Method for the Determination of Mercury in Very Small Solid Samples

Abstract

An alternative method for the determination of mercury (Hg) in solid samples is presented in this article. Gaseous Hg is evolved when a solid sample is heated above 500°C in the presence of oxygen. The evolved Hg is collected on silver wool and is analyzed using cold vapor methods. We have found greater than 95% Hg recovery with various sediment and ash standards.     

Accurate Calibration of Mercury Vapour Indicators for Occupational Exposure Measurements using a Dynamic Mercury Vapour Generator

Abstract

An accurate and rapid calibration procedure for mercury vapour indicators used for occupational exposure measurements is described, using a dynamic mercury vapour generator traceable to the standard bell-jar calibration apparatus. The method provides greater flexibility, accuracy, and trace ability than the usual methods for the calibration of mercury vapour indicators used for occupational exposure measurements. The calibration procedure allows a correction to be applied to the mass concentration value displayed by the mercury vapour indicator. Measurement results from the mercury vapour indicator at the occupational exposure limit of 25 µg ·m^?3, following calibration, have been estimated to have an expanded uncertainty of 8%.     

Modification of a Hilger E612 Raman Spectrometer to a Laser Excitation Source

SUMMARY

Since the advent of the continuous wave laser, it has been advantageous to employ lasers as excitation sources for Raman spectroscopy [1]. This communication reports details of an arrangement being used in our laboratory whereby a laser replaces the conventional mercury arc source with a Hilger E612 Raman Spectrometer.     

Use of a Microcomputer for Streaming Potential Technique

ABSTRACT

With the help of a microprocessor and an A/D converter it is possible to make zero charge potential measurements with an ideally polarized electrode (jet mercury). Potential ^E _pzc measurements have been obtained for water solutions of NaOH 0.1 to 18.97 M.     

A Cell Design for Minimizing iR Error in Controlled-Potential Polarography of High Specific Resistance Solutions

SUMMARY

A design is presented for a polarographic cell that minimizes the iR error in controlled-potential polarography of solutions possessing a high specific resistance. A sharpened Smoler 90° vertical orifice DME is used. With this electrode, the mercury drop grows principally in the downward direction. This and the fact that the end of the capillary is sharpened to a point allows the positioning of a micro reference electrode probe directly above the mercury drop and to within 0.1 of the maximum radius of the mercury drop from the mercury surface during the entire drop life time. With this apparatus it is also possible to observe the iR error as a function of the distance between the reference electrode tip and the mercury drop surface. The effect of reference electrode position on iR error introduced is illustrated by a series of uranium and cadmium polarograms in high specific resistance media. Controlled-potential polarograms with little distortion attributable to iR error can be obtained with this cell design in solutions with specific resistances up to at least 22,000 Ω-cm.     

Seawater Mercury Analysis at PPB Levels

Abstract

A new method of mercury detection at ng/mL concentrations in seawater, by total reflection x‐ray fluorescence (TXRF), is presented. Membranes that have complexation affinity to the mercury ions were produced on quartz reflectors. They were immersed in various seawater solutions containing mercury at low concentration (1–50 ng/mL) and they were left to equilibrate for 24 hours; membranes were well fixed on the reflectors. After the equilibration stage, they were taken out of the solution and they were analysed by TXRF; the minimum detection limit was determined to be equal to 0.4 ng/mL. The main ingredient of the membranes was the complexing reagent dithizone. The existence of high salt concentration in seawater did not prevent mercury's complexation from the membrane.     

Electronic Design Parameters for Optimizing Photometric Mercury Detectors

ABSTRACT

A system is described for optimizing the input-output electronic circuit parameters of photometric detectors. It is oriented directly to their use as mercury detectors in air pollution monitoring. Detailed procedures are given whereby the electronic power circuits can be permanently stabilized. In addition, a new input design is presented that eliminates the need for log-ratio concentration outputs in these devices. A direct application of such circuits is presented with actual results.     

Polarographic Reduction Wave of Hemoglobin and its Application to Micro‐Determination

Abstract

An adsorptive reduction wave of hemoglobin at about ?1.43 V (vs. SCE), in phosphate buffer solution, pH 6.8, was found by using single sweep polarography. Based on this wave, a simple, rapid, and reliable polarographic method for hemoglobin determination was developed. The wave height is linearly proportional to the concentration of hemoglobin in the range of 1.0–28 mg/L (correlation coefficient 0.997). The detection limit is 0.5 mg/L. Serum albumin, common amino acids, and metal ions present no interference with the hemoglobin determination.

The proposed method was applied to the determination of hemoglobin in human blood samples with satisfactory results. The polarographic wave is attributed to the direct reduction of hemoglobin at the dropping mercury electrode. The new method could be useful in biochemical, clinical, and pharmaceutical analysis.     

Fourier Transform Infrared Laser Spectroscopy of Water Vapor

ABSTRACT

Fourier transformation techniques are applied to high resolution laser spectra of water vapor to identify undesirable spectral features. Features such as interference fringes can be mathematically filtered from spectral information in the Fourier domain and the spectral data recovered by an inverse Fourier transformation. The combined use of second derivative detection and the Fourier transformation leads to significant enhancements of spectral information relative to both lower and higher frequency background interferences without a significant loss of resolution.     

On‐Site Monitoring and Cartographical Mapping of Heavy Metals

Abstract

This paper presents a portable electrochemical instrument capable of real‐time in situ detection and automatic identification of heavy metals. The instrument is equipped with an embedded Geographical Position System and is capable of storing the geographical position of the sample under test. Software has been developed to combine pollutant results with geographical position, in order to produce a cartographical presentation of the pollution of an area. The electrochemical instrument provides the facilities found in a traditional lab based instrument in a portable design for on‐site measurements. The instrument is capable of detecting lead, cadmium, zinc, nickel, mercury, and copper with good sensitivity and precision. The system is reliable, easy to use, safe, and it may be used in a variety of situations to help environmental assessment and control.     

VIRTUAL INSTRUMENTATION FOR STRIPPING VOLTAMMETRY ON THE ROTATING DISK ELECTRODE

ABSTRACT

This paper describes a dedicated virtual instrumentation system constructed for stripping voltammetry on a rotating disk electrode (RDE) covered with a thin film of mercury. The experimental configuration consisted of a purpose-built potentiostat, a rotating disk electrode assembly and a peristaltic pump. The sequence of operations (plating of the mercury film, preconcentration of the analyte, potential scan and data acquisition, cleaning of the electrode) was under full computer control. The software programme that was selected for interfacing and control was LabVIEW 4.0. The system was configured in such a way as to perform either single measurements, a series of consecutive measurements (i.e., standard additions) or even multi-scan experiments. The analytical utility of the apparatus was assessed for the determination of Cu(II), Cd(II) and Pb(II) by anodic stripping voltammetry (ASV) and for the detection of Co(II) by multi-scan adsorptive cathodic stripping voltammetry (AdCSV).     

Conductivity Detectors for Column or Paper Chromatography

SUMMARY

A conductivity detector, employing inexpensive operational amplifiers, has been constructed for chromatographic use. The detector is capable of observing conductance changes as small as 1 part in 10⁵ with bridge signals of 100 mV. Detector linearity is good over a wide dynamic range. When used in conjunction with a cell employing mercury strip electrodes, the detector can monitor the elution of ions in paper chromatography. The alkali metals were separated and detected on Whatman No. 1 paper with a sensitivity of less than 10 nmoles. This sensitivity limit was not determined by noise in the detector electronics, but by ionic impurities in the paper. The same detector, and a cell employing platinum electrodes separated from the effluent by ion-exchange membranes, was tested and found suitable for use in column chromatography. Again the sensitivity was not limited by the detector electronics.     

Accurate Molten Salt Viscometry

SUMMARY

The viscometer described in this note is of general applicability but its features are particularly suited for measurements with molten salts having appreciable vapor pressures and/or chemical reactivity to atmospheric moisture. While sealed viscometers are not unknown [1, 2], the present design ensures a constant starting volume and minimizes some of the inherent experimental difficulties, for example, calibration, repeated measurements, and kinetic energy and surface tension corrections. Magnitude and sources of errors are briefly considered, and results with this viscometer for KN0₃ (mp, 337°C), HgCl₂ (mp, 277° C; bp, 304°C), and CsN0₃ (mp, 414°C) are reported.     

The Use of Second Derivative and Digital Readout in Fast-Sweep Polarography†

SUMMARY

The use of the second derivatives of the polarographic waves for analytical work in fast-sweep polarography has been investigated. Three-electrode potentiostatic control circuitry and controlled-drop-time dropping mercury electrode apparatus was used. With active, operational amplifier derivative and filter circuitry, the theoretically greater resolution of overlapping waves and freedom from base-line effects can be realized. A circuit has been designed which makes possible the high-precision readout of polarographic peak heights on a digital voltmeter. With the digital readout system and second derivative waves, a short-term reproducibility of the measurements approaching 0.1% can be achieved for concentrations above 10^?4 M. Above about 10&^?5 M, analyses can be performed with 1% accuracy, using only a single polarographic cell with blank corrections or by peak-to-peak measurement of the second derivative wave. Below 10^?5 M it is advantageous to use a combination of second derivative and two-cell differential operation.     

A Lab‐Built Hydride Generation Nebulizer for AAS

Abstract

A nebulizer for the hydride generation atomic‐absorption spectrophotometry of As and Se, and Hg vapor generation is described, in which the gas flow, the reductant, and the sample are connected separately through three concentric channels. The sample and the reducing agent flow separately till they reach the air flow. The generated species are then mixed with the air carrier gas and transported into the flame of an AA spectrometer. Optimization of flame type, acid, and reductant concentrations was carried out. Interference of transition metals on the analytes' signals was minimized using EDTA. Good linear analytical range and short term stability are obtained.     

The Determination of Vapor Pressures of Low Viscosity Lubricants from Distillation Data

The vapor pressure of low viscosity aliphatic hydrocarbon lubricants is shown to be determined with good accuracy from data obtained from a modification of the ASTM Distillation Test D86-67. This test gives the initial boiling point of a lubricant from which the vapor pressure at any other temperature can be calculated by use of an empirical equation relating the boiling point to the vapor pressure.

Two other equations were derived, one relating the viscosity of an aliphatic hydrocarbon lubricant to the vapor pressure at any temperature, and the other extending the use of this distillation method to calculation of the vapor pressures of other types of lubricants as, for example, esters, alcohols, and acids.

The data presented indicate that this method is superior to the isoteniscope method in accuracy and ease of operation.     

Computerized Dynamic Voltammetric Detection in High Performance Liquid Chromatography

ABSTRACT

An automatic and reliable electrochemical detection system is described for on-line qualitative and quantitative determination of electro-active compounds in effluents from high-performance liquid chromatographic systems. Determination is performed by application of electrochemical detection at constant potential, cyclic voltammetry and square-wave voltammetry.

In the square-wave mode, the current and time-comparing mode for qualitative compound detection has been discussed. The system has been tested for the identification of etoposide at a glassy-carbon electrode (g.c.e.). Using a static mercury drop electrode (s.m.d.e.), such parameters of the nitro-imidazole derivatives Ro 07-0582, Ro 05-9963, Ro 07-0913 and Ro 03-8799 have been investigated. Applying square-wave voltammetry owns benefits like increased sensitivity and producing peaks at half-wave potential, enabling fast and easy identification of compounds. For square-wave voltammetry of etoposide at de g.c.e., a 10-fold improvement of the detection limit has been achieved with respect to cyclic voltammetry: 10 μ1 2.55E-4 M. Using a s.m.d.e. the detection limit of Ro 05-9963 (desmethylmisonidazole) is 10 μ1 2.67E-5 M.     

Planar Drift Tube for Ion Mobility Spectrometry

Abstract

The drift tube in ion mobility spectrometry is the component of central importance, where sample vapors are ionized and where ions are separated on the basis of gaseous mobility in a comparatively weak electric field. Construction of drift tubes is labor intensive and costly when built with precision machined components and an alternative design, fabricated using photolithography methods with planar drift plates, is described. Diagnostics of performance including response toward electric fields, peak shape of mobility spectra, determined values for reduced mobility coefficients, and patterns of response to changing vapor concentrations were consistent with conventional drift tubes. Neither ion losses nor band broadening were unexpectedly large though ultimate measures of performance were limited by the unavailability of drift tube components with rectangular profiles and by an imperfect reaction region design. The cost of making drift tubes is calculated as roughly 10% of that for conventional designs.     

A Phosphorimeter for Studying Delayed Fluorescence from Samples Immersed in a Magnetic Field

SUMMARY

The design and construction of a phosphorimeter especially suited for investigating the effect of a magnetic field on delayed luminescence processes is described. Although it is designed for the light levels and time domains usually pertinent to fluid-solution delayed fluorescence studies, it can be easily adapted to phosphorescence work. In order to avoid the influence of the applied field on the excitation and detection elements, these components are removed from the field and are heavily shielded. A medium-pressure mercury arc is used as an excitation source, and either frontal or right-angular illumination of the sample can be employed. Filters in both the excitation and emission beams provide the means of wavelength selection. The use of a single, rotating, slotted disk to time both beams gives the instrument a compact design and enhances its physical stability. Tests of instrument performance show that the phosphorimeter is useful for measurements at fields up to 8000 G.     

Vertical-Orifice Dropping Mercury Electrode of Polytetrafluoroethylene for Rapid Polarography in Glass-Corroding Media†

SUMMARY

A vertical-orifice dropping mercury electrode (dme) of polytetrafluoro-ethylene (Teflon) was fabricated and evaluated for rapid polarography in glass-corroding media. The orifice is in a vertical face of the Teflon segment of the dme capillary, which is positioned vertically. Capillaries of orifice diameter from about 70 to 120 μ were made. The geometric and performance characteristics of the dme were studied. Polarograms of Tl⁺, Cd²⁺, Pb²⁺, and UO₂ ^{2 +} were recorded; the supporting media were aqueous hydrofluoric acid or acid chloride solutions. The polarographic characteristics of the reference reaction T1⁺ ? Tl⁰ in 0.1 M KC1?1 mM HCl were determined to permit comparison of this dme with horizontal-orifice glass and Teflon dme's, for which similar data have been published. Results obtained with polyacrylamide present as a maximum suppressor agree with the known polarographic characteristics of the Tl⁺ ? Tl⁰ reaction. They thus show that the vertical-orifice dme of Teflon is satisfactory for the rapid polarography of glass-corroding media.