Generation Of Volatile Species Research Articles

Cadmium-bound species in human urine using high-performance liquid chromatography-vesicular hydride generation-inductively coupled plasma mass spectrometry

Anion-exchange liquid chromatography was coupled on-line with inductively coupled plasma mass spectrometry (ICP-MS) via a vesicular hydride generation (HG) interface. This hybrid arrangement was assessed for Cd speciation in standards of rabbit liver metallothionein (MT) and human urine. Commercial rabbit liver MTs were readily resolved using a concentration gradient (2-200 mM) of Tris-HCl buffer solution at pH 7.4 and a polymeric Protein-Pak DEAE-5PW anion-exchange column. Three Cd species were detected in rabbit liver MT 1 [retention times of 3.2 (I), 5.6 (II) and 9.3 (III) min] and two species in MT 2 (retention times of 16.7 and 24 min). In rabbit liver MT 1 and MT 2, mixtures of Cd and Zn were found to be evenly distributed between the two isoforms, whereas Cu was predominantly associated with the MT 1 isoform.The chromatographic behaviour of the Cd-containing species separated and detected in basal human urine seems to be similar to that of the Cd fractions I and II of rabbit liver MT 1. The efficiency of CdH 2 generation for Cd bound to both the main isoforms of rabbit liver was the same as for inorganic Cd 2+ from a vesicular medium. This highly selective and sensitive on-line HG-ICP-MS detection system provided a 4-fold (aqueous) or 16-fold (urine) sensitivity enhancement in comparison with ICP-MS detection with conventional nebulization. Unfortunately, only a 2-5-fold improvement was observed for the corresponding detection limits due to the high values of the blanks observed using volatile species generation.

Determination of cadmium in biological and environmental materials by isotope dilution inductively coupled plasma mass spectrometry: effect of flow sample introduction methods

Experimental parameters governing the instrumental precision and accuracy for isotope ratio measurements of cadmium in ICP-MS, including sampling time, mass bias, detector dead-time and spectroscopic interferences, were first characterised. The precision achieved for the isotope ratio determination of Cd was around 0.2% (RSD forn=5) both for 111:112 and 111:114 ratios. Two alternative flow approaches for the determination of ultratrace concentrations of cadmium by isotope dilution (ID) were explored and compared with the more conventional ID methodology: first, on-line mixing of the sample solution with the spike solution just before the ICP-MS nebuliser using a peristaltic pump and, second, the generation of volatile cadmium species using sodium tetraethylborate by merging zones flow injection ICP-MS. The three approaches were successfully applied to the determination of ultratrace levels of cadmium in biological and environmental certified reference materials (NIST SRM 2670 Freeze-Dried Urine, IAEA H-8 Horse Kidney, BCR TP-25 Lichens, PACS-1 Marine Sediment and SLRS-3 Riverine Water). The on-line ID method proved to be the most convenient for the determination of cadmium in such samples because it is fast, provides similar results to those of conventional ID and requires less sample preparation.

Merging zones flow injection for the determination of ultratraces of bismuth by volatile species generation atomic absorption spectrometry using sodium tetraethylborate(III)

The generation of a volatile Bi compound by its reaction in aqueous solution with sodium tetraethylborate(iii) has been achieved using a flow injection (FI) system with injection of Bi and NaBEt4 solutions in a ‘merging zones’ mode. This vapour generation (VG) system has been successfully interfaced with an atomic absorption spectrometric (AAS) detector for the determination of low levels of the metal. A detection limit of 0.8 µg l–1 (0.56 ng) of Bi was obtained after optimization of the chemical and instrumental parameters. This volatile species generation with AAS detection showed a precision of ±2.9% at the 40 µg l–1 level of Bi and a sample throughput of about 100 samples h–1 was observed. Interference studies were carried out for many potentially interfering elements. The proposed FI–VG-AAS method proved to be very selective for the determination of Bi and so it has been successfully applied to the determination of ultratraces of Bi in human urine after simple 1+1 dilution without any other preteatment; the detection limit in real urine samples was 1.6 µg l–1. Bismuth recoveries of 100% were found in spiked urine samples and also excellent agreement was achieved between results obtained by FI–VG-AAS and those obtained by ICP-MS for real urine samples. Finally, the proposed procedure was applied to the study of urinary clearance of Bi in three different people after intake, at therapeutic doses, of colloidal Bi subcitrate (CBS).

Gaseous sample introduction for the determination of silicon by ICP-AES

The generation of volatile species of silicon as a means to introduce silicon into an inductively coupled plasma has been studied. It is based on the reaction between silicon and fluoride ions in sulfuric acid media and it was carried out using different flow injection mountings. The first mounting works with an injection of 100 μL concentrated sulfuric acid and 150 μL silicon standard solution in a continuous 0.05 mol L–1 NaF solution flow. The method shows a linear response between the intensity of emission at 251.611 nm line and the silicon concentration from 0.1 to 200 μg mL–1, with a reproducibility of 2% and a detection limit of 0.004 μg mL–1. The second mounting produces the volatile species by the reaction between two opposed aerosol flows in a home-made nebulization chamber. This chamber has a Cross-Flow and a Meinhard nebulizer at either end. A linear response ranging from 0.1 to 1000 μg mL–1 of silicon solution is obtained and the reproducibility rises to 8%.The detection limit reached is 0.02 μg mL–1. The silicon content in real water samples was determined by applying both the above-mentioned methods and a third method for reference.

Flow Injection for Automation in Atomic Spectrometry

The use of FI methods to extend the capabilities of atomic spectrometric detectors is discussed with emphasis on developments in automation. Topics such as direct sample introduction and on-line dilution, calibration, dissolution, liquid–liquid extraction, precipitation reactions, ion-exchange preconcentration, generation of volatile species and microwave sample pre-treatment are used to illustrate the versatility of coupling FI with either FAAS, ETAAS, ICP-AES, ICP-MS and/or AFS. Finally a brief overview of the advances in this research field is presented.

Generation of Cadmium Atoms at Room Temperature Using Vesicles and Its Application to Cadmium Determination by Cold Vapor Atomic Spectrometry

The only metal recognized as able to form a monoatomic vapor at room temperature is mercury (cold vapor generation). This property has been widely used in many analytical techniques, particularly in atomic spectroscopy, to increase the efficiency of the transport of the metal to the measurement cell. In fact, cold vapor atomic absorption spectrometry (CV-AAS) has become the most common method for the determination of trace and ultratrace levels of mercury in the most varied samples. Evidence is shown here demonstrating that cadmium appears also to be able to form cold atomic vapor under appropriate reaction conditions. Experimental results show that some types of volatile cadmium species (most probably hydrides) can be produced by reduction with sodium borohydride of Cd 2+ in an aqueous solution of vesicles of didodecyldimethylammonium bromide. Such volatile species are able to transport the metal to the atomic absorption measurement cell, where Cd° cold vapor has been detected. The absorption profile of the absorbing species at room temperature has been measured in a typical absorption quartz cell by using a spectrograph/charged coupled device arrangement Results demonstrate the presence of monoatomic cadmium vapor in measurable concentrations in the absorption cell, the magnitude of the AAS signal being proportional to the metal concentration in the aqueous solution. This vesicular volatile species generation facilitates cadmium transport to the atomizer cell, thereby improving by about 20 times the detectability of cadmium by the cold vapor inductively coupled plasma atomic emission spectrometry technique (detection limit, 1 ng/mL Cd). Moreover, a highly sensitive determination of the metal based on these facts can be carried out by CV-AAS (detection limit, 0.08 ng/mL), and sensitivity can be further improved by working at lower temperatures for volatile species generation and transport to the absorption cell.

Effects of organised media on the generation of volatile species for atomic spectrometry

The use of surfactant-based organised assemblies, such as micelles and vesicles, to improve the characteristics of room temperature chemical generation of volatile species of metals and semi-metals (e.g. hydride generation, cold mercury vapour or alkylcompound generation), as a means to further enhance sample introduction efficiency/kinetics for atomic techniques, is reviewed. The complex influence of different organised media (including cationic, anionic, non-ionic and zwitter-ionic micelles and cationic and anionic vesicles) on the hydride generation of the elements As, Pb and Cd and on Hg 0 cold vapour generation have been revised and compared with organised media effects on alkylmetals generation of Se, Pb, Cd and Sn. Enhancements in efficiency/transport of volatile species formed in the surfactant-based media, increases in the reaction kinetics, stabilization of some room temperature unstable species and also changes in the observed selectivity of reactions taking place in conventional aqueous media are some of the discussed effects. Possible mechanisms and analytical potential and usefulness of this enhancement by surfactants of the generation of volatile species for atomic detection methodologies are summarized and illustrated with the determination of low levels of arsenic, lead, cadmium, tin, selenium and mercury.

Studies on the reaction between cadmium and potassium tetrahydroborate in aqueous solution and its application in atomic fluorescence spectrometry

The conditions for the vapour generation of cadmium by the reaction with potassium tetrahydroborate in aqueous solution were investigated using a programmable intermittent flow reactor. It was found that thiourea together with cobalt ion greatly enhanced the generation efficiency of the volatile species. Based upon the results of the investigation, the vapour generation system was used for the determination of ultra-trace amounts of cadmium by atomic fluorescence spectrometry. A detection limit of 8 pg ml −1 was obtained under optimized conditions and the precision of the measurements for 5 ng ml −1 of Cd was 1.2% R.S.D. The effects of 28 diverse ions on the generation of the cadmium volatile species were investigated. Serious signal depressions were observed from copper and lead but these were decreased by using potassium cyanide as masking agent for copper and by coprecipitation with barium sulphate for lead. The method was successfully applied to the determination of cadmium in NBS standard reference material (SRM) 1577a bovine liver, NBS SRM 1645 river sediment and other Chinese origin SRMs. The method was also applied to tap water analysis with full recovery of spiked samples.

Direct coupling of high-performance liquid chromatography to microwave-induced plasma atomic emission spectrometry via volatile-species generation and its application to mercury and arsenic speciation

The on-line coupling of vesicle-mediated high-performance liquid chromatography (HPLC) to low-power argon microwave-induced plasma (MIP) detection is described. The analytical potential of such a hybrid technique is illustrated for the speciation of mercury and arsenic compounds. Continuous cold vapour (CV) or hydride generation (HG) techniques were used as interfaces between the exit of the HPLC column and the MIP, held in a surfatron at reduced pressure. Detection was by atomic emission spectrometry (AES). The effect of different surfactants on mercury CV generation was evaluated using SnCl2 as the reducing solution instead of sodium tetrahydroborate(III). Emission signals increased by about 75% by adding the vesicle-forming surfactant didodecyldimethylammonium bromide (employed as the HPLC mobile phase for speciation). Enhancements of around 100% of signals were found in micelles of cetyltrimethylammmonium bromide. The detection limits by vesicular HPLC–HG-MIP-AES for the more toxic arsenic species investigated (namely, arseneous, arsenic, monomethylarsonic and dimethylarsinic acids) were in the range 1–6 ng ml–1. The detection limits for mercury speciation by vesicular HPLC–CV-MIP-AES were 0.15 ng ml–1 Hg for inorganic mercury and 0.35 ng ml–1 Hg for methylmercury. Both methods have been successfully applied to the speciation of mercury and arsenic in natural waters (sea-water and tap water) and in human urine.

Silver-induced volatile species generation from conductive die attach adhesives : Terry E. Phillipset al. IEEE Transactions on Components, Hybrids, and Manufacturing Technology, 15(6), 956 (1992)

Chip scaled opto-electronic packaging is introduced as a cost and size effective packaging solution for mobile phone with built in camera. The chip scaled assembly includes gold bumped CMOS image sensor device and its flip-chip bonding on substrate using the anisotropic conductive material. Two types of flip-chip module were designed to have flip-chip on flex and flip-chip on glass. It is shown that well controlled bumping process of thin film deposition and wet etching gives no damage to image sensing surface during the deposition and stripping of metal film. As results, smart and high degree miniaturized image sensor module is actualized for mobile phone and the reliability test results proved the robustness of module structure having flip-chip. Solder bumping was also reviewed and successfully introduced to verify the alternative of image sensor bumping.

Sensitive inductively coupled plasma atomic emission spectrometric determination of cadmium by continuous alkylation with sodium tetraethylborate

Continuous flow generation of volatile Cd species using NaBEt4 as a means of gaseous sample introduction into an inductively coupled plasma atomic emission spectrometry (ICP-AES) instrument has been investigated in detail. The assumed generation of CdEt2 is discussed and critically evaluated in terms of the sensitivity, selectivity and accuracy of the corresponding ICP-AES determination of low levels of Cd. The proposed method for the determination of Cd by ICP-AES using NaBEt4 provided detection limits of 0.4 ng ml–1, which are ten times better than those of conventional nebulization ICP-AES. A precision of ± 1.4% at the 50 ng ml–1 level of Cd was observed. Interference studies have been carried out, which demonstrated high selectivity of the proposed method. This method has been applied to the determination of low levels of Cd by ICP-AES in samples of sea-water and tea infusions. Satisfactory validation of the results obtained has been provided by electrothermal atomic absorption spectrometric analysis of the same samples.

Surfactant-based ordered media in analytical atomic spectrometry

During the last 10 years or so we have witnessed an enormous growth of interest and applications of surfactant-based ordered media in analytical chemistry. However, their use in analytical atomic spectroscopy (AAS) has been rather scarce and often controversial. The utilization of surfactants in this latter field is discussed here along two main lines: one refers to the favourable manipulation of physical properties of the sample solutions (Part A) while the other, demonstrated very recently, refers to the adequate manipulation of chemical reactions and/or interactions of analytes in solution by resorting to surfactants use (Part B). The control of physical properties of sample solutions, e.g. manipulation of the surface tension, allows three main applications of surfactants in atomic methods: possible increases of nebulization/atomization efficiencies in flame-AAS, improvement of aqueous/organic solvent compatibility (emulsification applications) and enhancement of the wettability of graphitic solid surfaces. The facts and controversies existing today on this method of utilization of surfactants to enhance atomic methodologies is critically discussed. The ability of surfactant-based “ordered media” to organize reactants at the molecular level has also been applied to enhance chemical generation of volatile species ( e.g. hydride generation or cold Hg vapour generation) used in atomic methods. The analytical potential and usefulness of micelles and vesicles to improve the detection power of hydride generation ICP-AES methodologies are summarized for the determination of arsenic, lead and cadmium by plasma emission. Increases up to two-fold in the sensitivity of As and Pb have been observed by addition of organized media. A volatile Cd species is formed very easily in cationic vesicles with NaBH 4. This Cd species can be used to increase by five times the detectability of Cd by ICP-AES. Moreover, synergic combinations of liquid chromatography separations/atomic detection are possible by resorting to the use of micellar or vesicular mobile phases. The successful application of this principle to the modern problem of toxic arsenic HPLC speciation by using a vesicular solution [as mobile phase for the HPLC separation of As(III), As(V), monomethylarsonic and dimethylarsinic acids] and “on-line” surfactant-enhanced arsine generation is also described in detail and completes the whole picture of the present interface between analytical atomic spectroscopy and surfactant assemblies.

Etching of copper and copper oxide at high rates via generation of volatile copper species

Two new chemical approaches to etching copper have been identified recently. The first involves oxidizing copper films with halogens and then generating various Lewis base adducts of CuX where X scmsim; Cl or Br (L n CuX, where n = 1 or 2 ). The second approach involves the reaction of Cu films with Cu(hfac) 2 (where hfac ≿ 1,1,1,5,5,5- hexafluoro-2,4- pentanedione ) and various Lewis bases to form two equivalents of (hfac)CuL ( L ≿ ligand ) . Spontaneous etching experiments have been carried out in a hot-wall reactor which showed that etch rates up to 1 μm min −1 can be achieved at temperatures below 420 K. The high etch rates are the result of the high vapor pressures of the L n CuX and (hfac)CuL which are on the order of 0.1–1 Torr at 330–370 K. The interaction of Cl 2 and triethyl phosphine (PEt 3) with a single-crystal copper surface was studied under ultrahigh vacuum conditions to provide a better understanding of the etching process. At temperatures above 320 K, PEt 3 reacts rapidly with a heavily chlorinated copper surface (10 000 L exposure ( 1 L ≿ 1 langmuir ≿ 1 × 10 −6 Torr s ) of Cl 2 at 300 K). The mass spectrum of the desorbing product is similar to that of CuCl(PEt 3) 2, suggesting that etching of copper occurs by reaction with Cl 2 and PEt 3 to form gaseous CuCl(PEt 3) 2. Subsequent examination of the substrate by Auger electron spectroscopy showed removal of chlorine (and presumably copper). Finally, the reactions of copper oxide with hfacH were investigated as a method for etching copper oxide films. Etch rates of up to 1 μm min −1 at an hfacH partial pressure of 1 Torr and temperature of 540 K were obtained in a differential cold-wall reactor.

Generation of volatile cadmium species with sodium tetrahydroborate from organized media: application to cadmium determination by inductively coupled plasma atomic emission spectrometry

Continuous flow generation of volatile cadmium species (assumed to be the hydride) as a means of gaseous sample introduction into an inductively coupled plasma atomic emission spectrometer has been investigated in detail. Different ‘organized molecular assemblies’(micelles and vesicles) have been tried in order to improve the generation of such cadmium species using NaBH4 as the reducing agent. Didodecyldimethylammonium bromide (DDAB) vesicles were found to be the most appropriate for the purpose. The advantages of this ‘assumed’ cadmium hydride generation from vesicular media are discussed and critically compared in terms of sensitivity, selectivity and accuracy, with the determination of low levels of cadmium by inductively coupled plasma atomic emission spectrometry (ICP-AES). The proposed method for the determination of cadmium by ICP-AES using DDAB and NaBH4 provided 5-fold lower detection limits (1 ng ml–1) as compared with conventional nebulization ICP-AES. A precision of 2% at the 50 ng ml–1 level of the metal was achieved and selectivity studies were carried out. The proposed method was applied to the determination of low levels of cadmium in tea infusion. Validation of the method was performed by analysis of the same samples by electrothermal atomic absorption spectrometry with satisfactory results.

Improvement in mercury cold vapour atomic techniques by resorting to organized assemblies and on-line membrane drying of vapour

The most commonly used technique for mercury determination today is cold vapour (CV) generation with atomic absorption spectrometry (AAS), although inductively coupled plasma atomic emission spectrometry (ICP-AES) has also been used for final detection in several continuous CV-ICP-AES methodologies. In this paper improvements in Hg CV generation for both ICP-AES and AAS detection have been tried. The metal transport/excitation in the ICP-AES was improved by incorporating on-line with the ICP, a commercially available ‘membrane drier tube’. The ability of such a membrane to eliminate water vapour from the gaseous sample stream enhanced Hg signals in ICP-AES and decreased baseline drift in flames. On the other hand, earlier work on the use of organized media in atomic spectrometry has shown the ability of micelles and vesicles to improve the kinetics of volatile species generation with sodium tetrahydroborate. In this vein the effect of different organized media on Hg CV generation has been studied. Micelles studied include: cationic hexadecyltrimethyl-ammonium bromide (CTAB), anionic sodium dodecyl sulfate (SDS) and non-ionic Triton X-100. Cationic vesicles studied were didodecyldimethylammonium bromide (DDAB). The best detection limits were obtained using DDAB vesicles. The detection limits obtained when the Hg vapour was generated from conventional aqueous techniques were 0.6 and 1 ppb using ICP-AES and AAS detection, respectively. When both vesicles of DDAB and drying membrane tube were used in the CV generation system, the detection limits obtained were 0.2 ppb both for ICP-AES and AAS techniques, showing the beneficial effect of using a drier tube on-line with the plasma in ICP-AES. The proposed CVAAS method has been applied to the determination of Hg in sulfuric acid and sea-water samples.

Silver-induced volatile species generation from conductive die attach adhesives

Commercial and model epoxy die-attach adhesives, with and without silver filler, were investigated to examine the effect the silver filler has on the outgassing characteristics of the organic matrix. The materials were subjected to typical temperature processing schedules including cure, preseal bake, and burn-in. The volatile species outgassing during each of the processing periods were analyzed by gas chromatography/mass spectrometry. Thermogravimetric and calorimetric analyses were also performed. It was determined that silver in the adhesive leads to a greater mass loss and a marked change in the outgassing species relative to the same adhesive system without silver.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>