Induced Plasma Optical Emission Spectrometry Research Articles

Multi-energy calibration and induced plasma optical emission spectrometry (MEC-MIP OES) as an alternative method for the multi-elemental determination of essential elements in cocoa.

The challenge of combining MEC-MIP OES arises from the limited number of emission lines available in this analytical technique. For the MEC-MIP OES optimization, the emission line wavelengths, sample dilution, proportion sample:standard for preparing MEC solutions, and nebulizer gas flow rate were studied. Then, the use of multi-energy calibration (MEC) and microwave-induced plasma optical emission spectrometry (MIP OES) was proposed as an alternative method for the determination of essential elements (Ca, K, Mg, Mn, and Na) in cocoa. In the optimized conditions, the method presented adequate analytical performance, with recoveries of 94-104% and relative standard deviations lower than 5%, showing adequate precision. The limits of detection (mg kg-1) were 12 for Ca, 2 for K, 3 for Mg, 3 for Mn, and 6 for Na. The proposed method was applied to analyze cocoa samples cultivated in Brazil and Ecuador after acid decomposition. The results were in the range (mg kg-1) of 409-1530 for Ca, 5520-13300 for K, 1460-3210 for Mg, 16-34 for Mn, and 28-61 for Na. Samples cultivated in Ecuador presented higher metal concentrations than the Brazilian samples. The proposed procedure was an easy and reliable approach for determining metals in cocoa samples, enabling multi-elemental determination with a lower cost and simplified calibration to be applied in routine applications.

Selection of Internal Standards for Determining Rare-Earth Elements by Microwave Induced Plasma Optical Emission Spectrometry

Selection of Internal Standards for Determining Rare-Earth Elements by Microwave Induced Plasma Optical Emission Spectrometry

Microwave-sustained inductively coupled atmospheric-pressure plasma (MICAP) for the elemental analysis of complex matrix samples

Microwave induced plasma optical emission spectrometry (MIP-OES) has gained widespread attention in the last few years for trace elemental analysis. Among the new generation of MIPs it is worth to mention the microwave-sustained inductively coupled atmospheric-pressure plasma (MICAP) for which previous works have shown similar detection capabilities to those afforded by ICP-OES. Nevertheless, this instrument has not been applied yet to complex matrix sample analysis. Therefore, the goal of this work is to evaluate MICAP-OES performance (e.g., analytical figures of merit, matrix effects, etc.) for elemental analysis of samples of different nature (e.g., environmental, food and polymers). To this end, both spectral and non-spectral interferences were investigated for 19 elements (Ag, Al, As, B, Ca, Cd, Co, Cr, Cu, Fe, Ga, In, Mg, Mn, Ni, Pb, Sr, Tl, Zn) in the presence of inorganic acid, organic and saline solutions and compared to a 5 % w w−1 HNO3 solution. Unlike previous MIPs, experimental data showed that the optimum nebulizer gas flow rate for a given emission wavelength was mostly independent of matrix characteristics. Regarding matrix effects, this device was highly robust operating both inorganic acid and organic matrices. Interestingly, when operating saline matrices, changes on emission signal by easily ionizable elements were less significant than those early reported by alternative MIP cavities. Moreover, due to MICAP spectrometer design employed allows real-time simultaneous analysis, Rh, Pd, Sc and Y were suitable internal standards to minimize non-spectral interferences. Finally, MICAP-OES can be successfully applied to the elemental analysis of different complex matrix samples (i.e., CRM-DW1 Drinking water; BCR-146 Sewage sludge industrial; BCR-185 Bovine liver; BCR-278R Mussel tissue; NIST-1549 Non-fat milk powder; ERM-EC681k Polyethylene (high level) and BCR-483 Sewage sludge amended soil).

Wear metal determination in lubricating oils by reversed-phase dispersive liquid–liquid microextraction and microwave induced plasma optical emission spectrometry

A synergetic combination of reversed-phase dispersive liquid–liquid microextraction and microwave induced plasma optical emission spectrometry as a green analytical method for wear metal determination in lubricating oils.

A Novel Biological, Environmental, and Food Micro-Amount Slurry Samples Injection Technique for Simultaneous Quantification of Metals Using a Microwave Induced Plasma Optical Emission Spectrometry

A Novel Biological, Environmental, and Food Micro-Amount Slurry Samples Injection Technique for Simultaneous Quantification of Metals Using a Microwave Induced Plasma Optical Emission Spectrometry

Determination of Cd, Pb and Zn in Polymers by Laser Ablation Microwave Induced Plasma Optical Emission Spectrometry

Abstract The potential of laser ablation microwave induced plasma optical emission spectrometry (LA-MIP OES) for the analysis of plastic materials has been investigated. Inorganic species, e.g., metals may be added to them as additives, anti-oxidising agents, stabilisers, plasticisers, colorants and catalytic residues, contaminants and may be present in a wide range of concentrations. The study revealed elevated content of trace elements (Cd, Pb and Zn) which are components of poly(vinyl chloride) (PVC) and polyethylene (PE). Laser ablation using wavelengths of 266 nm as a sampling method for MIP OES was used. The result achieved using elaborated system were compared with those obtained after polymer samples decomposition in high pressure-temperature focused microwave heating digestion system and standard sample pneumatic nebulisation (PN) to MIP OES spectrometer. The calibration strategy using cellulose pellets as support for qualitative analysis for element determination in polymers by LA-MIP OES was proposed. This analytical performance of the LA-MIP OES system was characterised by a determination of the limits of detection (LODs) and precision (RSDs) for elements tested. The experimental concentration detection limits for simultaneous determination, calculated as the concentration giving a signal equal to three times of the standard deviation of the blank (LOD, 3σblank criterion, peak height) were 2 µg g– 1, 3 µg g– 1 and 5 µg g– 1 for Cd, Pb and Zn, respectively. The method offers relatively good precision (RSD ranged from 3 % to 5 %) for micro sampling analysis.

Given the high intake of potatoes by the world population, reliable methodologies with very low limits of detection are needed for the determination of highly toxic elements such as arsenic. For that purpose, graphite furnace atomic absorption spectrometry could be considered one of the techniques of choice; notwithstanding the matrix effect prevented its application in arsenic determination in potatoes as

Given the high intake of potatoes by the world population, reliable methodologies with very low limits of detection are needed for the determination of highly toxic elements such as arsenic. For that purpose, graphite furnace atomic absorption spectrometry could be considered one of the techniques of choice; notwithstanding the matrix effect prevented its application in arsenic determination in potatoes as the analytical signal was absolutely depleted. The potential interferent was searched among the mineral content. As a result, it was found that the interference presumably could be attributed to phosphate. Attempts to overcome the matrix interference by different sample digestion methodologies, chemical modification and temperature variation in the graphite furnace ashing and ashing / atomization stage respectively, were unsuccessful. Consequently, an alternative methodology for determining arsenic in potatoes using hydride generation microwave induced plasma optical emission spectrometry was developed. Limit of detection was 0.0030 mg kg-1 in fresh potatoes. The developed method is a robust, simple and low cost alternative for total arsenic safe monitoring of this highly consumed worldwide vegetable.

Determination of essential and potentially toxic trace elements in natural and processed coconut water by microwave induced plasma optical emission spectrometry, and risk assessment

Determination of essential and potentially toxic trace elements in natural and processed coconut water by microwave induced plasma optical emission spectrometry, and risk assessment

Poly(lactic acid)/β-cyclodextrin based nanoparticles bearing ruthenium(II)-arene naproxen complex: preparation and characterisation. Analytical validation for metal determination by microwave-induced plasma optical emission spectrometry

The objectives of this work are to develop nanocarrier systems for the Ru(II)-p-cymene naproxen antitumor metallodrug, [Ru(η6-p-cymene)(npx)Cl] or Rupcy, based on polymeric nanoparticles (NPs) composed by the biodegradable poly(lactic acid) (PLA) and the hydrophilic polymerised β-cyclodextrin (PolyCD); to validate an analytical method for determination of Ru incorporated into the metallodrug loaded-NPs. The PolyCD was prepared by single step condensation and polymerisation reaction and incorporated as a polymer blend during the fabrication of PLA/PolyCD blends NPs and also as a core/shell structure built by adsorption of the PolyCD onto the surface of PLA NPs to give PLA(core)/PolyCD(shell) NPs. Three different loaded-systems incorporating the metallodrug (Rupcy-PLA NPs (1), Rupcy-PLA/PolyCD blends (2), and Rupcy-PLA(core)/PolyCD(shell) NPs (3)) were prepared by nanoprecipitation. The characterisation was performed by Proton Nuclear Magnetic Resonance, Matrix Assisted Laser Desorption/Ionization Time-of-Flight, Fourier-Transform Infra-red and UV-VIS Electronic Absorption Spectroscopies, Thermogravimetric Analysis, Differential Scanning Calorimetry, Dynamic Light Scattering, and Electrophoretic Light Scattering. Ru was determined by Microwave Induced Plasma Optical Emission Spectrometry (MIP-OES) with validation of the method. The metallodrug entrapment efficiency was around 90% (w/w) and drug loading was at 3–4% (w/w). The characterised metallodrug-loaded systems exhibited monomodal size distributions and appropriate hydrodynamic diameters [218.3 ± 13.5 (1), 205.4 ± 14.4 (2), 231.5 ± 22.0 (3) nm] and zeta potential values [−31.5 ± 2.2 (1), −26.1 ± 4.5 (2), −28.8 ± 6.1 (3) mV]. The validation of the MIP-OES method by evaluating selectivity, linearity, precision, accuracy, and limits of detection and quantification succeeded. The NPs parameters are compatible with colloidally stable systems. The MIP-OES method showed to be simple, reliable, and feasible to quantify indirectly the amount of the metallodrug-loaded into the PLA NPs.

Discrete micro-volume suspension injection to microwave induced plasma for simultaneous determination of cadmium and lead pre-concentrated on multiwalled carbon nanotubes in optical emission spectrometry

A discrete sample introduction system (DSIS) for the direct micro-volume nanomaterials (NMs) suspension injection has been developed toward the simultaneous determination of Cd and Pb pre-concentrated (by dispersive micro solid-phase extraction (DMSPE)) on oxidized multiwalled carbon nanotubes (MWCNTs) to microwave induced plasma optical emission spectrometry (DMSPE-DSIS-MIP OES). On-axis low-volume spray chambers with flow focusing micro nebulizer (continues mode) and v-groove type pneumatic nebulizer (discontinues mode) for microliter-volume suspension introduction were tested.A univariate approach and the simplex optimization procedure were used to achieve optimized conditions and derive analytical figures of merit. Minimum dead volume, high nebulization and suspension transport efficiency were obtained by using miniaturized spray chamber/v-groove pneumatic nebulizer interface for 10 μL suspension injection in discontinues mode (at 0.5 mL min−1 pump speed).Analytical performance of DMSPE-DSIS-MIP OES method was characterized by determination of the limits of detection (0.7 and 0.1 ng mL−1 for Cd and Pb, respectively) and precision ranged from 6% to 8%. Quantitative data obtained for water reference materials (ERM-CA011b and SRM 1643e) were in good agreement, according to the t-test, for a confidence level of 95%, with the corresponding reference values, proving the potential of this analysis system for trace analysis via MIP OES. The proposed method had been successfully applied for the determination of Cd and Pb in water real samples.

Matrix effects in simultaneous microwave induced plasma optical emission spectrometry: new perspectives on an old problem

Line-dependent analyte signal suppression/enhancement by 18 common matrix elements was simultaneously investigated for MIP-OES. Li caused the strongest matrix effect, even for concentrations as low as 20 mg L−1.

Applicability of microwave induced plasma optical emission spectrometry for wear metal determination in lubricant oil using a multinebulizer

A new multinebulizer is combined/associated with an on-line standard dilution analysis for wear metal determination in lubricating oils by MP AES.

Determination of elemental bioavailability in soils and sediments by microwave induced plasma optical emission spectrometry (MIP-OES): Matrix effects and calibration strategies.

In the past few years, microwave induced plasma optical emission spectrometry (MIP-OES) has generated great interest as an alternative technique to inductively coupled plasma-based techniques due to its lower operational cost. Since MIP-OES suffers from severe matrix effects due to easily ionizable elements (EIEs) (Na, Ca, etc.), it is unclear whether this technique could be employed for elemental bioavailability studies in soils and sediments since the main extractant solutions employed in such works may contain high levels of these elements. Thus, the aim of this work was to evaluate the feasibility of MIP-OES as a detector for such applications. To this end, the influence of different extractant solutions (0.25molL-1 MgCl2, 0.25molL-1 CaCl2, 0.10molL-1 acetic acid, 0.05molL-1 Na2EDTA, 0.25molL-1 NaNO3, 0.25molL-1 NaOAc/HOAc and 0.10molL-1NH2OH·HCl) on the analyte emission of several elements (As, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Rh, Se, Sr and Zn) was investigated. Results were compared to those obtained using a reference solution made of 5% w w-1 HNO3 solution. For saline extractant solutions, both the optimum nebulizer gas flow rate (Qg) and analyte emission were modified with regard to the reference solution. In general, the optimum Qg was reduced by between 0.1 and 0.2Lmin-1 for both ionic and atomic lines. Under optimum Qg conditions, analyte emission was supressed by saline solutions except for atomic lines with an upper electronic state below 4eV, which were enhanced. The magnitude of matrix effects was strongly dependent on EIE ionization energy. The lower the ionization energy, the greater the matrix effects were registered. No measurable matrix effects were registered on both Qg and analyte emission within experimental uncertainties for NH2OH·HCl and acetic acid extractant solutions. Experimental data suggest that matrix effects were related to changes in plasma characteristics and the analyte excitation/ionization mechanism. To mitigate matrix effects and improve long-term MIP-OES performance, internal standardization using either Rh (343.489nm and 369.236nm) or OH molecular emission band (308.958nm) was required. This calibration methodology was successfully applied to the study of the elemental bioavailability in soil samples from a vineyard affected by copper-based fungicides and sediment samples from an area affected by mining waste.

Lead determination by HG-MIP OES with nitrogen plasma after a variable optimization study

A hydride generation nitrogen microwave induced plasma optical emission spectrometry (HG-MIP OES) system was developed for lead determination.

Microwave induced plasma optical emission spectrometry (MIP OES) and laser-induced breakdown spectroscopy (LIBS) for multi-element determination and location in ceramic tableware

In the present study, the microwave induced plasma optical emission spectrometry (MIP OES) and laser-induced breakdown spectroscopy (LIBS) complementary techniques are used to determine and locate metals in ceramic tableware samples. For quantitative analysis by MIP OES, a new method for sample treatment is proposed, preparing the samples using ultrasonic decomposition aided by an acid mixture containing HNO3 and HF. The highest average concentrations were found in the group of Brazilian samples for most of the analytes. The accuracy of the quantitative method was assessed by comparing the results with two methods described in the literature. No significant differences were detected. Aiming at qualitative analysis and analyte locating by LIBS, a sample fragment was already sufficient for the analysis, being possible to observe that Al, Ba, Ca, Fe, K, Li, Mg, Na and Ti are present in the ceramic mass and decorated surface, while Cd, Co, Cr, Cu, Mn, Pb and Zn are found only on the sample surface. Besides, according to LIBS results, it would be essential to pay attention to pigmentation, which contains most of the potentially toxic elements, at locations in direct contact with food to minimize the risk of leaching and avoid human contamination. This study shows that MIP OES and LIBS can be used complementarily to improve the analytical information used to control the ceramic tableware quality and safety. The conclusions of this work can be extended to several other types of samples where both the average contents and the location of the elements are relevant.

Iron species determination by high performance liquid chromatography with plasma based optical emission detectors: HPLC–MIP OES and HPLC–ICP OES

The paper presents an independent application of two hyphenated techniques, wherein an identical chromatographic system i.e. high performance liquid chromatography (HPLC) was coupled to microwave induced plasma optical emission spectrometry (MIP OES) or inductively coupled plasma optical emission spectrometry (ICP OES). A cation–exchange column and a mobile phase based on pyridine–2,6–dicarboxylic acid (PDCA) were employed to separate Fe(II) and Fe(III) within 300 s. Additionally, two methods of sample preparation were employed. Optimization and validation of both methods were conducted parallel. The applicability was presented with different sample matrix types: post–glacial sediments, archaeological pottery, soils located in the proximity of industry wastes disposal site, river sediments and yerba mate (Ilex paraguariensis). Obtained results were compared in terms of the excitation source (microwave induced or inductively coupled) and supplied gas (nitrogen or argon). The research introduces HPLC–MIP OES for iron speciation analysis and its applicability were critically evaluated with HPLC–ICP OES.

Determination of total concentration and bioaccessible fraction of metals in tomatoes and their derivatives by MIP OES

This study presents information about the total concentration and bioaccessible fraction of barium (Ba), calcium (Ca), cadmium (Cd), copper (Cu), iron (Fe), mercury (Hg), potassium (K), lithium (Li), magnesium (Mg), manganese (Mn), molybdenum (Mo), lead (Pb) and zinc (Zn) in different cultivars of tomato (Gaucho, Paulista, Italiano and Cherry) and their derivatives (sauce and tomato extract). The determinations were performed by microwave induced plasma optical emission spectrometry (MIP OES). The bioaccessible fraction of the elements was evaluated through in vitro digestion process and the concentrations varied between 25 and 100 % ​for Cu, Fe, Mn and Zn, depending on the type of tomato sample and its derivatives. The total concentrations for all the elements studied were below the recommendation of dietary guidelines. For Ba, only the Italiano sample presented 22 % of bioaccessibility. For Pb, the highest percentage of bioaccessible fraction was found in sauces and tomato extracts. The elements Cd, Hg, Li and Mo presented concentrations lower than the limit of detection for the bioaccessibility method.

Effect of Plasma Gas and the Pressure on Spatially and Temporally Resolved Images of Copper Emission Lines in Laser Induced Plasma Optical Emission Spectrometry.

This paper investigated two-dimensional spatial and temporal images of a copper emission line in laser-induced breakdown spectroscopy (LIBS), in order to clarify the excitation/de-excitation processes occurring in a laser-induced plasma. The measurements were carried out under different plasma gases (argon, krypton, helium, and nitrogen), pressure levels (100 - 900 Pa) and delay times (100 - 1000 ns) with the aim of monitoring their effects on the behavior of the copper emission. Depending on the plasma gas type and the pressure level, large differences were found in the plasma shape and temporal intensity evolution of the copper emission profile. Namely, krypton produced the most compact plasma emitting larger intensities, compared to argon and helium, and an increase in the gas pressure made these plasmas to shrink, which could be related principally to the stopping power of the applied gases. Through temporally resolved analysis, the delay profiles could be obtained for each plasma gas, indicating that the helium plasma disappeared more rapidly than the argon and krypton plasmas. It was suggested that the variations in the emission intensity would be determined by interactions between gas particles and highly energetic particles in the plasma breakdown as well as interactions between excited gas particles and copper species during plasma expansion. These insights could prove to be useful in the understanding of the background of LIBS as well as the optimization of its practical applications.

Plasma molecular species and matrix effects in the Hummer cavity microwave induced plasma optical emission spectrometry

The effect of matrix elements with ionization potentials from 5.72 to 10.48 eV (In, Ga, Cu, Pb, Cd, Bi, Zn, P) on atom and ion excitation temperatures, magnesium ratio, plasma molecular species and analytical signals more 30 trace elements in atmospheric pressure nitrogen microwave induced plasma (Agilent 4100 AES MP) have been studied. The concentration of matrix elements was varied in the range of 0–1% w·w−1. It was shown that in the Hammer cavity, intensities of atomic and ionic lines with similar energies change in a similar way with increasing concentration of the matrix element. It was shown that, in general, the matrix effect doesn't correlate with the temperature. The Mg(II)/Mg(I) and both N2+/OH and N2+/N2 correlates with the ionization potential of the matrix element and reflect the degree of its manifestation.

Sensitive determination of bioaccessible mercury in complex matrix samples by combined photochemical vapor generation and solid phase microextraction coupled with microwave induced plasma optical emission spectrometry

The photochemical generation technique of mercury vapor (PCVG) coupled with headspace solid phase microextraction (SPME) and microwave induced plasma optical emission spectrometry (MIP-OES) has been developed and successfully applied for fast and sensitive determination of mercury in complex matrix samples. Mercury vapor was generated by UV photo-reduction of inorganic mercury and methylmercury to mercury vapor in 5% (v/v) formic acid with subsequent gas-liquid separation and preconcentration by solid phase microextraction. A stopped-flow mode of the PCVG-SPME unit was employed with the aim of increasing analyte preconcentration factor, thus improving both sensitivity of determination and detection limits for mercury. The calibration curves were linear up to 20 ng mL−1 with the limit of detection for inorganic mercury and methylmercury of 0.030 and 0.045 ng mL−1, respectively. This manifold allowed a repeatability, expressed as relative standard deviation, of below 5%. Due to differences in efficiency of Hg vapor generation for Hg2+ and CH3Hg+, the quantification was performed against external Hg2+ and CH3Hg+ aqueous standards, respectively. The method was validated by the analysis of two CRM materials of different matrix composition, i.e. estuarine sediment ERM CC580 for total mercury content and tuna fish ERM CE464 for methylmercury content, respectively. The results proved good accuracy of the method with recovery of 101% total mercury and 87.3% methylmercury and precision of 3.8% and 12.5%, respectively. Effect of concomitants in the stopped-flow generation of mercury vapor with the new manifold was also investigated. Next, the proposed method was successfully applied for monitoring of bioaccessible fraction of mercury during their incubation in simulated body fluid in the presence of selenium nanoparticles examined as a potential mercury detoxifying agent.