Lienemann C.-P.,French Institute of Petroleum | Mermet J.-M.,Spectroscopy Forever
Journal of Analytical Atomic Spectrometry | Year: 2010

The effects of the solvent dilution factor on the physical properties of the resulting organic solutions, the aerosol characteristics and the silicon sensitivity were studied in ICP-AES for four different petroleum products by using near total sample consumption systems. The four samples were two gasoline products having very different volatilities along with a kerosene and a diesel sample. Petroleum product samples were diluted with xylene using four sample dilutions; 1:2, 1:5, 1:10 and 1:50. The sample introduction systems were a single pass spray chamber associated with a micronebulizer and a demountable Direct Injection High Efficiency Nebulizer (d-DIHEN). A cyclonic spray chamber also associated with a micronebulizer was taken as the reference system. Silicon was used as the test element, because it has been previously demonstrated that the ICP-AES Si sensitivity was significantly modified according to its chemical form. Silicon was spiked in each diluted solution with the same concentration to test sensitivity. When considering the dilution factor as the key variable, it was found that for the two gasoline samples and the kerosene one, the higher this variable, the lower the sensitivity. This result was explained in terms of changes in the solution volatility and/or in the aerosol characteristics. It was also observed that the total sample consumption systems were less sensitive to changes in the properties of the resulting organic solutions than the system based on the cyclonic spray chamber. However, for the latter chamber, the properties of the resulting organic solution had a marked influence on the extent of the effect of the silicon chemical form on the sensitivity. This fact demonstrated the appearance of an undefined interaction between the analyte and the organic solution during the aerosol transport step. However, both the single pass spray chamber and the d-DIHEN mitigated this effect for all the samples. © 2010 The Royal Society of Chemistry.

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