Optical parametric oscillator-based lasers for analytical atomic spectrometry: Laser excited atomic fluorescence; resonant laser ablation-atomic emission; and laser atomic absorption

This dissertation describes some applications of an optical parametric oscillator (OPO) laser in analytical atomic spectrometry. New types of tunable solid-state lasers are reviewed, in Chapter 2, with respect to their principles and characteristic parameters for analytical atomic spectral applications. Then, in Chapter 3, a new commercial OPO laser system is described based on an extraordinary resonance design and experimental results demonstrate its usefulness for the applications in atomic spectrometry. It had a wide tuning range of 225–1680 nm with a narrow spectral linewidth of better than 0.1 cm−1 in the visible spectrum, with high output energy. The slew-scan and continuous scan speeds of the laser were up to 2.5 nm/s and 0.25 nm/s, respectively. A simple, sensitive, and fast method for Sequential Multielement Laser Excited Atomic Fluorescence Spectrometric (LEAFS) analysis of coal for lithium, sodium and strontium was realized by use of the rapid slew-scan speed of the optical parametric oscillator laser. In Chapter 4, the same OPO laser was further used in electrothermal atomization (ETA) LEAFS for the determination of lead in samples of paint by slurry sampling. The high sensitivity and wide linear calibration range of ETA-LEAFS have made multiple dilutions of samples unnecessary, and allowed the analysis of samples with a wide range of analyte concentration. ^ Chapter 5 was devoted to resonant laser ablation (RLA) of molybdenum from a standard steel sample into a microwave induced plasma (ICP) for detection by atomic emission. Compared to conventional non-resonant ablation, the RLA signals were enhanced by factors of greater than five, and the resultant spectra were simpler, which may result in reduced spectral interferences in real sample analysis. Based on the experimental observations, some possible mechanisms of RLA were proposed to begin the process to better understand and make use of RLA. ^ Finally, Chapter 6 describes a preliminary study of OPO Laser Atomic Absorption Spectrometry (OPO-LAAS). Results are presented that illustrate saturation broadening of the atomic profile of sodium, and the linear range of the calibration curves at the center and wings of the atomic spectral profile. In addition, possible applications of OPO-LAAS are discussed.

Thin film hydride generation: determination of ultra-trace copper by flow injection in situ hydride trapping graphite furnace AAS

A novel system which significantly enhances copper hydride generation efficiency was used for the determination of trace copper by coupling a flow injection system to a graphite furnace for in situ collection of the analyte and subsequent AAS detection. A single device integrated the functions of hydride generator and gas liquid separator. Solutions of the sample containing 0.0005% (m/v) phenanthroline and 1% formic acid were merged with tetrahydroborate reductant to yield a thin film wetting a reaction surface from which product vapor was efficiently liberated and transported to the heated furnace. Optimum operating conditions provided for a generation/transport/collection efficiency of 8\u201312%. Interferences from common transition and noble metals were effectively eliminated. A limit of detection of 100 pg ml 121 was obtained based on processing a 1 ml sample volume. A precision of better than 4% (RSD) at 1 ng ml 121 was typical. The methodology was successfully applied to the determination of Cu in several NRCC natural water and biological tissue Certified Reference MaterialsPeer reviewed: YesNRC publication: Ye

UV photochemical vapor generation sample introduction for determination of Ni, Fe, and Se in biological tissue by isotope dilution ICPMS

A novel, sensitive method is described for the accurate determination of Ni, Se, and Fe in biological tissues by isotope dilution inductively coupled plasma mass spectrometry (ID ICPMS) based on sample introduction arising from online UV photochemical vapor generation (UV-PVG). Volatile species of Ni, Se, and Fe were liberated from a formic acid medium following exposure to a UV source. Sensitivities were enhanced 27- to 355-fold compared to those obtained using pneumatic nebulization sample introduction. Although precision was slightly degraded (a factor of 2) with ultraviolet photochemical mediated vapor generation (UV-PVG), limits of detection (LODs) of 0.18, 1.7, and 1.0 pg g 121 for Ni, Se, and Fe, respectively, based on an external calibration, provided 28-, 150-, and 29-fold improvements over that realized with conventional pneumatic solution nebulization. Method validation was demonstrated by determination of Ni, Se, and Fe in biological tissue certified reference materials (CRMs) TORT-2 and DORM-3. Concentrations of 2.33 \ub1 0.03, 5.80 \ub1 0.28, and 109 \ub1 2 \u3bcg g 121 (1SD, n = 4) and 1.31 \ub1 0.04, 3.35 \ub1 0.18, and 353 \ub1 5 \u3bcg g 121 (1SD, n = 4) for Ni, Se, and Fe, respectively were obtained in TORT-2 and DORM-3, in good agreement with certified values.Cet article d\ue9crit une nouvelle m\ue9thode dont la sensibilit\ue9 permet de doser avec pr\ue9cision le nickel (Ni), le s\ue9l\ue9nium (Se) et le fer (Fe) contenus dans les tissus biologiques en combinant dilution isotopique et spectrom\ue9trie de masse par plasma \ue0 couplage inductif (ICP-MS ID). Cette m\ue9thode repose sur l'introduction de l\u2019\ue9chantillon par g\ue9n\ue9ration photochimique de vapeur \ue0 l\u2019aide d\u2019une source UV en ligne (UV-PVG). Les esp\ue8ces volatiles de Ni, de Se et de Fe ont \ue9t\ue9 extraites d\u2019une solution d\u2019acide formique par exposition \ue0 une source d\u2019UV. Cette m\ue9thode d\u2019introduction des \ue9chantillons s\u2019est av\ue9r\ue9e de 27 \ue0 355 fois plus sensible que la m\ue9thode de n\ue9bulisation pneumatique. Bien que le degr\ue9 de pr\ue9cision diminue l\ue9g\ue8rement (facteur 2) en raison de l\u2019UV-PVG, les limites de d\ue9tection (LD) \ue9tablies \ue0 partir d\u2019une courbe d\u2019\ue9talonnage externe sont de 0,18, 1,7 et 1,0 pg/g pour le Ni, le Se, et le Fe respectivement, ce qui repr\ue9sente une am\ue9lioration de 28, 150, et 29 fois par rapport aux valeurs obtenues avec un n\ue9bulisateur pneumatique conventionnel. Nous avons valid\ue9 cette m\ue9thode en effectuant des dosages de Ni, de Se et de Fe dans des tissus biologiques correspondant aux mat\ue9riaux de r\ue9f\ue9rence certifi\ue9s (MRC), TORT-2 et DORM-3. Les concentrations respectives de Ni, de Se et de Fe sont de 2,33 \ub1 0,03, 5,80 \ub1 0,28, et 109 \ub1 2 (1SD, n = 4) \u3bcg/g dans le cas de TORT-2 et de 1,31 \ub1 0,04, 3,35 \ub1 0,18, et 353 \ub1 5 \u3bcg/g (1SD, n = 4) dans le cas de DORM-3, et sont conformes aux valeurs certifi\ue9es.Peer reviewed: YesNRC publication: Ye

Versatile thin-film reactor for photochemical vapor generation

A novel thin-film reactor is described and evaluated for its analytical performance with photochemical vapor generation (TF-PVG). The device, comprising both the generator and a gas 12liquid separator, utilizes a vertical central quartz rod onto which the sample is pumped to yield a thin liquid film conducive to the rapid escape of generated hydrophobic species. The rod is housed within a concentric quartz tube through which a flow of argon carrier/stripping gas is passed to remove and transport the generated species to a detector, which in this study is an inductively coupled argon plasma optical emission spectrometer (ICP-OES). The concentric quartz tube is itself surrounded by a 78-turn 0.5 m long quartz coil low-pressure mercury discharge lamp operating at 20 W. The performance of this thin-film photoreactor was evaluated through comparison of analytical figures of merit for detection of a number of elements undergoing PVG in the presence of formic or acetic acid with those arising from conventional solution nebulization under optimized conditions. The TF-PVG reactor provided sensitivity enhancements, of 110-, 120-, 130-, 250-, 120-, 230-, 78-, 1.3-, 16-, and 32-fold for As, Sb, Bi, Se, Te, Hg, Ni, Co, Fe, and I, respectively, and detection limit enhancements of 110-, 140-, 170-, 270-, 200-, 300-, 160-, 2.7-, 50-, and 44-fold for these same elements. Vapor generation efficiencies ranged from 20 12100% for this suite of analytes. The utility of this technique was demonstrated by the determination of Fe and Ni in Certified Reference Materials DORM-3 (fish protein) and DOLT-4 (dogfish liver tissue).Peer reviewed: YesNRC publication: Ye

Protein quantitation using Ru-NHS ester tagging and isotope dilution high-pressure liquid chromatography\u2013inductively coupled plasma mass spectrometry determination

An accurate, simple, and sensitive method for the direct determination of proteins by nonspecies specific isotope dilution and external calibration high-performance liquid chromatography\u2013inductively coupled plasma mass spectrometry (HPLC\u2013ICPMS) is described. The labeling of myoglobin (17 kDa), transferrin (77 kDa), and thyroglobulin (670 kDa) proteins was accomplished in a single-step reaction with a commercially available bis(2,2\u2032-bipyridine)-4\u2032-methyl-4-carboxybipyridine-ruthenium N-succinimidyl ester-bis(hexafluorophosphate) (Ru-NHS ester). Using excess amounts of Ru-NHS ester compared to the protein concentration at optimized labeling conditions, constant ratios for Ru to proteins were obtained. Bioconjugate solutions containing both labeled and unlabeled proteins as well as excess Ru-NHS ester reagent were injected onto a size exclusion HPLC column for separation and ICPMS detection without any further treatment. A 99Ru enriched spike was used for nonspecies specific ID calibration. The accuracy of the method was confirmed at various concentration levels. An average recovery of 100% \ub1 3% (1 standard deviation (SD), n = 9) was obtained with a typical precision of better than 5% RSD at 100 \u3bcg mL\u20131 for nonspecies specific ID. Detection limits (3SD) of 1.6, 3.2, and 7.0 fmol estimated from three procedure blanks were obtained for myoglobin, transferrin, and thyroglobulin, respectively. These detection limits are suitable for the direct determination of intact proteins at trace levels. For simplicity, external calibration was also tested. Good linear correlation coefficients, 0.9901, 0.9921, and 0.9980 for myoglobin, transferrin, and thyroglobulin, respectively, were obtained. The measured concentrations of proteins in a solution were in good agreement with their volumetrically prepared values. To the best of our knowledge, this is the first application of nonspecies specific ID for the accurate and direct determination of proteins using a Ru-NHS ester labeling reagent.Peer reviewed: YesNRC publication: Ye

Analytical method for the determination of trace toxic elements in milk based on combining Fe3O4 nanoparticles accelerated UV fenton-like digestion and solid phase extraction

A UV Fenton-like digestion method was developed first time for a complete digestion of milk samples by using 1.6 g L-1 Fe3O 4 magnetic nanoparticles, 0.2% (v/v) nitric acid, and 6% (w/w) H 2O2. During the digestion, the liberated As-, Sb-, and Bi-containing species were preconcentrated onto the surface of Fe 3O4 magnetic nanoparticles, which were conveniently separated with a hand-held magnet and subsequently dissolved in hydrochloric acid prior to hydride generation atomic fluorescence spectrometric detection. Owing to the integration of UV Fenton-like digestion, solid phase extraction, and magnetic separation into a single step, the developed method significantly simplifies sample preparation steps and reduces chemical consumption and hazardous waste. Limits of detection of 0.0015, 0.0022, and 0.0025 \u3bcg L -1 were obtained for As, Sb, and Bi, respectively, using a 50 mL milk sample. The method was applied to the determination of these elements in a Certified Reference Material and milk samples.Peer reviewed: YesNRC publication: Ye

Applications of chemical vapor generation in non-tetrahydroborate media to analytical atomic spectrometry

Chemical vapor generation (CVG) using tetrahydroborate(III) remains the most popular and successful derivatization procedure enabling gaseous sample introduction into analytical atomic spectrometers that are routinely used for the determination of trace and ultratrace amounts of hydride-forming elements as well as Cd and Hg. The number of elements amenable to tetrahydroborate(III)-derivatization has recently been extensively enlarged. Despite its many obvious advantages, drawbacks remain, such as significant interferences from transition metals. Consequently, many alternative approaches have been developed to overcome these shortcomings and to further expand the suite of elements amenable to CVG for sample introduction. This article reviews these non-tetrahydroborate-based approaches, including photochemical vapor generation (photo-CVG), borane complexes CVG, alkylation based on Grignard reactions and derivatization with NaBEt4, cold vapor generation with SnCl2, halide generation, electrochemical hydride generation, oxide generation, and generation of volatile chelates. Special attention is given to two newly developed CVG approaches: photo-CVG and reduction in the presence of cyanoborohydrides.Peer reviewed: YesNRC publication: Ye