Analysis and stability of mercury speciation in petroleum hydrocarbons

Raw petroleum and natural gas often contain high concentrations of mercury, which can be damaging to the metal components of production facilities, as well as to the environment. Various Hg species have different properties in terms of mobility, reactivity and bioavailability. Thus, for cost-effective decisions regarding plant design, Hg extraction, and pollution control, speciation information must be available at the production facility. In this paper, a simple, wet chemical speciation method, which provides data on Hg(o), dissolved and particulate total Hg, Hg(II), and methyl Hg is presented. The method incorporates species-specific extraction and separation procedures, followed by cold vapor atomic fluorescence spectrometry (CVAFS). For each species, detection limits of approximately 0.1 ng/g were obtained. Storage experiments in various containers showed that organo-mercury species were stable for at least 30 days in all containers except those made of polyethylene; and Hg(o) was stable in all containers except those made of stainless steel or polyethylene. Hg(II) was rapidly lost from all containers except those made of aluminum, which rapidly converted it to Hg(o), which was stable. In general, most of the total Hg in petroleum products was particulate Hg, followed by dissolved Hg(II) and Hg(o). Sub-ng/g concentrations of methyl-Hg were observed in most samples.     

The rate of loss of mercury from aqueous solution when stored in various containers

Solutions of natural water and distilled water were spiked with mercury(II) (25 p.p.b.) and stored in polyethylene, polyvinyl chloride, and soft glass containers. Losses of mercury at different pH values were monitored by flameless atomic absorption for a total of 17 days. Severe losses of mercury were observed at pH 2 and 7. Mercury loss from solution followed first-order kinetics; the half-lives of mercury loss under various conditions were calculated. Acidification of the solutions to pH 0.5 with nitric acid curtailed mercury loss substantially. Possible ways of reducing the loss of mercury from environmental water samples are discussed.     

Storage and stability of inorganic and methylmercury solutions

Summary The storage behaviour of mercurychloride and methylmercury chloride solutions in deionized water and in seawater stored in polyethylene (PE), pyrex glass and teflon (PTFE) containers at various concentration levels (4 ppb, 50 ppt, natural seawater concentrations) was studied using various preservatives and container pretreament procedures. For PE bottles, the best results are obtained, after pretreatment of the bottles with an acidified KMnO₄ solution, with a 0.05% (v/v) H₂SO₄+0.02% (w/v) KMnO₄ preservative. However, the solution becomes heterogeneous rather fast, due to the formation of a MnO₂ precipitate. Acidified (pH 1 with HNO₃) deionized or seawater samples stored in pyrex glass BOD-bottles (analyses are carried out in these bottles too) or teflon containers are stable with respect to inorganic mercury for at least 1 month. Instead of acidification an oxidant such as BrCl can also be used to stabilize the solution. Methylmercury solutions (80 ppt) in deionized water (pH 6) and stored in teflon containers are stable for at least 1 month. In glass bottles, the solution should be acidified to pH 1. Methylmercury seems to be unstable in acidified seawater samples (pH 1 with HNO₃); after 2 weeks about 60% of the methylmercury is converted into inorganic mercury.     

New preservation method for inorganic arsenic speciation in acid mine drainage samples

A new preservation method has been proposed for the speciation of As(III) and As(V) in acid mine drainage (AMD) samples, characterised by low pH and high metallic content. Samples were taken from a polymetallic sulphides mining area in the province of Huelva (SW Spain), under exploitation until the 1960s for its Cu, Pb and Zn sulphides. The abandoned mine works and the numerous waste rocks heaps produce AMD with high As content, an aqueous pollution source for the nearby streams. Short-term (from few hours to 1 week) preservation of the two inorganic arsenic species was studied, trying different containers (polyethylene, glass), presence or absence of light, temperatures (ambient, refrigerated, frozen), preserving agents and procedures (EDTA, HCl or AcH acids, cation-exchange resin). The speciation results obtained by liquid chromatography-hydride generation-atomic fluorescence spectrometry (HPLC-HG-AFS) indicated a rapid conversion of the samples with most of the preservation procedures reported in the literature after 3 h after sample collection. A promising method for arsenic preservation has been developed in this work, which maintains the arsenic species distribution in the original samples for a longer time. It consists in the use of opaque glass containers, acidification of the samples with HCl and in situ cleanup with cationic exchange resin, which allowed to preserve the samples for As speciation for at least 48 h.     

Analysis and stability of mercury speciation in petroleum hydrocarbons

Raw petroleum and natural gas often contain high concentrations of mercury, which can be damaging to the metal components of production facilities, as well as to the environment. Various Hg species have different properties in terms of mobility, reactivity and bioavailability. Thus, for cost-effective decisions regarding plant design, Hg extraction, and pollution control, speciation information must be available at the production facility. In this paper, a simple, wet chemical speciation method, which provides data on Hg^o, dissolved and particulate total Hg, Hg(II), and methyl Hg is presented. The method incorporates species-specific extraction and separation procedures, followed by cold vapor atomic fluorescence spectrometry (CVAFS). For each species, detection limits of approximately 0.1 ng/g were obtained. Storage experiments in various containers showed that organo-mercury species were stable for at least 30 days in all containers except those made of polyethylene; and Hg^o was stable in all containers except those made of stainless steel or polyethylene. Hg(II) was rapidly lost from all containers except those made of aluminum, which rapidly converted it to Hg^o, which was stable. In general, most of the total Hg in petroleum products was particulate Hg, followed by dissolved Hg(II) and Hg^o. Sub-ng/g concentrations of methyl-Hg were observed in most samples. Received: 4 June 1999 / Revised: 18 October 1999 / Accepted: 22 October 1999     

捕汞金管富集-冷原子荧光光谱法测定空调颗粒物中的汞

对国产原子荧光仪进样系统进行改造,采用在线热解样品捕汞金管富集冷原子荧光法测定空调颗粒物中的汞。试样热解温度为700～750℃,捕汞金管释放温度为550℃,试样载气流速为120 mL/min。方法检出限为1 pg,汞含量在0～1.5 ng范围内呈线性关系,测定标准偏差为2.23%。用国家土壤标准GBW07410中的汞验证了方法的准确性,并对某医院空调颗粒物中汞含量进行了分析。     

Effect of container material, storage time and temperature on determinations of cadmium levels in human urine

The effect of container material (polyethylene, polypropylene, polystyrene, borosilicate glass and flint glass), storage time (0-86 days), and temperature (22 degrees and 4 degrees ) on the cadmium content found by graphite-furnace atomic-absorption spectrometry for spiked and unspiked urine samples has been studied. No loss of cadmium occurred for at least 10 and 28 days when unspiked and spiked samples respectively, were stored in polyethylene containers at 22 degrees . For storage up to 3-4 days at 22 degrees , polypropylene, polystyrene, borosilicate glass and flint glass containers were also found suitable. Storage at 4 degrees was not effective in preventing loss of cadmium.     

Investigation by automated differential pulse anodic-stripping voltammetry of the problem of storage of dilute solutions

The storage of dilute solutions of metal ions before their laboratory analysis presents a difficult problem in the examination of many environmental samples. By utilizing the solution container as an electrochemical cell and employing the method of differential pulse anodic-stripping voltammetry at a hanging mercury drop electrode, it is shown that an automated read-out system in an enclosed environment can be developed for monitoring the solution-container interactions that occur over short or extended periods of time. In the present work, interactions of dilute solutions (1-10 mug/l.) of cadmium(II), lead(II), copper(II), zinc(II), and thallium(I) in glass, polyethylene and Teflon containers have been investigated at various pH values and in different ionic environments. The results demonstrate the importance of factors other than pH.     

Determinated of Trace Amounts of Mercury by Non-Disperse Atomic Fluorescence Method

Abstract

A rapid and sensitive cold vapor method for the determination of trace mercury by non-disperse atomic fluorescence measurement is proposed. Mercury vapor generated from solution was swept into the nozzle (the funnel type of glass tube) by nitrogen, and the atomic fluorescence (AF) of mercury in the gas mixture was detected by a non-dispersive AF method using a solar-blind photomultiplier. The detection limit obtained was 0.5 ng per 5 ml sample solution.     

The effect of ammonium thiocyanate and sodium chloride on loss and recovery of mercury from water during storage

The effect of inorganic complexing agents such as thiocyanate and chloride on the stability of distilled water and natural waters spiked with 1 μg Hg l^-1 in polyethylene containers is reported. Distilled water solutions can be stored for several months without significant losses of mercury if they contain HNO₃(0.05–0.1 M) + NH₄SCN(0.001–0.01 M) or HNO₃(0.1 M) + NaCl(higher than 0.01 M). For river and pond waters, addition of HNO₃(0.1 M) + NH₄SCN(0.01 M) not only has a pronounced effect on preventing mercury losses, but also gives quantitative recoveries from spiked sample solutions from which mercury has been “lost”. Thiocyanate ion-favors desorption of mercury from solid phases; chloride is less effective in this respect.     

Losses of silver,arsenic, cadmium,selenium and zinc traces from distilled water and artificial sea-water by sorption on various container surfaces

Sorption losses were studied for Ag. As, Cd, Se, and Zn at a concentration level of 10^-7 M from distilled water and artificial sea-water during storage in containers made of borosilicate glass, high-pressure polyethylene, or polytetrafluoroetbylene. Apart from pH (1, 2, 4, and 8.5) and storage time (1 min to 28 days), special attention was paid to the effect of the ratio of inner container surface to sample volume. The results are compared with literature data. In addition, a survey is given of literature references on sorption of 41 elements from aqueous solutions under different experimental conditions.     

A preliminary comparative assessment by activation analysis of some of the materials and containers used in pharmaceutical manufacture

Neutron activation analysis has been used in a preliminary, comparative assessment of some of the materials and containers employed in pharmaceutical manufacture. Microgram and submicrogram amounts of manganese, copper, and sodium have been determined in water distilled and redistilled from stainless steel and pyrex glass stills. The leaching of these elements by distilled and doubly distilled water from stainless steel, pyrex glass, and polyethylene storage containers has also been studied. The Mn, Cu, and Na contents of polyethylene bottles were also determined. The same techniques were used to determined these impurities as well as As, Au, and Sb in adrenaline and vitamin C.     

Direct determination of mercury in cosmetic samples by isotope dilution inductively coupled plasma mass spectrometry after dissolution with formic acid

A new method was proposed for the accurate determination of mercury in cosmetic samples based on isotopic dilution (ID)-photochemical vapor generation (PVG)-inductively coupled plasma mass spectrometry (ICP MS) measurement. Cosmetic samples were directly dissolved in formic acid solution and subsequently subjected to PVG for the reduction of mercury into vapor species following by ICP MS detection. Therefore, the risks of analyte contamination and loss were avoided. Highly enriched ²⁰¹Hg isotopic spike is added to cosmetics and the isotope ratios of ²⁰¹Hg/²⁰²Hg were measured for the quantitation of mercury. With ID calibration, the influences originating from sample matrixes for the determination of mercury in cosmetic samples have been efficiently eliminated. The effects of several experimental parameters, such as the concentration of the formic acid, and the flow rates of carrier gas and sample were investigated. The method provided good reproducibility and the detection limits were found to be 0.6 pg mL⁻¹. Finally, the developed method was successfully applied for the determination of mercury in six cosmetic samples and a spike test was performed to verify the accuracy of the method.     

Evaporation rate in containers used for storing radioactive tracer solutions

In radiochemical analysis, the storage of a tracer solution is an important issue to bear in mind. The evaporation of the tracer solution depends on the type of container used for storing. In this paper the evaporation rate in four kinds of containers, i.e., flame-sealed glass ampoule, sealed glass flask, flame-sealed polyethylene ampoule and screw glass vial was studied. It is concluded that the evaporation rate depends on the system of closing.     

How accurate must a reference material be?

 This article deals with reference materials (RMs) used for calibration purposes. For most common spectroscopic and chromatographic methods, RMs which have a relative content uncertainty of up to 3% can be used without considerably increasing the overall measurement uncertainty of the complete procedure. It is vital that the correct amount of the RM is used to ensure the quality of the quantitative chemical analyses. This can only be guaranteed if, in addition to the correct determination of the amount, the stability of the RM in the sales packaging is considered in the quoted uncertainty. For instance when the RM is packed in a container made of polyvinylidene fluoride water losses in hot climates can result in an increase in concentration which cannot be neglected. This is also true for high density polyethylene containers (PE-HD) although to a lesser degree. When mercury solutions of 1000 mg/l to 10 000 mg/l are kept in diluted nitric acid in PE containers, a relevant reduction in amount can be measured despite the water losses. However, the solutions remain stable in glass containers.     

A spectroscopic study of mercury vapor adsorption on gold nanoparticle films

We have modified the surfaces of glass and Si(100) with 3-aminopropyltrimethoxy silane, a fourth generation amine-terminated poly(amidoamine) dendrimer, and poly(diallydimethyl ammonium chloride) to facilitate adsorption onto colloidal gold particles (average diameter 3, 5, 12, and 22 nm). UV-vis absorption spectroscopy and atomic force microscopy monitored the adsorption process, which is governed by particle diffusion to the surface. The differences in adsorption to the three adhesion layers as a function of pH are discussed. Mercury vapor was exposed to the gold particle films and quantified by X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy. The surface plasmon oscillation of 5-, 12-, and 22-nm particles blue-shifts after exposure to parts-per-million levels of mercury vapor in air. Particle films prepared from the 3-nm gold particles develop a broad peak centered near 530 nm after exposure to mercury vapor. The results demonstrate a novel "litmus" film for mercury vapor.     

Improved determination of gaseous divalent mercury in ambient air using KCl coated denuders

An improved method for the determination of gaseous divalent mercury (GDM) in ambient air using KCl coated denuders has been developed and tested. GDM collected in the KCl coated denuders can be quantitatively desorbed at 450 degrees C in 10 min. After being complete thermally reduced to Hg0 at 900 degrees C, all mercury released from the denuder is pre-concentrated on the analytical Au trap, and detected by cold vapor atomic fluorescence spectrometry (CVAFS). The absolute detection limit of the method is less than 3 pg. Preliminary data of GDM concentration in ambient air from different sampling stations show that GDM concentrations in the urban air of G?teborg are much higher than in rural air (R?rvik and Sasetta), which indicates the anthropogenic origin of GDM.     

Multivariate optimization of mercury determination by flow injection-cold vapor generation-inductively coupled plasma optical emission spectrometry

In this work a procedure for mercury determination by Flow Injection-Cold Vapor Generation-Inductively Coupled Plasma Optical Emission Spectrometry (FI-CVG-ICP OES) has been developed. The system uses a small homemade glass separator constructed to drive the Hg vapor to the plasma. An evolutionary operation factorial design was used to evaluate the optimal experimental conditions for mercury vapor generation, aiming at the low consumption of reagents, the improvement of the analytical signal and consequently greater sensitivity. The procedure allowed the determination of mercury and showed excellent linearity for the concentration range from 0.50 μg L(-1) to 100.0 μg L(-1), with Limits of Detection (LOD) and Quantification (LOQ) of 0.11 μg L(-1) and 0.36 μg L(-1), respectively, and a sampling rate of 36 analyses per hour. The optimized procedure showed good accuracy and precision, and the method was validated by the analysis of two certified reference materials: Buffalo River Sediment (NIST 2704) and human hair (IAEA 085). A good agreement with the certified values was achieved, with recovery values of 99% and 98% and relative standard deviation close to 2%.     

原子荧光法检验环境空气中汞的含量

目的采用原子荧光法检验环境空气中汞的含量。方法建立微波消解-原子荧光法,研究微波消解前处理效果,并进行精密度、准确度以及样品实验。结果样品空气中汞的含量为1.44、1.09、1.82 ng/m~3。结论原子荧光法检验环境空气中汞的含量前处理简单,样品消解完全,回收率高。     

An Instrumental Correction for the Determination of Mercury in Biological and Sediment Samples Using Cold Vapor Atomic Absorption Spectrophotometry

Low recovery rate and inconsistent measurements were found in the determination of mercury by method of cold vapor atomic absorption spectrophotometry using the hydride formation system (Hitachi HFS-2, Hitachi Ltd., Tokyo). To overcome this problem of insufficient reaction time we developed a simple T-joint device attaching to the commercial HFS-2 system for the determination of mercury in various biological tissues and sediment samples. The T-joint device was designed to combine sample and reductant injection which increased the reaction time of the sample allowing a complete formation of mercury vapor and speeding up the analysis process in comparison to the traditional cold vapor atomic absorption spectrometric method. Recoveries of mercury were in the range 95% - 100%. The corrected procedure gave precise and accurate readings with several certified reference materials: NIES No. 2 from the Japan Environment Agency; IAEA-356 from the International Atomic Energy Association, and DOLT-2, DORM-2, TORT-2, PACS-1 and MESS-2 from the National Research Council of Canada. Simple acid digestion methods were developed based on the sample Hg level and the nature of the sample. The sample detection limits were 0.0125 μg g⁻¹ fresh weight and 0.0625 μg g⁻¹ dry weight for biological samples, and as low as 0.0125 μg g⁻¹ dry weight for sediment samples. These analytical protocols we established met the general requirements in environmental research and monitoring of mercury pollution.