Microwave Digestion Method Research Articles

Investigation of Trace Elements in Vegan Foods by ICP-MS After Microwave Digestion.

Veganism is gaining popularity around the world day by day. Vegan nutrition is a diet in which not all animal foods are used. A vegan diet does not contain meat, fish, milk and dairy products, and eggs and consists of vegetables, fruits, grains, legumes, and nuts. Vegan diets maintain energy balances in a wide variety of plant foods. So, health problems can be seen due to nutrient and mineral deficiencies in the long-term continuation of the vegan diet. Due to insufficient intake of vitamins and minerals such as vitamin D, vitamin B12, calcium, iron, and zinc, energy and protein balance in the body may not be achieved by vegan individuals. The contents of aluminum, chromium, manganese, iron, cobalt, nickel, copper, zinc, arsenic, mercury, cadmium, and lead have been analyzed by inductively coupled plasma mass spectrometer (ICP-MS) in 10 different vegan foods purchased from Turkey. Certified reference material (1547 peach leaves) was used for validating the digestion procedure. Dry, wet, and microwave processes were compared, and it was found that the microwave digestion method was the best. Element levels in the analyzed samples were found below the legal limits. The purpose of this work is to investigate the trace element content of various foods used in vegan nutrition.

Chemical characterization methods for biodegradable organic wastes with relevance for the composting process. Case study

The study aimed to develop some methods for the compositional characterization of biodegradable waste with relevance to the composting process at the laboratory level. For testing, four waste fractions were selected, such as waste-based on dehydrated sludge, waste from parks (leaves, branches), market waste (mixture of vegetable and fruit), and cardboard waste. For metals and phosphorus, several microwave digestion methods were applied. The ammonium nitrogen content (NH4-N) was determined using a number of extraction procedures (water, CaCl2, and KCl). Three certified reference materials were used for testing the validity of the results. Recovery percentages higher than 90% were obtained. The developed and validated methods are suitable for biodegradable waste characterization used in composting processes.

A stepwise microwave synergistic pyrolysis approach to produce sludge-based biochars: Optimizing and mechanism of heavy metals immobilization

A technical approach of stepwise microwave synergistic pyrolysis (SMSP) had been proposed to produce value-added sludge-based biochar. The approach includes a conventional pre-pyrolytic stage and a sequential microwave pyrolysis stage. It is vital to adjust conventional pre-pyrolysis parameters (i.e. temperature and time) to improve immobilization effect of heavy metals and decrease toxicity of sludge-based biochar. In the paper, sludge-based biochars were generated from different pre-pyrolysis temperature (400 ∼ 700 °C) and time (5 ∼ 20 min) by the SMSP approach. For heavy metals (Cu, Zn, Ni, Pb) in biochars, residual ratio, leaching ratio, chemical fractions and ecotoxicity were measured by using microwave digestion method, toxicity characteristic leaching procedure (TCLP) method, modified european community bureau of reference (BCR) method and risk assessment code (RAC) method respectively. The results demonstrated that 600 ∼ 700 °C and 10 ∼ 20 min are more suitable pre-pyrolysis temperature and time for immobilization of heavy metals via vitrification. Heavy metals in optimum sludge-based biochar (SBC) would have high residual ratio, low leaching ratio and low ecotoxicity risk simultaneously. Residual ratio of heavy metals in SBC are about 15% higher than that in optimum conventional sludge-based biochar (CSC). And leaching ratio of heavy metals in SBC are about 60% lower than that in CSC. These are mainly attributed to the shortened pyrolysis time and the high-energy sites effect induced by microwave heating.

Differentiating Wild and Apiary Honey by Elemental Profiling: a Case Study from Mangroves of Indian Sundarban.

Honey is a natural substance produced by honeybees from the nectar or secretion of flowering plants. Along with the botanical and geographical origin, several environmental factors also play a major role in determining the characteristics of honey. The aim of this study is to determine and compare the elemental concentration of various macro and trace elements in apiary and wild honeys collected from different parts of Indian Sundarbans. The elemental analysis was performed in inductively coupled plasma optical emission spectroscopy preceded by microwave digestion method. The concentrations of 19 elements (Ag, Al, As, B, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Pb, Se and Zn) were investigated from thirteen locations of Indian Sundarbans. This comparative study shows in wild honey samples, the concentration of K was highest followed by Ca, Mg and Na and Zn was lowest among all. In contrast, in apiary honey samples, Ca had maximum concentration followed by K, Mg and Na and Ag had minimum among all. The elemental concentration in honey from apiary was either equal or higher than their wild counterpart. The results of the factor analysis of PCA algorithm for wild and apiary honey samples were highly variable which implies that the elements are not coming from the same origin. The concentration of element was found to be highly variable across sites and across sources of honey samples.

Relationships between Diatom Abundances in Rat Organs and in Environmental Waters.

A diagnosis of drowning remains one of the most challenging issues in forensic science, especially for decomposed bodies. Diatom analysis is considered as an encouraging method for diagnosing drowning. In this study, we developed a drowned rat model using different diatom densities in water. A total of 120 adult Sprague-Dawley rats were used and divided into six groups, wherein experimental groups 1-5 were drowned rats (group A) and postmortem submersion rats (group B) that were submerged in water with five different Cyclotella sp. diatom densities, while the remaining group was used as a blank control. The combination of microwave digestion and vacuum filtration method was used to accomplish efficient tissue digestion and ascertain higher accuracy of diatom determinations within organs. The abundances of diatoms in the lungs, livers, and kidneys were significantly different. The diatom abundances in the lungs, livers, and kidneys were directly proportional to the water diatom densities, and specific quantitative relationships could be approximated by separate regression equations for each organ type. However, the trends associated with the diatom increases among organs slightly differed. In addition, the diatom abundances in the lungs, livers, and kidneys were all positively correlated. Diatoms were not observed in the postmortem submersion groups nor in the blank control groups. The results of this study provide valuable information for establishing a quantitative diatom framework for informing future forensic medicine efforts.

Flame atomic absorption spectrometric determination of multi element in apricot and soil samples after wet and microwave digestion method

Iron, copper, zinc, manganese, nickel, cobalt, lead, cadmium and chromium in various apricot and soil samples were determined by atomic absorption spectrometry in this study. Microwave digestion method and wet ashing method efficiency were compared for digestion of the samples. Recovery values were nearly found quantitative. The analysis results were evaluated. The accuracy of the digestion procedures was confirmed by analyzing Montana Soil and Apple Leaves certified reference materials. There are no important differences between digestion methods. The results were compared with literature values. Relative standard deviations were found below 10 %. Heavy metal levels in analyzed samples were not found toxic limits.

Analysis of Tin, Arsenic and Lead in Soft Drinks by Microwave Digestion and Its Applicability

A microwave digestion method for the analysis of tin, arsenic and lead in soft drinks was studied and its performance was evaluated. The trueness, repeatability (RSD) and Intralaboratory reproducibility (RSD) of the method were estimated to be in the ranges of 93-100, 0.7-6.1 and 0.9-8.6%, respectively. In the preparation of the samples for tin analysis, the addition of sulfuric acid after microwave digestion improved the recovery rate and reproducibility. To verify the applicability of this method, recovery tests were conducted on five types of soft drinks, and the results were satisfactory. It was confirmed that this method is applicable to the digestion of a wide range of soft drinks and to the analysis of tin, arsenic, and lead, and that it reduces working time and makes the work easier compared to the conventional method.

Risk Assessment of Arsenic and Cadmium in Groundwater of Talukas Ghorabari and Mirpur Sakro, Sindh, Pakistan

The current study was carried out for quantitative and risk assessment of cadmium (Cd) and arsenic (As) from Talukas Ghora Bari and Mirpur Sakro. The concentration of Cd was determined using Atomic Absorption Spectroscopy instrument. The As concentration was measured with the help of the Arsenic Kit Method. For analysis of Cd, samples were prepared by the Microwave digestion method, whereas for As analysis, water samples were analyzed directly. The range of Cd content was observed from the studied areas as 1 – 10 μg/L and 1.2 – 11.2 μg/L, respectively. The groundwater water of Talukas Ghorabari and Mirpur Sakro showed the mean Cd content of 5 μg/L and 6.1 μg/L, respectively. The Cd contamination of 56% and 80% was found in Ghorabari and Mirpur Sakro, respectively. The range of As content of 0.00 – 50 μg/L and 10 – 80 μg/L was determined from Ghorabari and Mirpur Sakro, respectively. Hazard Quotient for Cd > 1 was found in 40% of both children and infants in the groundwater of the study area, which may cause non-carcinogenic risk. About 48% of water samples declared HQ values > 1 for adults in the water of Ghorabari. Since 84% of samples showed the HQ values > 1 for children and infants. The HQ values of As for Adults of the Mirpur Sakro were observed in 63.3% samples, whereas for children and infants, HQ values were found in 100% samples. It is therefore strongly recommended that groundwater must be treated before consumption by the people of the area under study.

Burdur ilinde Karayollarının Yakınından Toplanan Bazı Karayosunu Örneklerinde Ağır Metal Seviyelerinin Belirlenmesi

The main sources of atmospheric heavy metals deposition are agricultural activities, fossil fuels, central heating stations and the exhaust gases of motor vehicles. In this study, the total of 29 mosses samples were collected from contaminated points near the Isparta-Antalya, Burdur-Denizli, Burdur-Afyonkarahisar, Burdur-Fethiye (Muğla) and Burdur-Antalya highways (2-20m) and uncontaminated areas in 2012. Samples were analyzed by flame and graphite furnace atomic absorption spectrometry (AAS) later microwave digestion methods. The highest accumulation levels detected as µg.g−1 Fe (1419.02)>Zn (158.44)>Mn (362.77)>Ni (109.53)>Cr (60.51)>Pb (30.38)>Cd (35.866)>Cu (25.17) for mosses. Element levels are differ depending on moss species and the location of collecting localities.

Heavy metals concentration in soils and crop plants within the vicinity of abandoned mine sites in Nigeria: an integrated indexical and chemometric approach

ABSTRACT In the Okurumutet-Iyamitet Mine area, mining is done by the open-cast method, without environmental impact assessment, thereby exposing the environment and its inhabitants to risks. This study aimed to assess the toxicological processes that control the plants’ heavy metal uptake into their tissues, the suitability for human consumption, and the possible sources of heavy metals using an integrated approach. The concentration of selected trace metals in plant samples was analysed by the microwave digestion method using 1 mL and 6 mL of concentrated perchloric acid and nitric acid respectively. The concentration of heavy metals in soil samples was analysed by extraction and centrifugation following standard procedures. The extracts collected were analysed by placing them into the flame of the PerkinElmer Analyst 200 atomic absorption spectrophotometer and graphite furnace atomic absorption spectrophotometer for soil and plants respectively. The concentration of heavy metals decreased in the order: Fe > Zn > Mn > Ba > Pb > Cd and Fe > Zn > Ba > Mn > Pb > Cd for the soil and cassava plants respectively. When compared with the Food and Agricultural Organisation/World health organisation and soil quality guideline, Cd recorded values in soils above the required standards. Numerical models revealed a moderate to high extent of heavy metal pollution in soil with Cd and Fe posing the highest contamination level across all the samples. The translocation factor revealed that heavy metals are more accumulated in the leaves than tubers. Similarly, the bioconcentration factor (BCF) showed that the inhabitants are exposed to heavy metal contamination from the consumption of cassava tubers, as the BCF values were >1.00. Chemometric analyses identified anthropogenic activities as the major influence on the accumulation and bioavailability of heavy metals. Hence, emphasis should be placed on Cd and Fe to mitigate further heavy metal pollution in the area.

A Method for Silicon Analysis in Citrus and Horticulture Leaf Tissue

ABSTRACT Silicon (Si) is classified as a beneficial element in higher plants. Although there is an abundance of literature on Si extraction and analysis in graminaceous crops such as rice and sugarcane, there is limited information on the validation of these methods for most dicotyledonous horticultural crops. These methods include gravimetric extraction, which requires a larger sample size the smaller the Si content in the test plant. A autoclave inductive digestion is considered effective by some and criticized by others due to the use of a strong oxidant and its sensitivity to the level of Si in the plant material. Microwave digestion method occurs in a closed system, which avoids contamination, is quick and results in a high recovery rate due to its high extraction temperature. The aim of this experiment was to validate Si measurement following microwave digestion using inductively coupled plasma optical emission spectrometry (ICP-OES) and molybdenum blue colorimetry. The recovery of Si additions as SiO2 was 82%-96% by ICP-OES and 85–94% by colorimetry. The recoveries did not differ between measurement methods (P > .05) but the ICP-OES results were more consistent. The limit of detection for Si determination by means of ICP-OES and that for the spectrophotometry method were 48 µg L−1 and 200 µg L− 1, respectively.

Determination of Lanthanides in Coal Fly Ash, Sediment and Monazite Sand by Inductively Coupled Plasma Optical Emission Spectrometry After Separation Using Oxalate form of Ion-Exchange Resin

A method has been developed for the separation of lanthanides, Ce, Nd, Gd, La, Pr, Sm, Dy, Eu, Er, Ho, Yb, Tm, Tb and Lu, using oxalate form of Dowex-1, a reactive ion-exchanger. Lanthanides present in such samples as monazite sand, coal fly ash and sediment were separated from matrix at pH 2.5 in a column containing oxalate form of Dowex-1 resin. The samples have been decomposed in H2SO4 and taken in 0.36 M H2SO4 prior to separation. The lanthanides in the column were eluted with 2 M HNO3. Lanthanides present in the eluent were determined by inductively coupled plasma optical emission spectrometry (ICP−OES) and the recovery of analytes ranged from 92 to 105%. Matrix free solutions were analyzed for lanthanides by ICP−OES. The relative standard deviation was in the range of 4–7% and limits of detection were between 0.015–0.16 mg/kg. The developed procedure was applied to the separation and determination of lanthanides in a standard reference material NIST Coal Fly Ash 1633b, a lake sediment and monazite sand. The results obtained by the present method are in close agreement with certified values in case of certified reference material and microwave digestion method for other samples. Accuracy of other samples is ensured based on standard addition recoveries.

Determination of Ca3(PO4)2 in Bone China by Microwave Digestion-ICP-AES

The establishment of a microwave digestion method with the advantages of simple operation and complete digestion to process samples has shown that, high sensitivity, wide linear dynamic range, good precision, fast analysis speed and many other advantages of ICP-AES technology for rapid determination of tricalcium phosphate in bone china. Through the use of different P2O5 content of phosphate rock and kaolin national standard material configuration standard working solution for matrix matching to eliminate matrix interference, the microwave digestion sample processing condition selection, coexisting ion interference, method precision, accuracy, and detection limit tests were carried out. The results showed that the detection limit of the newly established method for tricalcium phosphate is 0.011mg.L-1; the HCl-HNO3-HF-H2O2 mixed acid decomposition system dissolves the best samples; the interference of the test results through the matrix matching coexisting ion pair is small; The relative standard deviation (RSD) is 1.08%~4.64%, and the recovery rate of standard addition is 92.4%~107.9%. The established method has high accuracy and precision; the bone china samples are analyzed and compared with the conventional digestion national standard method The t test method is used to prove that the two methods are not significantly different from the test results.

Comparison of microwave, dry and wet digestion procedures for the determination of trace metal contents in spice samples produced in Turkey

The concentrations of trace metals (Pb, Cd, Cr, Ni, Fe, Cu, Mn and Zn) in spice samples from Turkey were determined because similar studies have not been published. The experiments were carried out using atomic absorption spectrometry after dry ashing, wet ashing and microwave digestion methods. The study of sample preparation procedures showed that the microwave method was the best. The proposed method showed satisfactory recovery, detection limits and standard deviation for trace metal determination in spice samples. The concentrations of Pb, Cd, Cr, Ni, Fe, Cu, Mn and Zn in the samples were in the range of 0.47-1.89, 0.10-0.93, 0.67-7.15, 0.65-8.69, 88.9-376.3, 4.1-28.7, 11.9-211.3 and 7.84-47.6 μg/g, respectively. Correlations between metal concentrations were evaluated.

Simultaneous determination of ultra-trace Au, Pt, Pd, Ru, Rh, Os and Ir in geochemical samples by KED-ICP-MS combined with Sb-Cu fire assay and microwave digestion

Simultaneous and accurate determination of ultra-trace Au and platinum group elements (Pt, Pd, Ru, Rh, Os and Ir) in geochemical samples is always a difficult task for their low abundance and uneven distribution. In this work, a new method for the simultaneous determination of ultra-trace Au, Pt, Pd, Ru, Rh, Os and Ir was proposed. Novel antimony-copper (Sb-Cu) fire assay was used as pre-concentration method and Au, Pt, Pd, Ru, Rh, Os and Ir were separated from the sample matrix and concentrated into Sb-Cu alloy particle. Details in this process were fully discussed and a coating agent was introduced to obtain the complete enrichment of noble metal elements; Then a microwave digestion method was used for the dissolution of Sb-Cu alloy particle. Both occurrence state and volatile behavior of Os element in this stage were studied. Ascorbic acid was used innovatively in this work and a fixed volatile proportion of 22.3% with RSD of 3.52% for Os element was found; Finally, based on the correction coefficient of Os standard solution and mathematical correction of 206Pb2+ on 103Rh+, kinetic energy discrimination collision cell-inductively coupled plasma mass spectrometry was successfully used for the simultaneous determination of ultra-trace Au, Pt, Pd, Ru, Rh, Os and Ir elements. The analytical performance of this method was studied and the detection limits of Au, Pt, Pd, Ru, Rh, Os and Ir were ranged from 0.005 ng g−1 to 0.031 ng g−1. The precisions that were evaluated within five replicated results of GBW07293 were ranged from 4.83% to 11.0%. Further, the feasibility and accuracy of the proposed method were verified by comparing the determination results of Chinese national reference materials with their certified values. This method is sensitive and stable. Importantly, this work provides a reliable and efficient determination method for multiple noble metal elements, which is of great significance in batches of geochemical survey samples analysis.

Determination of Antimony in Recycled Polyester Fiber by ICP-OES with Different Pretreatment Methods

As consumer awareness of heavy metal content in textile increased, it is necessary to develop analytical methods that identify and quantify heavy metals. In order to comprehensively investigate the potential risks of antimony (Sb) in recycled polyester fiber to humans health, this study developed acid digestion method, with the condition that the volume ratio of concentrated sulfuric acid to hydrogen peroxide was 1, and digested at 200°Cfor 1.5h, which produced clear and colorless solutions.Currently, microwave and dry ashing are also common methods for digesting polyethylene terephthalate samples. Three pretreatment methods for determining the content of Sb in recycled polyester fibers was evaluated. Results showed that inductively coupled plasma-optical emission spectrometry (ICP-OES) analysis of acid digested recycled polyester samples resulted in Sb content higher than for the microwave and dry ashing digestion methods which incompletely digest recycled polyester. Moreover, compared with microwave digestion and dry ashing, acid digestion had a low detection limit of 0.0116 ug/mL, a high spike recovery of 82% to 106% and the RSD value less than 2%, which indicates that the data was accurate and reproducible. Therefore, in this study, acid digestion - ICP-OES was an effective method for detecting the content of heavy metal Sb in recycled polyester.

Simultaneous determination of mercury, cadmium and lead in fish sauce using Diffusive Gradients in Thin-films technique

Fish sauce is a popular seasoning liquid originating from southeastern Asian cuisine, consisting of fermented fish, salt and additional ingredients. Fish can contain high amounts of metals, some of which are hazardous for human health. Therefore, authorities responsible for food safety and quality should monitor the levels of these contaminants in fish and fish deviated products. In this work, the passive sampling technique of Diffusive Gradients in Thin-films (DGT) containing Chelex-100 and Purolite S924 resin gels, is used for the determination of dissolved mercury (Hg), cadmium (Cd) and lead (Pb) in fish sauce. The DGT performance test showed linear accumulation of Hg, Cd and Pb on the binding gels versus deployment time. A wide range of pH and salt concentration did not affect the performance of the DGT. The effective diffusion coefficients of Hg, Cd and Pb in diffusive gels were determined by applying a series of deployments in fish sauce solution. Besides the direct sampling with the DGT technique, fish sauce samples were also digested using a microwave oven. Analyses of DGT and microwave oven digested samples were performed with Sector Field Inductively Coupled Plasma Mass Spectrometry (SF-ICP-MS). Both methods were then used for the analysis of fish sauces from local retail stores. Due to the preconcentration ability of DGT, lower detection limits of Hg, Cd and Pb could be achieved compared to the microwave digestion method. The DGT technique offers a more sensitive method for trace element analysis in complex food matrices.

Validation of Mineral (Fe, Zn, and Cu) Analysis Methods in Carbohydrate, Protein and Fat-Rich Samples Using Microwave Digestion Method

Destruction process using both dry and wet conditions serves as a significant step in mineral quantification. Wet destruction using microwave-assisted digestion refers to the standard method of AOAC (2012); in this work, we modified the destruction procedures provided in microwave digestion manual book, including temperature, reagent volume (HNO3 and H2O2), and length of destruction. The experiment works aimed (1) to validate the procedures in destruction process using microwave digestion; (2) to quantify Fe, Zn and Cu in various food matrices (canned peas, canned fish, full cream powdered milk) using a validated method. The method was evaluated according to linearity, accuracy, precision, absolute and relative LOD, LOQ, and intra-reproducibility. Measurement of Fe, Zn and Cu were considered to have a satisfying accuracy at a range of 80–115%, with a good precision value (% RSD < 2/3 CV Horwitz), while regression curves R2 > 0.995. The results showed that data collected from the modified method was not significantly different compared to those from the AOAC method. The currently developed method also fulfilled the acceptability requirements for laboratory analysis.

Evaluation of essential and heavy metal levels in pasteurized and long-life cow milk

In the present investigation, 11 cow’s milk samples (pasteurized and long life) were collected from supermarkets in Misurata city, Libya. For the determination of metal contents, the milk samples were subjected to the optimized microwave digestion method using HNO3 and H2O2. The levels of Na, K, Mg, Ca, Fe, Cu, Cr, Mn, Co, Ni, Zn, Cd, and Pb were evaluated by Microwave Plasma - Atomic Emission Spectrophotometer (MP-AES 4100). It was found that potassium is the most concentrated essential metal while zinc is the highest detected heavy metal in all milk samples. The levels of Co and Cd were not detected in all milk samples under investigation (lower than instrumental detection limits). The mean concentrations of the detected metals were as follows: 828.05±0.82, 587.57±0.87, 512.38±0.30, 73.79±0.19, 2.014±0.19, 1.89±0.16, 0.178±0.03, 0.061±0.02, 0.074±0.01, 0.053±0.001, and 0.045±0.001 for: K, Ca, Na, Mg, Zn, Fe, Cu, Mn, Ni, Pb, and Cr ppm, respectively. There is no significant difference in the mean concentrations of Ni, Cr and Pb between the investigated milk samples. Though, the levels of essential and heavy metals observed were similar with other reported values in the literature. Â

Synthesis and characterization of nano zeolite-A with aid of sodium dodecyl sulfate (SDS) as particle size-controlling agent

Synthesis of Nano zeolite-A has received considerable attention in the past decade and attracted profound attention as very essential commercial materials due to its nanoganic behavior., LTA Zeolites A (Linde Type A) are synthesized via low-temperature hydrothermal crystallization or microwave digestion methods in the presence of the ‘organic templates’. Generally, Tetramethylammonium-hydroxide (TMAOH) has been used as a template however, non-recyclablity, numerous efforts have been hampered the synthesis of environmental friendly template. In this work, nano zeolite-A was synthesized via both hydrothermal and microwave methods. An anionic surfactant, Sodium dodecyl sulfate (SDS) was used for controlling the particle size and as a site directing agent (SDA). The effects of different crystallization conditions such as aging time, synthesis time and temperature on the changes in particle size, morphology were investigated. The synthesized nano zeolite A was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy-dispersive X-ray (EDX), Fourier-transform infrared spectroscopy (FTIR) techniques. The obtained SEM and XRD results showed that both methods have ability to produce pure LTA zeolites crystallites with a 300−500 nm range in size with a high degree of crystallinity. However, lower aging temperature may cause for formation of sodalite (SOD) phase. Compared to the hydrothermal method, microwave approach is effective because it requires less time and produced narrow particle size distribution. Therefore, surfactant based zeolite-A synthesis would be potentially important in the chemical industry due to its competitive advantages as a green approach and cost-effectiveness.