Extraction and Flameless AAS Determination of Germanium in Lignite Fly Ash

Abstract

The use of dicyclohexyl-18-crown-6 methyl isobutyl ketone solution in extraction and flamelessatomic absorption spectrophotometry (AAS) determination of germanium in lignite fly ashes have been studied.

Germanium is usually determined in lignites after the carbonaceous part of the sample has been burnt by a dry or wet ashing method. However, methods are described for direct determination of germanium.

In the present paper a wet ashing method is reported for the determination of germanium in lignite fly ashes by flameless AAS after extraction into dicyclohexyl-18-crown-6 methyl isobutyl ketone (MIBK) solution. Solvent extraction is a known hydrometallurgical method that could be applied in germanium recovery.     

The effect of palladium modifier on the efficiency of antimony hydride trapping in graphite furnace atomic absorption spectrometry (AAS)

A slurry fluorination electrothermal vaporization (ETV)-ICP-AES method for the determination of Cu and Cr in SiO₂ powders has been developed. A polytetrafluoroethylene (PTFE) emulsion is used as fluorinating reagent; the matrix (Si) is partially separated from the sample by selecting the ashing temperature and time to reduce the interference. Moreover, the vaporization behaviour has been investigated in detail. The detection limits are 1.1 ng/mL with 3.8% of RSD (Cu) and 1.6 ng/mL with 3.2% of RSD (Cr). The method is applied to analyze the SiO₂ powders with satisfactory results. Received: 6 January 1997 / Revised: 13 March 1997 / Accepted: 28 March 1997     

The Determination of Co in Plant Materials by Radiochemical Neutron Activation Analysis

The influence of irradiation conditions on the results of Co determination in plant samples by radiochemical neutron activation analysis (RNAA), after the conventional and microwave assisted wet digestion, has been investigated. Nine CRMs of botanical origin were examined. The study has demonstrated that the effectiveness of mineralization depended significantly on the kind of sample and the irradiation conditions. When analyzed CRMs were subjected to long-term irradiation in a high neutron flux, the mineralization using the microwave technique was necessary to obtain the correct results of Co determination in some of the plant samples. It has been proved that microwave digestion in a mixture of HNO₃+H₂O₂+HF should be a standard method of wet ashing, independent on matrix and irradiation conditions.     

The determination of copper in whetlerized carbon following destructive oxidation of carbon employing hot concentrated perchloric acid

The determination of copper in whetlerized gas mask carbon has been described. The sample is “ashed” by wet oxidation employing mixed HN0₃ + HCIO₄ + H₂SO₄. The reaction is catalyzed through the addition of small amounts of chromium.The copper recovered as copper sulfate following wet ashing is reduced to Cu(I) by potassium iodide in. acetic acid solution (with previous neutralization of sulfuric acid by sodium hydroxide). The liberated iodine is then titrated employing standard sodium thiosulfate solution with starch as indicator.Individual analyses require 25–30 minutes for complete analysis.     

Micro Dry Ashing for Trace Selenium Determination in Organic Matrices

Abstract

A specific sample treatment method was established for determination of ng levels of Selenium in microquantities of organic compounds. Our task was determination of Selenium traces, in a new pharmaceutical product, as a result of a laboratory scale synthesis, in an amount of several tens of mg. GFAAS was chosen as an analysis method, due to its sensitivity and rapidity. Among the wet and dry methods for organic material digestion tried, the low temperature dry ashing using ashing aid, was the only one which gave satisfactory recoveries of Selenium. Micro dry ashing was performed, using an Ethanol solution of Magnesium Nitrate on samples spiked with Selenium Nitrate in the range of concentration of 1–6ng mg^?1 at a temperature of 450°C for two hours. The presence of Magnesium Nitrate and the heating suppress the atomization with approximately 15–25%. Recoveries of Selenium varies as a function of the organic matrix: for polyaromate compounds as Chrysene and Fluoranthene they lie between 90–103% and for oxygenated compounds as Dimethoxybenzoic acid or Phthalates 23–50% respectively.

Another aspect of chemical interference by organic matrices and the way how to overcome it, has been clarified.     

Matrix removal for the ion chromatographic determination of some trace elements in milk

An ion chromatographic method has been developed for the determination of some microelements in different types of milk. It involves oxidative photodegradation of the organic matrix with H₂O₂ in a UV digester, equipped with a high-pressure mercury lamp. The temperature of the sample is maintained at 85±5 °C by a combined air/water cooling system. This procedure provides an efficient alternative to traditional dry ashing and wet digestion methods. Milk degrades in less than 2 h, while inorganic constituents, except for iodide, nitrate, nitrite, sulfite and manganese (II), are unaffected by UV radiation. Depending upon the type of milk (whole, skimmed, powdered, evaporated, etc.) to be analysed, the amount of sample and the UV photolysis time can be adjusted as per requirements. The clear solution resulting from the UV digestion is diluted, filtered and injected onto an ion chromatograph equipped with both conductivity and variable-wavelength UV-Vis detectors. The method has been tested with standards and real milk samples and has been found to be satisfactory for the determination of total chloride, bromide, phosphorus (as phosphate) and sulfur (as sulfate), and of copper, nickel, zinc, cobalt, iron and lead.     

Bestimmung von Arsen in biologischem Material mittels Atomabsorptionsspektralphotometrie

A modified determination of arsenic by means of AAS is described. AsH₃ generation is carried out in a reaction vessel by addition of NaBH₄. The gas evolved is swept into a nitrogen entrained air flame. The detection limit amounts to 10 ng of arsenic.In the dry ashing step used for biological materials Mg(NO₃)₂ is used as an ashing aid. It was found, that an excess of four times of Mg(NO₃)₂ is necessary for finding all arsenic present. An ashing temperature of 500° C is suitable. 2 h of ashing time is enough if the samples are carefully preashed. Various foods have been analysed, mainly all higher burdened species. Arsenic contents in drinking water and some detergents have also been investigated.     

A determination method of pristine multiwall carbon nanotubes in rat lungs after intratracheal instillation exposure by combustive oxidation-nondispersive infrared analysis

This paper describes a method for determination of multiwall carbon nanotubes (MWCNTs) in rat lungs after intratracheal instillation exposure. The MWCNTs were quantitatively decomposed to CO₂ by combustive oxidation and were then determined by non-dispersive infrared analysis. Samples were pretreated by acid digestion, muffle ashing and in situ preheating to remove interferences due to coexisting biological carbon from the lung tissue sample, while preserving the MWCNTs as in its their original form. The preservation was confirmed by transmission electron microscopic observation of the pretreated samples of exposed lung tissues and by the fact that the recoveries of MWCNTs spiked to the lung tissues were close to 100%. The detection limit for MWCNTs obtained by the proposed method was 0.30 μg and the repeatability as expressed by the relative standard deviation was 5.6% (n = 4). The method was sufficiently sensitive and precise to apply to real samples of rat lung to investigate the in vivo persistence of intratracheally instilled MWCNTs. To our knowledge, this is the first report of this type of sample pretreatment and direct determination of pristine MWCNTs without modification or tagging. Conventional indirect methods use tagging with other compounds or metal impurities in the CNTs for detection, and the detachment of these tags can increase uncertainties in the determination of the CNTs. The tags can also change how the CNTs persist in vivo, which can lead to an incorrect understanding of the persistence of pristine CNTs in vivo.     

碱熔融-电感耦合等离子体原子发射光谱法测定氧化铟锡烧结混合粉中5种杂质元素

采用氢氧化钠熔融样品,热水浸取后盐酸酸化,建立了碱熔融-电感耦合等离子体原子发射光谱(ICP-AES)法测定氧化铟锡烧结混合粉中Fe、Ca、Mg、Al和Si等元素的分析方法.试验结果表明:称取0.500 0 g试样,加入0.80 g氢氧化钠,在灰化炉中熔融120 min,可将样品完全溶解.基体铟和锡的干扰采用基体匹配法消除,被测元素之间没有光谱干扰.钠盐对硅的测定有一定影响,可在标准溶液中加入一定量氢氧化钠予以消除.对方法进行精密度和加标回收试验,测得结果的相对标准偏差均小于5%,方法加标回收率在90%~105%之间.     

Determination of iron in wine using 2,4,6-tripyridyl-s-triazine

Procedures are described for the determination of iron in wine using 2,4,6-tripyridyl-s-triazine, a new ferroine reagent. One procedure involving wet ashing with nitric and perchloric acids gives results comparable to those obtained using the usual 1,10-phenanthroline method while a direct extraction procedure often gives low but reproducible results indicating the presence of “complexcd iron” in the sample.     

Determination of Zn, B, Fe, Mg, Ca, Na and Si in anisette samples by inductively coupled plasma atomic emission spectrometry

A comparative study of several digestion methods of anisette samples has been carried out. Two dry ashing (DA) treatments as well as four wet ashing (WA) procedures using different mixtures of acids were applied for the sample mineralisation before analysis. Once the anisette samples were mineralised, the contents of Zn, B, Fe, Mg, Ca, Na and Si were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES). Each method has been studied statistically and also attending to their feasibility. After performing the optimisation of the different treatments tested, it was concluded that one wet ashing method employing a HNO₃:H₂O₂ (10:1) mixture was the most suitable. This method was applied to the analysis of anisette samples. Na, Ca, Mg and Si were present in concentrations up to 215 mg l⁻¹ for Na, 11.6 for Mg, 6.2 for Ca and 5.1 for Si. Fe and B concentrations were not higher than 0.12 mg l⁻¹ and lower for Zn.     

Extraction of trace amounts of mercury with sodium dodecyle sulphate-coated magnetite nanoparticles and its determination by flow injection inductively coupled plasma-optical emission spectrometry

A new method for solid-phase extraction and preconcentration of trace amounts Hg(II) from environmental samples was developed by using sodium dodecyle sulphate-coated magnetite nanoparticles (SDS-coated Fe₃O₄ NPs) as a new extractant. The procedure is based on the adsorption of the analyte, as mercury-Michler's thioketone [Hg₂(TMK)₄]²⁺ complex on the negatively charged surface of the SDS-coated Fe₃O₄ NPs and then elution of the preconcentrated mercury from the surface of the SDS-coated Fe₃O₄ NPs prior to its determination by flow injection inductively coupled plasma-optical emission spectrometry. The effects of pH, TMK concentration, SDS and Fe₃O₄ NPs amounts, eluent type, sample volume and interfering ions on the recovery of the analyte were investigated. Under optimized conditions, the calibration curve was linear in the range of 0.2-100 ng mL⁻¹ with r² = 0.9994 (n = 8). The limit of detection for Hg(II) determination was 0.04 ng mL⁻¹. Also, relative standard deviation (R.S.D.) for the determination of 2 and 50 ng mL⁻¹ of Hg(II) was 5.2 and 4.7% (n = 6), respectively. Due to the quantitative extraction of Hg(II) from 1000 mL of the sample solution an enhancement factor as large as 1230-fold can be obtained. The proposed method has been validated using a certified reference materials, and also the method has been applied successfully for the determination of Hg(II) in aqueous samples.     

Coating of borosilicate glass containers for preventing contamination in trace element analysis

Pyrex glass dishes are coated with amorphous 78 SiO₂—21 ZrO₂—1 Na₂0 (mol %) films ca. 50 nm thick. The coated dishes possess reasonable chemical resistance and can be successfully used in the dry ashing of a standard botanical sample for boron determinations and in the evaporation needed for aluminum determination in nitric acid.     

Microcolumn packed with YPA(4) chelating resin on-line separation/preconcentration combined with graphite furnace atomic absorption spectrometry using Pd as a permanent modifier for the determination of trace mercury in water samples

A new method using a microcolumn packed with YPA₄ chelating resin as solid-phase extractor has been developed for the separation and preconcentration of trace Hg prior to its measurement by GFAAS with Pd as a permanent modifier. Various parameters such as the amount of the modifier, pH, sample flow rate, the concentration and volume of eluent have been studied in order to find the best conditions for the determination of mercury. The detection limit of the method (3σ) for Hg based on an enrichment factor of 100 was 0.2 ng ml⁻¹. A characteristic mass of 114 pg was obtained for mercury using Pd as a permanent modifier. The relative standard deviation was 2.8% at the 10 ng ml⁻¹ level (n = 5). The method has been applied to the determination of trace mercury in environmental water samples and the recoveries for the spiked samples are in the range of 91-105%.     

Boron determination in biological materials by inductively coupled plasma atomic emission and mass spectrometry: effects of sample dissolution methods

This study compares four sample dissolution methods for Boron determination in two National Institute of Standard and Technology (NIST) botanical Standard Reference Materials (SRMs) and three Agriculture Canada/NIST RMs, each having a reference (certified or best estimate) B concentration. The dissolution treatments consisted of: 1) dry ashing at 500° C, 2) wet digestion with HNO₃ + H₂O₂, 3) extraction with hot HNO₃ and 4) closed vessel microwave dissolution. The samples were spiked before and after imposing dissolution treatments to study B recovery by inductively coupled plasma mass spectrometric (ICP-MS) analysis. Microwave digests of NIST SRM 1515 and some in-house RMs were also used to compare the B values of ICP-MS and ICP-AES (atomic emission spectrometry). While all three digestion methods (dry ashing, wet ashing and microwave) dissolved botanical samples, only the microwave method worked well for animal tissues. In terms of B values in these materials, there was no significant difference among the three digestion treatments. Near 100% recovery of B spiked before and after the sample dissolution indicates that there may not be a significant loss of B during the dissolution process used in this study. Extraction with hot HNO₃ was as effective as the three digestion treatments, and B values for this method agreed well with reference values. For the botanical materials studied, the B values determined by ICP-AES were not significantly different from ICP-MS values. This study shows that a simple, time and labor efficient hot HNO₃ extraction is as effective as other digestion/dissolution methods for quantitative B recovery from biological materials. Received: 13 June 1996 / Revised: 17 September 1996 / Accepted: 19 September 1996     

Ligandless-dispersive liquid-liquid microextraction of trace amount of copper ions

In the present work, a new ligandless-dispersive liquid-liquid microextraction (LL-DLLME) method has been developed for preconcentration trace amounts of copper as a prior step to its determination by flame atomic absorption spectrometry. In the proposed approach 1,2-dicholorobenzene and ethanol were used as extraction and dispersive solvents, respectively. Some factors influencing on the extraction efficiency of copper and its subsequent determination were studied and optimized, such as the extraction and dispersive solvent type and volume, pH of sample solution, extraction time and salting out effect. Under the optimal conditions, the calibration curve was linear in the range of 1.0 ng mL⁻¹-0.6 μg mL⁻¹ of copper with R² = 0.9985. Detection limit was 0.5 ng mL⁻¹ in original solution (3S_b/m) and the relative standard deviation for seven replicate determination of 0.2 μg mL⁻¹ copper was ±1.4%. The proposed method has been applied for determination of copper in standard and water samples with satisfactory results.     

微波灰化-液相色谱-电感耦合等离子体质谱联用测定干食用菌中的三价铬和六价铬

建立了干食用菌中三价铬(Cr(Ⅲ))和六价铬(Cr(Ⅵ))的液相色谱-电感耦合等离子体质谱(LC-ICP-MS)检测方法。采用微波灰化技术对食用菌样品进行灰化处理,灰化样品用乙二胺四乙酸(EDTA)二钠盐稳定其中的Cr(Ⅲ),并使其保留在阴离子交换柱(250 mm×4.6 mm,10 μm)上;用含有60 mmol/L硝酸(pH 9.3)的流动相分离其中的Cr(Ⅲ)和Cr(Ⅵ),电感耦合等离子体质谱仪测定。标准溶液中Cr(Ⅲ)和Cr(Ⅵ)的质量浓度在0.5~50 μg/L范围内呈良好的线性关系,线性回归系数均达到0.9999。食用菌样品中Cr(Ⅲ)和Cr(Ⅵ)不同加入量的平均回收率为78.0%~90.7%,相对标准偏差小于4%(n=6);定量限均为0.5 μg/L。该方法稳定、可靠、灵敏,可满足干食用菌中Cr(Ⅲ)和Cr(Ⅵ)的测定。     

Increasing the sensitivity of the spectrophotometric determinations of the oxygen content in YBCO superconducting samples using the I3-starch compound

The conditions for formation of the I₃⁻-starch compound and measuring its absorbance have been found, and a spectrophotometric method has been developed for the determination of the oxygen content in YBa₂Cu₃O_y superconducting bulk samples. The method involves the following stages: a decomposition of the sample in an acid medium in the presence of iodide ions under inert atmosphere; formation of a complex between Cu(II) and glycine; binding the I₃⁻-complex with a starch and the absorbance measurement of the colored I₃⁻-starch compound. The coefficient of the active oxygen is calculated by the ratio of the absorbances of two solutions and the method does not require both calibration and precise measuring sample mass. The accuracy of the results is confirmed applying the comparative spectrophotometric method that uses the yellow I₃⁻-complex. The precision of the results evaluated by the relative standard deviation is 2%. The developed method is sensitive and allows a sample mass about 2 mg to be used. The analysis is rapid and requires a simple and inexpensive apparatus. Thus the new method would be useful for an express analytical control of the oxygen content of YBCO-superconducting materials produced for the electronics.     

Direct analysis of palladium in active pharmaceutical ingredients by anodic stripping voltammetry

Anodic stripping voltammetry, a classical electroanalytical method has been optimized to analyze trace Pd(II) in active pharmaceutical ingredient matrices. The electroanalytical approach with an unmodified glassy carbon electrode was performed in both aqueous and 95% DMSO/5% water (95/5 DMSO/H₂O) solutions, without pretreatment such as acid digestion or dry ashing to remove the organics. Limits of detection (LODs) in the presence of caffeine and ketoprofen were determined to be 11 and 9.6 μg g⁻¹, with a relative standard deviation (RSD) of 5.7% and 2.3%, respectively. This method is simple, highly reproducible, sensitive, and robust. The instrumentation has the potential to be portable and the obviation of sample pretreatment makes it an ideal approach for determining lost catalytic metals in pharmaceutical-related industries. Furthermore, the simultaneous detection of Pd(II) with Cd(II) and Pb(II) in the low μg L⁻¹ range indicates that this system is capable of simultaneous multi-analyte analysis in a variety of matrices.     

Rapid fusion method for determination of plutonium isotopes in large rice samples

A new rapid fusion method for the determination of plutonium in large rice samples has been developed at the Savannah River National Laboratory (Aiken, SC, USA) that can be used to determine very low levels of plutonium isotopes in rice. The recent accident at Fukushima Nuclear Power Plant in March, 2011 reinforces the need to have rapid, reliable radiochemical analyses for radionuclides in environmental and food samples. Public concern regarding foods, particularly foods such as rice in Japan, highlights the need for analytical techniques that will allow very large sample aliquots of rice to be used for analysis so that very low levels of plutonium isotopes may be detected. The new method to determine plutonium isotopes in large rice samples utilizes a furnace ashing step, a rapid sodium hydroxide fusion method, a lanthanum fluoride matrix removal step, and a column separation process with TEVA Resin? cartridges. The method can be applied to rice sample aliquots as large as 5 kg. Plutonium isotopes can be determined using alpha spectrometry or inductively-coupled plasma mass spectrometry (ICP-MS). The method showed high chemical recoveries and effective removal of interferences. The rapid fusion technique is a rugged sample digestion method that ensures that any refractory plutonium particles are effectively digested. The MDA for a 5 kg rice sample using alpha spectrometry is 7 × 10^?5 mBq g^?1. The method can easily be adapted for use by ICP-MS to allow detection of plutonium isotopic ratios.