Increasing the sensitivity of atomic absorption determination of iron

We have studied the effect of the nature and concentration of surfactants on the atomic absorption of iron. We show that using sodium dodecylbenzenesulfonate as the modifier in flame atomic absorption determination of iron in real samples makes it possible to make the measurements in a low-temperature flame (propane-butane-air type) with increased sensitivity and selectivity and also a lower detection limit for iron. We have developed a procedure for atomic absorption determination of iron in food products using sodium dodecylbenzenesulfonate as the modifier. The detection limit for iron is C_min = 0.008 μg/cm³. Report given at the International Congress of Analytical Sciences, ICAS-2006, 20–30 June 2006, Moscow, Russia __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 263–266, March–April, 2007.     

Evaluation of Carbon Rod Atomizer for Routine Analysis of Vanadium in Crude Oil by Atomic Absorption Spectroscopy

Abstract

The Carbon Rod Atomizer (CRA) was evaluated for routine trace analysis of vanadium in crude oil by atomic absorption spectroscopy with a carbon (graphite) tube as a micro-furnace. Two crude oil samples were analyzed, both by standard addition and standard working curve methods, and the results confirmed by analysis with flame atomic absorption spectroscopy using a fuel-rich nitrous oxide-acetylene flame. Because of the relative involatility of vanadium at the temperature of the CRA, quantitative recoveries of vanadium in crude oil occur only when the vanadium content of the sample injected into the CRA does not exceed the limit of about 1 × 10^?8 g. A sensitivity (weight/1% absorption) of 7.0 × 10^?11 g and detection limit (signal-to-root-mean-square-noise equal to two) of 6.9 × 10^?12 are reported.     

Chemical Vapor Generation with Slurry Sampling: A Review of Applications to Atomic and Mass Spectrometry

Abstract

A critical review of published analytical methods and techniques for chemical vapor generation (CVG) with slurry sample introduction for detection by atomic and mass spectrometry is presented. The nstrumentation used for the reaction as well as separation and transport of the species, influence of chemical and physical factors, and efficiency of the process are considered. A brief comparison of detection limits obtained with atomic absorption, emission, and fluorescence as well as mass spectrometry along with practical applications to analytical samples are summarized. The current state-of-the-art, including advantages and limitations of this approach, is discussed.     

Continuum Source Atomic Absorption Spectrometry with Commercially Available Instrumentation. A Practical Solution

A calculating method is presented in this paper which may be used to correct for the curvature of the calibration curve in atomic absorption spectrometry due to the non-absorbed light within the monochromator bandpass when a continuum source of radiation is used. Thus a linear absorbance to concentration relationship is obtained. Cu, Cr and Ca have been determined using this method with a D₂ lamp as continuum source. The results agree with those obtained by the traditional method using hollow cathode lamps. The relative differences are below 6.2%. Earlier investigations concerning the use of continuum sources in atomic absorption spectrometry (aas) have shown that in some cases there are good results^1–4. However, there are two problems which are difficult to overcome in continuum source aas. First, a narrow slit must be used in order to obtain a bandpass of a width equivalent to the absorption line. However, in this case the light intensity transmitted to the monochromator and arriving to the detector is so small that the detection limits will be very poor. Of course the transmitted intensity may be increased if a wider slit is used. But in this case, the non-absorptive part on the two sides of the absorption line will also enter the monochromator and fall on the detector. As a result the sensitivity will be degraded and the calibration curve will bend towards the concentration axis. Problems such as those discussed above prevented the current use of continuum source aas. The whole field has been recently reviewd extensively^4a.

In this paper we consider a calculationg method which can overcome the influence of non-absorbed radiation and can also correct the non-linearity of the calibration curve. In the first part of the paper the calculating method is introduced and in the second part some factors affecting the method are discussed and the comparaison of some results obtained by this method and the traditional method are given.     

Radiative lifetime measurements of odd-parity high-excited levels of Sn I by time-resolved laser spectroscopy

Natural radiative lifetimes of five higher-lying odd-parity levels 5p7s ³P₁^o, 5p5d ¹P₁^o, 5p6d ³F₂^o, ³D₁^o and ³F₃^o in neutral tin are measured by the time-resolved laser-induced fluorescence (TR-LIF) technique and the atomic beam method. All these lifetimes are not longer than 100 ns and they are found to be shorter than the lifetimes of even-parity levels in the same energy region. The results reported in this paper provide important transition parameters for highly-excited atomic Sn, which may be useful for theoretically calculating excited heavy atoms.     

多光程吸收的频率调制光谱

采用可连续调谐的半导体二极管激光器作探测光源,将多光程吸收光谱技术、频率调制光谱技术和相敏检波技术相结合,建立了一套具有高检测灵敏度和分辨率的测量气态分子光谱和进行微量分析的研究装置并利用该装置研究了动态分压强为40Pa和120Pa时,H₂O分子在7462cm^-1和7473cm^-1附近的近红外吸收光谱,检测灵敏度远高于传统吸收光谱技术,为气态分子的光谱研究和微量分析提供了一种高灵敏度的光谱检测方法.     

Laser spectroscopy of stable Os isotopes

Doppler-free isotope shift measurements of the stable even ^184–192Os and ^187,189Os odd isotopes have been performed for the first time on the 5d ⁶6s ^{2 5}D₄→5d ⁶6s6p ⁷F₄ (305.9 nm) transition in the neutral atom by atomic beam laser spectroscopy and on the ionic 5d ⁶6s ⁵D_9/2→5d ⁶6p ⁶D_7/2 (228.2 nm) transition by fast collinear ion-laser spectroscopy. The measurements were carried out in Manchester and at the IGISOL facility in Jyväskylä in Finland, respectively. The results presented are the most precise measurements to-date of the absolute isotope shifts.     

Selective Quantification of Trace Silver in Water Samples by Displacement Solidified Floating Organic Drop Microextraction Coupled With Electrothermal Atomic Absorption Spectrometry

ABSTRACT

In this work, a novel displacement solidified floating organic drop microextraction (D-SFODME) technique was developed and coupled with electrothermal atomic absorption spectrometry (ETAAS) for the determination of trace silver in water samples without need of any masking agents. The method involved the formation of copper diethyldithiocarbamate (Cu–DDTC), extracted from the resultant Cu–DDTC with SFODME procedure using 1-undecanol. Then, the solidified floating organic drop was transferred into a sample solution containing silver ion, and another SFODME procedure was carried out. Trace Ag⁺ was selectively preconcentrated using 1-undecanol through a displacement reaction between Ag⁺ and the preconcentrated Cu-DDTC and the floating organic drop was diluted by ethanol for ETAAS detection. Interferences from coexisting heavy metal ions with lower stability of their DDTC complexes relative to Cu-DDTC were minimized. Under the optimal conditions, the limit of detection was 4.7 ng L^?1 (3σ) for silver with a sample volume of 5.0 mL, and an enrichment factor of 250 was achieved. The relative standard deviation under optimum conditions is 3.6% (n = 7). The proposed method was successfully applied to determine trace silver in some environmental samples with satisfactory results.     

XRF analysis of micronutrients in endive grown on soils with sewage sludge

A simple and fast method was developed for the determination of traces of Fe, Mn, Cu, Cr, Ni, Zn and Mo in endive using wavelength‐dispersive x‐ray fluorescence spectrometry. Plants were grown in different sewage sludge compositions for 60 days in greenhouse conditions. Samples were compacted and analyzed after drying, milling and homogenization. The method was validated using certified standard reference materials. The results were compared with those obtained by atomic absorption spectrometry. Good agreement for all elements was obtained. The detection limits were found to be Fe 1, Mn 3, Cu 2, Cr 5, Ni 1, Zn and Mo 3 µg g^?1. These results permitted the evaluation of the potential use of sewage sludge as an agricultural amendment. Copyright © 2003 John Wiley & Sons, Ltd.     

A Streak Camera System for Quantitative Fluorimetry

In conventional and laser excited molecular fluorescence spectrometry,^1,2 the excitation scatter and luminescence from the blank have been shown to be the major factors controlling the limits of detection. However, because of their high intensity, an increase in sensitivity (signal/concentration) is often noted with laser excitation as compared with conventional sources. From theoretical calculations,^3,4 as well as experimental results,⁵ pulsed source excitation with gated detection, using time resolution, can be used to improve the signal to noise ratio, S/N, in certain instances. Pulsed lasers are very well suited for these measurements because of their high intensities and short pulse widths.     

Lasers as Light Sources for Analytical Atomic Spectrometry

Abstract

Lasers have advantages compared to conventional light sources, which include high power, a monochromatic emission profile, stability, and rapid tuning across an atomic line. These advantages have resulted in superior analytical figures of merit and methods of background correction compared to conventional light sources. The most widely used lasers for atomic spectrometry include dye laser systems, optical parametric oscillator systems, and diode lasers. Three principal techniques employ lasers as light sources. Laser‐excited atomic fluorescence spectrometry (LEAFS) involves the use of laser light to excite atoms that emit fluorescence and serves as the analytical signal. Laser‐enhanced ionization (LEI) involves laser excitation of atoms to an excited state energy level at which collisional ionization occurs at a higher rate than from the ground state. Diode laser atomic absorption spectrometry (DLAAS) employs a DL as a source to excite atoms in an atom cell from the ground state to an excited state. The analytical signal is involves the ratio of the incident and transmitted beams. Recent applications of these techniques are discussed, including practical applications, hyphenated techniques employing laser‐induced plasmas, and work to characterize fundamental spectroscopic parameters.     

Determination of Silver by Chemical Vapor Generation with In Situ Trapping Flame Atomic Absorption Spectrometry

ABSTRACT

The hyphenation of chemical vapor generation with an integrated atom trap system for flame atomic absorption spectrometry (CVG-IAT-FAAS) was evaluated for determination of silver in real samples (coal fly ash, sediment, and nickel alloy). The volatile species of silver were formed by reaction with sodium tetrahydroborate(III) in the presence of nitric acid. A new CVG-IAT-FAAS design (versus a water-cooled single silica tube, double-slotted quartz tube) significantly improved the sensitivity and detection limits compared with conventional flame atomic absorption spectrometry (FAAS) for determination of silver. The concentration limit of detection was 0.7 ng mL^?1 for Ag. The overall efficiency of the vapor generation process was estimated to be ca. 12%. For a 2 min in situ preconcentration time, sensitivity was enhanced 143-fold for Ag using the vapor generation atom trapping technique, compared to conventional FAAS. Sensitivity can be further improved by increasing the collection time. The precision of measurement at 10 ng mL^?1 of Ag was 10% RSD. The accuracy of this method was validated by analyses of NRC GBW 07302 (Stream Sediment), BCS CRM No. 346 (Nickel Alloy), NIST SRM 2710 (Montana Soil), NRCC LUTS-1 (Lobster Hepatopancreas), and NIST SRM 1643e (Trace Element in Water) certified reference materials. The measured Ag contents in these five reference materials were in satisfactory agreement with the certified values (spanning the range of 0.066–35 µg g^?1).     

Monte Carlo studies of the resonance fluorescence technique for atmospheric atomic oxygen measurements

The resonance fluorescence of the O (³P³S) triplet has been used extensively for rocket-borne measurements of atomic oxygen in the mesosphere and lower thermosphere. The accuracy and compatibility of different experimental configurations are however still a subject of controversy. In order to better quantify the measurements, we have developed a 3-dimensional Monte Carlo model which simulates the radiative transfer inherent to atom detection by means of resonance lamps. Angle-dependent partial frequency redistribution describes the fluorescence process, natural broadening becoming significant when the line center optical thickness exceeds 10. Applying the model to a recently flown rocket instrument, a strong temperature dependence and nonlinear relations between atomic oxygen abundance and fluorescence signal are found at densities above 5.10¹⁰ cm⁻³. Above 1.10¹² cm⁻³, the signal gradually saturates and useful measurements cannot be obtained. The spatial distribution of the scattering events and effects of the payload motion are analyzed. A discussion of the results is applied to different calibration techniques for rocket instruments.     

Determination of Traces of Toxic Elements in Dimethylaminoborane upon Their Concentration for Atomic Emission Analysis

A technique of atomic emission determination of traces of toxic elements in dimethylaminoborane with detection limits of n·10^–5–10^–8 wt. % has been developed. To reduce the detection limits, a technique of separation of the basic component in the form of boron fluoride, with concentration of microimpurities on a graphite collector, was used.     

A Review of Tungsten Coil Electrothermal Vaporization as a Sample Introduction Technique in Atomic Spectrometry

Abstract

Tungsten coil electrothermal vaporization has served as an alternative sample introduction method in atomic spectroscopy for some time and is easily employed in a laboratory because of its mass production, ease of use, and small requirement for power. This review will focus on the use of the tungsten coil as an electrothermal vaporization sample introduction source in atomic absorption, emission, and fluorescence spectrometry over the past decade. Analyzed samples have both biological and industrial significance, illustrating the versatility of the technique. Since its conception 40 years ago, tungsten coil electrothermal vaporization continues to provide users with innovative options for spectroscopic analysis.     

A Review of Applications and Experimental Improvements Related to Diode Laser Atomic Spectroscopy

Abstract

This article attempts to review the major advancements made in the past 12 years, since 1993, in the field of diode laser atomic spectroscopy. The discussion covers experimental improvements (e.g., wavelength stabilization, frequency upconversion, enhancement of tuning characteristics, spectral bandwidth using external cavities, etc.), diagnostic applications in various atomizers, as well as analytical applications (e.g., absorption, fluorescence, and ionization spectroscopy; element‐selective detectors for chromatography; etc.). With potential new users of these methods in mind, a detailed overview of the properties relevant to atomic spectroscopy of commercial diode lasers is also given.     

Resonance fluorescence and quantum jumps in single atoms: Testing the randomness of quantum mechanics

When a single trapped ¹⁹⁸Hg⁺ ion is illuminated by two lasers, each tuned to an appropriate transition, the resulting resonance fluorescence switches on and off in a series of pulses resembling a bistable telegraph. This intermittent fluorescence can also be obtained by optical pumping with a single laser. Quantum jumps between successive atomic levels may be traced directly with multiple-resonance fluorescence. Atomic transition rates and photon antibunching distributions can be inferred from the pulse statistics and compared with quantum theory. Stochastic tests also indicate that the quantum telegraphs are good random number generators. During periods when the fluorescence is switched off, the radiationless atomic currents that generate the telegraph signals can be adjusted by varying the laser illumination: if this coherent evolution of the wave functions is sustained over sufficiently long time intervals, novel interactive precision measurements, near the limits of the time-energy uncertainty relations, are possible.     

Atomic Absorption Spectrometry of Silver with Absorption Tube Having Nebulization Chamber

In the atomic absorption spectrometry with the long absorption tube using a hydrogen-air flame, only the total consumption type of the burners, e.g., Beckman¹ or ring burners², have been used for the input of a sample solution to the flame. The use of the indirect input method with nebulization chamber has never been attempted, though, by use of a commercially available apparatus with nebulization chamber, the large increase of the sensitivity has been easily obtained by heating the chamber and nebulizing air^3–5.     

Determination of spatial temperature distributions in a laminar premixed ethylene/air flame by laser-induced atomic fluorescence

A quick and simple detection system for spatially resolved temperature measurements in flames based on laser-induced thermally assisted atomic line fluorescence of seeded rubidium atoms is described. The fluorescence light from two atomic states is dispersed and simultaneously recorded by a CCD camera. The fluorescence ratio distributions lead directly to absolute temperature distributions. The practical use, the spatial and temperature resolution and error limits of the method are discussed and compared with other procedures for temperature measurements.     

A diode laser spectrometer at 634nm and absolute frequency measurements using optical frequency comb

This paper reports that two identical external-cavity-diode-laser (ECDL) based spectrometers are constructed at 634 nm referencing on the hyperfine B-X transition R(80)8-4 of ¹²⁷I₂. The lasers are stabilized on the Doppler-free absorption signals using the third-harmonic detection technique. The instability of the stabilized laser is measured to be 2.8×10^-12 (after 1000 s) by counting the beat note between the two lasers. The absolute optical frequency of the transition is, for the first time, determined to be 472851936189.5 kHz by using an optical frequency comb referenced on the microwave caesium atomic clock. The uncertainty of the measurement is less than 4.9 kHz.