Determination of soluble ions and elements in ambient air suspended particulate matter: Inter-technique comparison of XRF, IC and ICP for sample-by-sample quality control

In this paper, we describe a validation procedure for chemical fractionation analysis of elements (Al, As, Ba, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, S, Sb, Si, Sr, Ti and V) and soluble ions (Cl⁻, NO₃⁻, SO₄²⁻, Na⁺, NH₄⁺, Mg²⁺, Ca²⁺) in suspended particulate matter (PM). The procedure applies three distinct measurement techniques (XRF, IC and ICP-OES) to the analysis of individual samples. The techniques used generate different outputs at different stages in the procedure. This makes it possible to identify the contributions of specific parameters to measurement uncertainty. On this basis, we propose a scheme for controlling the analytical quality of data from individual samples in which inter-technique comparisons is used in the same way many analytical methods use surrogates. We apply this scheme to about 310 samples of PM₁₀ and PM_2.5 identifying and assessing the main factors contributing to measurement uncertainty. This procedure successfully resolved a number of difficulties frequently encountered during the analysis of PM, including lack of appropriate reference materials and the low reliability of alternative techniques of quality control. The results demonstrate the critical importance of sample treatment prior to destructive analysis by IC and ICP.     

Deproteinization with ZnSO4–Ba(OH)2 reduces the photodegradation of montelukast during plasma sample preparation for HPLC analysis

Montelukast (MKT), a leukotriene receptor antagonist, degrades when it is exposed to light. The analysis of MKT content in blood plasma by high-pressure liquid chromatography requires several sample preparation steps including deproteinization. This study aimed to evaluate MKT photodegradation in blood plasma samples and optimize a deproteinization method to reduce MKT photodegradation, and thereby improve analytical quality. We evaluated the stability of MKT in water and plasma in real time using high-pressure liquid chromatography and optimized a sample deproteinization procedure by comparing the effectiveness of several deproteinization methods. When exposed to light, MKT photodegraded quickly. Although MKT photodegradation was slightly slower than that in water, a half portion (55%) of the MKT in plasma degraded within 2 h when exposed to light. The rate of MKT photodegradation was dramatically reduced by sample deproteinization using ZnSO₄–Ba(OH)₂, but it was accelerated by deproteinization through precipitation using methanol or acetonitrile. These results suggest that precautions should be taken when preparing plasma samples for the analysis of MKT, and that deproteinization of such samples using ZnSO₄–Ba(OH)₂ can reduce the risk of analytical error arising from MKT photodegradation.     

Space-resolved analysis of trace elements in fresh vegetables using ultraviolet nanosecond laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) has been applied to analyze trace elements contained in fresh vegetables. A quadrupled Nd:YAG laser is used in the experiments for ablation. Analyzed samples come from local markets and represent frequently consumed vegetables. For a typical root vegetable, such as potato, spectral analysis of the plasma emission reveals more than 400 lines emitted by 27 elements and 2 molecules, C₂ and CN. Among these species, one can find trace as well as ultra-trace elements. A space-resolved analysis of several trace elements with strong emissions is then applied to typical root, stem and fruit vegetables. The results from this study demonstrate the potential of an interesting tool for botanical and agricultural studies as well for food quality/safety and environment pollution assessment and control.     

Comparative study of bulk and partial digestion methods for airborne PM10-bound elements in a high mineral dust urban site in Constantine,Algeria

When high mineral loads in atmospheric particulate matter (PM) are present, particular attention should be paid to the selection of appropriate acidic digestion protocols for wet chemical analysis. We report on a comparative study of elemental recovery yields from five different pre-analytical acid digestion procedures for mineral-rich urban background PM₁₀ samples collected in the city of Constantine (Northeastern Algeria). Five reference materials (NIST 1633b, UPM 1648, NAT-7, SO-2 and SO-4) were also digested according to the same protocols. The selected acidic digestion/extraction procedures are widely used for PM chemical analysis and comprise P1 (HNO₃/HF/HCl), P2 (HCl/HNO₃), P3 (HCl/H₂O₂/HNO₃), P4 (HNO₃/HF/HClO₄) and P5 (HNO₃/H₂O₂); the latter assisted with microwave digestion. Elemental recovery yields were compared for major and trace elements typically determined in PM for source apportionment analysis and the results evidenced large differences. For most elements, the bulk extraction procedures (requiring the use of HF) allowed a full elemental recovery, particularly for elements that are associated with aluminium silicate species and oxides that are resistant to mild acid attack. In contrast, in the extraction protocols without HF low recovery yields were obtained for elements such as Al, Ti, Zr, Sc and other aluminium silicate-related elements in PM₁₀ samples with high mineral dust load. We highlight that the European standard digestion method EN-14902:2005 should be applied specifically for the metals for which this method was developed, but caution should be taken when the analysis of other elements in PM is required, especially in urban areas where road and vehicle wear dust is likely to be a major component of ambient PM. When using wet chemistry analysis for PM source apportionment studies, we strongly recommend HF bulk dissolution of samples to ensure the reliability of the geochemical information when coupled with an appropriate analytical tool.     

Stability of Mercury Dilute Aqueous Solutions: An Open Issue

In the framework of the activities of the European Commission Reference Laboratory (CRL) for residues at the Istituto Superiore di Sanità a number of analytical quality control trials on determination of trace analytes are being carried out. As regards trace elements it soon became apparent that the stability of Hg dilute aqueous solutions is rather unsatisfactory. An investigation was thus undertaken to ascertain the conditions under which the concentration of this metal does not appreciably change. Mercury solutions were prepared in high purity deionized water in the concentration range 1–10 ng g⁻¹and the effect of various amounts of HNO₃and K₂Cr₂O₇(alone or in combination) was elucidated by measuring the variations with time in the actual concentration of Hg. Determinations were performed by both inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry. Results show that solutions added with 5% (w/w) HNO₃and 0.01% (w/w) K₂Cr₂O₇do not undergo any significant alteration in the nominal content of the analyte for at least 1 month. Similar conclusions are reached in the case of solutions enriched in CaCO₃, NaCl, NaNO₃, KH₂PO₄, KNO₃, and Mg(NO₃)₂·6H₂O to mimic acid digests of meat samples. The improvement ensuing from the adoption of this approach on the performance of the Hg analytical quality control trials is discussed in detail.     

Preconcentration and determination of rare-earth elements in iron-rich water samples by extraction chromatography and plasma source mass spectrometry (ICP-MS)

A 100-fold preconcentration procedure based on rare-earth elements (REEs) separation from water samples with an extraction chromatographic column has been developed. The separation of REEs from matrix elements (mainly Fe, alkaline and alkaline-earth elements) in water samples was performed loading the samples, previously acidified to pH 2.0 with HNO₃, in a 2 ml column preconditioned with 20 ml 0.01 M HNO₃. Subsequently, REEs were quantitatively eluted with 20 ml 7 M HNO₃. This solution was evaporated to dryness and the final residue was dissolved in 10 ml 2% HNO₃ containing 1 μg l⁻¹ of cesium used as internal standard. The solution was directly analysed by inductively coupled plasma mass spectrometry (ICP-MS), using ultrasonic nebulization, obtaining quantification limits ranging from 0.05 to 0.10 ng l⁻¹. The proposed method has been applied to granitic waters running through fracture fillings coated by iron and manganese oxy-hydroxides in the area of the Ratones (Cáceres, Spain) old uranium mine.     

Äquidensitometrie-eine Methode zur Beurteilung von Plasmen—XI: Untersuchung des Einflusses von NaCl und Ba(NO3)2 auf die Intensität von Linien und die Verteilung von Teilchen im Gleichstrombogenplasma der Silberstein-Methode

The influence of NaCl and Ba(NO₃)₂ on the intensities of atomic lines of Al, Sn and Be and on the axial particle distribution of these elements in the d.c. arc plasma was investigated. As the analytical method we used the procedure of Silberstein in which micro-amounts of solutions were added to the cathode and also to the anode. The time of evaporation, the temperature, the electron pressure, and the intensities of lines were investigated. We used the combination of spectral photography and photographic equidensitometry to derive particle distribution. The results of these investigations were: (1) NaCl and Ba(NO₃)₂ reduced the temperature of the plasma. The electron pressure was constant both in the presence of fairly large amounts of NaCl or Ba(NO₃)₂ and in the hotter arc without additive. (2) The enhancement of the intensities was best in presence of rather large amounts of Ba(NO₃)₂. (3) The maximum of the particle concentration was shifted, by additives from the cathode, towards the middle of the arc. We found a correlation between intensity and this shifting. In the arc with Ba(NO₃)₂ the most homogeneous plasma was obtained.     

Selective volatilisation of trace metals from refractory solids into an inductively coupled plasma

Feasibility studies have been carried out on the use of a graphite electrode assembly for the introduction of U₃O₈ solid samples into a continuously running low-powered argon inductively coupled plasma for the assay of trace metallic elements in uranium. The d.c. arc carrier distillation procedure has been adopted here for the selective volatilisation of analyte elements from the refractory matrix by injecting analyte vapours into the central zone of the plasma using Scribner-Mullin electrodes covered with a graphite lid having a central opening. The experimental parameters have been optimised for the direct determination of B, Be, Cd, Co, Cr, Cu, Fe, K, Li, Mn, Na, Ni and Pb in U₃O₈ powders. The analytical performance of the method has been checked by analysing spiked U₃O₈ samples and is seen to be comparable to or better than d.c. arc methods for these analytes. These results indicate that the carrier-distillation-ICP combination shows promise as a sensitive and precise method for analysis of trace metallic elements in a refractory matrix with a complex spectrum.     

Determination of metal concentrations in lichen samples by inductively coupled plasma atomic emission spectroscopy technique after applying different digestion procedures

Three digestion procedures have been tested on lichen samples for application in the determination of major, minor and trace elements (Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, V and Zn) in lichen samples collected in Aegean Region of Turkey by inductively coupled plasma atomic emission spectrometer (ICP-AES). The acid mixture of concentrated HNO₃, H₂O₂ and HF were used. The instrument was optimized using lichen matrix considering RF power, nebulizer pressure, auxiliary flow rate and pump rate. The accuracy of the overall analyses was first estimated by analysis of two certified reference materials. Good agreement between measured and reference values were found for almost all elements. As the second way of determining the accuracy, results obtained from independent analytical techniques (ICP-AES and instrumental neutron activation analysis (INAA)) were compared for all elements by analyzing real samples. Correlation coefficients of two techniques for the elements ranged between 0.70 (Mg) and 0.96 (Fe). Among the three digestion systems, namely microwave, open vessel and acid bomb, microwave digestion system gave the best recovery results. The method detection limit (MDL) was computed using reagent blanks of microwave digestion system since it provides cleaner sample preparation. Detection limit is adequate for all elements to determine the elements in lichen samples. The precision was assessed from the replicate analyses of reagent blanks of microwave digestion system and was found to be less than 1.5% relative standard deviation (R.S.D.).     

A Sequential Extraction Method Measures the Toxic Metal Content in Fly Ash from a Municipal Solid Waste Incinerator

The purpose of this research was to develop an optimized pretreatment procedure for toxic metals (Pb, Cd, Zn and Cu) content in fly ash from a municipal waste incinerator. In addition, modified sequential extraction procedures were used to characterize the chemical composition of the fly ash samples. The sequential extraction resolved the fly ash elements into the following chemical forms: soluble, exchangeable, carbonate, oxide, organic, and silicate compounds. Certified reference city waste incineration ash (BCR.176) was used as target ash samples. A H₂O₂+HNO₃+HF mixed acid digestion solution with a low temperature evaporation procedure was selected as optimal for the fly ash digestion. The digested solution was analyzed by inductively coupled plasma mass spectrometry (ICP‐MS), which effectively determined the concentrations of the toxic metal elements in BCR.176. Except for Cd, the recovery of Pb, Zn, and Cu under H₂O₂+HNO₃+HF digestion and their sequential extraction procedures were higher than 95%. The relative standard deviations (RSD) for recoveries of the four elements were within 10%. Furthermore, the sequential extraction procedure's results provided information on the potential mobility of the studied elements. Most of the Cd was bound to water‐soluble and carbonate material in the fly ash samples. Most of the Pb, Zn, and Cu was released to carbonates and bound to organic matter in the fly ash samples.     

Determination of Rare Earth Elements in Navel Oranges from Different Geographical Regions of China by Inductively Coupled Plasma-Mass Spectrometry

There are three major production bases of navel oranges in China, including Southern Jiangxi Province, Southern Hunan Province, and the Three Gorges District of the Yangtze River. Southern Jiangxi and Southern Hunan are also famous for rare earth elements that are ionic, making them easily passed from soil to plants and fruits. To test the relative enrichment of rare earth elements in navel oranges from these production sites, ICP-MS analysis was performed following a microwave digestion procedure. The concentrations of La, Ce, Pr, and Nd in navel orange peels from Southern Jiangxi and Southern Hunan (1.26–1.86 µg g^?1) were much higher than results from the Three Gorges (0.23–0.46 µg g^?1). Moreover, yttrium is relatively enriched (0.25–0.29 µg g^?1) in navel orange peels from Southern Jiangxi at concentrations almost twice that from Southern Hunan (0.15 µg g^?1). The various concentrations and distribution of rare earth elements offers the possibility of traceability and authentication of navel oranges. Meanwhile, navel orange peels from Southern Jiangxi posed no risk in consumption, based on the maximum limit level (≤0.7 µg g^?1, wet weight) of rare earth elements in food issued in China (GB 2762-2005).     

Development of a method for automated quantitative analysis of ores using LIBS

This paper reports the development of a method for real-time automated quantitative analysis of mineral ores using a commercial laser-induced breakdown spectroscopy instrument, TRACER™ 2100, fitted with a recently developed computer controlled auto-sampler. The auto-sampler permits the execution of methods for performing calibrations and analysis of multiple elements on multiple samples. Furthermore, the analysis is averaged over multiple locations on each sample, thus compensating for heterogeneous morphology. The results for phosphate ore are reported here, but similar methods are being developed for a range of ores and minerals. Methods were developed to automatically perform metallic element calibrations for supplied phosphate ore samples containing known concentrations of the following minerals: P₂O₅, CaO, MgO, SiO₂ and Al₂O₃. A spectral line for each desired element was selected with respect to the best combination of peak intensity and minimum interferences from other lines. This is a key step, because of the observed matrix dependence of the technique. The optimum combination of the time interval between the laser firing (plasma formation), signal detection, and the duration of the optical detection was then determined for each element, to optimize spectral line intensity and resolution. The instrument was capable of analyzing the required elements in the phosphate ore samples supplied with 2–4% relative standard deviations for most elements. Calibrations were achieved for P, Ca, Mg, Al and Si with linear regression coefficients of 0.985, 0.980, 0.993, 0.987 and 0.985, respectively. Preparation and analysis time for each sample was less than 5 min.     

Application of high-surface-area ZrO2 in preconcentration and determination of 18 elements by on-line flow injection with inductively coupled plasma atomic emission spectrometry

A flow-injection analysis (FIA) system incorporating a micro-column of ZrO₂ has been used for the development of an on-line multi-element method for the simultaneous preconcentration and determination of Al, Bi, Cd, Co, Cr, Cu, Fe, Ga, In, Mn, Mo, Ni, Pb, Tl, V, Sb, Sn, and Zn by inductively coupled plasma atomic emission spectrometry (ICP–AES). The conditions for quantitative and reproducible preconcentration, elution, and subsequent on-line ICP–AES determination were established. A sample (pH 8) is pumped through the column at 3 mL min^–1 and sequentially eluted directly into the ICP–AES with 3 mol L^–1 HNO₃. With a sample volume of 100 mL and an elution volume of 1 mL signal enhancement 100 times better than for conventional continuous aspirating systems was obtained for the elements studied. The reproducibility (RSD %) of the method at the 10 ng mL^–1 level in the eluate is acceptable – less than 8% for five replicates. Recoveries between 95.4% and 99.9% were obtained for the elements analysed. ZrO₂, with a specific surface area of 57 m² g^–1 and a capacity of approximately 5 mg g^–1 for the elements studied, was synthesized by hydrolysis of ZrCl₄. The preconcentration system was evaluated for several simple synthetic matrices, standard water samples and synthetic seawater. The effect of foreign ions on the efficiency of preconcentration of the elements studied was investigated. The application of a micro-column filled with high-surface-area ZrO₂ and flow injection inductively coupled plasma atomic emission spectrometry enables preconcentration and simultaneous determination of 18 elements at low concentrations (ng L^–1) in different water samples.     

Determination of niobium and tantalum in some ores and special alloys by inductively coupled plasma atomic emission spectrometry

A fast analytical method for the determination of niobium and tantalum in ores and special alloys by inductively coupled plasma atomic emission spectrometry has been developed. Optimum conditions for the determination of both metals in the plasma were worked out and possible interferences were studied before attempting the determination in the real samples. Ores are dissolved in a mixture of HCl, HF and H₃PO₄ acids while for the special alloy a HCl+H₂O₂ mixture is used. The resulting solutions are diluted to the mark with tartaric acid before their final direct nebulization into the plasma. Other elements present did not interfere in the determination of Nb or Ta at concentration levels similar to those found in the analyzed samples. The results obtained determining niobium and tantalum in pyrochlore and special alloys by the proposed procedure are in good agreement with the certified values.     

Optimization of sample preparation and ICP-MS analysis for determination of 60 elements for characterization of the plant ionome

An ICP-MS method for determination of 60 elements in plant samples is proposed based on optimization of digestion, recommending use of HF besides HNO₃ and H₂O₂ and calibration procedures, using CRMs for construction of calibration curves. Adequate choice of analytical isotopes and various measurement conditions (cold plasma for the determination of Al, Ba, Ca, Fe, K, Mg, Mn, Na, Si and Sr and DRC mode for determination of Ag, As, Ni, Pd, Pt, Se and V) as well as introduction of appropriate corrections lead to determination of as large number of elements with quadropole ICP-MS as with the more expensive SF-ICP-MS. Two measurements are performed: cold plasma and standard/DRC mode. The analytical characteristics of the method are demonstrated by analysis of five CRMs and the agreement of the experimental results with the certified/information/literature values is very good. Detection limits are low enough to permit the determination of all elements but platinum metals at background level. The applicability of the method is demonstrated by analysis of Taraxacum officinale (dandelion) samples collected from regions with different anthropogenic influence. The results indicate high degree of pollution round the Pb-Zn smelter with As, Cd, Cu, Ni, Pb and Zn and increased concentrations of B, Be, Bi, Hg, In, Mn, Sb, Se, Sn, Ti, Tl, V and Zr. The dandelion sample, collected along a highway has increased concentrations of traffic released elements: Pt, Pd, Rh, Ce, La, Pb as well as Cu, Zn, Ba and Rb.     

An Improved HPLC Method for the Determination of Furosemide in Plasma and Urine

Abstract

A sensitive HPLC method with minimal sample preparation and good reproducibility for the determination of furosemide in plasma and urine is described. Acidified plasma samples were extracted using CH₂Cl₂ containing desmethylnaproxen as internal standard (IS). Fresh urine samples were incubated with β-gluc-uronidase for 15 minutes and then treated with CH₃CN containing IS.

Chromatography was performed on a C18 column with 10 mcl sample injection, Mobile phases were: a) for plasma: 0.01 M NaH₂PO₄, pH 3.5 - CH₃OH (65:35), and b) for urine: acetic acid, pH 3.5 - CHS3OH (60:40) at 3 ml/min and fluorescence detection at Ex 235/Em 389 nm. The plasma standard curve was linear from 0.01 to 15.0 mcg/ml and the urine from 0.5 to 200.0 mcg/ml. The within run CV's were 3,2% at 0.74 mcg/ml plasma and 2.0% at 10.7 mcg/ml urine. Recovery from plasma was 69.9% at 2.0 mcg/ml and 98.6% from urine at 5.0 mcg/ml. The stability of furosemide and its glucuronide were studied. Both methods have been applied to the analysis of plasma and urine samples obtained from human volunteers.     

Effect of transition element doping on crystal structure of rare earth borosilicides REB44Si2

On a previous study on samples of doped-YB₄₄Si₂, an improvement of thermoelectric properties has been achieved. Regarding the interesting effect of the doping of transition elements on the thermoelectric properties, a single crystal study has been carried out on Zn doped, Rh doped and Ni doped samples to assess how the transition element doping affects the crystal structure. Refinements were carried out based on the structural model solution of YB₄₄Si₂ reported in a previous study. Variations in the silicon contents were found in the doped single crystals. Splitting of partially occupied sites has also been detected for some of the doped samples. In this paper we present differences in the partial occupations of boron and silicon sites. Possibility of transition elements insertions based on the differences in crystal structures will be presented.     

Inductively coupled plasma mass spectrometry for the sequential determination of trace metals in sea water after electrothermal vaporization of their dithiocarbamate complexes in methyl isobutyl ketone

 A sensitive method has been developed for the sequential determination of V, Mn, Fe, Co, Ni, Cu, Zn, Mo and Sb in sea water using inductively coupled plasma mass spectrometry (ICP-MS) after electrothermal vaporization of their dithiocarbamate complexes in methyl isobutyl ketone (MIBK). After complexion with sodium diethyldithiocarbamate (NaDDTC), all trace analyte elements were simultaneously separated from sea water matrix and concentrated 20 fold in a single extract of MIBK, followed by introduction of 10 μL of the extract into argon plasma using a pyrolytic graphite rod electrothermal vaporizer (ETV). Sensitivity enhancement due to chemical modification using a mixed modifier of Pd(NO₃)₂-Mg(NO₃)₂ was observed for all the elements. The limits of detection ranged from 2 ng/L for Co to 329 ng/L for V. For replicate determinations of the elements in sea water, the repeatability was within 10% (as a coefficient variation), except for V (12.8%). The recovery test performed on a sea water sample resulted in a range value from 87% for Sb to 119% for V. The method has been successfully applied to sea water samples collected from the surface to the depth of 5000 m at a sampling station in the northwest Pacific Ocean. Received: 1 July 1996/Revised: 24 September 1996/Accepted: 25 September 1996     

Phase and Element Contents of the cBN Based Composites as Estimated by XPS

X-ray photoelectron spectroscopy (XPS) is used to estimate phase and element contents of the composites based on cubic boron nitride. A composite is a mixture of several compounds and the use of traditional X-ray diffraction for phase analysis in many cases can be difficult. By using XPS, we were able to evaluate the atomic concentration of elements and the content of different compounds of each element. SEM and XPS showed that samples are heterogeneous. The TiB₂ phase, expecting from thermodynamic calculations, was formed in both investigated samples of cBN/Ti₃SiC₂/TiC but in different amount. The Ti₃SiC₂ additive was found more chemically active then TiC.     

Influence of O2 Plasma on Surface Properties of PC-TiO2 Nanocomposite Film

In this work, polycarbonate-TiO₂ nanocomposite films were prepared with different percentages. The aim was to consider the effect of O₂ LF plasma (50 Hz) on the hydrophilicity, surface energy, and surface morphology of polycarbonate and polycarbonate-TiO₂ nanocomposite. Structure of samples was determined by using X-ray diffraction analysis. In comparison with the reference sample, the samples’ structure did not change after plasma treatment. Surface properties of polycarbonate and polycarbonate-TiO₂ nanocomposite films were studied by X-ray photoelectron spectroscopy (XPS), contact angle measurement, atomic force microscopy (AFM), and Vickers microhardness tester. XPS analysis showed that the surface of samples became more oxidized due to plasma treatment. The water contact angle significantly decreased from 88° to 15° after plasma treatment. It was observed that the hardness of the nanocomposite films was not modified after plasma treatment.