Chromium determination in sea water by electrothermal atomic absorption spectrometry using Zeeman effect background correction and a multi-injection technique

Electrothermal atomic absorption spectrometry (ETAAS) applying a Zeeman effect background correction system (ZEBC) and a tranverse heated atomizer was used to directly determine chromium in sea water. Calcium chloride (at a concentration of 20 mg L^–1) was applied as chemical modifier with optimum charring and atomization temperatures of 1600°C and 2000°C, respectively. The detection limit was 0.2 μg L^–1, by injecting 20 μL aliquot of sea water sample. This detection limit could be reduced further to 0.05 μg L^–1, using multiple injections (injection of five 20 μL aliquot of sea water). The accuracy of the methods developed were confirmed by analyses of different certified reference materials. Finally, interferences from major and minor components of sea water are studied. Received: 20 February 1997 / Revised: 26 May 1997 / Accepted: 8 June 1997     

Chromium determination in sea water by electrothermal atomic absorption spectrometry using Zeeman effect background correction and a multi-injection technique

Electrothermal atomic absorption spectrometry (ETAAS) applying a Zeeman effect background correction system (ZEBC) and a tranverse heated atomizer was used to directly determine chromium in sea water. Calcium chloride (at a concentration of 20 mg L^–1) was applied as chemical modifier with optimum charring and atomization temperatures of 1600°C and 2000°C, respectively. The detection limit was 0.2 μg L^–1, by injecting 20 μL aliquot of sea water sample. This detection limit could be reduced further to 0.05 μg L^–1, using multiple injections (injection of five 20 μL aliquot of sea water). The accuracy of the methods developed were confirmed by analyses of different certified reference materials. Finally, interferences from major and minor components of sea water are studied.     

Direct electrothermal atomic absorption spectrometry determination of nickel in sea water using multiple hot injection and Zeeman correction

Methods for the direct determination of Ni in sea water samples by ETAAS were developed using Zeeman effect background correction system (ZEBC) and a multi-injection technique. A mass of palladium nitrate of 2.5 mug (for an injection volume of 100 mul) was used as chemical modifier. The optimum pyrolysis and atomization temperatures were 1700 and 2100 degrees C, respectively. The characteristic mass (m(0)) and characteristic concentration (C(0)), precision and accuracy were studied for different injection volumes (20, 100 and 200 mul). For an injection volume of 100 mul (five 20 mul aliquot) of sample the accuracy analysis of different certified materials (saline and non saline water) was agreeable. The total time of the proposed procedure is 6 min. A m(0) and C(0) of 34.5 pg and 0.3 mug l(-1), respectively were obtained for this injection volume (100 mul). Finally, interferences from major and minor components of sea water was studied.     

Investigation of artifacts caused by deuterium background correction in the determination of phosphorus by electrothermal atomization using high-resolution continuum source atomic absorption spectrometry

The artifacts created in the measurement of phosphorus at the 213.6-nm non-resonance line by electrothermal atomic absorption spectrometry using line source atomic absorption spectrometry (LS AAS) and deuterium lamp background correction (D₂ BC) have been investigated using high-resolution continuum source atomic absorption spectrometry (HR-CS AAS). The absorbance signals and the analytical curves obtained by LS AAS without and with D₂ BC, and with HR-CS AAS without and with automatic correction for continuous background absorption, and also with least-squares background correction for molecular absorption with rotational fine structure were compared. The molecular absorption due to the suboxide PO that exhibits pronounced fine structure could not be corrected by the D₂ BC system, causing significant overcorrection. Among the investigated chemical modifiers, NaF, La, Pd and Pd + Ca, the Pd modifier resulted in the best agreement of the results obtained with LS AAS and HR-CS AAS. However, a 15% to 100% higher sensitivity, expressed as slope of the analytical curve, was obtained for LS AAS compared to HR-CS AAS, depending on the modifier. Although no final proof could be found, the most likely explanation is that this artifact is caused by a yet unidentified phosphorus species that causes a spectrally continuous absorption, which is corrected without problems by HR-CS AAS, but which is not recognized and corrected by the D₂ BC system of LS AAS.     

Determination of serum aluminum by electrothermal atomic absorption spectrometry: A comparison between Zeeman and continuum background correction systems

Excessive exposure to aluminum (Al) can produce serious health consequences in people with impaired renal function, especially those undergoing hemodialysis. Al can accumulate in the brain and in bone, causing dialysis-related encephalopathy and renal osteodystrophy. Thus, dialysis patients are routinely monitored for Al overload, through measurement of their serum Al. Electrothermal atomic absorption spectrometry (ETAAS) is widely used for serum Al determination. Here, we assess the analytical performances of three ETAAS instruments, equipped with different background correction systems and heating arrangements, for the determination of serum Al. Specifically, we compare (1) a Perkin Elmer (PE) Model 3110 AAS, equipped with a longitudinally (end) heated graphite atomizer (HGA) and continuum-source (deuterium) background correction, with (2) a PE Model 4100ZL AAS equipped with a transversely heated graphite atomizer (THGA) and longitudinal Zeeman background correction, and (3) a PE Model Z5100 AAS equipped with a HGA and transverse Zeeman background correction. We were able to transfer the method for serum Al previously established for the Z5100 and 4100ZL instruments to the 3110, with only minor modifications. As with the Zeeman instruments, matrix-matched calibration was not required for the 3110 and, thus, aqueous calibration standards were used. However, the 309.3-nm line was chosen for analysis on the 3110 due to failure of the continuum background correction system at the 396.2-nm line. A small, seemingly insignificant overcorrection error was observed in the background channel on the 3110 instrument at the 309.3-nm line. On the 4100ZL, signal oscillation was observed in the atomization profile. The sensitivity, or characteristic mass (m₀), for Al at the 309.3-nm line on the 3110 AAS was found to be 12.1 ± 0.6 pg, compared to 16.1 ± 0.7 pg for the Z5100, and 23.3 ± 1.3 pg for the 4100ZL at the 396.2-nm line. However, the instrumental detection limits (3 SD) for Al were very similar: 3.0, 3.2, and 4.1 μg L^− 1 for the Z5100, 4100ZL, and 3110, respectively. Serum Al method detection limits (3 SD) were 9.8, 6.9, and 7.3 μg L^− 1, respectively. Accuracy was assessed using archived serum (and plasma) reference materials from various external quality assessment schemes (EQAS). Values found with all three instruments were within the acceptable EQAS ranges. The data indicate that relatively modest ETAAS instrumentation equipped with continuum background correction is adequate for routine serum Al monitoring.     

Direct determination of arsenic in blood serum by electrothermal atomic absorption spectrometry

A method for the direct determination of arsenic in human blood serum is described. To suppress loss of arsenic by volatilization anal to remove chemical interferences in graphite-furnace atomic absorption spectrometry, the formation of involatile compounds with graphite, or with a matrix modifier is tested. With aqueous solutions, two sorts of interactions between graphite and arsenic are shown. But, in presence of serum, these interactions do not occur, Among 18 matrix modifiers tested, nickel gives the best sensitivity when used at high concentrations in the presence of Triton X-100. The proposed method allows direct arsenic determination, based on calibration with aqueous solutions. The method is applied to the serum of 20 normal subjects. The limit of detection is 0.4 μg l^?1 arsenic.     

Rapid determination of lead and cadmium in biological fluids by electrothermal atomic absorption spectrometry using Zeeman correction

Procedures for the electrothermal atomic absorption spectrometric determination of lead and cadmium in urine, serum and blood are developed. For serum and blood, the samples are diluted by incorporating 0.015% (w/v) Triton X-100 and 0.1% (w/v) ammonium dihydrogenphosphate to the solutions, which are then introduced directly into the furnace. A solution containing 15% (w/v) hydrogen peroxide and 0.65% (w/v) nitric acid is also introduced into the atomizer by means of a separate injection. Zeeman-based correction is recommended. Both conventional and fast-heating programs are discussed. Calibration is carried out using the standard additions method. The reliability of the procedures is checked by analyzing three certified reference materials and by recovery studies.     

Direct determination of molybdenum in mineral waters by atomic absorption spectrometry with electrothermal atomization

A new method for the direct determination of molybdenum by ETA-AAS in mineral waters without prior separation or concentration is proposed. With careful control of the graphite furnace conditions selective volatilization of the salt matrix is successfully attained. The possible spectroscopic interference due to common metals as well as the reproducibility, precision and repeatability of the method has been studied and the molybdenum content of 21 mineral waters measured.     

Direct determination of nickel in gas oil by atomic absorption spectrometry with electrothermal atomization

A rapid graphite-furnace atomic absorption procedure with simple dilution of samples was tested for the direct determination of sub-ppm levels of nickel in gas oils. The selection of appropriate graphite-furnace parameters, the type of solvent and organometallic standard, the effect of gas oil concentration in diluted samples, precision, accuracy and detection limit were investigated. Sample dilution was necessary because of high viscosity. Results obtained by standard addition for heavy gas oils were confirmed by a wet-ashing flame atomic absorption procedure. The relative standard deviation (r.s.d.) for consecutive determinations of nickel in gas oil solution containing 19 μg Ni l^?1 was 3.1%, and day-to-day r.s.d. for a reference gas oil sample was 5.3%. Accuracy was determined with an NBS standard reference oil GM-5 (4.6 ± 4.7% relative error in four determinations). Recovery experiments gas 104 ± 12% of the added nickel.     

Flow injection micelle-mediated methodology for determination of lead by electrothermal atomic absorption spectrometry

A simple and sensitive flow injection micelle-mediated method was developed for the determination of trace Pb by electrothermal atomic absorption spectrometric (ET-AAS). The formation of the analyte-entrapped surfactant micelles by online merging of the analyte solution with O,O-diethyldithiophosphate solution and Triton X-114 solution sequentially, the adsorption of the resultant analyte-entrapped surfactant micelles onto a microcolumn packed with silica gel. The adsorbed analyte was then eluted with methanol and determined by ET-AAS. With consumption of 6.0 mL sample solution, a detection limit of 0.016 μg L⁻¹, and a concentration factor of 21.6 were obtained at a sample throughput of 20 h⁻¹. The relative standard deviation was 5.1% (c = 2.0 ng mL⁻¹, n = 7). The method has been successfully applied to the analysis of trace Pb in water sample with recoveries ranging from 94.0 to 99.0%. The certified reference material was also analyzed for validation, and the determined value obtained was in good agreement with the certified value.     

Determination of arsenic in urine by atomic absorption spectrometry with electrothermal atomization

A cheap device which can be used to follow transient signals with a chart recorder is described.     

Comparative study of magnesium nitrate,palladium nitrate and reduced palladium for the direct determination of mercury in sea water by electrothermal atomization atomic absorption spectrometry

A comparative study of different chemical modifiers in graphite furnace atomic absorption spectrometry for the direct determination of mercury in sea water samples, in synthetic sea water sample of high (72.8%) and low 34.2%) salinity and in aqueous solutions, was carried out. The use of reduced palladium produces better results. The mixture of palladium nitrate and ascorbic acid, gives the best limit of detection (1.9 gl^–1). The use of reduced palladium and magnesium nitrate produced excellent recoveries (close to 100%) in the whole salinity range for all mercury concentration tested. The use of palladium nitrate alone or combined with magnesium nitrate gave good recoveries with respect to a real sea water sample for low salinities. The interference from the major components of sea water were completely removed by using reduced palladium and magnesium nitrate modifiers. Thus, a single calibration curve with synthetic sea water may be applied to the analysis of sea water samples of widely differing salinities.     

Direct determination of traces of molybdenum in synthetic sea water by atomic absorption spectrometry with electrothermal atomization and selective volatilization of the salt matrix

A simple and rapid method is described for the direct determination by graphite-furnace atomic absorption spectrometry (HGA-2100) of traces of molybdenum (O.1–4 ng) in synthetic sea water. It is shown that the salt matrix can be removed completely by selective volatilization at 1700–1850°C, but the original presence of NaCl, Na₂SO₄, and KCl causes a considerable decrease in molybdenum absorbance, and MgCl₂ and CaCl₂ a pronounced enhancement. The presence of MgCl₂ prevents the depressive effects. Samples of less than 50 μl can be analyzed directly without using a background corrector, with a precision of<10%.     

Determination of lead in whole blood by electrothermal atomic absorption spectrometry using Zeeman correction and sample stability

Summary A simple, selective and sensitive method was developed based on electrothermal atomic absorption spectrometry using Zeeman correction for quantitation of lead, in 100 ml of whole blood sample, as biological indicator for occupational exposure. Confidence parameters and stability of samples were considered. Ashing and atomization temperatures, considered critical, were 700 °C and 1,700 °C, respectively. The levels found during the validation process showed good sensitivity linearity, recovery, precision and accuracy. The stability results presented levels remaining constant for a 15 months period. The variations were not higher than 15% when comparing concentrations in zero time to those obtained after storage period.     

Comparison of different chemical modifiers for the direct determination of arsenic in sea water by electrothermal atomic absorption spectrometry

A comparative study of different chemical modifiers for the direct determination of arsenic in real and in synthetic sea water samples of high (72.8 per thousand ) and low (34.2 per thousand ) salinity was carried out. The use of lanthanum chloride and magnesium nitrate (LOD=3.0 microg l(-1)) offers good recoveries for low salinities, while for high salinities an enhancement higher than 200% was obtained, rendering this method unsuitable for sea water samples. The use of silver nitrate (LOD=2.0 microg l(-1)) produces unfavourable analytical recoveries, around 150 and 300% for synthetic sea water of low and high salinity. Zirconium oxychloride (LOD=1.8 microg l(-1)) and palladium nitrate alone or combined with magnesium nitrate and reducing agents (LOD=1.1-1.3 microg l(-1)) produce analytical recoveries close to 100% for all arsenic concentration tried over all salinities; thus, a single calibration curve using aqueous standard solutions may be applied to the analysis of sea water samples over all salinities. Finally, the addition of reducing agents and magnesium nitrate to palladium does not improve the sensitivity.     

Comparison of different chemical modifiers for the direct determination of arsenic in sea water by electrothermal atomic absorption spectrometry

A comparative study of different chemical modifiers for the direct determination of arsenic in real and in synthetic sea water samples of high (72.8) and low (34.2) salinity was carried out. The use of lanthanum chloride and magnesium nitrate (LOD=3.0 gl^-1) offers good recoveries for low salinities, while for high salinities an enhancement higher than 200% was obtained, rendering this method unsuitable for sea water samples. The use of silver nitrate (LOD=2.0 gl^-1) produces unfavourable analytical recoveries, around 150 and 300% for synthetic sea water of low and high salinity. Zirconium oxychloride (LOD=1.8 gl^-1) and palladium nitrate alone or combined with magnesium nitrate and reducing agents (LOD=1.1–1.3 gl^-1) produce analytical recoveries close to 100% for all arsenic concentration tried over all salinities; thus, a single calibration curve using aqueous standard solutions may be applied to the analysis of sea water samples over all salinities. Finally, the addition of reducing agents and magnesium nitrate to palladium does not improve the sensitivity.     

Development of a method for speciation of inorganic arsenic in waters using solid phase extraction and electrothermal atomic absorption spectrometry

A solid phase extraction (SPE) procedure based on Amberlite IRA 900 resin was developed for speciation and separation of inorganic arsenic species (III, V) and total As in water samples. The As species and total As in eluent solutions were determined by electrothermal atomic absorption spectrometry (ETAAS) using Ni chemical modifier with 1200°C pyrolysis temperature. Experimental parameters such as pH value, sample volume, flow rate, volume and concentration of eluent solution for As(V) were optimised and 98.0 ± 1.9% recovery was found at pH 4.0. Experimental adsorption capacity of the resin for As(V) was investigated and 229.9 mg g^–1 was found. Under optimised experimental conditions, instrumental parameters such as limit of detection (LOD) and limit of quantification (LOQ) found were 0.126 and 0.420 µg L^–1, respectively. Interference effects of coexisting ions in the sample matrix on the recovery of As(V) were investigated. Concentration of As(III) was obtained by subtracting As(V) concentration found at pH 4.0 from total As(III + V) found at pH 8.0. The accuracy of the method proposed by using the resin was tested for analysing As species in a waste water standard reference material (SRM, CWW-TM-D) and spiked real water samples with recovery above 95%. The method proposed was also applied to the determinations of As species and total As in underground hot waters and tap water with relative error below 3%.     

Direct determination of tin in tap waters by electrothermal atomization atomic absorption spectroscopy

Summary A method is described for the direct determination of tin in tap waters by electrothermal atomization atomic absorption spectroscopy (ETA-AAS), using magnesium-nitric acid and palladium-magnesium as chemical modifiers. The charring and atomization temperatures and times, and the amount of modifier were optimized. The calibration and addition graphs, detection limit, quantitation limit, precision, accuracy, interferences and characteristic mass were also investigated. The method was applied to the determination of tin in tap water samples.     

The atomic absorption spectrometric determination of arsenic and selenium in mineral waters by electrothermal atomization

A procedure for the determination of arsenic and selenium in mineral waters based on electrothermal atomic absorption spectrometry is described. Because of matrix effects and the inadequate detection limits for direct determinations, both elements are separated from the macrocomponents by co-precipitation in hydrated iron(III) oxide. The precipitate is dissolved in 0.2 M sulphuric acid for injection. The detection limits are 0.2 and 0.5 μg l^?1 for arsenic and selenium, respectively.     

An improved metal extraction procedure for the determination of trace metals in sea water by atomic absorption spectrometry with electrothermal atomization

A rapid carbamate extraction method with pyrrolidinedithiocarbamate and diethyldithiocarbamate is described for the simultaneous determination of Cd, Co, Cu, Fe, Ni, Pb and Zn in sea water by atomic absorption spectrometry with a graphite atomizer. The metal—carbamate complexes are extracted from 500 ml of sea water into Freon TF and back-extracted into 10 ml of 0.3 M nitric acid. The method has considerable advantages over previously recommended extraction procedures. The metals are transferred to a solution in which their concentrations do not change with time, and which can be easily stored for transportation. The sensitivity is high enough for analysis of open ocean waters.