Microwave digestion and acidic treatment procedures for the purification of multi-walled carbon nanotubes

Abstract
Multi-walled carbon nanotubes (MWCNTs) synthesized by thermal chemical vapor deposition have been successfully purified by
using efficient microwave digestion method. Recently, various purification methods have been provided to eliminate metal catalysts and most were acid treatment procedures that take long time and damage the structure of nanotubes. Comparing to these methods,
microwave digestion takes a tremendous advantage because the acid in this approach can absorb microwave energy rapidly and dissolve
metal efficiently without damaging the wall structure and the processing time could be the shortest. The ability of microwave digestion method was studied by various experimental parameters. The efficient purification proceeded for 90 min and at 210 8C with 5 M nitric acid treatment in the microwave digestion system to dissolve the metal catalyst. High-resolution transition electron microscopy and Raman spectra were used to characterize the specimen. Purities were characterized by thermogravimetric analysis (TGA). Results
showed that the amount of catalyst decreased with increasing acid treatment time and concentration. Purity of MWCNTs achieved as
high as about 99.9%. This study presents a highly efficient purification method for carbon nanotubes with high purity and no structure destruction. In addition, carbon nanotubes synthesized by various methods were also purified and the results were comprehensively discussed.

Microwave digestion and acidic treatment procedures for the purification of multi-walled carbon nanotubes

Microwave digestion of sludge, soil and sediment samples for metal analysis by inductively coupled plasma–atomic emission spectrometry

Abstract
Three digestion programs for the Anton Paar multiwave microwave were investigated to obtain a simple, rapid method for the determination of metals in sludge, soil and sediment samples. The digests were subsequently analysed for metal content by inductively coupled plasma–atomic emission spectrometry (ICP–AES). The trace metals determined were Mn, Ni, Zn, Pb, Cr, Cd, Cu and V, and the major elements determined were Mg, Ca, Fe and Al. In addition to the heating programs used, different combinations and volumes of hydrofluoric, nitric and hydrochloric acids were evaluated for digestion efficiency. Three standard reference materials (SRMs) were used in the comparison.

From the results obtained, the fastest microwave program (36 min) provided the most consistent recovery data for all three SRMs. Six millilitres of HNO3 was the optimum acid mixture for the digestion of LGC6136 sewage sludge (with the exception of Al) and for LGC6138 coal carbonisation site soil. For PACS-1 marine sediment (and for the determination of Al in LGC6136), a mixture of 3ml of HNO3 + 2ml of HF produced the best analytical results. The experimental
results were in agreement with the certified values and demonstrated that the proposed method was precise and accurate.

Microwave digestion of sludge, soil and sediment samples for metal analysis by inductively coupled plasma–atomic emission spectrometry

Microwave digestion with HNO3-H2O2 mixture at high temperatures for determination of trace elements in coal by ICP-OES and ICP-MS

Abstract
The purpose of this paper is to validate the microwave digestion method with a HNO3/H2O2 mixture for determination of 18 trace elements (Li, Be, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Cd, Cs, Ba, and Pb) in coal by inductively coupled plasma optical emission spectrometry and inductively coupled plasma mass spectrometry. The digestion with a HNO3/H2O2/minute HF mixture was conducted for comparison,and the results were evaluated with reference to three standard coals (SRM1632c, BCR180, and SARM19). It was found that the addition of HF was not required to extract quantitatively the above trace elements in all three coals with the exception of Rb in SARM19 coal by elevating the digestion temperature to 220 ◦C and pressure to 2MPa. Through this rigorous digestion, the organic matrices and clay minerals in coal were extensively decomposed even without HF. However, some trace elements such as V, Cr, Ni, Ga, Sr, and Ba in SARM19 coal were not quantitatively extracted under a milder condition (180 ◦C and 0.9MPa), probably because these trace elements partially remained in the organic matrix and clay residues.

Microwave digestion with HNO3-H2O2 mixture at high temperatures for determination of trace elements in coal by ICP-OES and [url=https://insevent.instrument.com.cn/t/yp]ICP-MS[/url]

Microwave-assisted alkaline digestion combined with microwave-assisted distillation for the determination of iodide and total iodine in edible seaweed by catalytic spectrophotometry

Abstract
Microwave energy has been novelty applied to speed up a tetramethylammonium hydroxide (TMAH) alkaline digestion of seaweed samples and to assist distillation of iodine from seaweed alkaline digests. Iodide in the alkaline digests from seaweed and distilled iodine, reduced back to iodine in a hydroxylamine hydrochloride solution, was determined by a catalytic spectrophotometric method based on the catalytic effect of iodide on the oxidation of As(III) by Ce(IV) in H2SO4/HCl medium (Sandell–Kolthoff reaction). The determination of iodide was directly performed in the alkaline digests, while total iodine was assessed by analyzing the hydroxylamine hydrochloride solution after the distillation process. Microwave-assisted alkaline digestion was performed using 7.5mL of TMAH and irradiating samples at 670W for two 5.5 min steps. Microwave-assisted distillation was carried out using 4.0mL of the alkaline digest and 3mL of a 2.2M hydrochloric acid and 0.05% (m/v) sodium nitrite solution, with a microwave power at 670W for two 90 s steps. The distillate (iodine vapor) was bubbled in 10mL of a 500
gmL−1 hydroxylamine hydrochloride solution (accepting solution). The linear calibration ranges were 0.30–20.0 and 0.40–20.0
gL−1 for iodide determination and total iodine determination, respectively. The limit of detection was 9.2
g g−1 for iodide and 28.5
g g−1 for total iodine. Repeatability of the overall procedures, expressed as R.S.D. for 11 determinations, was 2.6% for 196.3
g g−1 of iodide measured after microwave-assisted alkaline digestion, and 5.8% for 954.3
g g−1 of total iodine by microwave-assisted alkaline digestion followed by microwave-assisted distillation. Finally, accuracy of the methods was assessed by analyzing the NIST-09 (Sargasso) certified reference material and the methods were applied to the determination of iodide and total iodine in different Atlantic edible seaweed samples with satisfactory results.

附件

Microwave-assisted digestion procedure for the determination of palladium in road dust

Abstract
The present publication describes a microwave-assisted digestion procedure for the subsequent trace and ultra-trace analysis
of palladium in road dust of varying origin. Digestion reagents are nitric acid, hydrogen peroxide and hydrofluoric acid.
Boric acid is used as masking agent for fluoride ions to avoid removal of excess hydrofluoric acid by vaporization. After the
three-step digestion procedure, a colorless and residue-free solution is obtained in which the determination of palladium can
be directly performed using a recently developed highly selective on-line pre-concentration system, coupled with graphite
furnace atomic absorption spectrometry (GF-AAS). Dust samples of varying origin (tunnel dust, road dust, filter dust from
Frankfurt, Munich and Japan) and sampling dates (1987–2001) were investigated and characterized in detail with respect to matrix composition and palladium content. Validation of the analytical results was performed by recovery experiments.

附件

On the determination of platinum group elements in environmental materials by inductively coupled plasma mass spectrometry and microwave digestion

Abstract
The interferences from Cd, Cu, Hf, Pb, Sr, Zn, Zr and Y on the inductively coupled plasma quadrupole mass spectrometry
(ICP-MS) determination of Pt, Pd, Rh, Ru and Ir in geological (Pt-ore SARM-7, abundance range for platinum metals
0.07–3.74
g/g) and environmental samples (sediment JSd-2 abundance range for Pt and Pd 0.0167–0.021
g/g; road dust
and plant sample) are evaluated using model solutions, real samples and comparison to inductively coupled plasma atomic
emission spectrometry (ICP-AES) results. Pt, Rh, Ru and Ir can be determined usually after introduction of corrections for
the interference in all investigated materials though in sediments the direct determination of Pt might be a problem depending
on the actual Hf concentrations. The direct determination of Pd (after microwave-assisted acid digestion) is possible in
ores using all investigated isotopes (105Pd, 106Pd, 108Pd), in plants using 108Pd and correction for the interferences of Zr,
Mo and Cd, and not possible in sediments and road dust. Therefore, we developed a procedure for isolation of Pd using
its diethyl-dithio-carabamate (DDTC) complex. The detection limits for Pt, Pd and Ir are 0.015 ng/g, and for Ru and Rh
0.03 ng/g.

On the determination of platinum group elements in environmental materials by inductively coupled plasma mass spectrometry and microwave digestion

Optimisation of microwave assisted digestion of sediments and determination of Sn and Hg

Abstract
The determination of Sn by flow injection–hydride generation–quartz furnace atomic absorption spectrometric (FI–HG–QFAAS) was optimised following different experimental designs. The best conditions were: 0.2% HCl (v/v), 0.5% NaBH4 (w/v) and the furnace temperature 875 ◦C. Under those conditions, the limit of detection was 0.17 ng dm−3 and a precision of 5.3% was obtained. One of the aims of this work was to optimise the closed vessel microwave assisted digestion (MAD) of sediments for the determination of Sn and Hg in the same extract using the analytical conditions previously optimised for Sn in the FI–QFAAS. The optimisation of the MAD of sediments was accomplished following a D-optimal
design, including the composition of the HCl–HNO3 mixture, the pressure and irradiation time. However, we could not determine tin in the extracts due to the formation of foams, the optimisation of the digestion conditions were taken from the FI–cold vapour (CV)–QFAAS measurements of mercury. The optimum conditions were: 2.1 bar of pressure during 10 min of irradiation and two local optima composition of the acid mixtures: 80% HCl–20% HNO3 and 60% H2O–20% HCl–20% HNO3. The determination of mercury in sediments was validated with the CRM-580. In order to determine Sn in sediments the solutions from the same D-optimal design were analysed using an ICP-MS and the digestion conditions were optimised for Sn and for other 8 metals. In this case the same optimal conditions were obtained (2.1 bar and 10 min) but different acid mixture
composition 20% HCl–80% HNO3. The determination of Sn and the other metals in sediments was validated using two other CRMs (PACS-2 and
SGR-1).

Optimisation of microwave assisted digestion of sediments and determination of Sn and Hg

Speciation analysis of selenium compounds in yeasts using pressurised liquid extraction and liquid chromatography–microwave-assisted digestion–hydride generation–atomic fluorescence spectrometry

Abstract
Selenium species present in yeast samples were extracted using pressurised liquid extraction (PLE). Several experimental variables (dispersant agent, time, number of cycles, temperature, pressure and solvent) were evaluated for the extraction of selenocysteine, selenomethionine,selenoethionine, selenite, (Se(IV)) and selenate (Se(VI)) from spiked yeast. Only time, temperature and solvent had an influence on the recoveries. Subsequently, a central composite design was used to investigate the dependence of these operating variables on the recoveries from both spiked and native yeast. The results indicated that experimental conditions were different for spiked and native yeast. The optimum extraction conditions for the native yeast were 11 ml PLE cell, celatom as dispersant agent, 1:1 (v:v) H2O:MeOH, 1600 psi, 160 ◦C, 10 min static time, and 75 vol.% flush. The results obtained by PLE were compared to those obtained by mechanical agitation, sonication and Soxhlet extraction. The extracted selenium compounds were analysed by liquid chromatography (LC)–hydride generation (HG)–atomic fluorescence spectrometry (AFS).

附件

Ultrasound assisted microwave digestion

Abstract
Simultaneous microwave and ultrasound irradiation is shown as a new technique for digestion of solid and liquid samples suitable for chemical and food analysis. Its application in analytical chemistry has been shown by decreases in digestion time: determination of copper in edible oils and total Kjeldahl nitrogen.

Ultrasound assisted microwave digestion

以下是全部的文献的压缩包：
微波消解文献（英文）