Determination of 36 elements in plant reference materials with different Si contents by inductively coupled plasma mass spectrometry: Comparison of microwave digestions assisted by three types of digestion mixtures
Abstract Closed-vessel microwave digestion of nine standard reference plant materials (NIST, BCR, IAEA) and a laboratory standard of plant material with different Si contents assisted by HNO3 +H2O2 (procedure A), HNO3 +H2O2 +HF+H3BO3 (procedure B) and HNO3 +H2O2 + HBF4 (procedure C) were used to determine the recovery of 36 elements by ICP-MS: Ag, Al, As, Ba, Be, Bi, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, Ge, In, La, Li, Mn, Mo,Nd, Ni, Pb, Pr, Rb, Sb, Se, Sn, Sr, Th, Tl, U, V, W, Y, Zn. Additions of HF +H3BO3 and HBF4 in procedures B and C exceeded by 10% (B1, C1)and 100% (B2, C2) the equivalent concentrations of Si in the samples determined by ICP-OES. Most recoveries of certified elements (e.g., Al*,Cu, Mo*, Rb*, Sb*, Th) decreased significantly (*p≤0.05) with increasing Si content in plant reference materials digested by procedure A, while the recoveries from procedures B and C decreased insignificantly only for Mo and Sb. Digestions B and C gave significantly higher recoveries of Al, Sb,Wand REEs, which were tighter to the reference values of these elements. A similar effect was found for Cu, Fe, Li, Ni, Sn, Th, Tl, V, Zn,Ba, Rb and Sr recoveries in samples with Si contents exceeding 2000 g g−1. If the Si content in plant samples is less than 10 mg g−1, digestion of 0.5 g of plant samples through 0.05mL of HF and 0.5mL of 4% H3BO3 or 0.1mL of HBF4 is recommended to get satisfactory results for most of the elements. For materials with Si content exceeding 10 mg g−1 the weight of the sample for digestion should be reduced to 0.25 g. However, the operation of potential interferences should be taken into account and eliminated through correction equations and adequate dilution of the samples.
Comparative study of the instrumental couplings of high performance liquid chromatography with microwave-assisted digestion hydride generation atomic fluorescence spectrometry and inductively coupled plasma mass spectrometry for chiral speciation of selenomethionine in breast and formula milk
Abstract A comparison of chiral separation and analysis of selenomethionine in breast and formula milk, using high performance liquid chromatography (HPLC) on a glycopeptide teicoplanin-based chiral stationary phase (Chirobiotic T), coupled to atomic fluorescence spectrometry (AFS) and inductively coupled plasma (ICP) MS detectors has been performed. The coupling HPLC-microwave-assisted digestion hydride generation requires on-line post-column analytes treatment, and a severe sample clean-up for fat and proteins elimination using centrifugation and ultrafiltration. Underivatized dl-selenomethionine enantiomers were completely resolved in 10 min using unbuffered water mobile phase at 1ml min−1 flow. Good selectivity and sensitivities (detection limits 3.1 and 3.5 ng ml−1 as Se for l- and d-selenomethionine, respectively) were obtained, and method robustness and simplicity, together to the low cost of AFS detector, makes it suitable for infant milk routine analysis. HPLC–ICP-MS coupling exhibits very low detection limits (0.9 ng ml−1, as Se) for each dl-selenomethionine enantiomers, but the method suffers from matrix influence, that produces a poor S/N ratio and low reliability.
The methods were applied to breast and formula milk samples with recoveries of 80% of the total selenium presence, which is attributable to the existence of other unknown species. l-Selenomethionine was the only isomer present in breast milk, but a 30% of d-selenomethionine was also detected in formula milk. 附件
Ashing and microwave digestion of aerosol samples with a polypropylene fibrous filter matrix
Abstract Radionuclide monitoring is one of the key techniques required by the International Monitoring System (IMS) and On-Site Inspection (OSI) in the Comprehensive Nuclear Test Ban Treaty (CTBT). There shall be a global network of 80 radionuclide monitoring stations. Atmospheric aerosols are collected generally on filters in the stations. A polypropylene (PP) fibrous filter is often used in sampling atmospheric aerosols. There might be much information to be obtained by measuring aerosol samples after digestion rather than nondestructive analysis directly by -spectrometry. The present work focused on pretreatment of the filter samples, which includes the influence of different ashing or microwave digestion conditions on the recoveries of analytes. The inductively coupled plasma–atomic emission spectrometric detection results indicated that the recoveries of elements in the PP fibrous filters by ashing were influenced by ashing time, temperature and the properties of the elements. High recoveries of volatile elements and consistent recovery for other elements were obtained by using a closed microwave system to digest the filters. Higher sensitivity was also obtained when the intercomparison sample was measured by a HPGe well detector after pretreatment by the recommended ashing and microwave digestion procedures.
Comparison of EDXRF and ICP-OES after microwave digestion for element determination in plant specimens from an abandoned mining area
Abstract In this study an energy dispersive X-ray fluorescence (EDXRF) method has been applied to the analysis of some major and minor elements (K, Ca, Mn, Fe, Cu, Sr, Pb and Zn) in four higher plants growing on the waste landfills surrounding an abandoned Pb–Zn ore concentration factory.
The validation of the procedure was performed by using a certified standard reference material (NIST SRM 1571: “Orchard leaves” from National Institute of Standards and Technology) and by comparison with data obtained from two routine microwave assisted digestion procedures commonly applied to vegetation specimens (Dig A: HNO3 +H2O2, Dig B: HNO3 +H2O2 + HF) plus ICPOES.
No statistically significant differences at the 98% confidence level were found between EDXRF and Dig A results, concerning to Ca, Pb, Sr and Zn. On the contrary, statistically significant differences were found for K, Mn, Fe and Cu due to the presence of a silica residue. The addition of HF (Dig B) neither accomplishes the solubilization of these elements. After Dig B a solid residue is formed mainly composed by Ca and F, according to the results obtained by scanning electronic microscopy (SEM).
Taking into account all these facts, the EDXRF method proposed proved to be an effective tool for metal determination in vegetation specimens since it allows obviating the matrix destruction stage and the poor recoveries for some elements.
Comparison of three optimized digestion methods for rapid determination of chemical oxygen demand- Closed microwaves, open microwaves and ultrasound irradiation
Abstract In the present work, experimental design was used for the fast optimization of three kinds of sample digestion procedures with the final aim of obtaining the COD value of wastewater samples. The digestion methods evaluated were “closed microwave-assisted” (CMWD), “open microwave-assisted” (OMWD) and “ultrasound-assisted” (USD). Classical digestion was used as reference method. The optimum values for the different variables studied in each method were: 90 psi pressure, 475Wpower and 4 min irradiation time (CMWD); 150 ◦C temperature and 4 min irradiation time (OMWD); 90% of maximum nominal power (180 W), 0.9 s (s−1) cycles and 1 min irradiation time (USD). In all cases, interference concentration that produces a deviation of 10% in COD values is 13.4, 23.4, 21.1 and 2819 mg/L for S2−, Fe2+, NO2− and Cl−, respectively. Under optimum conditions, the proposed digestion methods have been successfully applied, with the exception of pyridine, to several pure organic compounds and COD recoveries for 10 real wastewater samples were ranged between 88 and 104% of the values obtained with the classical (open reflux) method used as reference, with R.S.D. lower than 4% in most cases. Thus, the use of ultrasound energy for COD determination seems to be an interesting and promising alternative to conventional open reflux and microwave-assisted digestion methods used for the same purpose since the instrumentation is simpler, cheaper and safer and the digestion step faster than the ones used for the same purpose.
Determination of Cd, Cu, Pb and Zn in environmental samples- microwave-assisted total digestion versus aqua regia and nitric acid extraction
Abstract We validated the determination of the content of Cd, Cu, Pb and Zn using two digestion protocols: a microwave-assisted total digestion and an aqua regia extraction procedure based on the International Organization for Standardisation (ISO) 11466 method. Our goal in validating these two protocols, along with a nitric acid digestion, is to propose a rapid, cheap and easily automated digestion method for monitoring heavy metal content in environmental samples. We applied the digestion protocols to samples with a wide range of organic matter such as sediments, soils, sludges and plant material.For samples with a low carbonate or organic matter contents, such as sediments and agricultural soils, aqua regia digestion in an aluminium block was revealed to be an optimum estimator for the total metal content. For samples with a high organic matter content, such as organic horizons of forest floor layers, plant material and organic soils, nitric acid digestion could substitute microwave (MW)-hydrofluoric acid (HF) digestion. Except in a few samples with high organic matter or low heavy metal content, the RSD values obtained after the application of the proposed digestion procedures were lower than 5%. Based on the obtained results, a decision flowchart for choosing the fit-for-purpose digestion procedure is suggested.
Determination of chromium, iron and selenium in foodstuffs of animal origin by collision cell technology, inductively coupled plasma mass spectrometry (ICP-MS), after closed vessel microwave digestion
Abstract The determination of chromium (52Cr), iron (56Fe) and selenium (80Se) isotopes in foodstuffs of animal origin has been performed by collision cell technology (CCT) mode using an inductively coupled plasma mass spectrometry (ICP-MS) as detector after closed vessel microwave digestion.To significantly decrease the argon-based interferences at mass to charge ratios (m/z): 52 (40Ar12C), 56 (40Ar16O) and 80 (40Ar40Ar), the gas-flow rates of a helium and hydrogen mixture used in the hexapole collision cell were optimised to 1.5 ml min−1 H2 and 0.5 ml min−1 He and the quadrupole bias was adjusted daily between −2 and −15mV. Limits of quantification (LOQ) of 0.025, 0.086 and 0.041 mg kg−1 for Cr, Fe and Se, respectively, in 6% HNO3 were estimated under optimized CCT conditions. These LOQ were improved by a factor of approximately 10 for each element compared to standard mode.
Precision under repeatability, intermediate precision reproducibility and trueness have been tested on nine different certified reference materials in foodstuffs of animal origin and on an external proficiency testing scheme. The results obtained for chromium, iron and selenium were in all cases in good agreement with the certified values and trueness was improved, compared to those obtained in standard mode.
Determination of heavy metals in crayfish by ICP-MS with a microwave-assisted digestion treatment
Abstract Contamination of the American red crayfish, from the Guadiamar riverside, is due to the disastrous toxic spill that occurred on 25 April 1998 in the mining area of Aznalc! ollar-Los Frailes, Spain. A high concentration of heavy metals in the waters from the mine pool and their spill to the river Guadiamar was the cause of the destruction of a great number of animal and vegetable organisms. An ICP-MS method for the total determination of heavy metals (Cu, Zn, Pb, and Cd) in whole bodies of American red crayfish (Procambarus clarkii) was used. Metals were extracted from the matrix in a closed-vessel microwave digestion system with nitric acid and hydrogen peroxide. A study of the uncertainty of the method for the determination of metals was carried out; at a concentration of 5 mg/L, the uncertainty was below 34%.
Determination of platinum and rhodium in dust and plant samples using microwave-assisted sample digestion and ICP-MS
Abstract The platinum group elements (PGEs), particularly platinum, palladium and rhodium, are nowadays increasingly emitted into the environment from automotive catalytic converters. Thus, a method for the determination of PGEs (especially platinum and rhodium) in dust and plant samples was developed. The developed method was based on microwave-assisted sample digestion and inductively coupled plasma mass spectrometric (ICP-MS) determination. Spectral interferences in ICP-MS determination were corrected using mathematical correction equations based on signal ratio measurement. In addition, platinum and rhodium concentrations in the digested dust samples were also determined after Te coprecipitation without correction of the interferences. The results for platinum and rhodium in reference materials (NIST SRM 2557, recycled monolith autocatalyst and BCR-723, road dust) were in good agreement with the certified values. Preliminary results for the anthropogenic platinum and rhodium emissions in Oulu, northern Finland, based on dust and plant samples, indicated a common traffic-related source of these metals.
Determination of trace elements in agricultural soil samples by inductively coupled plasma-mass spectrometry- Microwave acid digestion versus aqua regia extraction
Abstract Microwave acid digestion and aqua regia extraction techniques were investigated to obtain a simple, rapid and safe method for the determination of eight trace elements in soil (Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn). Soil samples were collected between 6 October and 3 November 2004, air dried, grinded, sieved (<63 m) and subjected to digestion. The digests were subsequently analyzed for metal content by inductively coupled plasma-mass spectrometry (ICP-MS). Various combinations and volumes of hydrofluoric, nitric and hydrochloric acids were evaluated for the microwave acid digestion efficiency. Two certified reference materials (CRM 142, light sandy soil, and CRM 143, over fertilized soil) were used in the comparison of these digestion protocols and good agreement between the two procedures and the certified values was found. The aqua regia microwave acid digestion with a mixture of 2ml of HNO3 and 6ml of HCl produced the fastest, safest and accurate analytical results with a recovery of 91–110% and a precision better than 5% in most cases. Very low limits of detection were obtained, below 0.05 g g−1, for all elements, except for Zn, 2.3 g g−1. A number of agricultural soil samples irrigated by the Tinishu Akaki River (TAR) and its tributaries, Ethiopia, were analyzed.
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