微波消解-FAAS法测定大别山区三种中药中的微量元素

采用微波消解-火焰原子吸收光谱(FAAS)法对大别山区3种中药(何首乌、黄精和拐枣)中的微量元素进行测定。用微波消解仪处理样品,对消解条件及消解程序进行优化,在最佳微波消解条件下,结合FAAS法测定上述3种中药中Ca、Mg、Cu、Zn、Fe、Mn 6种元素的含量。结果表明,微波消解的最佳条件为:何首乌和拐枣采用HNO3-H2O2混酸体系,配比分别为5∶2和5∶3,固液比1∶20,最高功率(700W)时的保温时间分别为8min和6 min;黄精采用HNO3-HCl,混酸体系,配比5∶2,固液比1∶28,保温时间为8 min。所建立的定量分析方法回收率为95.63%～101.36%,相对标准偏差小于3.0%,线性相关系数大于0.999,方法检出限为0.18～2.20 ng/mL。3种中药中均含有丰富的微量元素,尤其是黄精中Fe、Ca和Mn的含量较高;何首乌中Mg、Zn和Fe含量相对较高;拐枣中Fe和Ca含量相对较高。研究结果可为上述3种中药中微量元素的含量与其药效的相关性提供科学依据。     

微波消解-石墨炉原子吸收光谱法测定植物染发剂中的铅镉铜

建立了微波消解-石墨炉原子吸收光谱法测定植物染发剂中重金属铅、镉和铜的方法.采用L9(34)正交设计讨论了固液比、消解剂体积比、消解时间和消解压力对样品消解效果的影响,最佳的消解条件:固液比(g/mL)为1∶12,HNO3/H2O2(V/V)为4∶1,消解时间为5min,消解压力1.5MPa.在最佳微波消解条件下,进行了精密度实验、回收率实验,相对标准偏差为1.05%~3.35%,回收率为96.67%~105.43%.微波消解法处理植物染发剂样品,试剂用量少、消解完全、快速、简便,而且测定结果的精密度、准确度较好.     

微波消解和电感耦合等离子体发射光谱法同时测定煤灰中的14种元素

应用微波消解和电感耦合等离子体发射光谱法同时测定煤灰中的常量、少量和微量元素Si、Al、Ca、Fe、Mg、Ti、K、Ba、Mn、V、Pb、Cr、Cu和Zn。考察了微波消解体系和消解条件，0．1g煤灰用10mL硝酸和1mL氢氟酸分解，加入10mL4％硼酸溶液分解氟化物沉淀。用本法测定煤飞灰标准参考物质的结果与标准值一致。方法准确，快速，回收率为94．2％～102．3％；RSD均小于5％。     

Microwave digestion of "residual fuel oil" (NIST SRM 1634b) for the determination of trace elements by inductively coupled plasma-mass spectrometry

A microwave procedure for the digestion of the NIST 1634b reference material "residual fuel oil" in closed pressurized vessels was developed in an attempt to facilitate routine analysis and obtain reproducible conditions or comparable results. The influence of sample size, reagent composition and volume, microwave power, and duration of heating on the digestion procedure was studied. Pressure and temperature inside the reaction vessels were monitored to determine the progression of the reaction and to develop optimal conditions. A nine-step heating program requiring 36.5 min with microwave power not exceeding 450 W in the pulsed mode was found suitable for the digestion of approximately 250 mg fuel oil with a mixture of nitric acid (5.0 mL) and hydrogen peroxide (2.0 mL). The reproducibility of microwave power was determined in terms of the relative standard deviations (n = 3) for temperature (2.7%) and pressure (4.9%) data. The vapor pressures obtained with 5.0 mL Milli-Q water (heated) in an 80-mL digestion vessel showed good agreement with literature data. The excess acid in the resulting digests was removed by evaporation and the concentrations of 24 elements (Ag, Al, As, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mo, Ni, Pb, Sb, Sn, Sr, Ti, Tl, V, U, and Zn) were determined in the diluted digests by inductively coupled plasma mass spectrometry (ICP-MS). The experimental results were in good agreement with the certified and recommended concentrations for eight elements (Al, As, Co, Cr, Ni, Pb, V, Zn) in solutions obtained after one digestion step. An additional digestion step, consisting of intermediate cooling and venting stages, was required for the accurate determination of Fe. No agreement was reached for Ca and Ba even after two-step digestion. The proposed method of digestion provided precise results with relative standard deviations generally less than 5% for most of the elements determined.     

Optimized microwave preparation procedure for the elemental analysis of aquatic sediment

 This paper summarizes several key points in applying the microwave preparation technique to the elemental analysis of aquatic sediments and reports systematic experiments in searching for an optimal microwave preparation procedure for element analysis in sediment samples. The determination of the elements Cu, Pb and Cd in a standard reference aquatic sediment sample (CRM 280, COMEUR) was achieved by first digesting the samples in a microwave oven equipped with PFA advanced composite vessels, followed by AAS measurement. The influence of microwave power, digestion time, various dissolution reagents and the HF removing conditions was studied. It has been shown that for a 0.1 g sediment sample the optimal microwave preparation conditions are: 4–5ml HNO₃/HF/H₂O₂ as solvent, digesting time 30 min with 100% microwave power and evaporating the residual acid within 8 min in an open vessel at 80 °C. The element recovery rates with AAS measurement can reach up to 92.4–100.6%. Received: 23 July 1996/Revised: 23 September 1996/Accepted: 25 September 1996     

On the microwave digestion of soils and sediments for determination of lanthanides and some toxic and essential elements by inductively coupled plasma source mass spectrometry

Four digestion procedures for microwave dissolution of soils and sediments are investigated. Accurate results (accuracy better than 10%) for lanthanides, Be, Bi, Te, Th, U and Y are obtained only after an overnight stay with a mixture of 2 ml 48% HF and 2 ml 65% HNO(3) and afterwards stepwise microwave digestion with 1 ml 48% HF and 10 ml 5% H(3)BO(3). Only As is not be to be determined by this procedure due to significant interferences from Eu, Nd and Sm. For all other elements, accurate results are obtained by all four procedures.     

微波消解-火焰原子吸收光谱法测定黄芪中八种金属元素的含量

提出了微波消解-火焰原子吸收光谱法测定黄芪中的八种金属元素含量的方法.实验确定微波消解试样的最佳条件为:HNO_3与HClO_4体积比是4∶1,微波功率为600 W、时间为3 min.实验结果表明:黄芪中含有较丰富Ca、Mg、Fe,Cu、Zn、Mn含量较低,而Pb、Cr未测出.测定的相对标准偏差小于5.4%,加标回收率为93.6%～105.2%.     

Comparative study of different digestion procedures using supplementary analytical methods for multielement-screening of more than 50 elements in sediments of the river Elbe

The suitability of four different digestion procedures, i.e. i.) an aqua regia digestion according to DIN 38 414-S7, ii.) a pressure digestion using HNO₃/HF in PTFE-vessels, iii.) a HNO₃/HF + HCl-pressure digestion in PTFE-vessels and iv.) a HNO₃/HF + HCl-pressure digestion using microwave induction, has been evaluated with regard to the quantitative determination of about 50 elements in environmental samples. Three sediments of the river Elbe and two standard reference materials (MESS-1 and NIST 1645) have been employed. The analytical results from the dissolved samples, obtained using inductively coupled plasma mass- and optical emission spectrometry as well as total reflection X-ray fluorescence spectrometry, have been compared with those obtained by instrumental neutron activation analysis. Only digestion procedures using HNO₃/HF with a subsequent evaporation to dryness and dissolution in HCl have led to appropriate results for a wide range of elements (more than 50 elements in total). Because of its low contamination risk and its time saving, the microwave digestion is preferred. For this digestion procedure the accordance among the different instrumental methods used is high (better than 15% deviation) in general. A few elements (16) could be determined quantitatively only by a single method.     

Microwave digestion of “residual fuel oil” (NIST SRM 1634b) for the determination of trace elements by inductively coupled plasma-mass spectrometry

A microwave procedure for the digestion of the NIST 1634b reference material “residual fuel oil” in closed pressurized vessels was developed in an attempt to facilitate routine analysis and obtain reproducible conditions or comparable results. The influence of sample size, reagent composition and volume, microwave power, and duration of heating on the digestion procedure was studied. Pressure and temperature inside the reaction vessels were monitored to determine the progression of the reaction and to develop optimal conditions. A nine-step heating program requiring 36.5 min with microwave power not exceeding 450 W in the pulsed mode was found suitable for the digestion of ～ 250 mg fuel oil with a mixture of nitric acid (5.0 mL) and hydrogen peroxide (2.0 mL). The reproducibility of microwave power was determined in terms of the relative standard deviations (n = 3) for temperature (2.7%) and pressure (4.9%) data. The vapor pressures obtained with 5.0 mL Milli-Q water (heated) in an 80-mL digestion vessel showed good agreement with literature data. The excess acid in the resulting digests was removed by evaporation and the concentrations of 24 elements (Ag, Al, As, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mo, Ni, Pb, Sb, Sn, Sr, Ti, Tl, V, U, and Zn) were determined in the diluted digests by inductively coupled plasma mass spectrometry (ICP-MS). The experimental results were in good agreement with the certified and recommended concentrations for eight elements (Al, As, Co, Cr, Ni, Pb, V, Zn) in solutions obtained after one digestion step. An additional digestion step, consisting of intermediate cooling and venting stages, was required for the accurate determination of Fe. No agreement was reached for Ca and Ba even after two-step digestion. The proposed method of digestion provided precise results with relative standard deviations generally less than 5% for most of the elements determined.     

Determination of thirteen common elements in food samples by inductively coupled plasma atomic emission spectrometry: comparison of five digestion methods

Five sample digestion procedures were evaluated for the determination of Al, B, Ca, Cu, Fe, K, Mg, Mn, Na, P, S, Sr, and Zn in food samples by inductively coupled plasma atomic emission spectrometry. The 5 procedures include dry ashing at 500 degrees C, wet digestion with HNO3-HClO4, microwave digestion with HNO3, microwave digestion with HNO3-H2O2, and microwave digestion with HNO3-H2O2-HF. For microwave digestion with HNO3-H2O2-HF, silicon (IV) oxide was used to eliminate the excess HF, making it possible to determine total Al, B, and other common elements accurately and simultaneously. Seven National Institute of Standards and Technology standard reference materials (SRMs) were analyzed to compare the recovery of 13 elements with above digestion procedures. The results demonstrated that the microwave digestion procedure with HNO3-H2O2-HF yielded the best recoveries for all 13 elements in the selected SRMs. The determined concentrations of most elements were close for all 3 microwave digestion procedures with the exception of Al in oyster tissue, bovine liver, and spinach. Notably, the wet digestion with HNO3-HClO4 is the simplest and the most effective procedure for the selected elements except Al and B. Although there are several concerns with the dry ashing procedure, it might be a preferable procedure for those analyses where only nonvolatile elements are to be determined and the concentrations of the elements are low.     

微波消解-微波等离子体炬原子发射光谱测定啤酒中的铜、锌、铁、锰、硒、锶

建立了微波消解-微波等离子体炬原子发射光谱(MPT-AES)法测定啤酒中微量元素。考察了微波前向功率、工作气流量、载气流量等参数,确定了MPT-AES法测定各元素的最佳实验条件。在该条件下铜、锌、铁、锰、硒、锶的检出限分别为7ng.mL-1、46ng.mL-1、13ng.mL-1、8ng.mL-1、1.2ng.mL-1、5.6ng.mL-1。相对标准偏差(RSD)均在0.9%～4.8%之间,线性范围分别为0.1～100μg.mL-1、0.5～100μg.mL-1、0.5～100μg.mL-1、0.1～100μg.mL-1、0.01～10μg.mL-1、0.05～100μg.mL-1,加标回收率均在96%～110%之间。     

超级微波消解-电感耦合等离子体发射光谱（ICP-OES）法测定土壤中18种元素

为提高土壤多元素同时检测的效率,采用超级微波消解-电感耦合等离子体发射光谱法测定土壤中钾、钠、钙、镁、铜、铁、锰、锌、磷、硫、硼、砷、镉、铬、铅、钴、镓、锂等18种元素含量。比较了超级微波消解、常规微波消解和电热板消解的处理效果,采用超级微波消解法对样品进行前处理,并优化了消解条件。在最优条件下,各元素的检出限在0.05~20 mg/kg,加标回收率在86.2%~107.5%,RSD在0.1%~3.0%,方法准确度及精密度可以满足多元素同时测定的需求,且该方法具有简单、快速、成本低、用酸量少、重现性好等特点。     

Determination of total cationic and total anionic arsenic species in oyster tissue using microwave-assisted extraction followed by HPLC-ICP-MS

A microwave-assisted digestion procedure was developed in presence of concentrated nitric acid (2.0 ml) and 30% hydrogen peroxide (0.20 ml) using a closed pressurized microwave digestion system for the determination of total anionic and total cationic arsenic compounds reside in oyster tissue. At 450 W for 15 min digestion, 74% of anionic arsenic, and 31% of cationic arsenic (105% total arsenic) were retrieved. At 300 W microwave power, 68% of anionic and 30.5% of cationic arsenic (98.5% total arsenic), and 100 W, 63% of anionic and 31% of cationic arsenic (94% total arsenic) were extracted out. The methanol water mixture (9:1) was cull out, exclusively 31.6% of anionic and 29% of cationic arsenic compounds (60.6% total). The dimethylarsinoylriboside (phosphate-arsenosugar) was the predominant arsenic species, along with arsenobetaine (AB), dimethylarsinic acid (DMA), inorganic arsenic, methylarsonic acid (MA), arsenocholine (AC), trimethylarsineoxide (TMAO) and tetramethylarsonium ion (TMI). Some other arsenic compounds, those were not matched with the retention time of the available standards, were also detected. Arsenosugar was fragile and adequately transmuted to DMA (100%), AB and AC to TMAO (100%) when 450 W microwave power was applied for 15 min. The separation and quantification of arsenic compounds in the microwave digests and extracts, were carried out in anion (PRP-X100) and cation (LC-SCX) exchange columns using ICP-MS as arsenic specific detector. The procedure was also validated by determining the total cationic and total anionic arsenic compounds present in DORM 1.     

A clean up step of fat content previous to trace metal characterization in mussel tissues by inductively coupled plasma mass spectrometry

Inductively coupled plasma mass spectrometry analysis of trace and major elements of mussel tissues can be quickly and accurately analyzed after cleaning up the interfering fat content before the sample is digested in a microwave oven. Making use of experimental designs, the clean up procedure was achieved by the extraction of 1 g of freeze-dried tissue sample stirred with 5 ml of dichloromethane during five minutes. The microwave assisted digestion of the fat free samples was carried out with 0.2 g of tissue sample, 15 ml of 7.0% nitric acid with a power of 980 W during 18 min. The analytical method efficiency (accuracy and precision) was evaluated with a CRM: (NIST 2977, mussel tissue) and real mussel samples analyzed previously. The results confirmed the accuracy of the analysis by agreement with the previous results but the precision was significantly improved. The developed method allows operating routinely permitting to large numbers of samples to be quickly screened for trace metals.     

Digestion of titanium bearing geologic materials involving microwaves

An environmentally friendly and rapid digestion procedure involving 10 mL of acid mixture (HNO3 : HCl : HF = 2:2:1) for 0.1 g of sample in closed vessel microwave digester following heating program : 250W for 10 min., hold time 2 min., 600 W for 17 min, and Ventilation time 10 min was developed. The operating parameters were varied and optimized by factorial design approach using "Steepest Ascent" method. The validity of the recommended digestion procedure were examined by analyzing several well characterized standard reference materials such as diabase (W2), basalt (BIR-1, JB-3, BHVO-1), granite (G2), gabbro (JGb-1), Mn-nodule (Nod-A-1, Nod-P-1), sediment (STSD-4, LKSD-2), limestone (KH-2), soil (SAu-1), ilmenite (IGS-31), rutile (IGS-32), Zircon (IGS-35) and titanium dioxide (SRM-154b) employing both inductively coupled plasma-atomic emission spectrometry (ICP-AES) and well known spectrophotometric method. An excellent agreement between the methods and the certified values of standard reference materials suggest that the digestion procedure can be used for quality control and allied purposes.     

微波消解-ICP-MS测定塑料原料中14种催化剂残留元素

采用微波消解法预处理聚乙烯(PE)、聚丙烯(PP)、聚苯乙烯(PS)、聚对苯二甲酸乙二醇酯(PET)常用塑料原料,使用压力控制装置对消解过程进行监控并对消解条件进行摸索,考察了消解量、消解体系、消解温度和保持时间对消解结果的影响,优化选择了电感耦合等离子体-质谱法(ICP-MS)的测定参数和内标元素。建立了微波消解-电感耦合等离子体-质谱法测定塑料原料中Li、Ca、Mg、Al、Si、Ti、V、Cr、Co、Zn、Ga、Zr、Sb、Hf 14种元素的催化剂残留的检测方法。方法检出限在0.001～10.60μg/L,回收率在82%～120%之间,相对标准偏差小于20%。     

Low volume microwave digestion for the determination of selenium in marine biological tissues by graphite furnace atomic absorption spectroscopy

A microwave digestion method for the determination of marine biological tissues has been developed to allow determination of selenium in small sample sizes (< 0.1 g). The benefits of this technique include maintaining concentrates in extracts without the subsequent over dilution encountered when using larger vessels, increased sample throughput and reduced loss of volatile material. Freeze dried biological material (< 0.1 g) and nitric acid (1 ml) were placed into 7 ml screw top Teflon vessels which are completely sealed on capping. Two 7 ml vials were placed into larger 120 ml vessels fitted with a Teflon spacer and 10 ml of distilled water. The effects of microwave power and time, and sample mass on selenium recovery from three marine standard reference materials (NIST SRM 1566a Oyster Tissue, NRCC DORM-1 Dogfish Muscle and NRCC TORT-1 Lobster Hepatopancreas) were examined. The optimum conditions: 600 W, 2 min; 0 W, 2 min; 450 W, 45 min, allowed quantitative recoveries of selenium from these and three other standard reference materials (NRCC DOLT-1 Dogfish liver, NIST RM-50 Albacore tuna and IAEA MA-A-2 fish flesh). Studies on sample mass showed that the analysis of sample masses from 0.025 to 0.1 g gave selenium concentrations within the certified range. Six species of selenium: selenite, selenate, selenomethionine, selenocysteine, selenocystamine, and trimethyl selenonium were added to oyster, dogfish, and lobster tissues. Recoveries were near quantitative for all species (94–105%) except trimethyl selenonium (90–101%).     

A new procedure for bovine milk digestion in a focused microwave oven: gradual sample addition to pre-heated acid

Milk samples can be efficiently digested using a focused microwave oven, however the conventional procedure of addition of concentrated acids to the liquid sample leads to digestates with elevated acidity and residual carbon concentrations. In this work a focused microwave oven was applied for acid digestion of bovine milk samples using a conventional and an alternative procedure based on gradual sample addition to hot and concentrated acids. A two-level 2³ full factorial design experiment with eight runs was carried out to evaluate the optimum experimental conditions for reducing both the residual carbon and the final acidity of digestates. The three studied parameters were: temperature of the digestion medium for sample addition, addition of sulfuric acid before the sample or during the first step, and number of aliquots of the sample gradually added. The best conditions were attained by adding small aliquots of milk (ten-fold a volume of 0.5 ml added during 5.0 min) to a digestion mixture containing 3.0 ml nitric acid plus 1.0 ml sulfuric acid heated at 105 °C. It was demonstrated that the digestion efficiency of the alternative procedure was better than the conventional procedure, i.e. 98 and 80%, respectively. The alternative procedure was applied for determination of Ba, Ca, Cu, K, Mg, Na, P, and Zn in whole and non-fat bovine milk. The accuracy was proved using two certified reference materials (whole and non-fat milk powder).     

Study on the PTFE closed-vessel microwave digestion method in food elemental analysis

Summary A closed PTFE vessel microwave digestion method is described for the HNO₃/H₂O₂ digestion of food samples. 0.2–0.3 g of powdered samples are completely digested in 44 ml PTFE digestion vessels by 2 ml of 70% HNO₃ and 1 ml of 30% H₂O₂ within 2 min at 100% full power (500 W). After air-cooling for 10 min in a refrigerator at — 25°C the digestion solution is diluted to 25ml. The total elemental concentrations of Ca, Mg, Cu, Fe, Mn and Zn are determined by sequential ICP-AES. The accuracy of the procedure was tested by analysis of 3 SRMs. The results are in good agreement with certified values.

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Untersuchung zum Mikrowellenaufschluß im geschlossenen PTFE-Gefäß für die Elementanalyse in Lebensmitteln

     

Use of microwave digestion and atomic absorption spectrophotometry to determine chromic oxide as a digestibility marker in feed, feces, and ileal content.

Most conventional digestion procedures, such as dry ashing and wet ashing, are tedious and labor intensive. Microwave digestion is a good alternative, because microwave dissolution is faster, safer, and simpler, and provides more controlled reproducible conditions than conventional methods. The purpose of this study was to develop a microwave digestion method for mineralizing meat and bone meal diets, feces, and ileal contents. Each sample was heated on a hot plate for 10 min, dry ashed at 65 degrees C for 4 h, and transferred into microwave vessels. Then, 10 mL 70% HNO3 was added. Samples were digested for 7, 10, and 20 min at 95, 90, and 85% power, respectively. After the heating cycle, 6 mL 30% H2O2 was added, and samples were returned to the microwave for a second heating cycle of 1 and 7 min at 95% and 90% power, respectively. Finally, chromium concentration was determined by flame atomic absorption spectrophotometry. The digestion method was validated by using a standard reference material, SRM domestic sludge 2781, with a certified chromium value of 195 +/- 9 micrograms/g. The value obtained in this study was 178 +/- 11 micrograms/g, for a difference of 17 micrograms/g. Spike recovery experiments resulted in 103.16 and 100.35% recoveries of chromium from diet and feces samples, respectively. Coefficients of variation were 10.8 and 7.8%, respectively.