High Pressure Asher Research Articles

Platinum-rhenium-osmium isotope systematics of chromitite and native osmium from the Guli Massif (Maimecha-Kotui Province, Russia)

To gain insight into the source of ore material, this study presents the first Re-Os and Pt-Os isotopic and highly siderophile element (HSE) abundance data for chromitite and osmium minerals from the Guli massif of ultramafic, alkaline rocks and carbonatites located in the Maimecha-Kotui province, Polar Siberia. The study utilized a number of analytical techniques, including electron microprobe analysis, negative thermal ionization mass spectrometry (N-TIMS) and high pressure asher digestion and an isotope dilution-inductively coupled plasma-mass spectrometry. The HSE concentrations in chromitite samples range from 191 to 866 ppb with a predominance of Ir-group platinum-group elements (PGE) (Os, Ir and Ru) over Pt-group PGE (Rh, Pt and Pd) and Re, which is consistent with their platinum-group mineral control (i. e., Os-Ir alloys and laurite, RuS2) within the chromitite. The Re-Os and Pt-Os isotope data indicate that the HSE budget of the chromitite and osmium minerals from the Guli massif was largely controlled by that of the mantle source, which evolved with long-term near-chondritic Re/Os and Pt/Os ratios; this source is within the range of those for the majority of komatiite and abyssal peridotite sources.

Sample preparation for geochemical analysis: Strategies and significance

Accurate determination of elemental and isotopic compositions of geological samples must be a pre-requisite for successful mineral exploration, basic geochemical and geochronological studies. During rock analysis, sample digestion which involves steps from simple dilution to partial or total digestions, is a crucial step and is the limiting factor many times for achieving reproducible and accurate analytical results. Sample preparation is a critical step in the geochemical analysis, and complete sample dissolution is a pre-requisite for obtaining accurate and precise data for geological materials in most studies. Sample matrix, analytes of interest, the analytical technique, and intended purpose play a major role in selecting the optimum sample preparation method. This review focuses on the recent advances, developments, and trends in sample digestion methods, such as open-vessel acid digestion, closed digestions, microwave digestion, alkali fusion, use of NH4F for both open and closed digestions, sintering with Na2O2, fire-assay methods, infrared radiation digestions, high-pressure asher digestions, and automated sample preparation systems (based on artificial intelligence) along with examples of some important and exciting applications in geochemical and geochronological studies. Various sample decomposition methods have been compared to bring out advantages and limitations for a particular application.

Study on the hydrolysis process of food and feed samples using high pressure asher (HPA-S) to determine several amino acids by high performance liquid chromatography

The study researchs on the hydrolysis process of food and feed samples using High Pressure Asher (HPA-S) to determine several amino acids by high-performance liquid chromatography (HPLC). HPA-S equipment is mainly used for samples treatment in analysis of metals by spectroscopy. However, the study also found that HPA-S can be used in hydrolysis of food and feed samples in order to analyze amino acids. The temperature of HPA-S equipment could reach 300oC and maintain continuously at 130 bar pressure, completely digetsing the most complex samples matrix within an hour. The successful study of the application of HPA-S to hydrolyze samples in order to analyze amino acids makes the time of sample preparation significantly shorter but still gave the equivalent stability, even higher than the common samples hydrolyzation.

Photocatalytic properties of Zn2SnO4 powders prepared by different modified hydrothermal routes

In this work, different synthesis methods of zinc stannate (Zn2SnO4–ZTO) were proposed in order to obtain a material with a greater porous structure and higher surface area when compared to conventional hydrothermal method. Zn2SnO4 particles were prepared using a conventional oven method (CO), ultrasound (US), microwave (MW) and high pressure Asher (HPA), all followed by calcination at 500 °C. Fourier-transform infrared spectroscopy, X-ray diffraction, N2 adsorption–desorption (BET and BJH), diffuse reflectance spectroscopy, particle-size distribution and scanning electron microscopy were used to characterize the materials. ZTO prepared by HPA (20 bar) showed a greater surface area. On the other hand, particles with higher mesoporosity and band gap were obtained by CO route. The US route led to the formation of ZTO with larger average particle size. Therefore, all hydrothermal routes employed in this work were able to synthesize ZTO, each one with its peculiarity, producing particles with different characteristics. The ZTO photocatalytic properties were evaluated by the decolorization of Procion red dye solution. The ZTOs synthesized by HPA and MW routes showed higher photocatalytic activity, being able to decolorize more than 70% of the dye solution at 60 min under sunlight.

Re-Os and HSE in individual base metal sulfide grains: Evaluating micro-analytical procedures using a sulfide reference material

Two Fe-Ni sulfides, resembling the chemical composition of a typical mantle base metal sulfide (BMS), were synthesized and used to test micro-analytical procedures (sample digestion and chemical separation) to determine 187Os/188Os and highly siderophile element (HSE) mass fractions in single BMS grains. The bulk 187Os/188Os and HSE mass fractions of the synthetic sulfides were independently determined after high pressure asher (HPA) digestion and conventional HSE separation (Os solvent extraction and Ir, Ru, Pt, Pd, Re separation via anion exchange chromatography), while the homogenous distribution of HSE was assessed via LA-ICP-MS.Tests were performed following the protocol of Pearson et al. (1998), where sulfides are digested in H2SO4/CrO3 and Os is simultaneously extracted as OsO4. Additional tests were performed adding a pre-digestion step in HBr and/or HCl. The duration and the temperature of the pre-digestion and micro-distillation steps, as well as different chromatographic separations of the HSE were also evaluated. While the majority of the tests yielded 187Os/188Os in agreement with that obtained after HPA digestion, HSE mass fractions show large deviations from the reference content, depending on the used procedure. Such variations are interpreted as the result of incomplete sulfide digestion, Os spike loss, and the possible presence of undigested sub-micrometric platinum group minerals (PGM). Overall, the bulk sulfide HSE mass fractions obtained after HPA digestion are best reproduced (mean deviations ≤10%) using a pre-digestion step in HBr + HCl at 120 °C.This study highlights the need for matrix-matched sulfide reference materials for routine use in laboratories determining HSE mass fractions and Os isotope ratios on single BMS grains. Such an approach is fundamental for comparing and compiling Re-Os ages collected on BMS in many different laboratories. This study also demonstrates that there is need for further testing and for methodological developments/improvement of the analytical procedure(s) used for Re-Os dating and HSE mass fraction determinations in single BMS grains.

Antimony Assessment in PET Bottles for Soft Drink

The aim of this work was to develop a method for the determination of antimony (Sb) in polyethylene terephthalate (PET) bottles and to evaluate its migration into soft drink and simulant. In this context, a new procedure for PET sample preparation, using a high pressure asher (HPA), is presented for the determination of Sb by inductively coupled plasma optical emission spectrometry (ICP-OES). The concentration of Sb in PET bottles ranged between 272 and 650 mg kg−1. The migration of Sb into soft drink after 180 days at 35 °C was below the LOQ, 20 μg L−1. The specific migration of Sb from the bottle into simulant 3% of acetic acid after the contact per 10 days at 40 °C was less than the LOQ, 23.5 μg L−1. The results showed that all packaging evaluated contained Sb, but the maximum permissible migration value for Sb, 40 μg L−1, established by Anvisa and EU, was never exceeded.

Re–Os dating of maltenes and asphaltenes within single samples of crude oil

Re–Os geochronology of oil may constrain the timing of oil formation and improve oil-source and oil–oil correlations. Typically, asphaltene (ASPH), the heaviest and most Re–Os rich oil fraction, from multiple oils within an oil field or a larger petroleum system are analyzed to obtain sufficient spread in Re–Os isotopic ratios, a mathematical necessity for precise Re–Os isochrons.Here we offer a new approach for Re–Os geochronology of oil based on isotopic analyses of different fractions within a single sample of crude oil. We studied three oils from the Gela oil field, southern Sicily, Italy, recovered from Triassic–Jurassic stratigraphic intervals (Streppenosa, Noto, and Sciacca Formations) within the Gela-1 well. ASPH (insoluble in n-alkane) and maltene (MALT, soluble in n-alkane) fractions of oil were separated using n-pentane, n-hexane, n-heptane and n-decane solvents. The ASPH contents of the Sciacca and Noto oils (26–33wt%) are notably higher compared to the Streppenosa oil (7–12wt% ASPH).We present an optimized Re–Os procedure with sample digestion in a high-pressure asher, followed by isotopic measurements using negative thermal ionization mass spectrometry. Very high metal contents of Gela oils allowed acquisition of precise Re–Os data. Systematic variations between the type of solvent used for ASPH precipitation and the ASPH content of the oil (also known from the literature) and the Re–Os contents of the ASPH and MALT fractions (first observed in this study) provide important practical applications for Re–Os analyses of oil. Most Re and Os (∼96–98%) in the Noto oil are hosted in the ASPH fraction. In contrast, a significant portion of Re and Os (∼33–34%) is stored in the MALT fraction of the lighter, but heavily biodegraded Streppenosa oil.Collectively, our new data on alkane distribution, hopane and sterane biomarkers, major and trace element contents, and Re–Os concentrations and isotopic ratios of the oils and their fractions support the presence of two oil families. Streppenosa oil, a heavily biodegraded oil generated at an early stage of thermal maturation from a shaly source rock, is clearly distinct from the Noto and Sciacca oils, both generated at peak maturation from a carbonate source rock with no subsequent biodegradation.Two Re–Os ages were obtained. Crude oil and ASPH from Noto and Sciacca oil yield a Model 1 isochron age of 27.5±4.6Ma with an initial 187Os/188Os of 3.89±0.43 (MSWD=1.6, n=19). We interpret this Oligocene age as the time of initial oil generation, that was probably related to the onset of regional collisional tectonics in southern Sicily. ASPH and crude oil from the Streppenosa oil yield scattered data, perhaps related to effects of biodegradation. Streppenosa MALT yield a Model 1 age of 200.0±5.2Ma and initial 187Os/188Os of 1.39±0.11 (MSWD=0.52; n=4). This age and initial Os-isotopic composition are consistent with rapid oil generation shortly after Late Triassic source-rock formation, perhaps driven by magmatic-related heating.Here we document a potentially powerful geochronological tool that can be applied to single samples of crude oil. Within each oil, the 187Os/188Os and most of the 187Re/188Os ratios in the MALT fractions are lower than in the corresponding ASPH fractions. Crude oils, being physical mixtures of ASPH and MALT, have intermediate Re–Os isotopic ratios. Hence, the needed spread in data points for a Re–Os isochron is obtained by analyzing components of a single crude oil. This approach eliminates pitfalls in interpretation of Re–Os data from multiple oils with possibly different generation, migration, or reservoir modification history.

Simultaneous Determination of 10 Ultratrace Elements in Infant Formula, Adult Nutritionals, and Milk Products by ICP/MS After Pressure Digestion: Single-Laboratory Validation.

A single-laboratory validation (SLV) is presented for the simultaneous determination of 10 ultratrace elements (UTEs) including aluminum (Al), arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), mercury (Hg), molybdenum (Mo), lead (Pb), selenium (Se), and tin (Sn) in infant formulas, adult nutritionals, and milk based products by inductively coupled plasma (ICP)/MS after acidic pressure digestion. This robust and routine multielemental method is based on several official methods with modifications of sample preparation using either microwave digestion or high pressure ashing and of analytical conditions using ICP/MS with collision cell technology. This SLV fulfills AOAC method performance criteria in terms of linearity, specificity, sensitivity, precision, and accuracy and fully answers most international regulation limits for trace contaminants and/or recommended nutrient levels established for 10 UTEs in targeted matrixes.

Method for Analysis and Study of Migration of Lead, Cadmium, Mercury and Arsenic from Polypropylene Packaging into Ice Cream and Simulant

The aim of this study was to propose a method for analysis of lead (Pb), cadmium (Cd), mercury (Hg) and arsenic (As) in polypropylene packaging intended for contact with ice cream and migration of these elements using the food itself and 3 % acetic acid as food simulant. Ten commercial samples of ice cream marketed in Campinas-Sao Paulo (Brazil) were used for the analysis. Both the packaging and ice cream were digested in high-pressure ashing equipment (HPA), as a new proposal to the sample preparation and the migration of the elements into stimulant directly in the solution. The determinations were carried out using an inductively coupled plasma optical emission spectroscopy (ICP-OES) and two different nebulizers (cross flow and Miramist, when necessary). The results obtained showed that the levels of Hg and As of all packaging were below the limit of quantification (LOQ) corresponding to 1.0 and 1.7 μg L−1, respectively. The highest levels of Cd and Pb were 0.45 and 1.64 mg kg−1, respectively. The migration of these elements into the ice cream after 365 days of contact at −20 °C was below the LOQs for all the samples assessed. The results of specific migration into 3 % acetic acid simulant showed concentrations of Cd, Hg and As below 5, 5 and 10 μg kg−1, respectively. The method developed can be applied for the determination of inorganic elements in polypropylene, ice cream and acetic acid by ICP-OES.

Mass Fractions of S, Cu, Se, Mo, Ag, Cd, In, Te, Ba, Sm, W, Tl and Bi in Geological Reference Materials and Selected Carbonaceous Chondrites Determined by Isotope Dilution ICP‐MS

Mass fractions of S, Cu, Se, Mo, Ag, Cd, In, Te, Ba, Sm, W and Tl were determined by isotope dilution sector field ICP‐MS in the same sample aliquot of reference materials using HF‐HNO3 digestion in PFA beakers in pressure bombs and glassy carbon vessels in a high‐pressure asher (HPA‐S) for comparison. Additionally, Bi was determined by internal standardisation relative to Tl. Because isobaric and oxide interferences pose problems for many of these elements, efficient chromatographic separation methods in combination with an Aridus desolvator were employed to minimise interference effects. Repeated digestion and measurement of geological reference materials (BHVO‐1, BHVO‐2, SCo‐1, MAG‐1, MRG‐1 and UB‐N) gave results with < 5% relative intermediate precision (1s) for most elements, except Bi. Replicates of NIST SRM 612 glass digested on a hot plate were analysed by the same methods, and the results agree with reference values mostly within 2% relative deviation. Data for the carbonaceous chondrites Allende, Murchison, Orgueil and Ivuna are also reported. Digestion in a HPA‐S was as efficient as in pressure bombs, but some elements displayed higher blank levels following HPA‐S treatment. Pressure bomb digestion yielded precise data for volatile S, Se and Te, but may result in high blanks for W.

Re-evaluating digestion methods for highly siderophile element and 187Os isotope analysis: Evidence from geological reference materials

Here we evaluate measurement procedures currently used for the combined determination of highly siderophile element concentrations (HSEs: Re, Ir, Os, Ru, Pt and Pd) and Os isotope ratios in geological samples by isotope dilution mass spectrometry (ID-MS) applying high-temperature sample digestion using inverse aqua regia in closed glass vessels, such as Carius tubes or a high-pressure asher system (HPA). In particular, we address the question of whether an additional hydrofluoric acid dissolution step is required to release HSEs hosted in the silicate portions of rock samples. To do so, we conducted systematic experiments for basaltic (TDB-1 and BIR-1), ultramafic (UB-N and JP-1) and sedimentary (SCo-1, SDO-1 and JCh-1) reference materials with and without HF desilicification. Through the extensive tests on TDB-1—varying apparatus (microwave, Carius tube, high-pressure asher), conditions (temperature, duration, sample size) and protocol (HF desilicification before or after aqua regia attack)—we find the optimum digestion method is to use inverse aqua regia for digesting 1–2g of powder over long durations, such as Carius tubes heated to 240˚C for 72h, followed by an HF desilicification step after CCl4 solvent extraction of Os. For basaltic reference materials, the method provides significantly improved HSE recoveries—particularly Ru—largely due to the use of HF. Strong linear correlations between Os and Ir–Ru–Pt concentrations and isochronous behavior on a 187Re/188Os vs. 187Os/188Os diagram (1240±59Ma, MSWD=1.4) are observed for repeat dissolutions of TDB-1, reflecting sample heterogeneity due to minor minerals enriched in Os, Ir, Ru and Pt—most likely sulphides. In comparison, excellent reproducibilities were obtained for BIR-1: relative standard deviations (RSDs) for 1–2g aliquots were 6.9% Os, 5.1% Ir, 2.0% Ru, 5.1% Pt, 1.5% Pd and 0.7% Re (n=9). Thus, BIR-1 might be a useful candidate reference material for obtaining certified values with small measurement uncertainties. Unlike the basaltic reference materials, extraction of HSEs from ultramafic and sedimentary reference materials is largely independent of the use of HF. The data obtained by Carius tube for UB-N and JP-1 agree well with the literature data obtained using apparently more aggressive digestion techniques. The precision of our data for 0.5–2g aliquots of the sedimentary reference materials also compares favourably with limited data available in the literature.

Using ICP-qMS to trace the uptake of nanoscale titanium dioxide by microalgae–potential disadvantages of vegetable reference material

As nanoscale materials have gained in economic importance over recent years, concerns about accumulation in the environment and, consequently, analysis of nanoparticles in biological material have increasingly become the focus of scientific research. A nanomaterial used in a wide range of food, consumer and household products is titanium dioxide (nTiO2). Monitoring of nTiO2 via determination of elemental titanium (Ti) can be very challenging because of a variety of possible interferences. This work describes problems during the development of a quantification method for titanium dioxide (TiO2) using inductively coupled plasma-quadrupole mass spectrometry (ICP-qMS). To evaluate the analytical method, certified vegetable reference material NCS DC 73349 was used. Interestingly, measurements of NCS DC 73349 seemed to result in acceptable recovery values-however, this was without considering interferences or conceivable differences in the natural isotopic abundance of the certified titanium calibration solution and NCS DC 73349. Actually, recoveries were lower than initially assumed. The potential interferences causing augmented recovery could be attributed to the presence of the elements sulfur (S) and phosphorus (P), which were able to form oxide ions and nitrogen-interfering species. The effect of such interfering cluster ions could be prevented by dry ashing as a sample preparation step, to evaporate S and P, before digestion with aqua regia in a high-pressure asher (HPA). Final practicability of the analysis method was proved by monitoring the uptake of nTiO2 by the microalgae Scenedesmus acutus in an environmental exposure study.

Determination of Osmium Concentrations and 187Os/188Os of Crude Oils and Source Rocks by Coupling High-Pressure, High-Temperature Digestion with Sparging OsO4 into a Multicollector Inductively Coupled Plasma Mass Spectrometer

The (187)Os/(188)Os ratio that is based on the β(-)-decay of (187)Re to (187)Os (t1/2 = 41.6 billion years) is widely used to investigate petroleum system processes. Despite its broad applicability to studies of hydrocarbon deposits worldwide, a suitable matrix-matched reference material for Os analysis does not exist. In this study, a method that enables Os isotope measurement of crude oil with in-line Os separation and purification from the sample matrix is proposed. The method to analyze Os concentration and (187)Os/(187)Os involves sample digestion under high pressure and high temperature using a high pressure asher (HPA-S, Anton Paar), sparging of volatile osmium tetroxide from the sample solution, and measurements using multicollector inductively coupled plasma mass spectrometry (MC-ICPMS). This methods significantly reduced the total procedural time compared to conventional Carius tube digestion followed by Os separation and purification using solvent extraction, microdistillation and N-TIMS analysis. The method yields Os concentration (28 ± 4 pg g(-1)) and (187)Os/(188)Os (1.62 ± 0.15) of commercially available crude oil reference material NIST 8505 (1 S.D., n = 6). The reference material NIST 8505 is homogeneous with respect to Os concentration at a test portion size of 0.2 g. Therefore, (187)Os/(188)Os composition and Os concentration of NIST 8505 can serve as a matrix-matched reference material for Os analysis. Data quality was assessed by repeated measurements of the USGS shale reference material SCo-1 (sample matrix similar to petroleum source rock) and the widely used Liquid Os Standard solution (LOsSt). The within-laboratory reproducibility of (187)Os/(188)Os for a 5 pg of LOsSt solution, analyzed with this method over a period of 12 months was ∼1.4% (1 S.D., n = 26), respectively.

Characterizing metal(loid) solubility in airborne PM10, PM2.5 and PM1 in Frankfurt, Germany using simulated lung fluids

The purpose of this study is to assess the solubility of traffic-related metal(loid)s associated with airborne PM of human health concern, employing a physiologically-based extraction test with simulated lung fluids (artificial lysosomal fluid (ALF) and Gamble's solution). Airborne PM (PM10, PM2.5 and PM1) samples were collected in Frankfurt am Main, Germany, using a high volume sampler. Following extraction of the soluble metal(loid) fractions, sample filters were digested with a high pressure asher. Metal(loid) concentrations (As, Ce, Co, Cr, Cu, Mn, Ni, Pb, Sb, Ti and V) were determined in extracts and digests per ICP-Q-MS.All metal(loid)s occurred at detectable concentrations in the three airborne PM fractions. Copper was the most abundant element in mass terms, with mean concentrations of 105 and 53 ng/m3 in PM10 and PM2.5, respectively. Many of the metal(loid)s were observed to be soluble in simulated lung fluids, with Cu, As, V and Sb demonstrating the highest overall mobility in airborne PM. For instance, all four elements associated with PM10 had a solubility of >80% in ALF (24 h). Clearly, solubility is strongly pH dependent, as reflected by the higher relative mobility of samples extracted with the acidic ALF.Given their demonstrated solubility, this study provides indirect evidence that a number of toxic metal(loid)s are likely to possess an enhanced pulmonary toxic potential upon their inhalation. The co-presence of many toxic elements of concern in airborne PM suggests an assessment of health risk must consider the possible interactive impacts of multi-element exposures.

Examining the possibility of using ratios of element mass fractions as markers for origin determination of soya and canola based biodiesels. Measurement procedure validation to underpin this study

It is shown how ratios of element mass fractions could possibly be used as markers for origin determination of biodiesel materials of the 1st generation. This is a feasibility study on three samples of soya beans, three samples of canola/rape seeds and the six corresponding final biodiesel products. It is underpinned by a careful validation of the measurement procedures developed.Sample digestion was performed with acids in a high pressure asher or a microwave oven depending on samples. Followed, under ultra-clean laboratory conditions, evaporations to dryness of the digests, re-dissolutions of the solid residues in 2% HNO3 and, for raw plant materials, a final dilution step with 2% HNO3 (1:100 and 1:1000). Mass fractions of B, Mg, P, S, V, Cu, Sn, Fe and Zn were measured in all samples by inductively coupled plasma mass spectrometry. These elements were selected from preliminary screening results on 105 and 33m/z values in biodiesel samples at low and medium mass resolutions, respectively. Selection criteria were: measurement signals better than 10% repeatable and at least 3times larger than the standard deviation on procedural blanks; and less than 5% relative difference between the measured (not corrected for mass discrimination effects) and natural isotope ratios. Efforts were made at reducing procedural blanks and stabilising their reproducibility to 10–30%. Procedure validation consisted in identifying the factors influencing the results, estimating combined uncertainties and assessing trueness from recovery tests on the certified reference material BCR-191 and simulated biodiesel samples. Recoveries larger than 70% were obtained for [B], [P], [S], [Cu], [Fe] and [Zn]. Ratios of mass fractions were computed for all possible combinations of results obtained for these elements in all samples. These ratios appeared to be good markers of the biological origin of the raw products of this study, with strong correlations between results from plant samples of the same type, and strong anti-correlations between results from plant samples of the other type (R2=between 0.86 and 0.96, and from 0.3 to 0.7 when the rapeseed sample was involved). The [S]/[Cu] ratio correlated well too between the biodiesels and their corresponding raw plant samples (R2=0.82 to 0.97). Relative expanded (k=2) uncertainties on the ratios of mass fractions were estimated to be no larger than 23% in the raw plant materials (and up to 33% for the ratios involving Fe), and 45% for the [S]/[Cu] ratio in biodiesels.

Abundances of Sulfur, Selenium, Tellurium, Rhenium and Platinum‐Group Elements in Eighteen Reference Materials by Isotope Dilution Sector‐Field ICP‐MS and Negative TIMS

Geological reference materials (RMs) with variable compositions and NIST SRM 612 were analysed by isotope dilution mass spectrometry for bulk rock concentrations of chalcogen elements (sulfur, selenium and tellurium), rhenium and platinum‐group elements (PGEs: Ru, Pd, Os, Ir and Pt), including the isotope amount ratios of 187Os/188Os. All concentrations were obtained from the same aliquot after HCl‐HNO3 digestion in a high pressure asher at 320 °C. Concentrations were determined after chemical separation by negative TIMS, ICP‐MS and hydride generation ICP‐MS (Se, Te). As in previous studies, concentrations of the PGEs in most RMs were found to be highly variable, which may be ascribed to sample heterogeneity at the < 1 g level. In contrast, S, Se and Te displayed good precision (RSD < 5%) in most RMs, suggesting that part of the PGE budget is controlled by different phases, compared with the chalcogen budget. The method may minimise losses of volatile chalcogens during the closed‐system digestion and indicates the different extent of heterogeneity of chalcogens, Re and PGEs in the same sample aliquot. OKUM, SCo‐1, MRG‐1, DR‐N and MAG‐1 are useful RMs for the chalcogens. NIST SRM 612 displays homogenous distribution of S, Se, Te, Pt and Pd in 30 mg aliquots, in contrast with micro‐scale heterogeneity of Se, Pd and Pt.

Method for assessing lead, cadmium, mercury and arsenic in high-density polyethylene packaging and study of the migration into yoghurt and simulant

The purpose of this paper was to assess the concentration of lead (Pb), cadmium (Cd), mercury (Hg) and arsenic (As) in high-density polyethylene (HDPE) packaging intended for contact with yoghurt and the migration of these elements using the food itself and 3% acetic acid as a food simulant in accordance to ANVISA, the Brazilian Health Surveillance Agency. In order to perform this study, it was necessary to develop and validate a method by inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis. For method validation, the parameters linearity, limits of detection (LODs) and quantification (LOQs), accuracy and precision were determined. Fifteen commercial samples of yoghurt, marketed in Campinas – São Paulo (Brazil), were used for the analysis. The packaging and yoghurt were digested in high-pressure ashing equipment (HPA) and the migration of the elements into simulant were determined directly in the solution. The validated method proved adequate and the results obtained showed that all the packaging had levels of Hg and Cd below the LOQ, corresponding to 1.0 and 1.5 μg l−1, respectively. The highest levels of As and Pb were 0.87 and 462.3 mg kg−1, respectively. The migration of these elements to the yoghurt after 45 days of contact at 4ºC was below the LOQ for all the samples assessed. The results of specific migration into 3% acetic acid simulant showed the concentrations of Cd, Hg and As below 5, 5 and 10 µg kg−1, respectively, which are the maximum limits set by ANVISA. However, for three samples the packaging lid showed migration of Pb into simulant ranging from 30.6 to 40.2 μg kg−1, exceeding the limit set by ANVISA of 10 μg kg−1.

High Pressure Asher (HPA-S) Decomposition of Biodiesel Samples for Elemental Analysis by Inductively Coupled Plasma Optical Emission Spectrometry (ICP OES)

The presence of some inorganic elements in biodiesel can compromise the fuel quality and enhance the emission of pollutants. In this context, a new procedure for biodiesel sample preparation using a high pressure asher (HPA) is presented, aiming the determination of Al, Ca, Cu, Fe, K, Mg, Mn, Na, Ni, P, Sr, and Zn, in soybean, sunflower, animal fat, cotton and castor oil, by inductively coupled plasma optical emission spectrometry (ICP OES). The digestion conditions of the HPA were optimize to digest 1.5 g of biodiesel, with HNO3 and H2O2, at a temperature of 300 °C and pressure of 435 psi, which considered the sample dilution factor, the total solids in solution and the acidity for ICP OES determinations. Analytes concentrations in these biodiesels were calculated using standard addition method. Detection limits from 0.05 to 0.7 mg kg - 1 were suitable to attend biodiesel quality parameters, government policy and legislations worldwide. Therefore, the proposed procedure proved to be efficient to eliminate the major organic interferences typically present in oil based samples allowing a fast, precise, interference-free and robust analytical condition for biodiesel characterization.

Determination of toxic elements in tricyclic active pharmaceutical ingredients by ICP-MS: a critical study of digestion methods

The determination of As, Cd, Hg and Pb in tricyclic active pharmaceutical ingredients (APIs) was performed by ICP-MS after digestion by both combustion and wet digestion methods. Carbamazepine was digested using the dry ashing method recommended in United States Pharmacopeia 35th edition and significant losses of analytes were observed in recovery tests (38.0 ± 8.9, 99.5 ± 7.1, and 89.4 ± 6.3% of recovery for As, Cd and Pb, respectively). Mercury was completely lost by volatilization during digestion. The digestion of carbamazepine, amitriptyline hydrochloride and imipramine hydrochloride by microwave-assisted wet digestion in closed vessels (MW-AD) was not effective and a yellow-orange solid residue was observed for all substances. 1H NMR of the carbamazepine residue indicated the nitration of carbamazepine aromatic rings forming stable nitro compounds. High pressure asher digestion systems were also used and solid residues were observed for carbamazepine and amitriptyline hydrochloride even under drastic digestion conditions (280 °C, 120 min). A complete digestion of all substances was obtained only by the use of high temperature and long time of digestion and reduction of sample mass to 0.08 g (320 °C, 180 min). The microwave-induced combustion (MIC) method for digestion of tricyclic APIs allowed the digestion of 0.5 g of all substances with high efficiency (RCC lower than 1%) using diluted nitric acid as absorbing solution (7 mol l−1). The recoveries using this method were between 94 and 103% for the evaluated elements. The low RCC and acidity of digests obtained using MIC allowed the compatibility with ICP-MS and makes MIC a promising alternative as a sample preparation method for subsequent determination of toxic elements in APIs by ICP-MS.

Comparison of digestion methods for the determination of ruthenium in catalyst materials

A fusion method, an acid digestion method with a high pressure asher (HPA) and two microwave (MW)-assisted acid digestion methods were compared to investigate their suitability for the determination of Ru in catalyst materials. Ru contents in the digested samples were determined with inductively coupled plasma optical emission spectrometry (ICP-OES). Ru powder and three Ru compounds (RuO2 · xH2O, anhydrous RuO2 and RuCl3), possibly present in Ru catalysts, were digested and analyzed to compare the digestion efficiencies of the methods. Significant differences among the digestion efficiencies of the methods were observed; the fusion method having the best digestion efficiency for the compounds studied. The methods were applied for the determination of Ru in alumina- and carbon-supported catalysts. No differences among the methods were observed for these samples.