Extension of the dynamic range of flame atomic absorption spectrometry using flow injection analysis with variable-volume dilution chambers

A simple and inexpensive procedure is proposed for the extension of the dynamic range of flame atomic absorption spectrometry measurements using on-line dilution. The proposed methodology is based on the use of a manifold with two coupled dilution chambers and a zone injection system. The samples are prediluted in a closed system which includes a variable-volume mixing chamber (10–120 ml) and two injection valves. The samples are injected through one of these valves, and the other is employed to take 100 μl of prediluted samples which are then passed through a new dilution chamber (volume 1–10 ml) and aspirated by the nebulizer of the instrument. A third injection valve mounted in the last part of the manifold is used for the direct injection of diluted standard solutions. Various dilution factors are obtained, ranging from 2 to 130 000 times, thus extending the analytical range of copper determination to more than 100 000 mg l⁻¹.     

Flow injection flame atomic absorption spectrometry for slurry atomization: Determination of manganese, lead, zinc, calcium, magnesium, iron, sodium and potassium in cements

A flame atomic absorption spectrometric procedure for the rapid determination of manganese, lead, zinc, calcium, magnesium, iron, sodium and potassium in cements is described. For minor components, slurries are prepared in the 0.05–0.25% m/v range by direct suspension of the samples in a medium containing 2% v/v nitric acid, 2% hydrofluoric acid and 30% v/v glycerol. 50–200 l aliquots are injected in a simple flow injection manifold using water as the carrier. When determining major components, the FI manifold includes an easy-to-construct variable volume chamber allowing the on-line dilution of the suspensions. The degree of dilution can be easily modified to obtain signals within the linear response range of the instrument. Aqueous standards are used for calibration. The data obtained for six cements agree with those obtained by conventional procedures based on the compl ^M v£e ^w ete dissolution of the samples.     

Study of Analytical Methods for Iron Determination in Complex Organic Liquids by Atomic Absorption Spectrometry

Abstract

In the determination of iron in complex organic liquids by atomic absorption spectrometry (A. A. S.), methods of sample preparation, such as dilution with an organic solvent and sample pretreatment to destroy organic material, are investigated. Moreover, methods of analysis using calibration curve and standard additions are presented. The possible cause of error associated with iron determination in organic samples by flame (F-A. A. S.) and graphite furnace (GF-A. A. S.) atomic absorption spectrometry are discussed.

From all of these studies, the use of graphite furnace atomic absorption spectrometry after sample dilution with methyl isobutyl ketone, and the use of the method of standard additions are advised for iron determination.     

Direct FIA-AS determination of potassium and magnesium in cement samples by use of the slurries approach

A direct procedure has been developed for the flame atomic determination of potassium and magnesium in cement samples. A 50-mg sample is dispersed in 25 ml of 0.13M nitric acid; 100 mul of this slurry is injected in a double channel FIA manifold simultaneously with 100 mul of a 10% (w/v) lanthanum solution. This procedure allows the rapid extraction of potassium and magnesium by leaching of the sample; nitric acid is not necessary if only potassium must be determined and the sample can be diluted with only distilled water. Aqueous standards are used. The manifold employed includes a well-stirred mixing chamber, which provides an adequate on-line dilution of the sample, in order to obtain emission or absorbance measurements in the dynamic range of the elements to be determined. The results obtained in the analysis of real samples agree with those found by flame atomic spectrometry after a previous alkaline fusion with lithium carbonate, and exhibit better precision. The limit of detection of the procedure is 0.007% for K(2)O and 0.01% for MgO and the precision of the entire procedure corresponds to a relative standard deviation of 1%.     

Flame AAS/flame AES for trace determination in fresh and used lubricating oils with sample introduction by hydraulic high-pressure nebulization

In hydraulic high-pressure nebulization (HHPN) an aerosol is produced by means of an HPLC-pump and a special nebulization nozzle, applying a pressure of about 200 bar. This spray technique has been employed for sample introduction of mineral oil samples in flame atomic absorption/flame emission spectrometry. The determination of the trace elements Al, Cr, Cu, Fe, K, Na, Ni, Pb, Si and V has been investigated. Viscosity hardly acts upon the sensitivity of the determination, thereby avoiding a time consuming dilution of oil samples. By means of two interconnecting sampling valves a calibration method based on the standard addition technique can be performed which is both simple and easy to carry out. In samples of used oils, results for Cu and Pb equalled those of XRF-analysis. Regarding Fe traces, data obtained from AAS and XRF measurement correlate. In comparison with sample uptake by pneumatic nebulization, which is restricted to diluted oil samples, detection limits decrease by a factor of 2 to 4, indicating the dilution required in pneumatic nebulization.     

Flame AAS/flame AES for trace determination in fresh and used lubricating oils with sample introduction by hydraulic high-pressure nebulization

In hydraulic high-pressure nebulization (HHPN) an aerosol is produced by means of an HPLC-pump and a special nebulization nozzle, applying a pressure of about 200 bar. This spray technique has been employed for sample introduction of mineral oil samples in flame atomic absorption/flame emission spectrometry. The determination of the trace elements Al, Cr, Cu, Fe, K, Na, Ni, Pb, Si and V has been investigated. Viscosity hardly acts upon the sensitivity of the determination, thereby avoiding a time consuming dilution of oil samples. By means of two interconnecting sampling valves a calibration method based on the standard addition technique can be performed which is both simple and easy to carry out. In samples of used oils, results for Cu and Pb equalled those of XRF-analysis. Regarding Fe traces, data obtained from AAS and XRF measurement correlate. In comparison with sample uptake by pneumatic nebulization, which is restricted to diluted oil samples, detection limits decrease by a factor of 2 to 4, indicating the dilution required in pneumatic nebulization.     

Determination of platinum originated from antitumoral drugs in human urine by atomic absorption spectrometric methods

Cisplatin and carboplatin are the most common platinum-based drugs used in cancer treatment. Pharmacokinetic investigations, the evaluation of the body burden during the treatment, as well as baseline levels of platinum in humans have attracted great interest. Thus, accurate analytical methods for fast and easy Pt monitoring in clinical samples become necessary. In the present study atomic absorption spectrometric methods for the determination of platinum in the forms of cisplatin and carboplatin in human urine were investigated. Platinum, in these different forms, could be determined in urine, after simple sample dilution. Regarding electrothermal atomic absorption spectrometry, the optimum parameters were defined by a central composite design optimization. Multiplicative matrix effects were overcome by using a mixture of HCl and NaCl as modifier. The limit of detection (LOD) was 0.004 mg L⁻¹ of platinum in the original sample. For the analysis of more concentrated samples, high resolution continuous source flame atomic absorption spectrometry was also investigated. Flame conditions were optimized by a multivariate D-optimal design, using as response the sum of the analyte addition calibration slopes and their standard deviations. Matrix matched external calibration with PtCl₂ calibration solutions, was possible, and the LOD was 0.06 mg L⁻¹ in the original sample. The results obtained by the proposed procedures were also in good agreement with those obtained by an independent comparative procedure.     

Determination of Nickel,Manganese, Copper and Zinc in Blood Serum by Atomic Absorption Spectrometry after Deproteinization by Microwave Irradiation

ABSTRACT

Deproteinization of serum was performed by microwave irradiation combined with a small volume of diluted trichloracetic acid. The procedure reduced the protein level of the samples to less than 99% of the total with a small dilution factor (1+1) and allowed the determination of nickel and manganese by electrothermal atomic absorption spectrometry and copper and zinc by flame atomic absorption spectrometry directly without modifiers or matrix interferences. As metallic ions are normally bonded to serum proteins they must be released during protein precipitation. Spiked serum samples were submitted, before the deproteinization, to an incubation treatment to bond the added ions to the proteins. To check the efficiency of the incubation time for each ion, serum samples were ultrafiltered at set time intervals and the metals determined in the ultrafiltrate. The proposed method was compared with the common deproteinization by acids for the separation of the proteins. The reduction of proteins allowed a small dilution of the sample and the use of faster temperature programmes for the determination of nickel and manganese by electrothermal atomic absorption spectrometry and the aspiration of samples more similar to aqueous standards for copper and zinc determination by flame atomic absorption spectrometry. Recoveries from spiked, incubated and deproteinized samples compared to only diluted samples show that the method can satisfactorily be used for atomic absorption spectrometric determination of these elements.     

Speciation of tetraalkyllead compounds by flow injection — atomic absorption spectrophotometry

Summary The on-line demetallation of alkyllead compounds, with iodine, and further emulsification, provides a fast determination of total lead content in liposoluble matrices, such as gasolines. It can be carried out in a double channel manifold, using a magnetically well stirred dilution chamber for the emulsification of the samples, previous to their analysis by flame atomic absorption spectrophotometry. On the other hand, the different behaviour of tetraethyllead (TEL) and tetramethyllead (TML) can be employed for speciation of both compounds in the sample. The effect of the flow injection parameters on the sensitivity and accuracy has been studied and the figures of merit of the proposed methods evaluated.     

The determination of cadmium,copper, iron,lead and zinc in aerosols by atomic-absorption spectrometry

The determination of five elements in filter papers loaded with air particulate matter has been investigated. After a wet destruction of about 10 cm² of filter material by a standard procedure, analysis was carried out with a flame atomic absorption method for zinc and a flameless procedure for Cd, Cu, Fe and Pb. Furnace program parameters for each of the elements in different acid solutions are reported. The interferences of some common anions and the most abundant cations in aerosol material are described. For some urban and industrial samples, the results are compared with those obtained by energy-dispersive x-ray fluorescence. Accuracy was checked against standard samples.     

Extending the dynamic range of flame atomic absorption spectrometry: a comparison of procedures for the determination of several elements in milk and mineral waters using on-line dilution

Three approaches based on continuous flow methodology are assessed for the purpose of extending the dynamic range of flame atomic absorption spectrometry. The determination of several elements in infant liquid and powdered milk and water samples is used to check the performances of the manifolds. Two of the systems are fully computer-controlled and permit a calibration graph to be obtained by using a single standard solution. The results confirm that continuous flow methodology is a reliable alternative to the time-consuming common dilution procedures based on glassware. Since the systems are versatile and permit a wide range of degrees of dilution to be obtained, they can be easily adapted for the automated or semi-automated analysis of other liquid samples which are too concentrated to be aspirated directly into the atomic absorption spectrometer.     

Extending the dynamic range of flame atomic absorption spectrometry: a comparison of procedures for the determination of several elements in milk and mineral waters using on-line dilution

Three approaches based on continuous flow methodology are assessed for the purpose of extending the dynamic range of flame atomic absorption spectrometry. The determination of several elements in infant liquid and powdered milk and water samples is used to check the performances of the manifolds. Two of the systems are fully computer-controlled and permit a calibration graph to be obtained by using a single standard solution. The results confirm that continuous flow methodology is a reliable alternative to the time-consuming common dilution procedures based on glassware. Since the systems are versatile and permit a wide range of degrees of dilution to be obtained, they can be easily adapted for the automated or semi-automated analysis of other liquid samples which are too concentrated to be aspirated directly into the atomic absorption spectrometer.     

Quantitative Untersuchungen von Bauxiten Zentralgriechenlands mittels Atomabsorptionsspektroskopie und Flammenatomemission

Summary A rapid two-part procedure was described for the determination of the elements Al, Fe, Ti, Cr, Ni, V, Mn, Cu, Ag, Au, Ga, Si, Ca, Mg and K in bauxite samples from central Greece. After an NaOH decomposition and an HCl pressure decomposition as well as an aqua regia decomposition carried out in addition, an optimization of the measuring program in time was achieved by constant alternation of atomic absorption spectrometry and atomic flame emission. The elements Ga and Au were measured directly in their extracts using AAS.     

Flow injection flame atomic spectrometric determination of iron, calcium, magnesium, sodium and potassium in ceramic materials by using a variable-volume injector

Summary A series of different ceramic materials, such as porcelain, feldspar, kaolin, varnish, clay and stoneware have been analyzed. Iron, calcium and magnesium have been determined in these materials by flame atomic absorption and sodium and potassium by flame emission. The use of a variable-volume injector enables one to carry out these analyses in a flow system (after fusion of samples with lithium metaborate) and does not require different dilutions for the determination of each type of sample considered, nor the use of different flow injection manifolds. The developed procedure provides a limit of detection of 100 g/l for Na, 70 g/l for Ca, 50 g/l for both Fe and K and 8 g/l for Mg. The coefficient of variation obtained for the absorbance measurement is of the order of 0.5–2%. A series of 17 real samples were analyzed by the proposed procedure and the obtained results turned out to be comparable to those found by batch analysis.     

Flow injection flame atomic absorption spectrometry for slurry atomization. Determination of iron, calcium and magnesium in samples with high silica content

A study on the use of slurries in flame atomic absorption spectrometry is reported. Samples with a very high silica content are ground and then slurried in a solution containing 2% hydrochloric and 3% v/v hydrofluoric acids. The suspensions are prepared in the 0.01-1% m/v range and introduced into the flame by means of a simple flow injection manifold. Relative standard deviations for the measurements of iron, calcium and magnesium in diatomaceous earth samples are in the 1.5-2.8, 2.2-5.3 and 2.8-5.0% ranges, respectively. To avoid the use of suspensions prepared with a very low percentage of solid sample and to improve the reproducibility, an on-line dilution manifold is tried. The use of an easy-to-construct variable volume dilution chamber allows the on-line dilution of the slurries, thus permitting the determination of calcium and magnesium over a wide range of concentrations. Calibration is performed using aqueous standards. The experimental conditions, optimized for the determination of iron, calcium and magnesium in diatomaceous earth samples, can also be applied to other silica-based materials, as is shown by the analysis of several standard reference materials.     

Rapid Procedure to Determine Wear Metals in Lubricating Oils and the Analysis of Variance in the Evaluation of Sample Preparation Procedures

 A new sample treatment is proposed based on a partial wet digestion in closed reactors assisted by microwaves for wear metal determinations by flame atomic absorption spectrometry (FAAS). It is rapid, precise and sensitive and allows the use of inorganic standards. Problems concerning solubility have been overcome with mixed solvents. The repeatability, stability, calibration curve and limit of detection were established. Six samples, with different degree of wear were analyzed for Fe, Cu, Pb and Cr by FAAS using the procedure proposed and other sample treatment procedures from the literature. Pb and Cr were not found in all samples. The one-way analysis of variance for Fe applied to each sample confirms the need of an acid attack and the importance of HCl for the digestion. The results obtained for Cu led us to use a two-way analysis of variance for all the samples considering the preparation procedures and the samples as variation sources. It showed no significant differences for the preparation procedures used. Therefore, treatments implying the use of acids are recommended when several wear metals are analyzed. On the other hand, the differences between the simple dilution and the procedures, implying the dissolution of metallic particles is an index to predict an imminent engine failure. Received March 1, 2001. Revision July 10, 2001.     

Use of membrane micropumps for introducing the sample solution in flame atomic absorption spectrometry

The advantages of using membrane micropumps to introduce sample or standard solutions in flame atomic absorption spectrometry are discussed, using two entirely computer-controlled manifolds which allow a wide range of dispersion coefficients to be obtained. Coupling micropumps to the manifold facilitates calibration graphs to be obtained using a single standard solution. Other advantages include a handy on-line dilution stage for excessively concentrated samples as well as the possibility of obtaining pulsed absorbance-time profiles that once submitted to the Fourier transformation, provide amplitude-frequency plots representing an innovative, not yet fully exploited vision of atomic absorption analytical data.     

Isotope pattern deconvolution-tandem mass spectrometry for the determination and confirmation of diclofenac in wastewaters

Isotope dilution mass spectrometry (IDMS) based on isotope pattern deconvolution (IPD) has been applied here to MS/MS (QqQ) in order to carry out the quantification and confirmation of organic compounds in complex matrix water samples without the use of a methodological IDMS calibration graph. In this alternative approach, the isotope composition of the spiked sample is measured after fragmentation by SRM and deconvoluted into its constituting components (molar fractions of natural abundance and labeled compound) by multiple linear regression (IPD). The procedure has been evaluated for the determination of the pharmaceutical diclofenac in effluent and influent urban wastewaters and fortified surface waters by UHPLC (ESI) MS/MS using diclofenac-d₄ as labeled compound. Calculations were performed acquiring a part and the whole fragment cluster ion, achieving in all cases recoveries within 90–110% and coefficients of variation below 5% for all water samples tested. In addition, potential false negatives arising from the presence of diclofenac-d₂ impurities in the labeled compound were avoided when the proposed approach was used instead of the most usual IDMS calibration procedure. The number of SRM transitions measured was minimized to three to make possible the application of this alternative technique in routine multi-residue analysis.     

Determination of total magnesium in biological samples using electrothermal atomic absorption spectrometry

Magnesium content is an important diagnostic parameter in medicine. It is recognized that its determination in one compartment is not sufficient for reliable information about the magnesium status in the body. In addition to the common procedures of magnesium determination in blood by flame atomic absorption spectrometry, the procedure of electrothermal atomization has also been developed and applied to the analysis of blood fractions, mononuclear cells and isolated nuclei of liver cells.Electrothermal atomization is preferred in cases where the sample size is limited and the magnesium content low. The total errors are in the order of 3–4%. Various techniques of sample pretreatment have been tested and direct dilution with 0.05 mol l⁻¹ nitric acid was optimal when the samples were not mineralized. The calibration graph based on standards containing albumin was found to give the best results, as the form of magnesium in the samples may influence the ashing and atomization processes. Good agreement was obtained for determination of magnesium in standard serum. The results are compared with those obtained by the standard flame atomization technique.     

Determination of some heavy metals in sea water by atomic absorption spectrophotometry

Summary Direct determination of trace metals in sea water by flame atomic absorption technique suffers from serious interferences caused by the high salt content. Separation of the metals from the matrix has been effected by chelation and extraction with ammonium pyrrolidine dithiocarbamate and methyl-isobutyl-ketone. Besides a separation preconcentration and increased sensitivity is achieved with this extraction. Organic substances and metal-organic complexes are destroyed with UV-radiation before extraction is carried out. Flameless atomic absorption has been tried using the Heated Graphite Furnace combined with a) a selective volatilization procedure, b) removing of sodium from the samples using hydrated antimon pentoxide (HAP). Both methods were used to remove the interfering substances (mainly sodium salt). All the techniques have been compared by analysing the same sea water samples, some of which were also analysed by other laboratories.

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Bestimmung einiger Schwermetalle in Meereswasser durch Atomabsorptions-Spektralphotometrie

Zusammenfassung Die direkte Bestimmung der Spurenmetalle in Meereswasser durch Flammen-Atomabsorption wird durch den hohen Salzgehalt behindert. Die Abtrennung der Metalle von der Matrix wurde durch Komplexierung und Extraktion mit Ammoniumpyrrolidindithiocarbamat und Methylisobutylketon erreicht, wodurch außerdem eine Anreicherung und Steigerung der Empfindlichkeit erzielt wird. Organische Substanzen und metallorganische Komplexe können durch UV-Bestrahlung vor der Extraktion zerstört werden. Die flammenlose Technik mit Hilfe des erhitzten Graphitrohres wurde in Kombination mit a) einer selektiven Verdampfungsmethode und b) der Entfernung des Natriums mit hydratisiertem Antimonpentoxid eingesetzt. Alle Verfahren wurden an Hand der gleichen Wasserproben verglichen. Tests wurden auch von anderen Laboratorien durchgeführt.

This work was made possible by substantial grants from International Atomic Energy Agencies (IAEA) and from the Royal Norwegian Council for Scientific and Industrial Research.