Injection-cold Vapor Atomic Absorption Spectrometry Research Articles

Ultrasound assisted-dispersive-ionic liquid-micro-solid phase extraction based on carboxyl-functionalized nanoporous graphene for speciation and determination of trace inorganic and organic mercury species in water and caprine blood samples

The carboxyl-functionalized nanoporous graphene (NG-COOH) as solid phase sorbent was prepared and investigated in a new and simple ultrasound assisted-dispersive-ionic liquid-micro-solid phase extraction (US-D-IL-μ-SPE) procedure for rapid preconcentration and speciation of trace Hg (II) and R-Hg (CH3Hg+ and C2H5Hg+) in water and caprine blood samples. Both of inorganic and organic mercury were extracted by NG-COOH at pH8. Hydrophobic ionic liquid (IL) was used to fast trap of the mercury loaded sorbent from the sample solution. The loaded NG-COOH/IL phase was then eluted by 500μL of HNO3 (0.3molL−1) and finally Hg (II) concentration of the eluent phase was determined with flow injection-cold vapor-atomic absorption spectrometry (FI-CV-AAS) after dilution with deionized water up to 1mL. By microwave assisted-UV system, organic mercury (R-Hg) species of the eluent were converted to Hg (II) and total Hg amount was also measured. Finally, R-Hg content was determined by mathematically subtracting the Hg (II) content from the total Hg. Under the optimal conditions, the linear range, limit of detection and preconcentration factor were obtained 0.03–6.3μgL−1, 0.0098μgL−1 and 10.4 for caprine blood samples, respectively (RSD<3%). The developed method was successfully applied to natural water and human/caprine blood samples. The Validation of methodology was confirmed by two standard reference materials (SRM).

Polymer-supported ionic liquid solid phase extraction for trace inorganic and organic mercury determination in water samples by flow injection-cold vapor atomic absorption spectrometry

A simple and green technique named polymer-supported ionic liquid solid phase extraction (PSIL-SPE) was developed for mercury (Hg) species determination. Inorganic Hg (InHg) species was complexed with chloride ions followed by its introduction into a flow injection on-line system to quantitatively retain the anionic chlorocomplex (HgCl42−) in a column packed with CYPHOS® IL 101-impregnated resin. The trapped InHg was then reduced with stannous chloride (SnCl2) and eluted with the same flow of reducing agent followed by cold vapor atomic absorption spectrometry (CV-AAS) detection. Organic mercury species (OrgHg) did not interact with the impregnated resin and were not retained into the column. Total concentration of OrgHg was evaluated by difference between total Hg and InHg concentration. A 95% extraction efficiency was achieved for InHg when the procedure was developed under optimal experimental conditions. The limit of detection obtained for preconcentration of 40mL of sample was 2.4ngL−1 InHg. The relative standard deviation (RSD) was 2.7% (at 1µgL−1 InHg and n=10) calculated from the peak height of absorbance signals (Gaussian-shape and reproducible peaks). This work reports the first polymer-supported IL solid phase extraction approach implemented in a flow injection on-line system for determination of Hg species in mineral, tap and river water samples.

Determination of mercury in size fractionated road dust samples by flow injection-cold vapor-atomic absorption spectrometry

An investigation was carried out to explore the effect of citric, hydrochloric, oxalic and tartaric acids on mercury vapor generation in a flow injection system in conjunction with atomic absorption spectrometry detection (CV-AAS) for its determination in road dust samples. Samples were collected in Buenos Aires (Argentina) during two months at 15 sites grouped in five zones with different urban characteristics and traffic profile. They were sieved in four fractions (with the following particle diameter (d): A: d<37μm, B: 37<d<50μm, C: 50<d<75μm, and D: 75<d<100μm) before Hg determination. The operating conditions (chemical and physical parameters) and the type and concentration of the acids studied (citric, hydrochloric, oxalic and tartaric) were assessed for the efficient generation of Hg. The interfering effect of metals and metalloids, present as minor and major concentrations in road dust, on Hg signal were evaluated using the four acids. Hydrochloric acid resulted to be the most convenient reaction medium in terms of sensitivity but a suitable control of interferences was not reached. For a complex matrix such as road dust, the best control of interferences was achieved when oxalic acid was tested, even when lower Hg signal was obtained in comparison with HCl. The detection limit (3σ criterion) turned out to be 0.3ngg−1. For checking accuracy, two certified reference materials were analyzed and results were in good agreement with certified values. Mercury concentrations in road dust ranged between 0.1μgg−1 and 4.6μgg−1 and the mean concentration value resulted to be 1.09μgg−1. In the four fractions, Hg concentrations (μgg−1) varied as follows: Fraction A (<0.0003–3.51); Fraction B (0.49–4.63); Fraction C (0.20–1.36) and Fraction D (0.16–1.88). The procedure is simple, rapid and robust.

Trace mercury determination in drinking and natural water samples by room temperature ionic liquid based-preconcentration and flow injection-cold vapor atomic absorption spectrometry

A liquid–liquid extraction procedure (L–L) based on room temperature ionic liquid (RTIL) was developed for the preconcentration and determination of mercury in different water samples. The analyte was quantitatively extracted with 1-butyl-3-methylimidazolium hexafluorophosphate ([C 4mim][PF 6]) under the form of Hg-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Hg-5-Br-PADAP) complex. A volume of 500 μl of 9.0 mol L −1 hydrochloric acid was used to back-extract the analyte from the RTIL phase into an aqueous media prior to its analysis by flow injection-cold vapor atomic absorption spectrometry (FI-CV-AAS). A preconcentration factor of 36 was achieved upon preconcentration of 20 mL of sample. The limit of detection (LOD) obtained under the optimal conditions was 2.3 ng L −1 and the relative standard deviation (RSD) for 10 replicates at 1 μg L −1 Hg 2+ was 2.8%, calculated with peaks height. The method was successfully applied to the determination of mercury in river, sea, mineral and tap water samples and a certified reference material (CRM).

Mercury determination by FI-CV-AAS after the degradation of organomercurials with the aid of an ultrasonic field: The important role of the hypochlorite ion

Due to new findings, the methodology based on room-temperature ultrasonic irradiation (sonolysis) for conversion of organomercurials into inorganic mercury [J.L. Capelo, I. Lavilla, C. Bendicho, Anal. Chem. 72 (2000) 4979–4984.] is further investigated. Inorganic mercury is selectively determined by Flow Injection-Cold Vapour Atomic Absorption Spectrometry (FI-CV-AAS) using SnCl 2/HCl. Complete oxidation of methyl-mercury can be accomplished within 90 s whilst phenyl and diphenyl-mercury can be degraded within 10 s using a 50% sonication amplitude (100 W nominal power) provided by a probe ultrasonic device (20.5 kHz frequency) and a 1 mol L −1 HCl liquid medium with the presence of hypoclorite ion. The importance of hypochlorite in reduction of organomercurials by stannous chloride is highlighted. Oxidation kinetics indicated a pseudo first-order reaction for methyl-mercury, phenyl-mercury, and dipheny-mercury.

Advanced oxidation processes for degradation of organomercurials: determination of inorganic and total mercury in urine by FI-CV-AAS

A new methodology, based on advanced oxidation processes, for the determination of inorganic and total mercury in human urine is proposed. Ultrasound in conjunction with ozone (sonozone) was used to avoid urine dilution for inorganic mercury determination. A new oxidation method in urine based on KMnO4–HCl–focused ultrasound is proposed for conversion of methylmercury into inorganic mercury and subsequent determination by flow injection-cold vapour atomic absorption spectrometry (FI-CV-AAS). The methodology was applied to the determination of inorganic and total mercury in spiked urine from different non-exposed volunteers.

Determination of inorganic mercury and total mercury in biological and environmental samples by flow injection-cold vapor-atomic absorption spectrometry using sodium borohydride as the sole reducing agent

A simple, fast, precise and accurate method to determine inorganic mercury and total mercury in biological and environmental samples was developed. The optimized flow-injection mercury system permitted the separate determination of inorganic mercury and total mercury using sodium borohydride as reducing agent. Inorganic mercury was selectively determined after reduction with 10 −4% w/v sodium borohydride, while total mercury was determined after reduction with 0.75% w/v sodium borohydride. The calibration graphs were linear up to 30 ng ml −1. The detection limits of the method based on three times the standard deviation of the blank were 24 and 3.9 ng l −1 for total mercury and inorganic mercury determination, respectively. The relative standard deviation was less than 1.5% for a 10 ng ml −1 mercury standard. As a means of checking method performance, deionized water and pond water samples were spiked with methylmercury and inorganic mercury; quantitative recovery for total mercury and inorganic mercury was obtained. The accuracy of the method was verified by analyzing alkaline and acid extracts of five biological and sediment reference materials. Microwave-assisted extraction procedures resulted in higher concentrations of recovered mercury species, lower matrix interference with mercury determination and less time involved in sample treatment than conventional extraction procedures. The standard addition method was only needed for calibration when biological samples were analyzed. The detection limits were in the range of 1.2–19 and 6.6–18 ng g −1 in biological and sediment samples for inorganic mercury and total mercury determination, respectively.

Determination of Mercury in Seafood by Flow Injection–Cold Vapor Atomic Absorption Spectrometry after Microwave Digestion: NMKL Interlaboratory Study

Ten laboratories participated in an interlaboratory method-performance (collaborative) study of a method for the determination of mercury in foods of marine origin by flow injection-cold vapor atomic absorption spectrometry after wet digestion using a microwave oven technique. The study was preceded by a training round of samples of known identity. The method was tested on a total of 7 seafood products: blue mussel (Mytilus edulis), cod muscle (Gadus morhua), crab (Cancer pagurus), scampi (Nephrops norwegicus), black scabbard fish (Aphnopus carbo), longnose velvet dogfish (Centroscymus crepidater), and Portuguese dogfish (Cenbroscymus coelolepis) with mercury concentrations of 0.14, 0.24, 0.35, 0.59,11.42, 4.2, and 13.2 microg/g, respectively. The materials were presented to the participants in the study as blind duplicates, and the participants were asked to perform single determinations on each sample. Repeatability relative standard deviations (RSDr) for mercury ranged from 2.4 to 14.0%. Reproducibility relative standard deviations (RSDR) ranged from 7.7 to 16.6%. HORRAT values for all samples were <1.0.

Separation and preconcentration of inorganic and organomercury species in water samples using a selective reagent and an anion exchange resin and determination by flow injection-cold vapor atomic absorption spectrometry

An on-line inorganic (InHg) and organomercury (OrHg) species separation, preconcentration and determination system consisting of cold vapor atomic absorption spectrometry (CV-AAS) coupled to a flow injection (FI) method was studied. The inorganic mercury species was retained on a column (id, 3 mm; length, 80 mm) charged with a Dowex 1X-8 resin (particle size 50–100 mesh) as the anionic complex formed with Methylthymol Blue (MTB), at pH 6.3. Previous oxidation of the organomercurial species permitted the determination of total mercury. Therefore, the separation of mercury species was obtained with the combined use of on-line selective formation of the InHg–MTB complex and the retention of this anionic compound on the anion exchange resin. The difference between total and inorganic mercury determined the organomercury content in the samples. The inorganic mercury was removed on-line from the micro-column with 3 M nitric acid. The mercury cold vapor generation was performed in an on-line system with 7.0% (w/v) SnCl2 and 20% (v/v) HCl as reducing solution. A preconcentration factor of 180 was obtained for the preconcentration of 250 ml of aqueous solution. The detection limit for InHg and OrHg was 0.8 ng l−1. The precision for ten replicate determinations at the 15 ng l−1 Hg level was 4.4% relative standard deviation (RSD), calculated from the peak heights obtained. The calibration graph using the separation and preconcentration system for mercury species was linear, with a correlation coefficient of 0.9994 at levels near the detection limit up to at least 100 µg l−1. The accuracy of the method was evaluated by the analysis of a certified reference material QC Metal LL3 Mercury in Water. The method was successfully applied to the speciation of mercury in water samples.

Determination of Mercury by Cold-Vapor Atomic Absorption Spectrometry with Preconcentration on a Gold-Trap

The determination of trace levels of mercury by flow injection cold-vapor atomic absorption spectrometry with gold amalgamation was evaluated for organic and inorganic mercury species. The effect of the sodium tetrahydroborate(III) and hydrochloric acid concentrations as well as various instrumental parameters on the analytical performance was studied. The influence of the blank as well as the laboratory procedure for reagent purification was evaluated. The procedure was applied to the determination of mercury in lake water, while focusing on the importance of the sampling protocols.

Room temperature sonolysis-based advanced oxidation process for degradation of organomercurials: application to determination of inorganic and total mercury in waters by flow injection-cold vapor atomic absorption spectrometry

A new oxidation method based on room-temperature ultrasonic irradiation (sonolysis) is proposed for conversion of organomercurials into inorganic mercury and subsequent determination by flow injection-cold vapor atomic absorption spectrometry. This advanced oxidation process eliminates the need for chemical oxidants, high temperature, and pressure for degradation of organomercurials so that total mercury can be determined with sodium tetrahydroborate(III) or tin(II) chloride as reducing agents. Complete oxidations can be accomplished within 3 min, using a 40% sonication amplitude (100 W nominal power) provided by a probe ultrasonic device (20 kHz frequency) and a 1 mol L(-1) HCl liquid medium. The presence of HCl was seen to be necessary for fast oxidation of organomercurials, in contrast to other chemical oxidants such as H2O2 or HNO3 which yielded incomplete oxidation. Further advantages of the proposed method over existing methods which are currently employed for oxidation prior to total Hg determination are the removal of hazardous wastes and the decreased risk of Hg losses by volatilization. Oxidation kinetics indicated a pseudofirst-order reaction with apparent rate constants (k) of 3.2 x 10(-2) and 1.6 x 10(-2) s(-1) for methylmercury and phenylmercury, respectively. Oxidation experiments in the presence of foreign substances acting as OH radical scavengers showed a tolerance at least up to a concentration of 1000 mg L(-1). Likewise, model wastewaters with chemical oxygen demand of up to 1000 mg L(-1) could be processed without diminishing the oxidation efficiency. The method was applied to determination of inorganic and total mercury in simulated wastewaters and spiked environmental waters in combination with selective reduction.

Determination of total and inorganic mercury in biological and environmental samples with on-line oxidation coupled to flow injection-cold vapor atomic absorption spectrometry

A method for determination of inorganic and total mercury by flow injection-cold vapor atomic absorption spectrometry (FI-CVAAS) with on-line oxidation was developed. Potassium peroxodisulphate and sulphuric acid were used as oxidizing agents so that decomposition of organomercury compounds could be achieved. Depending on the temperature selected, inorganic or total mercury could be determined with the same FI manifold. In order to assess the method performance, synthetic wastewater, wastewater, urine and saline water samples were spiked with inorganic mercury, methylmercury and phenylmercury. Quantitative recoveries were obtained for the three mercury species, except with the synthetic wastewater when the chemical oxygen demand value was higher than 1000 mg l−1. In most cases, the standard addition method was usually needed for calibration. LODs calculated as 3 σ/m were 0.47 μg l−1 for inorganic mercury and 0.45 μg l−1 for total mercury. R.S.D. values corresponding to peak height measurements were 1.5 and 2.2% for inorganic mercury and total mercury, respectively. The accuracy of the method was tested by analyzing 5 mol l−1 hydrochloric acid extracts of seven biological and environmental CRMs. LODs in the solid CRMs ranged from 0.032 to 0.074 μg g−1.

Determination of mercury in estuarine sediments by flow injection-cold vapour atomic absorption spectrometry after microwave extraction

A flow injection-cold vapour atomic absorption spectrometric (CVAAS) method was developed for the determination of mercury at trace level in estuarine sediments using sodium tetrahydroborate (III) as reductant. The mercury was solubilized with nitric acid in closed vessels and microwave oven heating. Instrumental and operational conditions (volume and concentration of reagents, reaction time, etc.) were optimized. The effect of several ions on the analytical signal was also studied; no interferences were recorded excepting for copper and nickel which caused a serious depressing effect. The detection limit obtained was 0.01 μg g -1 . The validation of the method was performed analyzing a certified reference sediment, BCR CRM 277 Estuarine Sediment. Good recovery (c.a. 98%) and precision (< 3%, RSD) were achieved. The proposed method was successfully applied to the determination of mercury in sediment samples from Ares-Betanzos Estuary (Galicia, NW Spain).

Ultrasound-assisted extraction for mercury speciation by the flow injection-cold vapor technique

A simple and rapid ultrasound-assisted extraction method with hydrochloric acid for mercury speciation in fish tissues was developed. Centrifuged extracts were directly injected into a flow injection-cold vapor atomic absorption spectrometry system. First, methylmercury was separately determined using sodium tetrahydroborate as reducing agent after selective extraction with 2 mol dm –3 hydrochloric acid. Second, inorganic mercury was determined by selective reduction with stannous chloride in 5 mol dm –3 hydrochloric acid extracts containing both mercury species. Total mercury could not be determined in the sonicated acid extracts using sodium tetrahydroborate as reducing agent because the methylmercury and inorganic mercury sensitivities were different. The detection limit was 11 and 5 ng g –1 for methylmercury and inorganic mercury, respectively. The recovery was >92% and the precision (RSD) ranged from 5 to 10% for three replicates of each sample analyzed by the standard additions method. Total mercury, calculated as the sum of methylmercury and inorganic mercury, was in agreement with the total mercury content determined after microwave digestion. The method was validated by means of three fish certified reference materials. The concentrations found were in good agreement with the certified values.

Slurry sampling combined with ultrasonic pretreatment for total mercury determination in samples containing inorganic and methylmercury by flow injection-cold vapor-atomic absorption spectrometry

A method for the determination of total mercury in solid biological and environmental samples by slurry sampling combined with flow injection-cold vapor-atomic absorption spectrometry (FI-CV-AAS) was developed. The slurries were prepared in 15% m/m nitric acid (mussel tissue, aquatic plant) or a (9 + 1) 15% m/m nitric acid–15% m/m hydrochloric acid mixture (river sediment, sewage sludge) containing 0.02% v/v Triton X-100 as dispersing agent, and subjected to ultrasonic pretreatment before being injected into the FI manifold. Ultrasonic pretreatment of slurries was proved to be necessary in order to improve the low mercury recoveries obtained. The effect of several FI parameters on the effectiveness of cold vapor generation for total mercury determination in slurries of mussel tissue was investigated. Mercury concentrations obtained by the proposed method were compared with those obtained after microwave-assisted digestion of mussel tissue samples. The method was validated against CRM BCR 278 mussel tissue, CRM BCR 60 aquatic plant, CRM BCR 320 river sediment and CRM BCR 145R sewage sludge. LODs were 3, 26, 28 and 8 ng g–1 for mussel tissue, river sediment, sewage sludge and aquatic plant, respectively. The precision, expressed as relative standard deviation [RSD (%)], ranged from 4 to 7% for three replicates of each sample analysed by the standard additions method.

Evaluation of the determination of mercury at the trace and ultra-trace levels in the presence of high concentrations of NaCl by flow injection–cold vapour atomic absorption spectrometry using SnCl2 and NaBH4 as reductands

The influence of different concentrations of NaCl (0–20%m/v) on the analytical figures of merit for the determination of mercury by flow injection–CVAAS was studied. The determination was performed with and without preconcentration by gold amalgamation and by employing different reducing agents, NaBH4 and SnCl2. When using the reductand SnCl2, stable operation both with and without preconcentration was obtained, resulting in RSDs below 5% (n 30), even in the presence of high concentrations of NaCl. Without preconcentration the sensitivity was a function of the concentration of NaCl (between 0.033 and 0.013 ml ng–1). With preconcentration the sensitivity could be improved by a factor of 2.5 (i.e., from 0.084 to 0.037 ml ng–1, depending on the concentration of NaCl). With the reducing agent NaBH4, sufficient stability for routine analysis was observed only without preconcentration (RSD ⩽ 2%, n = 45) and a sensitivity of 0.022 ml ng–1 was obtained for matrix-free solutions. In the presence of high concentrations of NaCl the sensitivity increased up to 0.030 ml–1 ng, but owing to the unsystematically unstable blank values it was not a monotonic function of the concentration of NaCl. The use of preconcentration in the case of NaBH4 was hampered by the gold trap being covered with gaseous reaction products or entrained droplets as a result of the generation of foam in the gas–liquid separator. This could be improved by the use of two gas-washing bottles (NaOH, H2O). With the different methods, for which the detection limits finally were between 15 and 230 pg ml–1 (without) and 2 and 11 pg ml–1 (with preconcentration), mercury was determined in five standard reference samples of soil and sedimented sludge at the ng g–1 to µg g–1 level subsequent to their dissolution with aqua regia.