Microwave-assisted Sample Digestion Research Articles

An acidless microwave-assisted wet digestion of biological samples as a greener alternative: applications from COVID-19 monitoring to plant nanobiotechnology.

Sample preparation in an analytical sequence increases the number of errors, is highly time-consuming, and involves the manipulation of hazardous reagents. Therefore, when an improvement in an analytical method is required, the sample preparation step needs to be optimised or redesigned. Moreover, this step can involve significant toxic reagents and a high volume of waste. In that regard, this study proposes a new procedure based on microwave-assisted wet digestion combining two green strategies: a miniaturised system (with a few microlitres of volume) and the only use of hydrogen peroxide. Three biological samples (human serum, urine, and plant in vitro material) were chosen due to their high potential for disease monitoring, toxicological studies, and biotechnology applications. Several trace elements (Ca, Cd, Co, Cu, Fe, Mg, Mn, Mo, Ni, Se, and Zn) were determined by inductively coupled plasma optical emission spectroscopy and inductively coupled plasma mass spectrometry. For human serum and urine, a certified reference material was used to check for accuracy; the recovery ranged from 72% (Cd, ICP-MS) to 105% (Mg, ICP OES) for serum, while for urine, they varied from 82% (Ni, ICP-MS) to 122% (Zn, ICP-MS). For the soybean callus sample (in vitro plant material), a comparison between the proposed method and the acid digestion method was conducted to evaluate the accuracy, and the results agreed. The detection limits were 0.001-60µg L-1 (lowest for Cd), thus demonstrating a suitable sensitivity. Moreover, the decomposition efficiency was demonstrated by determining the residual carbon, and a low amount was found in the final product digested (below 0.8% w v-1). A green metric approach was calculated for the proposed method, and according to AGREEprep software, it was found to be around 0.4. Finally, the method was applied to urine samples collected in patients with COVID-19 and soybean callus cultivated with silver nanoparticles. This sample preparation method is a new acidless and miniaturised alternative for elemental analysis involving biological samples.

Optimization of vortex-assisted supramolecular solvent-based liquid liquid microextraction for the determination of mercury in real water and food samples

A novel method was developed for sample preparation for spectrophotometric determination of Hg(II) in water and food samples. The method was based on vortex-assisted supramolecular solvent-assisted liquid-liquid microextraction (VA-SUPRASs-LLME). Analytical parameters such as pH, chelating agent, solvent type and volume, vortex time and salting out effect were optimized. Surface and normal probability plots were drawn for the variables using the optimization data. Microwave-assisted digestion of samples was performed before the extraction procedure. L-cysteine was found to be more effective as a ligand for Hg(II). Five different SUPRASs were prepared and used for the extraction of Hg(II). A 1-decylamine/thymol/water at a 1:2:1 molar ratio assisted by a salting effect was found most effective for optimal extraction. Limits of detection and limit of quantification were found 0.6 μg L−1 and 2.0 μg L−1 with a very good linearity range of 2–350 μg L−1. Intra-day and inter-day precisions were in the range of 1.8–4.0 % with a preconcentration factor 150. The accuracy of the method estimated by analysis of certified reference materials was 96–98.5 %. Finally, the new method was used for the determination of Hg(II) in real water, food samples, and certified reference materials (NIST, IAEQ/W-4(simulated freshwater), and DORM-4; fish protein).

Optimization of a pre-concentration method for the analysis of mercury isotopes in low-concentration foliar samples.

Hg isotope analysis in samples from background regions is constrained by the presence of low Hg concentration and therefore requires a pre-concentration method. Existing Hg pre-concentration methods are constrained by long sample processing time and limited sample loading capacity. Using foliar samples as a test case, an optimized Hg pre-concentration method is presented that involves the microwave-assisted digestion of samples for Hg isotope analysis with the addition of a pre-digestion step. Microwave-digested foliar samples and CRMs were transferred to an impinger, reduced with SnCl2, and collected in a 2.25 mL concentrated inverse aqua regia (3:1 HNO3:HCl, v/v). This resulted in an optimal acid concentration in the solution ideal for analysis on MC-ICP-MS. The time for purging with Hg-free N2 was optimized to 30 min and the efficiency of the pre-concentration method was tested using a combination of approaches. Tests performed on pure reagents and matrix of foliar samples spiked with 197Hg radiotracer showed recoveries averaging 99 ± 1.7% and 100 ± 3.0%, respectively. Mercury at concentrations as low as 1.83 ng g-1 was pre-concentrated by digesting aliquots of foliage samples in individual digestion vessels. Recoveries following their pre-concentration averaged 99 ± 6.0%, whereas recoveries of 95 ± 4.7% and 95 ± 2.5% were achieved for NIST SRM 1575a (pine needle) and reagents spiked with NIST SRM 3133, respectively. Analysis using multicollector-ICP-MS showed low fractionation of δ202Hg during sample pre-concentration with no significant mass-independent fractionation. The proposed method is a relatively simple and robust way to prepare Hg samples for Hg isotopic analysis and is suitable even for complex biological matrices.

Multi-year monitoring of atmospheric dust fall as a sink for lead in an agro-industrial and petrochemical city of Argentina. Geo-accumulation and ecological risk assessment.

A multi-year monitoring data set of potentially harmful elements (PHEs), which are present in the chemical composition of atmospheric settleable particulate matter (SPM) in the urban, industrial and port areas in Bahía Blanca, was studied in order to assess potential ecological risk. The selected PHEs were metal elements of local and regional environmental importance (Cd, Cr, Cu, Ni, Pb, and Zn). Seventeen sampling campaigns were carried out between April 2013 and September 2019. After the microwave-assisted acid digestion of samples, the total contents of the PHEs were determined by ICP-OES. The annual dry deposition rate, the indexes associated with the potential ecological risk (RI) and the degree of geo-accumulation (Igeo) of each PHE were calculated. The results indicated that: (a) there are 3 groups (I, II, III) of PHEs with differentiated concentration levels, ranked I (Pb > Zn > Cu) > II (Cr ≈ Ni) > III (Cd) (p < 0.01) in all the studied areas; (b) the median of the total deposition rate was 1mgcm-2. month-1 with a significant relative contribution of Pb; (c) a considerable increase in geo-accumulation of Pb indicated that SPM was functioning as a sink for Pb, and also reflected a significant progressive increase in the potential ecological risk in all sites (p < 0.01); and (d) there were chemometrically identified potential sources of Pb, Cu and Zn emissions that would be associated mainly to the resuspension of dust from geogenic, industrial and urban origin, and to a lesser extent, to other gaseous emissions of the industrial sector. This work highlights three major aspects of environmental assessment: (a) the value of continuous monitoring as an important tool to detect long-term trends; (b) the importance of the role of dust fall as a useful environmental indicator of lead geo-accumulation; and (c) the great utility of geo-accumulation and potential ecological risk indices as rapid quantitative assessment tools of environmental pollution.

Microwave-assisted digestion method using diluted nitric acid and hydrogen peroxide for the determination of major and minor elements in milk samples by ICP-OES and ICP-MS

A novel method for microwave-assisted digestion of milk samples using diluted HNO3and H2O2 with a single reaction chamber was developed for elemental analysis by ICP-based techniques. The optimal conditions for digestion were 0.25 g of sample mass, 6 mL of 0.1 molL−1HNO3and 2 mL of 30% H2O2 at 250 ℃ and 160 bar. The optimized procedure resulted in low residual carbon content and residual acidity of 260 mgL−1 and 0.06 mol L−1, respectively. The limits of detection ranged from 0.286ոg g−1(Ca) to 82.990ոg g−1(Fe). In addition, the proposed method was considered an excellent green analysis method with a final score of 87 based on the analytical Eco-Scale. Finally, the method was validated and applied to the determination of Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sb, Se, and Zn in milk samples from South Korea.

Determination of Macro, Micro and Toxic Elements using Argon-Based Plasma Spectroanalytical Methods in order to support Brazilian Regulations on Inorganic Constituents in Infant Foods

Children's cereal-based foods and supplements are widely consumed by newborn and infant population. The Resolution RDC no. 193/2017 of the Brazilian National Health Surveillance Agency (ANVISA) established maximum tolerated limits (MTL) for toxic elements in infant foods aiming to control health risks. Complementarily, the determination of macro and microelements based on values of recommended daily intake (RDI) is regulated by Resolution RDC no. 269/2005. Two analytical procedures were developed using inductively coupled plasma mass spectrometry (ICP-MS) for determination of As, Cd, Sn and Pb and inductively coupled plasma optical emission spectrometry (ICP OES) for determination of Ca, Fe, K, Mg, Mn, Na, P and Zn attending both Brazilian regulations. Microwave-assisted acid digestion of solid samples was carried out in closed vessels using 7 mol L-1 HNO3. Two rice flours reference materials as well as addition and recovery experiments were applied to check accuracy. Recoveries ranged from 70 to 128% for ICP OES and from 82 to 128% for ICP-MS using internal standardization. The analytical procedure presented LOQs lower than maximum limits allowed by both regulations. Fifteen samples of cereal-based infant foods were analyzed and all analyte concentrations were lower than the respective MTLs recommended by RDC no. 193, except to Pb concentration in one milk flour sample. According to the RDI established by RDC no. 269 and the average concentrations of Ca, Fe, K, Mg, Mn, P and Zn in samples, it was possible to assign a minimum mass value of food that meets the recommendations of the Brazilian resolution for different population groups.

Multi-element determination in chocolate bars by microwave-induced plasma optical emission spectrometry

Macro- and microelement determination in chocolate bars by microwave-induced plasma optical emission spectrometry (MIP OES) was evaluated after microwave-assisted sample digestion. Optimization of the sample digestion was carried out, and the recommended conditions were obtained at a temperature of 190 °C, with a digestion time of 40 min and in a mixture constituted by 2.3 mL of nitric acid, 1.0 mL of hydrogen peroxide and 4.7 mL of water. The method was applied in the analysis of chocolate bars, and the concentration ranges of the elements determined were (in mg kg−1): Ca (653–3096); Cr (<0.6–2.8); Cu (<0.16–19.5); Fe (<1.6–227); Mg (147–2775); K (3554–8573); Mn (<0.03–25.2); Na (45.6–1095); Ni (3.2–10.2); P (1111–22594) and Zn (4.8–33.3). The association of the proposed microwave-assisted acid digestion with the MIP OES technique was adequate for multi-element determination in chocolate bars for routine analysis.

Minerals and heavy metals in Labisia pumila var. alata folia of Selected Geographic Origins

Labisia pumila var. alata leaves (LP) with a long history of use folk remedy and endemic to the Malay Archipelago, is now supplied worldwide as ingredient of functional foods and beverages. Minerals and heavy metal concentrations in Labisia pumila var. alata folium (LP) of selected geographic origin based on microwave-assisted sample digestion and inductively coupled plasma mass spectrometry (ICP-MS) were determined.n Fifteen elements comprising minerals (Ba, Ca, Cr, Co, Cu, Fe, K, Mg, Na, Ni, Rb and Zn) and heavy metals (As, Cd and Pb) were analyzed with an inductively coupled plasma – mass spectrometer (ICP-MS). The highest nutrient concentration was measured in LP from Tilu Mountain (Cu, Na, K, Mg and Zn). The highest values of Ba, Ca, Co, Cr and Fe were detected in LP from Raub. Ni and Rb were highest in LP from Cibeundey Village. As was highest in LP from Raub (0.04 ± 0.00 mg/kg). The highest Pb contents were in LP from Tilu Mountain (2.90 ± 0.10 mg/kg) and LP from Halimunan-Salak Mountain (3.12 ± 0.03 mg/kg), all of which were well within the permissible limits as specified by the U.S. FDA for edible plant parts. n

Greening microwave-assisted acid digestion of animal feed samples

The combination of dilute nitric acid digestion followed by recovery of the acid digests, represents steps towards green chemistry approaches: “reduce the use, recycle and reuse”, strictly following the major green chemistry recommendations.

Environmental biomonitoring of essential and toxic elements in human scalp hair using accelerated microwave-assisted sample digestion and inductively coupled plasma optical emission spectroscopy

Human scalp hair samples were collected and used to assess exposure to toxic elements and essential elements in the state of North Carolina, USA using accelerated microwave assisted acid digestion and inductively coupled plasma optical emission spectroscopy (ICP-OES). The figures-of-merit of the ICP-OES were appropriate for elemental analysis in scalp hair with detection limits as low as 0.0001 mg/L for Cd, good linearity (R2 > 0.9978), and percent recoveries that ranged from 96 to 106% for laboratory-fortified-blanks and 88–112% for sample spike recovery study. The concentrations of essential elements in scalp hair were larger than those of toxic elements, with Ca having the highest average concentration (3080 μg/g, s = 14,500, n = 194). Some of the maximum concentrations observed for As (65 μg/g), Ni (331 μg/g), Cd (2.96 μg/g), and Cr (84.6 μg/g) in individual samples were concerning, however. Samples were statistically analyzed to determine the influence of race, gender, smoking habits, or age on the elemental concentrations in scalp hair. Higher concentrations of essential elements were observed in the scalp hair of Caucasians, females, and non-smokers, and the differences were often significant at a 90% confidence level. Several pairs of essential elements, for example Ca-K, Ca-Mg, and Ca-Zn, were strongly correlated in Caucasian hair but uncorrelated in African-American hair. Similarly, essential elements were strongly correlated in female hair but weakly correlated in male hair. Toxic element pairs (As-Cd, As-Se, Pb-As, and Se-Cd) were strongly correlated in the hair of smokers but uncorrelated in that of non-smokers, suggesting that cigarette smoke is a common source of toxic elements in humans.

High-Throughput ICP-MS and Chemometrics for Exploring the Major and Trace Element Profile of the Mediterranean Sepia Ink

Microwave-assisted sample digestion and inductively coupled plasma-mass spectrometry (ICP-MS) were considered for exploring major and trace elements in the Mediterranean Sepia ink. The present work aims to (a) fully validate the employed ICP-MS method and compare the Hg determinations by ICP-MS with those obtained by a direct mercury analyzer (DMA) and (b) interpret quantitative data by chemometrics and perform a risk/benefit analysis for assessing the quality/safety of Sepia ink. DMA gave Hg determinations similar to the ICP-MS counterpart (p > 0.05), confirming its reliability for food analysis. Sepia ink demonstrated to be both a reservoir of “healthy” elements and a sink of potential toxic metals. In fact, a good contribution of major and essential trace metals to the established RDAs was revealed, and, at the same time, potentially toxic elements showed to accumulate depending upon the environmental conditions, although not representing a risk for human consumers.

Investigation of analyte losses using microwave-assisted sample digestion and closed vessels with venting

Microwave-assisted sample digestion using closed vessels is becoming the standard for trace analysis because contamination and losses can be better controlled. Gases are generated during digestion and there is an increment of the internal vessel pressure. Consequently, vessels venting may occur depending on the design of the vessel and the maximum pressure it can stand for. In the present work it was observed that it is possible to allow venting during the digestion without losing volatile analytes, such as As, when properly controlling heating and chemical conditions. Recoveries for As in certified reference materials of animal tissues ranged from 94 to 112% despite mass losses as high as 62%mm−1 observed in the digests. However, for Hg(II) in medium containing chlorides recoveries were poor. The efficiency of digestion was measured by determination of organic carbon contents in digests and they ranged from 0.10 to 0.19% for plant and animal tissues. The temperature gradient along the vessel height is important for avoiding losses of volatile elements.

Trace element biomonitoring in hair of school children from a polluted area by sector field inductively coupled plasma mass spectrometry

In the current study, a biomonitoring of 18 hair trace elements (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb, Se, V, Zn, Ca, Na and P) in school children from Leningradskaya Oblast’ is reported. A case group, residing in a proximity to the toxic waste disposal grounds (Krasniy Bor), has been assessed vs. controls from a non-urban settlement Seltso. In total, 166 hair samples were analysed using double focusing sector field inductively coupled plasma mass spectrometry after microwave-assisted sample digestion with nitric acid. For the determination of Ca, Na and P inductively coupled plasma optical emission spectrometry was employed. For the validation, a reference material and spiked hair samples were analysed. The data obtained was processed using parametric statistics and factor analysis. Determined concentrations of trace elements were in agreement with the previously published results on chemically polluted areas. In the case group, linear correlations between Al, Cr, Cu, Fe, Ni and V were observed. Also, these metals correlated to selenium hair content in the case group. Additionally, a correlation between hair Se and P was observed in the case subjects. Several gender differences in trace content were observed within each group. However, no age- or body index-related difference was found. The obtained results show that closely located waste disposal grounds intensifies trace element exposure in school children of Krasniy Bor. However, judging from rather high values for the controls, total environmental status of the region seems to be unstable, so additional monitoring and chemical safety measures are required.

Levels of platinum group elements and rare-earth elements in wild mushroom species growing in Poland

Due to limited data-describing abilities of mushrooms to accumulate platinum group elements (PGEs) and rare-earth elements (REEs), the aim of this study was to determine, by inductively coupled plasma optical emission spectrometry followed by microwave-assisted sample digestion by nitric acid, the content of these elements in 20 mushroom species (10 above ground and 10 growing on wood), mostly edible, collected near a busy trunk road. The highest content of PGEs in above-ground mushroom species was observed in Lepista gilva and Suillus bovinus fruit bodies (0.38 ± 0.05 and 0.37 ± 0.03 mg kg−1 DW, respectively), while in mushrooms growing on wood, the highest content was observed in Pleurotus ostreatus (0.35 ± 0.04 mg kg−1 DW). The mean content of PGEs for both these groups was 0.23 ± 0.08 and 0.26 ± 0.07 mg kg−1 DW, respectively. The highest content of REEs in Suillus luteus and Tricholoma equestra was 5.03 ± 0.50 and 2.18 ± 0.56 mg kg−1 DW, respectively, but within mushrooms growing on wood in Ganoderma applanatum fruiting bodies it was 4.19 ± 0.78 mg kg−1 DW. Mean contents of REEs were 1.39 ± 1.21 and 1.61 ± 0.97 mg kg−1 DW in above-ground species and species growing on wood, respectively. Generally, the group of mushroom species growing on wood was capable of slightly higher accumulation of both REEs and PGEs. No limits have been established for both the groups until now.

Determination of arsenic in Helianthus annuus l. by hydride generation atomic absorption spectrometry

&lt;p&gt;This study represents new research on the sunflower (&lt;em&gt;Helianthus annuus&lt;/em&gt; L.) including new data on arsenic contents in Ergene River Basin. In this study, the concentrations of arsenic in soil and sunflower plant have been investigated. The area has suffered significant pollution as a result of industrial and agricultural activities in Turkey. Sunflower are produced in this area that approximately %70 in Turkey. Arsenic concentrations in &lt;em&gt;H.annuus&lt;/em&gt; L. plants collected from different regions in Turkey were determined by hydride-generation atomic absorption spectrometry (HGAAS) after microwave-assisted acid digestion of samples. The accuracy of the techniques was evaluated by using certified reference materials; NIM-GBW07404 (GSS-4) for soil and WEPAL-IPE-168 for sunflower plant. The precision of the technique, expressed as relative standard deviation, was less than 8% for HGAAS. Concentrations of total arsenic in root, seed, and soil collected from different regions were in the range of 0.01&amp;ndash;2.82 mg&amp;nbsp;kg&lt;sup&gt;&amp;minus;1&lt;/sup&gt; for &lt;em&gt;H. annuus &lt;/em&gt;L. growing in Turkey in 2010 and 2011.&lt;/p&gt;

ULTRASOUND-ASSISTED EXTRACTION FOR COLORIMETRIC DETERMINATION OF IRON IN SOIL: A COMPARISON WITH INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY

A simple procedure for ultrasound-assisted extraction and colorimetric determination of iron in soil samples was developed. The iron concentration in the analyzed samples was determined by the colorimetric method and the results compared with inductively coupled plasma mass spectrometry (ICP-MS). Fifteen soil samples were analyzed and the iron concentration results compared with those obtained by ICP-MS using microwave-assisted sample digestion. The proposed procedure showed good efficiency for iron extraction and the results obtained by colorimetric determination exhibited good agreement with ICP-MS. Moreover, ultrasound-assisted extraction and colorimetric determination is a simple, fast and low-cost procedure for application in routine analysis.

Determination of Rhodium in Rhodium-Loaded Carbon Catalysts Using Microwave-Assisted Sample Digestion and ICP-OES

A novel method for the determination of rhodium in rhodium-loaded carbon catalyst samples was established by inductively coupled plasma atomic emission spectrometry after samples digested by microwave oven with aqua regia. Such experiment conditions were investigated as the influence of sample digestion methods, digestion time, digestion temperature and interfering ions on the determination. Under the optimized conditions, the limits of detection (LODs) of Rh for tested solutions were 9 ng mL-1. The relative standard deviations (RSDs) for Rh were 2.11 (CRh = 1 mg L-1, n = 7). The linear ranges of calibration graphs for Rh were 0 ~ 150.00 mg L-1. The proposed method was applied to determine the practical samples with good recoveries and satisfactory results.

Determination of Palladium in Waste Palladium-Loaded Carbon Catalyst Samples Using Microwave-Assisted Sample Digestion and ICP-OES

A novel method for the determination of palladium in palladium-loaded carbon catalyst samples was established by inductively coupled plasma atomic emission spectrometry after samples digested by microwave oven with aqua regia. Such experiment conditions were investigated as the influence of sample digestion methods, digestion time, digestion temperature and interfering ions on the determination. Under the optimized conditions, the linear range of calibration graph for Pd was 0 ~ 250.00 mg L-1, and the recovery was 97.89% ~ 102.00%. The relative standard deviation (RSDs) for Pd was 1.93 %. The proposed method was applied to determine the same samples with atomic absorption spectrometry with the results consistently, which is suitable for the determination of palladium in palladium-loaded carbon catalyst samples.

Simultaneous determination of As and Sb in soil using hydride generation capacitively coupled plasma microtorch optical emission spectrometry – comparison with inductively coupled plasma optical emission spectrometry

A method using a miniature analytical system based on hydride generation capacitively coupled plasma microtorch optical emission spectrometry with a QE65 Pro microspectrometer was developed and evaluated for the simultaneous determination of As and Sb in soil samples. The use of this microspectrometer allows the examination of the spectral range between 190 and 220 nm where the continuum background emission of the plasma is low and the most intense resonance lines As 193.759; 197.262 nm and Sb 206.833; 217.581 nm are located. The method involves microwave-assisted digestion of samples in aqua regia, prereduction of As(V) and Sb(V) to their (+3) species with 0.3% L-cysteine by heating in a boiling water bath at 90 ± 5 °C and hydride generation in 0.01 mol L−1 HCl (pH = 2.00 ± 0.01) medium with 0.5% NaBH4 solution. The method was optimized in order to provide the simultaneous determination of As and Sb. The figures of merit were evaluated at different emission wavelengths under the optimum conditions of plasma microtorch operation (10 W, 150 mL min−1 Ar), and the best performances were obtained at 193.759 nm (As) and 217.581 nm (Sb). The figures of merit of the method were compared to those of the traditional hydride generation inductively coupled plasma optical emission spectrometry taken as a reference method. Analysis of CRMs revealed recoveries of 101 ± 9% As and 102 ± 3% Sb comparable to 102 ± 7% As and 98 ± 4% Sb in the reference method. The precision of determinations was 2–10% for 90–210 mg kg−1 As and 40–130 mg kg−1 Sb, close to 3–8% in hydride generation inductively coupled plasma optical emission spectrometry. The Bland and Altman test performed on 10 soil samples indicated no significant difference between the results obtained by the two methods, so that the miniature analytical system could be successfully applied for As and Sb monitoring in environmental samples. The proposed method is attractive in terms of analytical costs due to limited consumption of high purity HCl, power and Ar to sustain the plasma, and therefore more advantageous than hydride generation inductively coupled plasma optical emission spectrometry.

Effect of simultaneous cooling on microwave-assisted wet digestion of biological samples with diluted nitric acid and O2 pressure

The present work evaluates the influence of vessel cooling simultaneously to microwave-assisted digestion performed in a closed system with diluted HNO3 under O2 pressure. The effect of outside air flow-rates (60–190m3h−1) used for cooling of digestion vessels was evaluated. An improvement in digestion efficiency caused by the reduction of HNO3 partial pressure was observed when using higher air flow-rate (190m3h−1), decreasing the residual carbon content for whole milk powder from 21.7 to 9.3% (lowest and highest air flow-rate, respectively). The use of high air flow-rate outside the digestion vessel resulted in a higher temperature gradient between liquid and gas phases inside the digestion vessel and improved the efficiency of sample digestion. Since a more pronounced temperature gradient was obtained, it contributed for increasing the condensation rate and thus allowed a reduction in the HNO3 partial pressure of the digestion vessel, which improved the regeneration of HNO3. An air flow-rate of 190m3h−1 was selected for digestion of animal fat, bovine liver, ground soybean, non fat milk powder, oregano leaves, potato starch and whole milk powder samples, and a standard reference material of apple leaves (NIST 1515), bovine liver (NIST 1577) and whole milk powder (NIST 8435) for further metals determination by inductively coupled plasma atomic emission spectroscopy (ICP-OES). Results were in agreement with certified values and no interferences caused by matrix effects during the determination step were observed.