Piezoectric Crystal Detection of Hydrogen Chloride Via Sulfur Dioide/Mercury Displacement

Abstract

Magnesium thiosulfate converts hydrogen chloride to sulfur dioxide, which then reduces mercurous ion to free mercury. This is detected as a mercurygold amalgam using a piezoelectric crystal detector. the reaction sequence has a response time of 2 minutes, is fully reversible, and is made specific for the analyte by the use of appropriate scrubber reagents placed before and after the magnesium thiosulfate. the detector has a linear response with a sensitivity of 8.3 Hz per ppm in the 0.5–92 ppm range, a relative standard deviation less than 5 percent, and an estimated limit of detection of approximately 20 ppb HCI.     

Use of Piezoelectric Crystals as Sensitive and Specific Detectors for So2

Abstract

A general purpose gas chromatograph using a piezoelectric crystal as detector has been constructed and a piezoelectric crystal detector sensitive and selective for sulfur dioxide has been designed and developed. From 1 to 100 ppm of SO₂ can be quickly and easily determined.     

Determination of Total Sulfur in Soils and Plants by an Automated Dry Combustion Method

Abstract

Determination of total sulfur in environmental samples can be accomplished using automated dry combustion techniques. The analytical performance of an elemental analyzer (CE Instruments) was compared with a method involving dry ashing followed by ion chromatographic detection of sulfate (IC). Samples included certified reference materials, confirmation materials with a known content of sulfur, and several soils and plants. There was a close agreement between both methods. Superior accuracy, precision and detection limits were obtained using the dry combustion method. Current results suggest that the automated dry combustion technique has developed into an adequate method for the determination of the relatively low total sulfur contents commonly encountered in soils and plants.     

Monitoring inorganic mercury and methylmercury species with liquid chromatography-piezoelectric detection

A piezoelectric detection system coupled with a liquid chromatographic system is developed for the speciation of inorganic mercury(II) and methylmercury. Piezoelectric detection has been demonstrated to be a very sensitive detection system for total mercury determination when a gold-coated piezoelectric quartz crystal was used. The analytical features of this detection unit make it very suitable to be used as a detector coupled with a liquid chromatographic system for monitoring mercury species. After separation by a chromatography column (Spherisorb ODS-2, 5 μm,  mm i.d.), mercury species are liberated and reduced, by using stannous chloride, and are detected as an amalgam on the gold-coated piezoelectric quartz crystal, the sensor subsequently was regenerated by passing a peroxydisulfate solution. This detector exhibits good sensitivity, it allows the determination of mercury at sub-ppb concentration levels (0.30-1.20 μg l⁻¹). The precision, expressed as relative standard deviation, was ±2.7% (n=11) for a 0.5 μg l⁻¹ total mercury concentration. The proposed method is free of interferences and it allowed the determination of inorganic mercury and methylmercury species in natural waters.     

Crystal structures of [Hg(<Emphasis Type="Italic">N</Emphasis>-ethylthiourea)<Subscript>2</Subscript>(CN)<Subscript>2</Subscript>] and [Hg(<Emphasis Type="Italic">N</Emphasis>-propylthiourea)<Subscript>2</Subscript>(CN)<Subscript>2</Subscript>]

Two mercury(II) cyanide complexes of N-ethylthiourea (Ettu) and N-propylthiourea (Prtu) ligands, [Hg(Ettu)₂(CN)₂] (1) and [Hg(Prtu)₂(CN)₂] (2), were prepared and their crystal structures were determined by X-ray crystallography. In both structures, the mercury atom is coordinated to two sulfur atoms of thioureas and two cyanide carbon atoms in a pseudo-tetrahedral mode with the bond angles in the range of 90.52(11)–162.2(3)°. The structures are stabilized by N-H—S, N-H—N, and C-H—N intramolecular and intermolecular hydrogen bonds.     

Subnanogram Determination of Inorganic and Organic Mercury by Helium-Microwave Induced Plasma-Atomic Emission Spectrometry

Abstract

Inorganic and organic mercury were determined by helium-microwave induced plasma-atomic emission spectrometry following cold vapor generation. Whereas only inorganic mercury was reduced by stannous ion in an acidic medium, both inorganic and organic mercury (total mercury) were reduced by stannous ion in the presence of cupric ion in a basic medium. Organic mercury was determined as the difference between total and inorganic mercury. Detection limits for inorganic and organic mercury were 11 and 10 pg, respectively, The accuracy of the proposed method was verified through the determination of inorganic, total and organic mercury in two marine biological standard reference materials, DORM-1 and TORT-1.     

Cathodic Stripping Voltammetric Study Of DL-N-Acetylhomocysteine Thiolactone (Citiolone)

Abstract

The behaviour of DL-N-acetylhomocysteine thiolactone (citiolone) at a hanging mercury drop electrode is studied by cathodic stripping voltammetry (c.s.v.) as an example for determination of thiolactones. Voltammetric response is only obtained at pH> 9.3, when the cyclic structure of thiolactone is open. A spectrometric study is made in order to ascertain this behaviour. Under the recommended conditions and at pH> 9.3, the sulfur containing group can form mercury complexes and citiolone can be determined from the stripping peak that appears at about -0.470 V within the concentration range 3.5 10^?7- 1 10^?9 mol l^?1. Calibration functions are reported and detection limits calculated. The interference of several organic compounds is reported.     

Organophosphine transition metal complexes as selective surfaces for the reversible detection of sulfur dioxide with piezoelectric crystal sensors

Some organotransition metal complexes, bis (sulfur dioxide)tetrakis (triphenylphosphine oxide) manganese(II)dioxide [Mn(OPPh₃)₄I₂(SO₂)₂] and bis(tribenzylphosphine)copper(II) thiophenolate [Cu(PBz₃)₂SPh], were identified as candidate coatings for the detection of sulfur dioxide on piezoelectric crystal sensors. After treatment to form the mono (sulfur dioxide) adduct, the first complex binds sulfur dioxide to reform the bis adduct, and can be used as a coating for an integrating piezoelectric sensor. The initial complex can be regenerated by placing the coated piezoelectric sensor under vacuum for 4 h. The specified copper complex was found to act as a reversible coating for the detection sulfur dioxide in the range 10–1000 mg l^?1.     

Fullerene‐Crown Ether Coated Piezoelectric Crystal Liquid Chromatographic Detector for Metal Ions and Polar/Nonpolar Organic Molecules

Fullerene(C60)‐dibenzo‐16‐crown‐5‐oxyacetic acid (DBI6C5‐OCH₂‐COOC₆₀) was prepared and applied as the coating material on piezoelectric quartz crystals for detection of various metal ions and polar/nonpolar organic molecules. The C60‐crown ether‐coated piezoelectric crystal sensor with a home‐made computer interface for signal acquisition and data processing was applied as an ion chromatographic (IC) detector for various metal ions, e.g., alkali metal, alkaline earth metal and transition‐metal ions. The piezoelectric detector exhibited quite good sensitivity of 10⁴ ～ 10⁶ Hz/M and good detection limit of 10^?3 ～ 10^?4 M for these metal ions. The C60‐crown ether piezoelectric detector compared well with the commercial conductivity detector conventionally used for metal ions. The ionic size and ionic charge seemed to have significant effect on the frequency response of the piezoelectric detector. The C60‐crown ether coated piezoelectric crystal sensor was also employed as a high performance liquid chromatographic (HPLC) detector for various polar organic molecules with frequency responses in the order: amines > carboxylic acids > alcohols > ketones. Furthermore, nonpolar organic molecules, e.g., n‐hexane, 1‐hexene and 1‐hexyne, were also detected with this piezoelectric crystal detector. The frequency responses of the piezoelectric crystal detector for these nonpolar organic molecules were in the following order: alkynes > alkenes > alkanes. The effects of solvents and flow rate on the frequency responses of the piezoelectric crystal detector were investigated. The C60‐crown ether coated piezoelectric crystal detector also showed short response time (< 1 min.) and good reproducibility.     

The Detection of Source Levels of Sulfur Dioxide Using a Piezo-Electric Detector and Permeation Membrane

Abstract

The detection of gaseous pollutants using a coated vibrating quartz crystal has been the topic of several studies. Detection of sulfur dioxide with an alkanoamine-coated crystal has already been shown feasible for ambient air pollution levels. Detection of sulfur dioxide at source levels using the piezo-electric method has previously not been proven successful. This work presents the refinements, calibration, and performance of a source monitoring instrument which incorporates a sulfur dioxide permeable membrane as a dilution interface.     

Determination of low sulfur concentrations in oils and organic solids

A rapid and reasonably precise method was needed for determining low sulfur concentrations (<2oo p pm ) in organic solids, gas oils, and heavier liquids This level of sullfur is below the useful range of conventional procedures, therefore, the development of a new method became necessary and a satisfactory combustion-colorimentic method was developed The method is haded on the oxidation of sulfur to sulfur dioxide by combustion and the subsequent formation of stable. non-volatile dissulfitomercurete(II) ion. A red-violet color develops when disulfitomercurate, p-rosaniline, hydrochloric acid, and formaldeliydc are mixed The absorption of the solution is measured at 560 mμ and is directly proportional to sulfur concentrationThe method is rapid, accurate and piecise The short-term 2-sigma precision limits arc 5 9 p p m sulfur at the' 90 p p m level and 36 p p m At the 10 p p in level Two samples can be analyzcd per hour The succes of the method is due in part to the use of two furnaces at different temperatures during the combustion step This airrangment affords good control of the combustion and is particularly useful where various types of samples are to be analysed     

Thiophene-fused DCNQI Derivatives: Their Copper Iodide Complexes as a New Family of Molecular Conductors

Organic sulfur compounds have played important roles in developing new organic materials. Recently we have reported that thiophene-fused DCNQI (DTQl)1 forms a new family of highly conducting CuI complex.¹ However, all our attempts to grow a single crystal suitable for an X-ray analysis have been unsuccessful. The presence of the configurational isomers with respect to the =N-CN orientation was suspected to prevent the growth of a single crystal of 1. Thus we have designed 2 and 3 that bear the substituents at β-position of the condensed thiophene rings; the β-substituents could fix the cyano-group on the opposite side of the substituent. We have also characterized compound 4 for comparison.     

Determination of Sulfur in Trace Amounts

Abstract

An absolute method for the determination of trace amounts of sulfur in water and organic matrices is described. The method involves decomposition of organic samples in an oxygen bomb or oxidation of water samples with hydrogen peroxide. The resultant sulfates are reduced and distilled as hydrogen sulfide by the action of stannous phosphate in anhydrous phosphoric acid. The evolved hydrogen sulfide is absorbed in zinc acetate solution, converted to methylene blue and measured spectrophotometrically at 665 mm. The range is from 2 to 40 μg of sulfur using 1 cm cells.     

Determination of nanogram quantities of mercury in water with a gold-plated piezoelectric crystal detector

The use of a gold-coated piezoelectric crystal, coupled with a direct reduction technique, is described for the determination of mercury in water. The linear range is 5–100 ng with a sensitivity of 1.78 Hz ng^-1 of mercury. Reversibility of the detector is achieved by thermal desorption at 170°C. The effect of carrier gas flow rate, sample size and detector cell configuration on the sensitivity are discussed.     

Determination of Sulfur in Hydrocarbons by Oxidative Pyrolysis and Microcoulometric Titration

Abstract

Conditions are described which give 95%+ conversion of sulfur to sulfur dioxide in an oxidative pyrolysis - microcoulometric determination of sulfur in hydrocarbons. There is no significant variation in combustion efficiency due to matrix effects or type of sulfur compound present. Samples containing from 0.1 to 500 ppm sulfur may be run without dilution. The mean relative standard deviation over this range is about 2.5%.     

Optimisation of a Flow Injection System with a Piezoelectric Quartz Crystal Detector for the Determination of Inorganic Mercury

ABSTRACT

A new method combining flow injection methodology with quartz crystal microbalance (QCM) detection is proposed for inorganic mercury analysis. A modified simplex method is used in order to maximise the observed analytical signals (crystal frequency decrease). Six parameters were optimised: the concentration of the acidic carrier solution, the lengths of the sample loop and mixing coil, and the flow rates of the sample carrier, the reductant stream (SnCl₂), and the carrier of the mercury vapour (N₂). An increase of 18% in the signal of the centroid of the calibration line was achieved, as well as an increase in the sensitivity from 290 Hz μg^? to 313 Hz μg^?. Following the proposed procedure, detection limits of 47 μg L^? of inorganic mercury were found for sample volumes of 0.5 mL.     

A Rapid Method for Determination of Growth of Thiobacillus Ferrooxidans by Series Piezoelectric Quartz Crystal

ABSTRACT

A rapid and simple method for monitoring the growth of Thiobacillus ferrooxidans is put forward by using a series piezoelectric quartz crystal (SPQC). The SPQC was applied to continuously determine the variation of frequency shift during the culture of Thiobacillus ferrooxidans, with a conductive electrode as the probe. The frequency shift as a function of time agrees with a typical 'S - shape' model, a piezoelectric sensor responding well to the growth of Thiobacillus ferrooxidans. The fundamentals for determination of the bacterial growth activity using the SPQC is also described; the frequency shift is only dependent on the electrical conductivity of the solution and the dielectric constant.     

Electroanalytical Chemistry of Sulfur Compounds For the New Coal Conversion Technologies

Abstract

Polarographic methods are described “tailor-made” for the speciation and determination of sulfur contaminants in synfuels and coal gasification/liquefaction process streams. In samples containing the anions, S^2? _x, sulfidic sulfur was quantitated by anodic depolarization of the dropping mercury electrode, while polysulfidic sulfur was determined with the aid of an electroreduction process implicating 2(x-1) electrons. Polythionates were electroreduced to thiosulfate, sulfite, sulfide and/or mixtures thereof, under judiciously controlled experimental conditions. Thiosulfate and sulfite were quantitated by differential pulse polarography at dropping mercury anodes via reactions involving formation of thiosulfato- and sulfitomercurates.     

Piezoelectric Detection of Ricin and Affinity-Purified Goat Anti-ricin Antibody

Abstract

Detection of ricin, in a piezoelectric quartz crystal microbalance format, can be accomplished with the use of capture antibody techniques. These techniques allow for the specific attachment of ricin to immobilized capture antibodies on the quartz crystal transducer area. A reversed format can also be used to detect antibody in solution. In this case, the antigen is immobilized and antibody attaches specifically, thus increasing the overall mass and decreasing the resonant frequency. In this report we describe detection of both ricin and anti-ricin antibody using immunological piezoelectric quartz crystal microbalance techniques.