Different Lubricating Oil Treatments for the Determination of Cu,Cr, Fe,Ni, Sb,Pb, and Zn by HR-CS FAAS

Abstract

Microwave-assisted acid decomposition, direct dilution in kerosene, and oil-in-water emulsion were evaluated as lubricating oil pretreatment procedures for Cu, Cr, Fe, Ni, Pb, Sb, and Zn determination by High-Resolution Continuum Source Flame Atomic Absorption Spectrometry (HR-CS FAAS). For wet digestion, results were compared with those obtained by Flame Atomic Absorption Spectrometry (FAAS). The ultrasound probe used in emulsions sonication contaminated samples with Cr, although better results have been observed for the other six elements in this condition. In general, recovery percentages ranging from 81–106% (Cu), 80–107% (Cr), 85–114% (Fe), 82–116% (Ni), 86–117% (Pb), 85–115% (Sb), and 81–114% (Zn) were obtained. The HR-CS FAAS showed to be faster and more sensitive than FAAS.     

Determination of Wear Metals in Marine Lubricating Oils by Microwave Digestion and Atomic Absorption Spectrometry

 The difficulties associated with the development of a microwave-assisted acid digestion of lubricating oils in determination of wear metals are presented. The interest of this sample treatment lies in its basis for determining the total metal contents with enough sensitivity by flame atomic absorption spectrometry (FAAS). It allows earlier diagnosis of the engine state than is obtained by the widely applied simple dilution procedure. Another advantage is the avoidance of contamination and loss of the metals to be determined. The procedure employs nitric acid and hydrogen peroxide in a four-stage programme. Fe, Cu, Cr and Pb are determined by FAAS as representative of engine wear. The limits of detection are 0.1 μg/g for Fe and Cr and 0.05 μg/g for Cu and Pb. A comparison with other procedures is presented for spiked samples. Different types of used lubricating oils supplied by an oil company were analysed to prove the suitability of the procedure proposed. Received November 11, 1998. Revision Februray 20, 1999.     

Direct μ-flow injection isotope dilution ICP-MS for the determination of heavy metals in oil samples

The determination of trace elements in oil samples and their products is of high interest as their presence significantly affects refinery processes and the environment by possible impact of their combustion products. In this context, inductively coupled plasma mass spectrometry (ICP-MS) plays an important role due to its outstanding analytical properties in the quantification of trace elements. In this work, we present the accurate and precise determination of selected heavy metals in oil samples by making use of the combination of μ-flow direct injection and isotope dilution ICP-MS (ICP-IDMS). Spike solutions of ⁶²Ni, ⁹⁷Mo, ¹¹⁷Sn and ²⁰⁶Pb were prepared in an organic solvent, mixed directly with the diluted oil samples and tested to be fit for purpose for the intended ID approach. The analysis of real samples revealed strong matrix effects affecting the ICP-MS sensitivity, but not the isotope ratio measurements, so that accurate results are obtained by ICP-IDMS. Typical relative standard deviations were about 15% for peak area and peak height measurements, whereas the isotope ratios were not significantly affected (RSD < 2%). The developed method was validated by the analysis of a metallo-organic multi-element standard (SCP-21, typically applied as a calibration standard) and the standard reference material SRM1084a (wear metals in lubricating oil). The obtained results were in excellent agreement with the certified values (recoveries between 98% and 102%), so the proposed methodology of combining μ-flow direct injection and ICP-IDMS can be regarded as a new tool for the matrix-independent, multi-element and reliable determination of trace elements in oil and related organic liquids.     

The application of butanol as dilution agent for the inductively coupled plasma-atomic emission spectrometric determination of boron and phosphorus in lubricating oils

An evaluation of butanol-1 as dilution solvent for the determination of boron (B) and phosphorus (P) in lubricating oils by inductively coupled plasma-atomic emission spectrometry (ICP-AES) has been performed. Standard solutions of boric acid and tri-n-butyl phosphate (TBP) in butanol were employed as calibrants for B and P, respectively. Solutions of phosphoric acid and tris(2-ethylhexyl)phosphate (TEHP) in butanol were also tested as possible P standards. Increased concentrations of oil in the sample in the range of 0 to 20% showed no significant effects on B and P emission intensities indicating that matrix matching is not required for lubricating oils of about 2–15 cPoise. Detection limits in absence of spectral interferences were 0.06 μg B/g oil and 2 μg P/g oil. Overall estimated precision was 2.5% for B concentrations above 4 μg/g oil, and 6.5% for P concentrations above 20 μg/g oil. We evaluated the performance of a high resolution scanning spectrometer for mitigating the effects of overlapping spectral interferences from iron (Fe) and copper (Cu) on B and P emission lines. An interference from Fe 249.782 nm on the primary B line at 249.773 nm is observed for Fe concentrations higher than 100 μg/g oil, but a secondary B line at 249.678 nm is completely resolved from Fe 249.653 nm. In the case of P 213.618 nm, a contribution of the right wing of a Cu line at 213.598 nm generates a signal equivalent to P 18 μg/g oil for Cu 1000 μg/g oil. Received: 25 June 1997 / Revised: 16 September 1997 / Accepted: 7 October 1997     

The application of butanol as dilution agent for the inductively coupled plasma-atomic emission spectrometric determination of boron and phosphorus in lubricating oils

An evaluation of butanol-1 as dilution solvent for the determination of boron (B) and phosphorus (P) in lubricating oils by inductively coupled plasma-atomic emission spectrometry (ICP-AES) has been performed. Standard solutions of boric acid and tri-n-butyl phosphate (TBP) in butanol were employed as calibrants for B and P, respectively. Solutions of phosphoric acid and tris(2-ethylhexyl)phosphate (TEHP) in butanol were also tested as possible P standards. Increased concentrations of oil in the sample in the range of 0 to 20% showed no significant effects on B and P emission intensities indicating that matrix matching is not required for lubricating oils of about 2–15 cPoise. Detection limits in absence of spectral interferences were 0.06 μg B/g oil and 2 μg P/g oil. Overall estimated precision was 2.5% for B concentrations above 4 μg/g oil, and 6.5% for P concentrations above 20 μg/g oil. We evaluated the performance of a high resolution scanning spectrometer for mitigating the effects of overlapping spectral interferences from iron (Fe) and copper (Cu) on B and P emission lines. An interference from Fe 249.782 nm on the primary B line at 249.773 nm is observed for Fe concentrations higher than 100 μg/g oil, but a secondary B line at 249.678 nm is completely resolved from Fe 249.653 nm. In the case of P 213.618 nm, a contribution of the right wing of a Cu line at 213.598 nm generates a signal equivalent to P 18 μg/g oil for Cu 1000 μg/g oil. Received: 25 June 1997 / Revised: 16 September 1997 / Accepted: 7 October 1997     

自动回流萃取-MPT全谱仪测定航空润滑油中磨损金属的含量

将萃取与回流相结合, 建立了一种处理航空润滑油中磨损金属的新方法, 并用MPT全谱仪对磨损金属含量进行了同时检测. 该方法基本上实现了样品处理的全自动化,克服了常用方法的部分缺点, 对Zn, Cd, Cu, Fe和Pb的检出限(3σ)分别为0.084, 0.043, 0.022, 0.052和0.064 μg/g; 相对标准偏差均小于5%(n=5); 回收率为94.5%~107.4%. 对3个润滑油样品的检测结果令人满意.     

A biomonitoring study: <Superscript>210</Superscript>Po and heavy metals in mussels

In various samples of Mytilus galloprovincialis, ²¹⁰Po was determined by alpha-spectrometry while Mn, Fe, Ni, Cu, Zn, Cd, Sn, Hg and Pb by energy dispersive, polarised X-ray fluorescence spectrometry (EDPXRF). The mussels of different sizes were taken from 7 sites in the central Adriatic Sea along the Marche coastal region during the four seasons of the year. ²¹⁰Po activity concentration ranged between 57 and 343 Bq·kg⁻¹ dry weight. The concentration ranges of heavy metals (μg·g⁻¹ dry weight) were as follows: Mn: 72.9–83.1; Fe: 45.1–754; Ni: 1.3–7.6; Cu: 17.9–156; Zn: 60.9–189; Cd: 0.6–1.0; Sn: 0.6–3.9; Hg always <0.5; Pb: 2.0–9.0. The data obtained depend upon the site and the period of the sampling and they are also compared with those obtained by other authors for the same organism in the Mediterranean and other Italian seas.     

Application of nondestructive X-ray fluorescence analysis to determine the element composition of medicinal plants

A nondestructive X-ray fluorescence technique has been developed to determine Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, Ba, and Pb in plants. The line element intensities were measured by an S4 Pioneer X-ray sequence spectrometer (Bruker AXS, Germany). The inversely proportional relationship was obtained between the analyte line intensity and mass of the plant, pressed on boric acid backing, for elements with an atomic number 11 < Z < 20. It was found that reduction of plant mass from 6 to 1 g leads to an increase in element determination sensitivity. The detection limits for 1 g of pressed plant were evaluated as μg/g: 5–20 (Na, Mg, Al); 1–4 (Si, P, S, Cl, K, Ca, Ti, Ba, Pb); 0.4-0.8 (Cr, Mn, Fe, Ni, Br, Cu, Zn, Rb and Sr). This technique was applied to determine the element composition of violets of Violaceae family, which are used in medicine.     

Simultaneous spectrophotometric determination of trace amounts of cobalt, nickel, and copper using the partial least-squares method after the preconcentration of their 2-aminocyclopentene-1-dithiocarboxylate complexes on microcrystalline naphthalene

A spectrophotometric method for the determination of trace amounts of cobalt(II), nickel(II), and copper(II) after the adsorption of their 2-aminocyclopentene-1-dithiocarboxylate complexes on microcrystalline naphthalene has been developed. These complexes are adsorbed on microcrystalline naphthalene at pH 4.5 by shaking for 5 min. The formed solid mass is separated by filtration, and dissolved in dimethylformamide. The absorption spectra were processed using the partial least-squares multivarate calibration method for the analysis of a ternary mixture of Co(II), Ni(II), and Cu(II). The detection limits for Co(II), Ni(II), and Cu(II) were 3.3, 10.0, and 0.8 ng/mL, respectively. The total relative standard error for applying the method to 20 synthetic samples in the concentration ranges of 20–400 ng/mL Co(II), 60–400 ng/mL Ni(II), and 4–400 ng/mL Cu(II) was 1.53%. The proposed method was also successfully applied to the determination of Co(II), Ni(II), and Cu(II) in alloys. The text was submitted by the authors in English.     

Combination of ultrasonic extraction and stripping analysis: an effective and reliable way for the determination of Cu and Pb in lubricating oils

The determination of metals in lubricating oil has been used as an important way to prevent components failures, to provide environmental information and in some cases, to identify adulteration. In this work, an effective and simple procedure is proposed for Cu and Pb determination in lubricating oils. An ultrasonic bath was employed for extraction of these elements from oil samples in a mixture 1:1 (v/v) of concentrated HCl and H₂O₂. A very efficient extraction of Cu and Pb (∼100%) was attained after 30 min of ultrasound, allowing the simultaneous determination of both metals using square-wave anodic stripping voltammetry at thin-film gold electrodes. The extraction procedure was performed in 4 mL polypropylene closed vessels and dozens of samples could be treated simultaneously in the same ultrasonic bath. The regions of the ultrasonic bath, where the maximum efficiency of extraction was attained were evaluated. Over the optimized region, 30 samples can be treated simultaneously. Used lubricating oils from automotive engines were analyzed by using the optimized extraction procedure.     

Colorimetric determination of manganese(II) in natural and waste waters after preconcentration on a polymeric adsorbent

A combined procedure has been developed for the colorimetric determination of manganese(II) in natural and waste waters based on the selective preconcentration of metal ions on a polymer complexing adsorbent,—polystyrene-2-oxy-〈1-azo-1′〉-2′-oxy-3′-sulfo-5′-nitrobenzene, followed by the digital detection of the analytical signal. Manganese(II) is extracted (95–100%) in the batch mode in the pH range from 4.9 to 6.8. The determination is not interfered by n × 10⁵-fold excess (by weight) of K, Na; n × 10⁴-fold excess of Ca, Mg; n × 10³-fold excess of Ba, Sr, Al, Fe(III); n × 10²-fold excess of Ti(IV), Ni, Co, Zn, Pb, Cu. The accuracy of the procedure has been examined by the standard addition method. The relative standard deviation varies from 9 to 16%. The advantages of the procedure include simplicity, availability of the apparatus, rapidity, and the possibility of its application in field conditions.     

Determination of Cd, Co, Cr, Cu, Fe, Ni and Pb in Milk, Cheese and Chocolate

 Combined analytical procedures consisting of wet digestion step followed by instrumental determination – differential pulse cathodic stripping voltammetry (DPCSV) or electrothermal atomic absorption spectrometry (ETAAS) – as well as a direct analysis method – slurry sampling ETAAS – for the determination of Cd, Co, Cr, Cu, Fe, Ni and Pb in milk, cheese and chocolate are described and compared. Wet digestion using a mixture of HNO₃-HClO₄-H₂O₂ is proposed for complete matrix decomposition prior to trace analyte determinati on by DPCSV or ETAAS. A mixture of HNO₃-H₂O₂ is used for slurry preparation. Optimal instrumental parameters for trace analyte measurements are presented. The reliability of the procedures has been verified by analyzing standard reference materials. Results obtained are in good agreement with the certified values and the relative standard deviations (for these results) are in the range 5–10% for wet digestion DPCSV or ETAAS and 3–9% for slurry sampling ETAAS in the range of 2 μgċg⁻¹ (Cd) to 12 μgċg⁻¹ (Fe). Received August 24, 1999. Revision January 20, 2000.     

Column solid-phase extraction with Chromosorb-102 resin and determination of trace elements in water and sediment samples by flame atomic absorption spectrometry

A column, solid-phase extraction (SPE), preconcentration method was developed for determination of Bi, Cd, Co, Cu, Fe, Ni and Pb ions in drinking water, sea water and sediment samples by flame atomic absorption spectrometry. The procedure is based on retention of analytes in the form of pyrrolidine dithiocarbamate complexes on a short column of Chromosorb-102 resin from buffered sample solution and then their elution from the resin column with acetone. Several parameters, such as pH of the sample solution, amount of Chromosorb-102 resin, amount of ligand, volume of sample and eluent, type of eluent, flow rates of sample and eluent, governing the efficiency and throughput of the method were evaluated. The effects of divers ions on the preconcentration were also investigated. The recoveries were >95%. The developed method was applied to the determination of trace metal ions in drinking water, sea water and sediment samples, with satisfactory results. The 3σ detection limits for Cd, Cu, Fe, Ni and Pb and were found to be as 0.10, 0.44, 11, 3.6, and 10 μg l⁻¹, respectively. The relative standard deviation of the determination was <10%. The procedure was validated by the analysis of a standard reference material sediment (GBW 07309) and by use of a method based on coprecipitation.     

Coulometric determination of lead(II) and lead(IV) in high-T c superconductors containing copper and bismuth

The behavior of Pb(II) and Pb(IV) was studied by voltammetry in supporting electrolytes containing 0.1 M NaOH or 0.1 M NaOH + 0.1 M Na₃Cit at a graphite and a mercury thin-film electrodes. The best conditions were found for the coulometric determination of Pb by the oxidation of Pb(0) to Pb(II) in the presence of 5- to 20-fold amounts of Bi(III) and Cu(II) within the range 0.2–2 mg Pb(II) with an error and a relative standard deviation of less than 0.5%. Along with the procedure proposed previously for the determination of Pb(II) and Pb(IV) present simultaneously using a platinum gauze electrode, this procedure was applied to the determination of Pb(II) and Pb(IV) in samples of high-T_c. Cu-Bi superconductors. For samples of high-T_c. Bi-Pb-A-Cu-0 superconductors (A = Ba or Sr-Ca) containing from 2 to 12% Pb(II), the relative standard deviation was less than 0.5%; for 0.6–7% Pb(IV), it was 1-0.2%.     

A biomonitoring study: 210Po and heavy metals in marine organisms from the Adriatic Sea (Italy)

In various samples of marine organisms from the central Adriatic Sea ²¹⁰Po was determined by alpha spectrometry and thirteen heavy metals (Mn, Fe, Co, Cr, V, Ni, Cu, Zn, Cd, As, Sn, Hg and Pb) by energy dispersive, polarised X ray fluorescence spectrometry (EDPXRF). ²¹⁰Po activity concentration ranged between 0.3 and 44.6 Bq kg⁻¹ fresh weight. The data obtained depend upon the type of the marine organism; among the pelagic species, anchovy displayed the highest polonium concentration. Typical concentration ( \upmu \textg·\textg_(\textfresh) ^{- 1} ) \left( {\upmu {\text{g}}\cdot{\text{g}}_{{({\text{fresh}})}}^{ - 1} } \right) ranges were as follows: Mn: <1.32–1.73; Fe: 4.11–94.27; Co < 0.13–0.23; Ni: <0.13–0.52; Cu: 0.37–145.31; Zn: 0.46–16.46; Cd: <0.10–0.25; As: 0.36–60.52; Hg: <0.13–0.70; Pb: <0.13–0.35, Sn: <0.20–12.67; V and Cr were always <1.32. The data obtained are also compared with those obtained by other authors for the same organism coming from other Italian seas.     

Trace metals in mussel shells and corresponding soft tissue samples: a validation experiment for the use of <Emphasis Type="Italic">Perna perna</Emphasis> shells in pollution monitoring

The uptake of Cr, Mn, Ni, Cu, Zn, Cd and Pb in soft tissue of Perna perna mussels and their shells has been studied in aquarium experiments in which mussels were exposed for 30 or 60 days to seawater spiked with different concentrations of these contaminants (125 and 500 μg L⁻¹). Tissue samples were analyzed after acid digestion by conventional solution nebulization ICP–MS. Laser ablation ICP–MS was used for the quantitative determination of trace elements in different areas of the corresponding shells. With the exception of Mn and Zn, all other elements studied showed a significant concentration enhancements in soft tissue, with the magnitude of this enhancement following the order: Cr > Ni > Cd > Cu > Pb. A corresponding increase in most contaminants, although less pronounced, was also observed in the newly formed growth rings of mussel shells, contributing to the validation of Perna perna mussel shell as a bioindicator of toxic elements.     

微波灰化-电感耦合等离子体原子发射光谱法测定原油中的金属元素

采用微波灰化技术消化原油样品,并使用电感耦合等离子体原子发射光谱法(ICP-AES)测定其中Na、Mg、Ca、Fe、V、Ni和Cu的含量。探讨了原油样品中金属元素测定的称样量和微波灰化程序,并优化了仪器工作参数和实验条件。样品经微波灰化处理后,用盐酸溶解残渣,方法对Na、Mg、Ca、Fe、V、Ni和Cu元素的检出限分别为0.07、0.01、0.01、0.01、0.02、0.04和0.03mg/kg,回收率在84.5%～96.6%之间,相对标准偏差在2.1%～6.9%范围。方法简便、可靠,可用于原油中Na、Mg、Ca、Fe、V、Ni和Cu 7种金属元素的检测。     

TLC separation of some inorganic ions on diethylenetriamine impregnated layers

Summary A suitable TLC method for the separation of Co, Zn, Ni, As, Pb, Cd, Hg, Ag, Th, Se, Sn(IV), Fe(II), U, V, Cu, Ti, Zr and Sb on silica gel impregnated with diethylenetriamine and using ethanol-acetone-acetic acid (70∶50∶20) or (40∶50∶20) as solvent systems and employing 1% K₄Fe(CN)₆ or 0.5% dithizone as visualisation reagents has been developed.     

Determination of Cu,Cd, Ni,Pb and Zn in Edible Oils Using Reversed-Phase Ultrasonic Assisted Liquid–Liquid Microextraction and Flame Atomic Absorption Spectrometry

A simple and green reversed-phase ultrasonic assisted liquid?liquid microextraction method for determination of Cu, Cd, Ni, Pb and Zn in edible oils was developed. Detection was carried out by flame atomic absorption spectrometry. The influence of main parameters including ultrasonic time and temperature, disperser solvent, volume of extracting solvent and centrifuging time on the extraction efficiency of target analytes were investigated and optimized. In the proposed method, a few microliters of water (containing 3%, v/v, nitric acid) as extracting solvent was injected into the oil sample and mixture transferred to ultrasonic bath. Then, the mixture was centrifuged in order to accelerate in phase separation. Finally, the aqueous phase was removed and delivered to flame atomic absorption spectrometer. Calibration curves for all metals were linear in the range of 5?100 ng/mL. The limit of detections for Cu, Cd, Ni, Pb and Zn were 0.8, 0.3, 0.5, 1.5 and 0.5 ng/mL, respectively. Relative standard deviation (RSD) values were in the range of 0.6?1.9%. The recoveries were in the range of 95.2–101.2% with RSD values ranging from 0.8 to 1.9%. The proposed method was applied successfully for the determination of interested metals in commercial edible oils.     

New sorbents and indicator powders for preconcentration and determination of trace metals in liquid samples

Two approaches to immobilize complex-forming analytical reagents (PAN, PAR, Xylenol orange, Brombenzothiazo, Crystal violet, Cadion, and Sulfochlorophenolazorhodanine) for the preparation of new sorbents and indicator powders are suggested: on-line coating of reversed-phase silica gel by reagents or doping of porous sol-gel silica with reagents. The retention of Ag, Cd, Cu(II), Co(II), Fe(III), Mn(II), Ni, Pb, and Zn on the sorbents developed was investigated. Quantitative sorption and desorption conditions were optimized. Procedures for the determination of Cd, Cu(II), Fe(III), Pb, and Zn with flame atomic absorption, spectrophotometric, and diffusion scattering spectrometric detection were elaborated. Detection limits for Cd, Cu(II), Fe(III), Pb, and Zn were 3 μg/L, 6 μg/L, 5 μg/L, 40 μg/L, and 1 μg/L, respectively. The procedures were used for the analysis of various real samples, e.g., natural and waste waters, and food. Received: 17 July 1997 / Revised: 20 January 1998 / Accepted: 5 February 1998