Microwave-assisted Wet Digestion Research Articles

Comparisons of Different Digestion Methods for Heavy Metal Analysis from Fruits

Fruit juices are produced in home or industrially from horticultural crops by pressing the liquid part. They are rich in sugar, vitamins, and minerals like iron, copper, potassium, folate minerals, and vitamins A, B, and C which are essential for giving the body the nutrients it needs to stay healthy since fruits contain vital mineral components like copper (Cu), iron (Fe), and manganese (Mn), which is necessary for human growth and respiration. However, they may have heavy metals which may poison health risk and toxic even the presence is in little amount. Since fruit juices doesn’t pass through different processes, except extracting the liquid from the fruits of vegetables contamination and heavy metals affect human health. Before determination of heavy metals different procedures are applied for analysis. Digestion is the key component for determination of heavy metals from different samples. In this paper we are concerned on wet digestion methods for analysis. Closed system wet digestion is preferred since it lower the risk of contamination. There are different wet digestion types. Some of them are conventional wet digestion, ultraviolet digestion, ultrasound-assisted acid decomposition, conventional heating, microwave-assisted wet digestion etc. From thus, microwave digestion procedure was preferred for the digestion of samples for determination of heavy metals due to its ability to oxidize almost all of the organic samples.

Microwave-induced combustion for further determination of potentially toxic elements in honey by ICP-MS.

Microwave-induced combustion (MIC) was proposed in this study for honey decomposition aiming for As, Cd, Hg, and Pb determination by inductively coupled plasma mass spectrometry (ICP-MS). Sample mass (up to 1.0g), absorbing solution (0.5 to 14.4mol L-1 HNO3, and H2O), heating program, and combustion aids were evaluated. The Eurachem guidelines were used for method validation. The proposed method enabled combustion of a high sample mass (0.8g of honey, with 0.4g of microcrystalline cellulose and 100 µL of 6mol L-1 NH4NO3) using 6mL of an absorbing solution consisting of 1mol L-1 HNO3, which resulted in low residual carbon in solution (< 25mg L-1). Honey samples from different geographical origins were analyzed. Results showed no significant difference in comparison to other two microwave decomposition methods, based on microwave-assisted wet digestion with single reaction chamber (MAWD-SRC) and microwave-assisted wet digestion (MAWD). Standard addition experiments resulted in recoveries higher than 98%. The limits of detection ranged from 1.10 (As) to 4.60ngg-1 (Pb). In addition to using only diluted reagents and resulting in digests virtually free of interferences, the proposed method was faster (< 30min) than most of those presented in the literature.

Preparation of Food Samples Using Homogenization and Microwave-Assisted Wet Acid Digestion for Multi-Element Determination with ICP-MS.

Sample preparation is crucial for elemental determination, and various techniques are available, one of which involves homogenization followed by acid digestion. Special care is required during sample handling in the preparation stage to eliminate or minimize potential contamination and analyte loss. Homogenization is a process that simultaneously reduces particle size and uniformly distributes sample components. Following homogenization, the sample undergoes acid digestion, wherein it is digested with acids and auxiliary chemicals at elevated temperatures, transforming solid samples into a liquid state. In this process, metals in the original sample react with acids to form water-soluble salts. Samples prepared through acid digestion are suitable for elemental analysis using techniques such as inductively coupled plasma mass spectrometry, inductively coupled plasma optical emission spectroscopy, atomic absorption spectroscopy, electrochemical methods, and other analytical techniques. This work details the preparation of food samples for multi-element determination using inductively coupled plasma mass spectrometry. The step-by-step procedure involves the homogenization process using a laboratory-sized mixer with ceramic blades, followed by acid digestion in closed vessels using microwave-assisted wet acid digestion. A mixture of 5.0 mL of 68 wt% HNO3 and 1.0 mL of 30 wt% H2O2 serves as an auxiliary reagent. This guide provides an explanation of the processes involved in both stages.

Microwave-assisted UV digestion of starch and skimmed milk powder: Environmentally friendly protocol for essential and toxic elements determination

The present work evaluated a microwave-assisted wet digestion method using diluted HNO3 with in situ UV radiation for the digestion of starch and skimmed milk powder for further metals determination by spectrometric plasma-based techniques. The sample digestion was conducted using an in situ UV lamp (electrodeless discharge lamp), and the digestion efficiency was improved by employing O2 (20 bar) and 2 mL 30 % H2O2 as auxiliary reagents. The accuracy of the proposed digestion method was evaluated by metals determination (Ca, Cd, Cu, Fe, K, Mg, Mo, Mn, Na, Pb, and Zn) in certificated reference material, which agreed with certified values (Student t-test <0,05). With the use of a UV lamp an environmentally friendly protocol was developed for starch and skimmed milk powder digestion using 0.1 mol L−1 HNO3 with auxiliary reagents (H2O2 or O2). The RCC value ranged from 0.9 to 1.2 % (starch and skimmed milk powder, respectively). The simultaneous cooling approach further improved the digestion efficiency (RCC <0,3 % for both samples), allowing to use milder digestion conditions, or even just water, being environmentally friendly, reducing the waste generation and reagents consumption, allowing food quality control through a greener approach.

Greening microwave-assisted digestion method using hydrogen peroxide for determination of elemental impurities by ICP-OES in antihypertensive active pharmaceutical ingredients

Microwave-assisted wet digestion (MAWD) using only H2O2 was proposed for oxidizing active pharmaceutical ingredients (APIs) for hypertension treatment and subsequent determination by inductively coupled plasma optical emission spectrometry (ICP-OES). Diltiazem hydrochloride (DIL) presented the most refractory characteristic for oxidation using MAWD-H2O2. This proposed MAWD-H2O2 method was validated for specificity, accuracy, and precision according to United States Pharmacopeia (USP) Chapter 233 guidelines. Regarding specificity, the most sensitive emission lines were utilized to analyze all elemental impurities in the digests, and no significant spectral interferences were observed. Sample masses of 500 mg for all APIs and a digestion temperature of 250 °C provided digests with residual carbon (RC) below 2400 mg L−1 of C. Additionally, the residual acidity of the MAWD-H2O2 digests was lower than the acidity presented by the HNO3 digests. The highest and lowest residual carbon content (RCC) for digests were observed for DIL and captopril (CAP), respectively, using MAWD-H2O2. When comparing the RCC for MAWD-H2O2 and MAWD-HNO3 digests for APIs containing aromatic rings, it was evident that H2O2 offered equivalent conditions for digesting these compounds. Accuracy tests showed recovery values of 91–110% for all elemental impurities, as recommended by USP chapter 233. Validation experiments for precision presented relative standard deviation (RSD) values below 6.4% and 10% under repeatability and intermediate precision conditions, respectively. The limits of quantification (LOQs) provided by MAWD-H2O2 are at most half of those recommended by of USP and International Council for Harmonisation of Technical Requirements (ICH). In conclusion, MAWD-H2O2 can be considered an alternative method for API digestion, aligning with green analytical chemistry principles, as it does not employ toxic reagents, minimizes waste, and the main products of H2O2 oxidation are water and oxygen. Considering the analytical Eco-Scale, the MAWD-H2O2 method scored 81, classifying it as an excellent green analysis.

Quantification of elements in dietary supplements by total reflection x‐ray fluorescence and inductively coupled plasma optical emission spectrometry

AbstractThe main purpose of this study was the comparison of the results of quantification obtained via different sample preparation approaches such as microwave‐assisted wet digestion (MAWD) and suspension preparation. Two total reflection x‐ray fluorescence (TXRF) spectrometers equipped with Mo x‐ray tubes were used to compare results obtained via two different paths of sample preparations which would further be compared to the conventional way of analysis by inductively coupled plasma optical emission spectrometry (ICP‐OES) including MAWD. Three dietary supplement samples with different sets and concentrations of elements were analyzed. The benefits and limitations of the simplified path of sample preparation were highlighted. A round‐robin test between TXRF and ICP‐OES was discussed. Accuracy as the percentage of recovery in all measurements ranged from 80 to 120. Precision for all results did not exceed 8% for TXRF and 5% for ICP‐OES. Limits of quantification by TXRF are ranged from 1 to 0.01 mg/pill for different elements. It was shown that suspension preparation of samples might be a useful response to increasing demand for quality control of dietary supplements since it is less time consuming and cost efficient.

Ultrasound-assisted Extraction Method for Element Determination in Lignocellulosic Biomass

In this work, a sample preparation method based on ultrasound-assisted extraction (UAE) for the determination of Al, Ba, Ca, Fe, K, Mg, Mn, Na, P, Sr, and Zn in lignocellulosic biomasses (sugarcane bagasse, eucalyptus wood residues, and pine wood residues) was evaluated. Reference values were achieved following the EN ISO 16967, which was based on a microwave-assisted wet digestion sample preparation method for further element determination by inductively coupled plasma optical emission spectrometry (ICP OES). The optimizations for the proposed UAE method were performed using 250 mg of sugarcane bagasse sample, where the ultrasonic bath frequency (25, 35, 37, 45, 80, and 130 kHz), and acoustic amplitude (50, 70 and 100%) were evaluated. After selecting the most efficient extractant solvent (20 mL of 1 mol L-1 of H2O2, HNO3, H2SO4, H2O, or CH2O2), the extraction temperature (20, 50, or 70 ºC) and time (15, 30, or 40 min) were evaluated. The most efficient extraction condition using the UAE method employed 45 kHz (70% amplitude), 20 mL of 1 mol L-1 of H2SO4, and 50 °C for 30 min. The optimized UAE was used for extraction and subsequent element determination in residues of pine wood and eucalyptus wood. Although poor recoveries were observed for Al, Ba, and Fe (lower than 75%), the results for Ca, K, Mg, Mn, Na, P, Sr, and Zn were in agreement (Student t-test, 95% confidence level) with those obtained by EN ISO 16967. Therefore, the proposed UAE method proved to be efficient for the determination of most of the evaluated elements in lignocellulosic biomasses with different matrix complexity, employing milder extraction conditions and diluted reagents.

Mass spectrometric investigations into 3D printed parts to assess radiopurity as ultralow background materials for rare event physics detectors

New data are reported for polyvinylidene fluoride (PVDF), polyphenylene sulfide (PPS), and two forms of polyetherimide (PEI, branded ULTEM 1010 and 9085). Data for starting filaments and both simple and complex printed parts are reported. PVDF filaments and simple printed beads, were found to have values of approximately 30 and 50 ppt for Th-232 and U-238, respectively, while a more complex spring clip part had slightly elevated Th-232 levels of 65 ppt, with U-238 remaining at 50 ppt. PPS filament was found to have concentrations of 270 and 710 ppt for Th-232 and U-238, respectively, and were not chosen to be printed as those levels were already higher than other material options. ULTEM 1010 filaments and printed complex spring clip parts were found to have concentrations of around 5 and 7 ppt for Th-232 and U-238, respectively, illustrating no significant contamination from the printing process. ULTEM 9085 filaments were found to have concentrations of around 9 and 5 ppt for Th-232 and U-238, respectively, while the printed complex spring clip part was found to have slightly elevated concentrations of 25 and 7 ppt for Th-232 and U-238, respectively. These results were all obtained using a novel dry ashing method in crucibles constructed of ultralow background electroformed copper or, when applicable, microwave-assisted wet ashing digestion. Samples and process blanks were spiked with Th-229 and U-233 as internal standards prior to dry/wet ashing and determinations were made by inductively coupled plasma mass spectrometry (ICP-MS). In order to maintain high radiopurity levels, pre-cleaning the filaments before printing and post-cleaning the parts is recommended, although the printing process itself has shown to contribute very minute amounts of radiocontaminants.

A miniaturized liquid-liquid extraction method for further Na, K, Ca, and Mg determination in crude oil by FAAS

In this study, a miniaturized liquid-liquid extraction (LLE) method for pre-concentration of Na, K, Ca, and Mg in crude oil was proposed. Analytes in crude oil were quantitatively extracted to the aqueous phase, followed by flame atomic absorption spectrometry (FAAS) determination. The following parameters were evaluated: type of extraction solution, sample mass, heating temperature and time, stirring time, centrifugation time, and the use of toluene and chemical demulsifier. Accuracy was evaluated by comparing the results obtained by the proposed method (LLE-FAAS) with those obtained after high-pressure microwave-assisted wet digestion and FAAS determination (reference values). No statistical difference was observed between the reference values and those using the optimized conditions for LLE-FAAS: 2.5 g of sample; 1000 μL of 2 mol L−1 HNO3, 50 mg L−1 of chemical demulsifier in 500 μL of toluene, 10 min of heating at 80 °C, 60 s of stirring, and 10 min of centrifugation. Relative standard deviations were lower than 6%. The limits of quantification (LOQ) were 1.2, 1.5, 5.0, and 0.50 μg g−1 for Na, K, Ca, and Mg, respectively. The proposed miniaturized LLE method presents several advantages, such as ease-of-use, high throughput (up 10 samples can be processed per 1 h), uses a high sample mass reaching low LOQs. In addition, the use of a diluted solution for extraction reduces the amount of reagents (around 40 times) and consequently laboratory residue generation, becoming an environmental friendly method. Suitable LOQs were achieved for analyte determination at low concentration even using a simple and low-cost sample preparation system (miniaturized LLE method) and a relatively low-cost determination technique (FAAS), avoiding the use of microwave ovens and more sensitivity techniques, which are required for routine analyses.

Fast and green microwave-assisted digestion with diluted nitric acid and hydrogen peroxide and subsequent determination of elemental composition in brown and white rice by ICP-MS and ICP-OES

For the elemental determination of rice, a microwave-assisted sample preparation method employing diluted HNO3 and H2O2 under high temperature and pressure was developed in a rapid and eco-friendly manner. The analysis was performed using inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectrometry (ICP-OES). At 280 °C and 160 bar, the optimal condition for microwave-assisted wet digestion in a single reaction chamber was achieved with a mixture consisting of 3 mL of 0.1 mol L−1 HNO3 and 5 mL of 30% H2O2 (0.25 g rice sample). The optimized procedure yielded a low residual acidity (RA) of 0.017 mol L−1 and low residual carbon content (RCC) of 355 mg L−1. The limits of detection (LODs) were from 0.159 (Sb) to 9.863 (Fe) μg kg−1. Additionally, the developed method received a total score of 85 on the analytical Eco-Scale, indicating an excellent green analysis method. Furthermore, the method was validated by determining 19 elements (Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Ni, P, Pb, S, Sb, Se, and Zn) in brown and white rice cultivated in South Korea.

Determination of Some Elements in Canned and Frozen Vegetables sold in Balıkesir (Türkiye) Markets and Nutritional Assessment

In this work, determination of some elements including Pb, Ni, Ba, Fe, Zn, Mg, Mn, Al, Cu, Mo, Ca, B, Cr, Cd, V and Co were carried out in some canned and frozen vegetable samples sold in Balıkesir, Türkiye. The study covered randomly chosen 13 canned and frozen samples such as green peas, okra, shell bean, sweet corn, green beans, garniture and tomato paste. Mineralization of the samples was achieved using microwave assisted wet digestion in closed vessels. The element contents were determined using ICP OES. The element contents were between 0.16-1.86 mg kg-1 for Ni; 0.33-5.02 mg kg-1 for Ba; 4.20-32.22 mg kg-1 for Fe; 1.65-14.64 mg kg-1 for Zn; 124.83-1016.79 mg kg-1 for Mg; 0.87-4.99 mg kg-1 for Mn; 0.32-1.74 mg kg-1 for Al; 0.78-14.97 mg kg-1 for Cu; 0.38-4.24 mg kg-1 for Mo; 42.60-1607.40 mg kg-1 for Ca and 0.96-7.56 mg kg-1 for B. Additionally, Pb was determined in only frozen green peas as 1.3±0.1 mg kg-1. In general, the highest element contents were found in frozen samples. In terms of nutritional assessment, estimated daily intakes of the elements were compared with recommended dietary allowances (RDA), nutrition reference values (TFC) and daily tolerable upper intake levels (UL) which were established by World Health Organization, Turkish Food Codex and Institute of Medicine, respectively. The results showed that the element contents of the analysed samples did not exceeded the permissible limits set by various health organizations. It is concluded that the contamination of these products may be an important threatening for public health. Therefore, monitoring of these samples should be a vital strategy for food industry.

Validation of microwave-assisted wet digestion of natural rubber for ICP-AES mineral analysis

Validation of microwave-assisted wet digestion of natural rubber for ICP-AES mineral analysis

Development of Green Methods for the Determination of Elemental Impurities in Commercial Pharmaceutical Tablets

In this study, two methods based on the use of diluted acids were developed: microwave-assisted wet digestion (MAWD) and microwave-assisted ultraviolet digestion (MAWD-UV). These methods are evaluated for the digestion of oral pharmaceutical drugs and further determination of elemental impurities from classes 1 (As, Cd, Hg and Pb) and 2A (Co, Ni and V) by inductively coupled plasma optical emission spectrometry (ICP-OES). Commercial drugs for the treatment of type 2 diabetes are used. No prior comminution is performed. For MAWD, the optimized conditions were 2 mol L−1 or 3 mol L−1 HNO3, 1 mL of 50% H2O2 and a 45 min or 55 min irradiation program. For MAWD-UV, the condition using 1 mol L−1 HNO3, 1.6 mL of 50% H2O2 and a 55 min irradiation program enabled the digestion of all samples. In this way, efficient methods are proposed for the digestion of commercial pharmaceutical tablets for further determination of class 1 and 2A elemental impurities (ICH Q3D guidelines).

Microwave-Assisted Solid Sampling Analysis Coupled to Flame Furnace Atomic Absorption Spectrometry for Cd and Pb Determination in Food-Contact Polymers

Microwave-assisted solid sampling analysis coupled to flame furnace atomic absorption spectrometry (MW-SS-FF-AAS) was used for Cd and Pb determination in food-contact polymer samples, with the aim of minimizing reagents and laboratory waste. Operational parameters, such as the FF tube design, the oxygen flow rate, the flame stoichiometry, the sample mass, among others, were evaluated and optimized. Calibration was performed using only reference solutions, and the limits of quantification were 1.7 and 4.6 μg g−1 for Cd and Pb, respectively. Accuracy was assessed by the analysis of certified reference materials (CRMs), and by comparison with the results obtained by inductively coupled plasma mass spectrometry after microwave-assisted wet digestion. The MW-SS-FF-AAS results for the CRMs showed no statistical difference with the certified values, and good agreement was observed with the results of the digestion method. The MW-SS-FF-AAS method was considered suitable for Cd and Pb determination in food-contact polymers. The concentrations of Cd and Pb in the analyzed samples varied from &lt;1.7 to 628 μg g−1, and from &lt;4.6 to 614 μg g−1, respectively. As sample digestion is not necessary, the use of concentrated acids can be avoided by using the proposed MW-SS-FF-AAS method, greatly reducing waste generation.

Development and Validation of an Analytical Method for Determination of Al, Ca, Cd, Fe, Mg and P in Calcium-Rich Materials by ICP OES.

Four procedures based on closed-vessel microwave-assisted wet digestion with different oxidative reagents, including HNO3 (P1), HNO3 + H2O2 (P2), aqua regia (P3) and Lefort aqua regia (P4), for preparation of calcium (Ca)-rich materials prior to determination of total concentrations of Al, Ca, Cd, Fe, Mg and P by inductively coupled optical emission spectrometry (ICP OES) were compared. It was found that digestion with Lefort aqua regia (P4) provided the best results for all examined elements, i.e., precision of 0.30–4.4%, trueness better than 2%, recoveries of added elements between 99.5–101.9%, and limits of detection within 0.08–1.8 ng g−1. Reliability of this procedure was verified by analysis of relevant certified reference materials (CRMs), i.e., Natural Moroccan Phosphate Rock—Phosphorite (BCR-O32). Additionally, selection of appropriate analytical lines for measurements of element concentrations, linear dynamic ranges of calibration curves and matrix effects on the analyte response were extensively investigated. Finally, the selected procedure was successfully applied for routine analysis of other Ca-rich materials, i.e., CRMs such as NIST 1400 (Bone Ash), CTA-AC-1 (Apatite Concentrate Kola Peninsula) and NCS DC70308 (Carbonate Rock), and six natural samples, such as a dolomite, a phosphate rock, an enriched superphosphate fertilizer, pork bones, pork bones after incineration, and after steam gasification.

The Toxicological Risk Assessment of Dermal Exposure of Patients Exposed to Nickel and Chromium due to Application of Ointments with Marjoram Herb Extract (Majoranae Herbae Extractum) Available in Polish Pharmacies

For elemental impurities that have been studied for transcutaneous absorption, the available data are rarely suitable for proper toxicological risk assessment — there are multiple factors that can influence this dermal absorption. Hence, in our studies, we applied generic and conservative approach — cutaneous permitted daily exposure (CPDE) described in International Conference on Harmonisation’s Q3D Guideline on Elemental Impurities (ICH Q3D). The aim of this article is toxicological risk assessment (TRA) of dermal exposure of patients exposed to nickel and chromium due to application of ointments with Marjoram herb extract (Majoranae herbae extractum) available in Polish pharmacies (n = 5, because only five manufacturers produce this kind of pharmaceutical products in Poland). To make the appropriate TRA approach, we considered (1) raw results (metal per kg of ointment), (2) one-time administration of applied ointments, and (3) daily exposure versus CPDE. Due to the fact the concentrations of Ni generally present in cutaneous products as impurities are not considered sufficient to induce sensitization, the cutaneous and transcutaneous concentration limits (CTCLs) approach was applied for this element assessment. The toxicological analysis was carried out using microwave-assisted wet digestion with concentrated nitric acid and electrothermal atomization atomic absorption spectrometry. Our results show that the ointments with Marjoram herb extract from pharmacies in Poland represent a potential health hazard to patients; however, there may be a requirement for the monitoring of impurities of nickel in future. To the best of our knowledge, this paper is the first study about nickel and chromium content in ointments with Marjoram herb extract (Majoranae herbae extractum).

Determination of iron, nickel, and vanadium in crude oil by inductively coupled plasma optical emission spectrometry following microwave-assisted wet digestion

The complexity of crude oil samples is the primary difficulty in reliable quantitation of their metal contents. However, substantial advances in sample digestion procedures have been presented as a result of the utilization of microwave radiation. Herein, a new method based on microwave-assisted digestion (MW-AD) for the decomposition of crude oil samples has been developed for efficient determination of iron, nickel, and vanadium by inductively coupled plasma optical emission spectrometry (ICP OES). Yttrium was used as an internal standard to achieve as accurately as possible quantitation. The digestion efficiency was optimized using various HNO3 concentrations (14.5, 9.1, 6.5, and 4 mol L−1) and different volumes of H2O2 by determining the residual carbon content (RCC) and residual acidity (RA) of the final digests. The obtained results revealed that 9.1 mol L−1 HNO3, 2 mL H2O2, and sample mass of 300 mg were the appropriate compromise conditions for efficient digestion and suitable final digests since RCC values and RA were below 10% and 35%, respectively. The MW-AD method was successfully validated by the analysis of samples spiked with the target metals at different concentration levels. The results demonstrated a satisfactory recovery in the range of 95–104.2% with intra-day and inter-day relative standard deviation of less than 10%. The method was also applied to the determination of the analyte metals in crude oil samples, and the results were compared with those obtained by the application of the ASTM D5708 method as a reference method.

Advances in Sample Digestion Using Microwave-ultraviolet Radiations: Phosphorus and Sulfur Determination in Animal Feed

Background: Conventional analytical methods for phosphorus and sulfur determination in several matrices present normally analytical challenges regarding inaccuracy, detectability and waste generation. Objective: The main objective is proposing a green and feasible analytical method for phosphorus and sulfur determination in animal feed. Methods: Synergic effect between microwave and ultraviolet radiations during sample preparation was evaluated for the first time for the animal feed digestion associated with further phosphorus and sulfur determination by ion chromatography with conductivity detection. Dissolved carbon and residual acidity in the final digests were used for the proposed method assessment. Phosphorus and sulfur values were compared with those obtained using conventional microwaveassisted wet digestion in closed vessels associated with inductively coupled plasma optical emission spectrometry and with those obtained using an official method (Association of Official Analytical Chemists International). Recovery tests and certified reference material analyses were performed. Animal feeds were analyzed using the proposed method. Results: Sample masses of 500 mg were efficiently digested using only 2 mol L-1 HNO3. The results obtained by the proposed method were not differing significantly (p &gt; 0.05) from those obtained by conventional and by official methods. Suitable recoveries (from 94 to 99%), agreement with certified values (101 and 104%), and suitable relative standard deviations (&lt; 8%) were achieved. Phosphorus and sulfur content in commercial products varied in a wide range (P: 5,873 to 28,387 mg kg-1 and S: 2,165 to 4,501 mg kg-1). Conclusion: The proposed method is a green, safe, accurate, precise and sensitive alternative for animal feed quality control.

Development of an eco-friendly sample preparation protocol for metal determination in food samples: an oxygen pressurized single reaction chamber using diluted nitric acid.

Many efforts have been recently made to improve the digestion efficiency by using powerful equipment or by using an auxiliary reagent. In this work, an alternative method is reported, which explores a digestion system based on a single reaction chamber (SRC) technology pressurized with O2 for reducing the amount of acid, without impairing the digestion efficiency. Before digestion, the system was pressurized with compressed air (20 bar, 20% O2) while the temperature was evaluated from 180 up to 270 °C. The procedure was also carried out under O2 pressure (20 bar). For each temperature several acid concentrations were evaluated (0.1 to 3 mol L-1 HNO3), being possible to correlate the effectiveness of each acid concentration with temperature. The proposed method was applied to the simultaneous digestion of several organic matrices with variable content of fat, protein, and carbohydrate (whole milk powder, bovine liver, parsley, and linseed). The residual carbon content was lower than 4% (C lower than 200 mg L-1 in digests), showing the high digestion efficiency of the proposed approach. Up to 250 mg of all food matrices were digested using a sub-stoichiometric amount of HNO3 (1 mol L-1 solution), which was only achieved due to the use of O2 as an auxiliary reagent. Barium, Ca, Cu, Fe, K, Mg, Mn, Na, Sr, and Zn were determined by ICP-OES, and the accuracy was better than 95% for standard reference materials of corn bran, whole milk powder, and bovine liver. It is an important feature, being in agreement with green chemistry recommendations because very low amounts of reagents are required for sample digestion, as well as low amounts of residues are generated.

Sodium and potassium content in sports supplements based on whey protein

Diferentes marcas de três tipos de suplementos esportivos à base de proteína de soro de leite foram avaliadas: 15 do tipo à base de proteína de soro de leite, 4 "hipercalóricos" e 7 barras de proteína. Um procedimento de preparo de amostras foi estudado empregando digestão ácida assistida por micro-ondas para determinar os teores de sódio e potássio usando Espectrometria de Emissão Atômica com Chama (Fotometria de Chama). As concentrações de sódio obtidas variaram na faixa de: 0,30 a 5,9 mg/g, de 0,52 a 2,8 mg/g e de 2,3 a 5,0 mg/g para suplementos a base de proteínas do soro de leite, suplementos hipercalóricos e suplementos em barra de proteína, respectivamente. Enquanto as concentrações de potássio, variaram de: 1,3 a 13 mg/g, de 0,47 a 5,4 mg/g e de 1,7 a 12 mg/g para as mesmas amostras, respectivamente. A razão entre os níveis de sódio e potássio, um parâmetro associado à hipertensão incidente, foi calculada e mostrou que, para algumas amostras, os valores excederam a recomendação da Organização Mundial de Saúde. O método desenvolvido apresentou alta frequência analítica, com boa exatidão e precisão sendo adequado para aplicação em rotinas de controle de qualidade.