Headspace single drop microextraction of methylcyclopentadienyl-manganese tricarbonyl from water samples followed by gas chromatography-mass spectrometry

Headspace single drop microextraction coupled to gas chromatography-mass spectrometry yielded a simple, fast and virtually solventless analytical protocol used for the headspace analysis of aqueous samples contaminated with methylcyclopentadienyl-manganese tricarbonyl (MMT). Initially, several experimental parameters were controlled and optimized and the optimum conditions found were 2.5 μl octane microdrop exposed for 20 min to the headspace of a 10 ml aqueous sample (15 ml vial) containing 20% (w/v) NaCl and stirred at 1250 rpm. The calculated calibration curves gave a high level of linearity for MMT with correlation coefficients >0.9995 after conducting a 3-day study. The limit of detection was calculated to be 0.21 μg l⁻¹. The proposed method achieved an enrichment factor of the order of 2100 and a 53% recovery after extracting the spiked aqueous solution for 20 min under the optimized experimental conditions. The repeatability and intra-day reproducibility of the proposed method, expressed as relative standard deviation were 8.4 and 6.4%, respectively. Finally, analysis of spiked tap and wastewater samples revealed that matrix had little effect upon extraction.     

Determination of methylcyclopentadienyl-manganese tricarbonyl by solid phase microextraction-direct thermal desorption-quartz furnace atomic absorption spectrometry

A new procedure that uses a pre-concentration system based on solid phase microextraction (SPME) and detection by quartz furnace-atomic absorption spectrometry after thermal desorption from the microextraction fiber has been proposed for the determination of methylcyclopentadienylmanganese tricarbonyl (MMT) in gasoline and water. Working MMT solutions were prepared in 40 ml amber vials, and sampling was performed by exposing the SPME fiber to the headspace over vigorously stirred samples for 15 min. The analytical performance characteristics of the proposed procedure were as follows: the detection limit for MMT was 0.71 ng ml⁻¹ (as Mn), with a relative standard deviation of 4% for MMT determination of 25 ng ml⁻¹ (as Mn, n=6) while the calibration curve was linear up to 100 ng ml⁻¹ range. The proposed procedure was finally applied to the determination of MMT in gasoline and water samples and non significant differences (Student's t-test) were found between obtained values (using direct calibration and standard additions) and those expected values.     

Ionic liquid-based single drop microextraction combined with electrothermal atomic absorption spectrometry for the determination of manganese in water samples

Room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate [C₄MIM][PF₆], was used as an alternative to volatile organic solvents in single drop microextraction-electrothermal atomic absorption spectrometry (SDME-ETAAS). Manganese was extracted from aqueous solution into a drop of the ionic liquid after complextaion with 1-(2-thiazolylazo)-2-naphthol (TAN) and the drop was directly injected into the graphite furnace. Several variables affecting microextraction efficiency and ETAAS signal, such as pyrolysis and atomization temperature, pH, TAN concentration, extraction time, drop volume and stirring rate were investigated and optimized. In the optimum experimental conditions, the limit of detection (3 s) and the enhancement factor were 0.024 μg L⁻¹ and 30.3, respectively. The relative standard deviation (RSD) for five replicate determinations of 0.5 μg L⁻¹ Mn(II) was 5.5%. The developed method was validated by the analysis of a certified reference material (NIST SRM 1643e) and applied successfully to the determination of manganese in several natural water samples.     

Determination of trace Cd and Pb in natural waters by direct single drop microextraction combined with electrothermal atomic absorption spectrometry

A new method of direct single-drop microextraction combined with electrothermal atomic absorption spectrometry (ETAAS) is presented for the determination of trace Cd and Pb with dithizone (H₂DZ) as chelating reagent. Factors influencing the microextraction efficiency and determination, such as pH, microdrop volume, stirring rate, extraction time were evaluated. Under the optimized experimental conditions, the detection limits of the method are 2 and 90 pg mL⁻¹ for Cd and Pb, and the relative standards deviations for 0.5 ng mL⁻¹ Cd and 10 ng mL⁻¹ Pb are 11 and 12.8%. After 10 min of extraction, the enrichment factors for Cd and Pb are 118 and 90, respectively. The results for the determination of Cd and Pb in tap water, spring water, river water, pond water, lake water and spiked water samples demonstrate the accuracy, recovery and applicability of the method. An environmental water certified reference material (GSBZ 50009-88) was analyzed, and the determined values are in a good agreement with the certified values. Correspondence: Bin Hu, Department of Chemistry, Wuhan University, Wuhan 430072, P.R. China     

Determination of methylmercury by electrothermal atomic absorption spectrometry using headspace single-drop microextraction with in situ hydride generation

A new method is proposed for preconcentration and matrix separation of methylmercury prior to its determination by electrothermal atomic absorption spectrometry (ETAAS). Generation of methylmercury hydride (MeHgH) from a 5-ml solution is carried out in a closed vial and trapped onto an aqueous single drop (3-μl volume) containing Pd(II) or Pt(IV) (50 and 10 mg/l, respectively). The hydrogen evolved in the headspace (HS) after decomposition of sodium tetrahydroborate (III) injected for hydride generation caused the formation of finely dispersed Pd(0) or Pt(0) in the drop, which in turn, were responsible for the sequestration of MeHgH. A preconcentration factor of ca. 40 is achieved with both noble metals used as trapping agents. The limit of detection of methylmercury was 5 and 4 ng/ml (as Hg) with Pd(II) or Pt(IV) as trapping agents, and the precision expressed as relative standard deviation was about 7%. The preconcentration system was fully characterised through optimisation of the following variables: Pd(II) or Pt(IV) concentration in the drop, extraction time, pH of the medium, temperatures of both sample solution and drop, concentration of salt in the sample solution, sodium tetrahydroborate (III) concentration in the drop and stirring rate. The method has been successfully validated against two fish certified reference materials (CRM 464 tuna fish and CRM DORM-2 dogfish muscle) following selective extraction of methylmercury in 2 mol/l HCl medium.     

Determination of selenium in water by electrothermal atomic absorption spectrometry

Summary The electrothermal atomization of selenium has been investigated for the accurate determination of selenium in water samples. Hydrogen seriously affects the atomization temperature of selenium in a molybdenum micro-tube atomizer. The atomization of selenium also suffers from serious interferences caused by salts and other elements. The extraction of selenium diethyldithiocarbamate complex serves to eliminate the interferences from the matrix. The addition of copper allows the suppression of interferences from elements extracted with selenium. The method permits the determination of selenium(IV) and selenium(VI) separately.This research was in part funded by the Ministry of Education, Science and Culture, Japan, under Grant-in-Aid for Scientific Research, for which we express our appreciation.     

Determination of Mo and V in multiphase gasoline emulsions by electrothermal atomic absorption spectrometry

This paper proposes an alternative analytical method using electrothermal atomic absorption spectrometry to determine Mo and V in multiphase gasoline emulsions. Samples were prepared by mixing gasoline with a nitric acid solution (0.1% v/v) and two cationic surfactants. The mixture was sonicated, resulting in an emulsive system. Calibration was done by using the aforementioned solutions with added analyte. The detection limits (3σ) of Mo and V were 0.9 μg l^− 1 and 4.7 μg l^− 1, respectively. The accuracy and precision of the proposed method were evaluated by the analysis of samples spiked with metallo-organic standard and the relative standard deviation obtained ranged from 1.2% to 4.4% in samples spiked with 2 μg l^− 1 of each metal. The recovery rates varied from 91.2% to 101.6%. The proposed method was applied to determine Mo and V in samples of gasoline from different gas stations.     

Determination of butyltin stabilizers in PVC using Liquid-Phase microextraction with electrothermal atomic absorption spectrometry

A rapid and highly sensitive method is described for the extraction and determination of di- and tributyltin in PVC samples using headspace liquid phase microextraction followed by an analysis with graphite furnace atomic absorption spectrometry (HSLPME/ GFAAS). The analytes were derivatized in situ with sodium tetraethylborate and concentrated in a 2 ??l microdrop of benzyl alcohol suspended from the tip of a conventional GC microsyringe. The ethylated species then were directly transferred into a graphite furnace and quantified. The extractions were carried out for 5 ml sample solution (8 ml vial) adjusted at pH 5, with derivatization at 22 °C for 15 min in a 2% sodium tetraethylborate. The experimental parameters impacting the performance of HS-LPME were also investigated. According to the analysis, the linearity range was from 5.0 to 250.0 ng l^-1 with a detection limit of 0.5 ng l^-1 for dibutyltin and from 1.7 to 170.0 ng l^-1 with a detection limit of 0.17 ng l^-1 for tributyltin. Method RSD values were below 1.5%. Finally, the analysis of spiked PVC and water samples revealed that matrix had little effect upon extraction.     

电沉积-钨丝电热原子吸收光谱法测定水样中的铅

研制了一种便携式钨丝电热原子吸收光谱分析装置,其主要包括:钨丝电热原子化器、多道微型CCD光谱仪、仪器电源系统以及控制系统。并将电沉积分离富集技术与该钨丝电热原子吸收光谱分析仪器结合,完成环境水样中铅的现场分析。并对铅的电沉积条件作了研究,最佳电沉积电位为负650 mV(vs.SCE),方法检出限:0.20μg/L,线性范围:1~15μg/L,对4μg/L Pb标准溶液10次重复测试,RSD为4.4%。     

Determination of inorganic selenium species in water and garlic samples with on-line ionic liquid dispersive microextraction and electrothermal atomic absorption spectrometry

A non-chromatographic separation and preconcentration method for Se species determination based on the use of an on-line ionic liquid (IL) dispersive microextraction system coupled to electrothermal atomic absorption spectrometry (ETAAS) is proposed. Retention and separation of the IL phase was achieved with a Florisil^®-packed microcolumn after dispersive liquid-liquid microextraction (DLLME) with tetradecyl(trihexyl)phosphonium chloride IL (CYPHOS^® IL 101). Selenite [Se(IV)] species was selectively separated by forming Se-ammonium pyrrolidine dithiocarbamate (Se-APDC) complex followed by extraction with CYPHOS^® IL 101. The methodology was highly selective towards Se(IV), while selenate [Se(VI)] was reduced and then indirectly determined. Several factors influencing the efficiency of the preconcentration technique, such as APDC concentration, sample volume, extractant phase volume, type of eluent, elution flow rate, etc., have been investigated in detail. The limit of detection (LOD) was 15 ng L⁻¹ and the relative standard deviation (RSD) for 10 replicates at 0.5 μg L⁻¹ Se concentration was 5.1%, calculated with peak heights. The calibration graph was linear and a correlation coefficient of 0.9993 was achieved. The method was successfully employed for Se speciation studies in garlic extracts and water samples.     

Dithizone–chloroform single drop microextraction system combined with electrothermal atomic absorption spectrometry using Ir as permanent modifier for the determination of Cd in water and biological samples

A simple and sensitive method using dithizone–chloroform single drop microextraction has been developed for separation and preconcentration of trace Cd prior to its determination by electrothermal atomic absorption spectrometry with Ir as permanent modifier. Parameters, such as pyrolysis and atomization temperature, solvent type, pH, dithizone concentration, extraction time, organic drop volume, stirring rate and sample volume were investigated. Under the optimized conditions, a detection limit (3σ) of 0.7 ng/l and enrichment factor of 65 were achieved. The relative standard deviation was 7.4% (c = 0.2 μg/l, n = 5). The developed method has been applied to the determination of trace Cd in water samples and biological reference materials with satisfactory results.     

Determination of aluminium in silicon by electrothermal atomic absorption spectrometry

The sample is decomposed with hydrofluoric and nitric acids and the diluted solution is injected into the graphite furnace. For a 100-mg sample, the detection limit (3 σ) is 1.2 μg AI g^-1. The coefficient of variation is 3–13% for 9–7000 μg Al g^-1 in silicon.     

Determination of vanadium in urine by electrothermal atomic absorption spectrometry

After wet ashing of the urine sample with nitric acid, vanadium is chelated with cupferron, extracted into 4-methylpentan-2-one and determined by atomic absorption spectrometry with a pyrolytically-coated graphite furnace atomizer. The sensitivity allows the precise determination of 1–500 μg V l^-1 in urine. The coefficient of variation for triplicate urine measurements is <8% for 10 μg V l^-1.     

Determination of traces of lead and cadmium using dispersive liquid-liquid microextraction followed by electrothermal atomic absorption spectrometry

Microchimica Acta - A procedure is presented for the determination of very low concentrations of lead and cadmium in water samples. Dispersive liquid-liquid microextraction with ammonium...     

Determination of Cu,Co and Pb in gasoline by electrothermal atomic absorption spectrometry using aqueous standard addition in gasoline–ethanol–water three-component system

Single phase gasoline–ethanol–water mixture was prepared for performing standardization with aqueous standards and for the elimination of difficulties with pipetting of gasoline. Standard addition calibration method was applied to the determination of Cu, Pb and Co in gasoline by electrothermal atomic absorption spectrometry. Good agreements were found for the analysis results of the present “direct” method compared with those obtained by digesting gasoline in microwave furnace with nitric acid. The limit of detection values were 1.5 μg kg⁻¹ Co, 2.5 μg kg⁻¹ Cu and 4.0 μg kg⁻¹ Pb in original gasoline samples.     

Rapid determination of lead in water samples by dispersive liquid-liquid microextraction coupled with electrothermal atomic absorption spectrometry

The need for highly reliable methods for the determination of trace and ultratrace elements has been recognized in analytical chemistry and environmental science. A simple and powerful microextraction technique was used for the detection of the lead ultratrace amounts in water samples using the dispersive liquid-liquid microextraction (DLLME), followed by the electrothermal atomic absorption spectrometry (ET AAS). In this microextraction technique, a mixture of 0.50 mL acetone (disperser solvent), containing 35 microL carbon tetrachloride (extraction solvent) and 5 microL diethyldithiophosphoric acid (chelating agent), was rapidly injected by syringe into the 5.00 mL water sample, spiked with lead. In this process, the lead ions reacted with the chelating agent and were extracted into the fine droplets of CCl(4). After centrifugation (2 min at 5000 rpm), the fine CCl4 droplets were sedimented at the bottom of the conical test tube (25+/-1 microL). Then, 20 microL from the sedimented phase, containing the enriched analyte, was determined by ET AAS. The next step was the optimization of various experimental conditions, affecting DLLME, such as the type and the volume of the extraction solvent, the type and the volume of the disperser solvent, the extraction time, the salt effect, pH and the chelating agent amount. Moreover, the effect of the interfering ions on the analytes recovery was also investigated. Under the optimum conditions, the enrichment factor of 150 was obtained from only a 5.00 mL water sample. The calibration graph was linear in the range of 0.05-1 microg L(-1) with the detection limit of 0.02 microg L(-1). The relative standard deviation (R.S.D.) for seven replicate measurements of 0.50 microg L(-1) of lead was 2.5%. The relative lead recoveries in mineral, tap, well and sea water samples at the spiking level of 0.20 and 0.40 microg L(-1) varied from 93.5 to 105.0. The characteristics of the proposed method were compared with the cloud point extraction (CPE), the liquid-liquid extraction, the solid phase extraction (SPE), the on-line solid phase extraction (SPE) and the co-precipitation, based on bibliographic data. The main DLLME advantages combined with ET AAS were simplicity of operation, rapidity, low cost, high-enrichment factor, good repeatability, low consumption of extraction solvent, requiring a low sample volume (5.00 mL).     

Determination of barium in sea water by cation- exchange separation and electrothermal atomic absorption spectrometry

A method is described for the routine determination of barium in sea water by graphite-furnace atomic absorption spectrometry. Barium is separated from the main sea- water cations by collection on a cation-exchange resin. The barrium is extracted into nitric acid from a portion of the resin for injection into the pyrolytically-coated graphite furnace. The method is satifactory for the low μg l^?1 levels of barium present in ocean water, with recoveries ?99% and a relative standard deviation of <5%.     

顶空固相微萃取气相色谱-质谱单离子监测法测定水中的多种己二酸酯

采用顶空固相微萃取和气相色谱 质谱单离子监测技术,以己二酸二(1 丁基戊基)酯为内标,对水中的己二酸二乙酯、己二酸二异丁酯、己二酸二丁酯、己二酸二(2 丁氧基乙基)酯、己二酸二(乙基己基)酯进行了测定,考察了盐效应、萃取温度、萃取时间和热解吸时间等因素对方法灵敏度的影响。该方法对5种己二酸酯的检测限量为0.0220～5.49μg L,回收率为86.9%～102.0%,相对标准偏差为1.5%～7.3%。     

Determination of gallium in biological materials by electrothermal atomic absorption spectrometry

In this determination of gallium, the condition of the graphite tubes influences the peak height. Common acids and salts seriously affect the results, but in the presence of EDTA, interferences of nitric and hydrochloric acids are suppressed completely, and interferences of phosphoric acid and some salts are suppressed partly. To compensate for the effects, a standard addition procedure is proposed, and is applied to healthy and tumor.bearing mice. A linear calibration is obtained for 0.12–12 ng Ga in 50-μl aliquots. The method is applied to tissues and body fluids with good recovery and precision.