Ultrasensitive determination of gold in geogas by laser excited atomic fluorescence spectrometry

Ultratrace gold (Au) in geogas samples has been determined by means of laser excited atomic fluorescence spectrometry combined with graphite electrothermal atomization and time-gate technique. Gold atoms were excited from the ground state to the 6p²P_3/2 state by a pulsed laser beam with a wavelength of 242.8 nm. Fluorescence photons with a wavelength of 312.3 nm were measured by a photon-counting unit. The time-gate technique was used to reduce the background radiation caused by the furnace. This method has proved to be highly sensitive with minimal background interference. Eighty-two geogas samples were analysed and the Au contents obtained were in the range of 0.002–0.182 ng l⁻¹. The study of Au concentration of geogas in soil is of great interest in prospecting gold deposits.     

Development of a new microelectrolysis system for in-situ electrodeposition of ultra-traces of gold prior to measurement by ETAAS

Electrodeposition is known to be suitable for separation and preconcentration of extremely low concentrations of analyte from bulk samples and is instrumentally is very simple. In this approach a new combined system was designed for in-situ electrodeposition of ultratrace levels of gold from micro samples on to a graphite furnace prior to determination by electrothermal atomic absorption spectrometry (ETAAS). Sediment samples were digested and traces of the gold content were extracted with boiling aqua regia. To prevent the highly corrosive effect of aqua regia media, the graphite tube surface was pre-coated by electrodeposition of ppm amounts of Pd prior to sample introduction. Separation of the analyte from the matrix was achieved by electrodeposition of the analyte in situ on the Pd/C surface of the furnace tube. Vanadium was also used as a modifier to stabilize the analyte from decomposition at charring temperatures. By using the proposed microelectrolysis preconcentration technique a considerable improvement in sensitivity and detection limit was achieved compared with conventional ETAAS. Characteristic masses for ED-ETAAS techniques in both nitric acid and aqua regia were reported to be m(o)=4.1 pg, with %RSD=2.9; the calculated LOD was 0.105 ppb, and typical calibration graphs for this element in nitric acid and aqua regia for both techniques were linear up to 70 microg L(-1) with about 99% recovery. Six reference sediments samples were tested by the proposed technique and by the Conv-ETAAS method. The results were in agreement with recommended values (reported by a reference laboratory using UV-visible spectrometry), demonstrating the efficiency of extraction and preconcentration of ultratrace levels of gold.     

A high selective ion‐imprinted polymer grafted on a novel nanoporous material for efficient gold extraction

In this work, for the first time, an ion‐imprinted polymer was developed for selective extraction and determination of gold ions. To increase the sorbent efficiency, this polymer was coated on a novel nanoporous carbon‐based material, carbohydrate‐derived Max‐Planck Gesellschaft 1, which is also the first example of grafting imprinted polymer on nanoporous‐carbon material. These particles were applied successfully for preconcentration of ultratrace amount of gold ions, following determination by flame atomic absorption spectrometry. Some effective factors on the efficiency of gold ions extraction, such as concentration and volume of eluent, sample and eluent flow rates, and also effect of interfering ions especially palladium and platinum ions, were investigated. The LOD was determined to be 0.27 ng/mL. Furthermore, the precision of the method was calculated to be 2.14% under optimal conditions with recovery more than 97.3%. The technique was also used to determine the concentration of gold ions in mine stone samples with satisfactory results. The accuracy of this method was investigated by determination of gold ions concentrations in several reference materials with certified gold content.     

The determination of gold in geochemical samples by non-dispersive atomic fluorescence spectrometry

Non-dispersive flame atomic fluorescence spectrometry is a very sensitive method for the determination of gold, with a limit of detection in aqueous solution of about 0.5 ng ml^?1. However, the application of the technique to aqua regia digests of geochemical samples is limited by large scatter signals which are due mainly to aluminium. The use of an auxiliary lamp to provide correction for scatter is suitable for samples containing low concentrations of elements which form refractory compounds in the flame or for samples where the full sensitivity of the fluorescence technique is not required. To obtain both high accuracy and sensitivity, gold must be separated from the scattering matrix and this can be achieved by a simple extraction with a 0.1% (w/v) solution of a trioctylmethyl-ammonium salt (Aliquat-336) in di-isobutyl ketone. The use of fluorescence avoids the need for a large extraction ratio and a subsequent washing step to remove iron, as is normally required for atomic absorption measurements.     

Application of laser-induced fluorescence for determination of trace uranium, europium and samarium

Trace amounts of uranium, europium and samarium can be determined by means of laser-induced fluorescence. The fluorescence emission and excitation spectra were observed by adding fluorescence enhancing reagents. The fluorescence lifetimes of these elements were also measured. The intensities of emission were found to be linear with respect to the concentration of the element over a wide range. The detection limits for U(VI), Eu(III), and Sm(III) were established as 0.05, 0.1, and 10 ng/ml, respectively. The study suggested that this is a suitable technique for the trace determination of uranium and rare earth elements.     

Polymer monolithic capillary microextraction combined on‐line with inductively coupled plasma MS for the determination of trace rare earth elements in biological samples

A rapid and sensitive method based on polymer monolithic capillary microextraction combined on‐line with microconcentric nebulization inductively coupled plasma MS has been developed for the determination of trace/ultratrace rare earth elements in biological samples. For this purpose, the iminodiacetic acid modified poly(glycidyl methacrylate‐trimethylolpropane trimethacrylate) monolithic capillary was prepared and characterized by SEM and FTIR spectroscopy. Factors affecting the extraction efficiency, such as sample pH, sample flow rate, sample/eluent volume, and coexisting ions were investigated in detail. Under the optimal conditions, the LODs for rare earth elements were in the range of 0.08 (Er) to 0.97 ng/L (Nd) with a sampling frequency of 8.5 h^?1, and the RSDs were between 1.5% (Sm) and 7.4% (Nd) (c = 20 ng/L, n = 7). The proposed method was successfully applied to the analysis of trace/ultratrace rare earth elements in human urine and serum samples, and the recoveries for the spiked samples were in the range of 82–105%. The developed method was simple, rapid, sensitive, and favorable for the analysis of trace/ultratrace rare earth elements in biological samples with limited sample volume.     

Inorganic trace analysis by mass spectrometry

Mass spectrometric methods for the trace analysis of inorganic materials with their ability to provide a very sensitive multielemental analysis have been established for the determination of trace and ultratrace elements in high-purity materials (metals, semiconductors and insulators), in different technical samples (e.g. alloys, pure chemicals, ceramics, thin films, ion-implanted semiconductors), in environmental samples (waters, soils, biological and medical materials) and geological samples. Whereas such techniques as spark source mass spectrometry (SSMS), laser ionization mass spectrometry (LIMS), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), glow discharge mass spectrometry (GDMS), secondary ion mass spectrometry (SIMS) and inductively coupled plasma mass spectrometry (ICP-MS) have multielemental capability, other methods such as thermal ionization mass spectrometry (TIMS), accelerator mass spectrometry (AMS) and resonance ionization mass spectrometry (RIMS) have been used for sensitive mono- or oligoelemental ultratrace analysis (and precise determination of isotopic ratios) in solid samples. The limits of detection for chemical elements using these mass spectrometric techniques are in the low ng g⁻¹ concentration range. The quantification of the analytical results of mass spectrometric methods is sometimes difficult due to a lack of matrix-fitted multielement standard reference materials (SRMs) for many solid samples. Therefore, owing to the simple quantification procedure of the aqueous solution, inductively coupled plasma mass spectrometry (ICP-MS) is being increasingly used for the characterization of solid samples after sample dissolution. ICP-MS is often combined with special sample introduction equipment (e.g. flow injection, hydride generation, high performance liquid chromatography (HPLC) or electrothermal vaporization) or an off-line matrix separation and enrichment of trace impurities (especially for characterization of high-purity materials and environmental samples) is used in order to improve the detection limits of trace elements. Furthermore, the determination of chemical elements in the trace and ultratrace concentration range is often difficult and can be disturbed through mass interferences of analyte ions by molecular ions at the same nominal mass. By applying double-focusing sector field mass spectrometry at the required mass resolution—by the mass spectrometric separation of molecular ions from the analyte ions—it is often possible to overcome these interference problems. Commercial instrumental equipment, the capability (detection limits, accuracy, precision) and the analytical application fields of mass spectrometric methods for the determination of trace and ultratrace elements and for surface analysis are discussed.     

用共振电离飞行时间质谱仪分析土壤中超痕量气态金

采用激光共振电离飞行时间质谱技术（简称ＲＩＳ－ＴＯＦ技术）对土壤中超痕量气态金的含量进行了分析研究。ＲＩＳ－ＴＯＦ谱仪具有极高的灵敏度和很强的选择性，避免了对样品的预富集过程。本文给出了该谱仪对金元素的检测限和６５个土壤中气态金样品的分析结果，以及用中子活化法随机抽样检查的结果。     

State of the art in time-resolved laser-induced fluorescence for actinides analysis: Applications and trends

Time-resolved laser-induced fluorescence (TRLIF) is a method of choice for actinides and lanthanides determination at low level in nuclear, biological and environmental samples. This technique is based on pulsed laser excitation followed by temporal resolution of the fluorescence signal. This technique has many advantages such as: high sensitivity, rapidity, triple selectivity and is applicable in a wide range of activity concentrations. TRLIF has been used in several fields such as; geology, in the PUREX process, in the medical field, in the environments and for nuclear waste disposal applications. Trends are towards the use of TRLIF for remote determination via fiber optics and optode as well a speciation.     

Capillary zone electrophoresis separation and laser-induced fluorescence detection of zeptomole quantities of fluorescein thiohydantoin derivatives of amino acids

Capillary zone electrophoresis, when combined with laser-induced fluorescence, is a very powerful technique for the separation and determination of minute amounts of labeled amino acids. This paper presents the determination of the fluorescein thiohydantoin derivative of 17 amino acids which takes 13.5 min. The detector, based on laser-induced fluorescence, is optimized with respect to laser power to produce detection limits, three standard deviations above background, ranging from 1 to 2 zeptomoles (1 zeptomole = 1 zmole = 10(-21) = 600 analyte molecules) injected onto the capillary.     

Fluorescence determination of trace amounts of uranium(VI) in various materials by a repetitive laser technique

A laser-induced fluorescence method (LFM) is described for determination of trace amounts of uranium(VI), with a detection limit of 4 x 10(-11) g/ml. A repetitive pulsed laser, time discrimination and an averaging technique are used. The optimum time discrimination is obtained when the uranyl ion is complexed with phosphoric acid or sodium polysilicate. LFM does not need a preconcentration step or separation of uranium from interfering elements. The time needed for analysis is only 1-2 min.     

Inductively Coupled Plasma(ICP) Mass Spectrometry(MS) Hyphenated with Atomic Emission Spectrometry(AES) for Simultaneous Determination of Major, Minor and Micro Amounts of Elements in Geochemical Samples

Introduction Geological resource survey demands for determining various constituents including major, minor, micro, trace and ultra-trace levels of elements for preparing the map of resource distribution of our country. As a powerful and popularly used technique for multi-element analysis, inductively coupled plasma(ICP) atomic emission spectrometry (AES) has been applied to this field for a period of time[1-3]. However, ICP spectrometric determination of those micro, trace and ultratrace elements needs enrichment procedures for improving the detection limit, which is unacceptable in case a great mass of samples should be analyzed as that in the task of geological resource survey. On the other hand, although ICP mass spectrometry(MS) is considered the most powerful method for trace elements determination[4,5], it is difficult for ICP-MS to be used to determine the trace and major analytes simultaneously in a spectrum.     

Electrothermal atomization-laser induced fluorescence determination of iridium,rhodium, palladium,platinum and gold at the ng/l level in pure water

Trace determination of Au, Rh, Ir, Pd and Pt in pure water solution has been performed by electrothermal atomization-laser induced fluorescence (ETA-LIF). Limits of detection obtained are in the ng/l⁻¹ range, improving previously published absolute limits of detection by one or two orders of magnitude. The day to day reproducibility for iridium is around 8%. Thus, the ETA-LIF technique can be used routinely for the determination of precious metals at ultratrace concentrations.     

Trace and ultratrace analysis of purified water samples and hydrogen peroxide solutions for phosphorus by flow-injection method.

A highly sensitive fluorescence-quenching method for the determination of phosphorus based on the formation of an ion associate between molybdophosphate and Rhodamine B (RB) was developed. A simple flow-injection system coupled with a fluorescence detector was used to measure the fluorescence intensity at 560 nm and 580 nm as an excitation and an emission wavelength, respectively. The calibration graph for phosphorus showed a good linearity in the range of (0 - 1) x 10(-7) M (1 M = 1 mol L(-1)), and a detection limit of 1 x 10(-9) M (S/N = 3). The proposed method was successfully applied to the determination of ultratrace amounts of phosphorus in ultrapurified and purified water samples, and to the determination of trace amounts of phosphorus in commercially-available hydrogen peroxide solutions with satisfactory results.     

Sorption–Atomic Absorption Determination of Trace Elements in Natural Waters with Dynamic Preconcentration in Electrothermal Atomizers

A sorption–atomic absorption method was proposed for the determination of ultratrace amounts of suspended and soluble forms of Ag, Cd, Bi, Pb, and Tl in natural waters using a dynamic preconcentration of these forms (separately or simultaneously) on the DETATA sorbent placed in a crucible atomizer and the subsequent direct atomic absorption analysis of the concentrate. This method is characterized by high a sensitivity and provides for the determination of elements in small volumes of unique samples. The accuracy of the determination of element species was verified by different methods in the analysis of sea and river water, atmospheric precipitation, and suspensions.     

Minimum value assured by a method to determine gold in alloys by using laser-induced breakdown spectroscopy and partial least-squares calibration model

A procedure for estimating the minimum value assured by an analytical method has been developed. It is applied to the determination of gold in jewellery alloys by means of a recently proposed spectroscopy technique. The laser-induced breakdown spectroscopic data of 17 gold alloys, with gold concentration ranging between 50 and 100% were used as calibration set for carrying out the partial least-squares regression (PLS). Ninety alloys, with known gold concentration, were used to evaluate the method’s accuracy. Finally, the minimum guaranteed value of the gold content was analysed, taking into account the values for gold hallmark in Spanish regulations.     

Immersed single-drop microextraction interfaced with sequential injection analysis for determination of Cr(VI) in natural waters by electrothermal-atomic absorption spectrometry

Single-drop microextraction (SDME) and sequential injection analysis have been hyphenated for ultratrace metal determination by Electrothermal-Atomic Absorption Spectrometry (ETAAS). The novel method was targeted on extraction of the Cr(VI)-APDC chelate and encompasses the potential of SDME as a miniaturized and virtually solvent-free preconcentration technique, the ability of sequential injection analysis to handle samples and the versatility of furnace autosamplers for introducing microliter samples in ETAAS.     

Separation and enrichment of palladium and gold in biological and environmental samples, adapted to the determination by total reflection X-ray fluorescence

The reductive co-precipitation of trace and ultra-trace elements together with mercury followed by complete evaporation of the mercury makes it possible to determine palladium and gold by total reflection X-ray fluorescence. Both elements can be detected without interferences at optimal sensitivity in the pg range. Thus, detection limits of, e.g., 2.5 ng L-1 for palladium and 2.0 ng L-1 for gold, in urine, were obtained. The precision was determined to 0.04 at a palladium concentration of about 200 ng L-1 urine and to 0.19 at a gold concentration of only 18 ng L-1. The recovery for a urine sample spiked with known amounts of palladium and gold amounted to > 95%. Results of the combined procedure are given for the determination of palladium and gold in the urine of non-exposed and occupationally exposed persons and in some other environmentally relevant samples.     

测定超痕量铁的高灵敏指示反应

在稀 H2 SO4 介质中 ,1 ,1 0 -邻菲 口罗啉存在下基于 Fe( )催化过氧化氢氧化棉红的新指示反应建立了测定超痕量铁的一个新方法。方法检出限 1 .0× 1 0 - 11g/m L ,线性范围 0 .0 0～ 1 .2 ng/m L。用于井水、一次蒸馏水、黄豆、芹菜中痕量及超痕量铁的测定获得满意结果     

全反射X射线荧光光谱法同时测定地气样品中锰、镍、铜、锌、铅、铷和锶

论述了利用自行研制的有３个反射体的全反射分析装置，用钼靶Ｘ光管激发，以Ｓｅ为内标，同时测定了地气样品中Ｍｎ、Ｎｉ、Ｃｕ、Ｚｎ、Ｐｂ、Ｒｂ和Ｓｒ等元素。对纳克级元素含量，方法的精密度为７．２％．绝对检出限为１０－１０～１０－１１。其分析结果的准确度与无火焰原子吸收相符。