Ultrasonic Extraction–Ozonation Sequential Sample Treatment for the Determination of Arsenic in Environmental Certified Reference Materials by Hydride Generation–Atomic Fluorescence Spectrometry

Abstract

A sample pretreatment method based on ultrasound‐assisted extraction followed by ozonation is developed for sensitive determination of total As in biological and environmental certified reference materials and an unknown plant sample (Acacia dealbata) by flow injection and continuous‐flow hydride generation–atomic fluorescence spectrometry. The method is meant to minimize the use of corrosive and oxidizing acids for sample decomposition and common errors in trace analysis. Problems derived from introduction of sonicated extracts in continuous flow and flow injection manifolds in combination with an atomic fluorescence detector, such as excessive foaming and flame instability, are addressed. The following certified reference materials (CRMs) were employed for method assessment: BCR CRM 482 lichen; BCR CRM 60 and 61 aquatic plants; BCR CRM 279 sea lettuce; NIST 1633b fly ash; BCR 320 river sediment; RTC CRM 024‐050 soil. Effect of variables such as extraction time, ultrasound amplitude, concentration of extractant acid, sample mass, drying mode, and particle size was investigated. Leaves of Acacia dealbata were also employed for method development. Limits of detection ranged from 0.03 to 0.15 µg/g As depending on the sample. Between‐batch precision values ranged from 2% to 11%. Sample throughput was 40 hr^?1 with flow injection.     

Thermal Lens Spectrometric Detection in Flow Injection Analysis and Separation Techniques

Abstract

Recent applications of thermal lens spectrometry in liquid chromatography (HPLC, ion chromatography), capillary electrophoresis, and flow injection analysis are reviewed. Possible effects of performing TLS measurements in flows are discussed initially for different TLS configurations. The emphasis is given to the analysis of real samples, and the performances of various detection schemes in combination with chromatographic techniques and FIA are discussed particularly in terms of sensitivity, sample throughput, and eventual interferences from complex matrices. Coaxial TLS detection with continuous wave excitation is most suitable for detection in HPLC, ion chromatography, and FIA using long‐path length cells, when large volume samples are available. On the other hand, transverse or crossed beam TLS was found most suitable for detection in CE where it provides low absolute LODs, which are lowered even further by thermal lens microscopy on microchips, where the capability of detecting a single molecule in the detection volume was demonstrated.     

Sensitive Chemiluminescence Assay for Patulin in Apple Juice by Flow Injection

Abstract

A sensitive chemiluminescence (CL) procedure for the determination of patulin by flow injection is described. It was found that patulin inhibits the CL generated from the luminol–dissolved oxygen system significantly. The decrement of chemiluminescence intensity was linear with the patulin concentration over the range from 0.04 to 10.0 ng mL^?1 with a detection limit of 0.01 ng mL^?1 (3σ_noise). At a flow rate of 2.0 mL min^?1, a complete analytical process could be performed within 0.5 min, including sampling and washing, with a relative standard deviation of less than 3.0% (n=5). The proposed method was applied successfully in the determination of patulin in apple juice, and the recovery was between 96.9% and 103.9%.     

大气中SO2顺序注射光度测定方法的初步研究

基于SO2在微碱性条件下使孔雀绿褪色的反应原理, 结合顺序注射进样技术建立了光度分析测定大气中SO2的方法. 对试剂加入顺序、各种试剂的浓度、注入体积、反应系统流速等实验参数进行了优化. 采用顺序注射进样, 极大地节省了试剂和试样的用量, 显著地提高了分析速度, 可达到60样·h-1. 方法的线性响应范围0.25～4.0 μg·mL-1, 检出限为0.15 μg·mL-1, 11次重复测定的相对标准偏差为1.5%. 对实际样品的回收率为94%～108%.     

Molybdenum,Platinum, and Tantalum Metal Atomizers or Vaporizers in Analytical Atomic Spectrometry

Abstract

The application of metal (tantalum, molybdenum, and platinum) devices in analytical atomic spectrometry is reviewed in this article. These metal devices have been employed in various analytical atomic spectrometric techniques for more than three decades, mainly as electrothermal atomizers or electrothermal vaporizers, in various physical shapes, such as tubes, platforms, loops, and wires (or coils/filaments). Their application spans from atomic absorption spectrometry (AAS), atomic emission spectrometry (AES) atomic fluorescence spectrometry (AFS), inductively coupled plasma atomic emission spectrometry (ICP‐AES) to inductively coupled plasma mass spectrometry (ICP‐MS). The analytical figures of merit and the practical applications reported for these metal devices are reviewed, and the atomization mechanism on these metal atomizers is briefly summarized, too. In addition, other applications of the metal devices are discussed, including analyte preconcentration by electrodeposition and sequential metal vapor elution analysis (SMVEA). Furthermore, the application of these metals in graphite furnaces encompasses the schemes with the metals in the form of furnace linings, platforms, or impregnated salts.     

在线流动注射N1923萃淋树脂预富集火焰原子吸收法测定痕量金

研究了富集酸度、进样体积、洗脱流速、富集时间、洗脱液的浓度和酸度、共存离子的影响 ,建立了N1 92 3萃淋树脂富集在线流动注射火焰原子吸收法测定痕量金的新方法。富集倍率为 32倍 ,检测限为 1 μg·L- 1 。用于电镀金废液的在线测定 ,方法灵敏度高、操纵简便、结果较好。     

Hydrodynamic Sequential Injection Spectrophotometric System for Determination of Manganese in Soil

ABSTRACT

A novel hydrodynamic sequential injection (HSI) spectrophotometric system for determination of manganese was developed. It is based on the complexation of Mn(II) with formaldoxime in basic solution (pH ≥ 10) to produce product that could be monitored spectrophotometrically at 450 nm. Based on the HSI concept, both sample and reagents were aspirated through solenoid valves to fill a defined volumes conduit between 3-way connectors connected in series, forming stacked zones of solutions similar to those in normal SI. The concept was successfully demonstrated for manganese determination. A linear calibration graph over a range of 0.5 to 30 mg L^?1 Mn(II) with a detection limit of 0.2 mg L^?1 was obtained. Relative standard deviations for 11 replicated injections of 5 and 20 mg Mn L^?1 were 5.6% and 2.4%, respectively. A sample throughput of 45 h^?1 was achieved. The results from investigation of exchangeable manganese in soil samples by the developed method were found to be in good agreement with the results obtained by a batch spectrophotometric method, despite the proposed system employed simpler and more cost-effective devices/instruments, had higher degrees of automation with full microcontroller control of the operation, and consumed smaller amounts of chemicals (250 µL each of hydroxylamine, sample, and formaldoxime solutions and 2.5 mL of buffer carrier solution per operation cycle).     

Effect of different lipid extraction methods on δ13C of lipid and lipid-free fractions of fish and different fish feeds

For many ecological applications of stable carbon isotope techniques, it is necessary to separate the lipid and lipid-free fractions. The effect of different lipid extraction methods on the isotope signature of the remaining lipid-free matter as well as the lipid fraction was tested. A hot extraction form of the Soxhlet method using petrol-ether was compared with two liquid-liquid extraction methods for lipid determination described by Bligh and Dyer and Smedes. Solid samples of fish and different natural food items were subjected to extraction and the carbon isotope ratios in lipid and lipid-free matter determined by IRMS. All methods were suitable for lipid extraction from all samples analysed here and did not cause biologically relevant differences (>1) in carbon isotopic ratios, except the Bligh and Dyer extraction method using chloroform which caused systematic errors for δ ¹³C when applied to diatoms.     

Determination of Trace Amounts of Zinc in Welding Fumes by Flow‐Injection Flame Atomic Absorption Spectrometry

A flow‐injection flame atomic absorption spectrometric method for the determination of zinc in welding fumes has been developed. The method is based on the continuous ultrasound‐assisted dissolution of the zinc oxide collected on the air filter. Variables such as sonication time, nature and concentration of the acid solution used as dissolving solution, dissolution temperature, flow rate of the continuous manifold, and dissolving solution volume were simultaneously studied by applying a Plackett–Burman design. Results showed that only the concentration of nitric acid solution used as dissolving solution was a statistically significant variable (confidence interval of 95%). Factors such as dissolution temperature and sonication time were finally optimized by using a central composite design. The detection limit was 1.1 µg/m³ and the repeatability of the overall method is 1.6% (n=11) for a zinc concentration of 75.4 µg/m³. The proposed method was applied to the determination of zinc in welders' workplace environments.     

Flow Injection Kinetic Spectrophotometric Determination of Cerium Based on the Decolorization Reaction Between Arsenazo III and Cerium (IV)

ABSTRACT

Trace amounts of cerium were analyzed by flow injection kinetic spectrophotometry, based on the decolorization reaction between arsenazo III and Ce(IV) in sulfuric acid medium at room temperature. The absorbance difference (ΔA) of decolorization was linear with the concentration of Ce(IV). The flow injection technique was used to precisely control the timing. Under the optimum conditions, the determination of Ce(IV) in the range 0.0–8.0 µg mL^?1 with a correlation coefficient (r) of 0.9982, the regression equation was ΔA = 0.0014 + 0.0406c (µg mL^?1). The detection limit (3σ) of 0.2 µg mL^?1 was achieved at a sampling frequency of 60 h^?1. The proposed method was applied to the analyses of Ce in soil successfully.     

Flow‐Injection Online Reduction Atomic Fluorescence Spectrometry Determination of Se(IV) and Se(VI) with Electrochemical Hydride Generation

Abstract

A new flow‐injection online reduction electrochemical hydride generation system for the determination of Se(IV) and Se(VI) by atomic fluorescence spectrometry (AFS) was developed. In the system, an electromagnetic induction oven was used as heating resource to reduce Se(VI) to Se(IV) and a homemade tubular electrolytic cell as hydride generator. All analytical procedures were automatically controlled by a computer. The conditions of online reduction, including temperature, HCl concentration, and reduction time, have been studied in detail. The detection limits (3σ) of Se(IV) and Se(VI) in aqueous solution were 0.26 µg L^?1 and 0.23 µg L^?1, respectively. The precision for 11 replicate measurements of 50 µg L^?1 Se(IV) and Se(VI) was 2.2% and 2.5%. This proposed method has been applied to the determination of Se(IV) and Se(VI) in springwater samples.     

Flame Furnace Atomic Absorption Spectrometry: A Review

Abstract

Flame atomic absorption spectrometry (FAAS) is one of the most widespread traditional analytical techniques for trace element determination, but it often suffers from poor sensitivity due to the low nebulization efficiency and the short residence time of free atoms in the flame. On the basis of conventional FAAS, flame furnace atomic absorption spectrometry (FF-AAS) is developed with a tube (flame furnace) placed on top of the FAAS burner for the atomization. Sample is introduced via beam injection (BIFF-AAS) or thermospray (TS-FF-AAS). Due to the total sample introduction and prolonged residence time of free atoms in the flame furnace, marked sensitivity improvement is obtained for volatile and semivolatile elements over conventional FAAS. TS-FF-AAS can be employed as an element-selective detector for GC, HPLC, or CE for studying of metal speciation analysis and metallomics. In addition, three newly developed sample introduction methods, including ultrasonic nebulization, hydride generation, and pneumatic nebulization, are discussed. The analytical figures of merit and practical applications of FF-AAS in analytical atomic spectrometry are reviewed in this article.     

Interfacing Microfluidic Handling with Spectroscopic Detection for Real‐Life Applications via the Lab‐on‐Valve Platform: A Review

Abstract

One of the current needs within the analytical spectrometric community is the development of straightforward and cost‐effective, yet rugged, sample processing procedures aimed at precluding both spectroscopic and nonspectroscopic matrix interferences while fostering concomitant sample enrichment. Illustrated via selected representative examples, this review presents and discusses the current state of the art in implementing miniaturised and automated sample treatments for environmental and biochemical assays via microfluidic systems exploiting the lab‐on‐valve (LOV) platform in hyphenation with syringe pump propelling devices as a front end to a plethora of spectroscopic detection schemes including ultraviolet‐visible (UV‐Vis) spectrometry, spectrofluorimetry, chemiluminescence, atomic absorption spectrometry (AAS), atomic flourescence spectrometry (AFS), and inductively coupled plasma‐atomic emission spectrometry/mass spectrometry (ICP‐AES/MS). In contrast to lab‐on‐a‐chip units, the versatile configuration of the micromachined LOV readily facilitates the implementation of on‐line unit operations at will encompassing not merely the introduction of minute, well‐defined volumes of sample followed by chemical derivatization, but the potential for accommodation of solid‐phase extraction, hydride/vapor generation, precipitation/coprecipitation, and bead injection protocols with no need for chip redesign.     

Theoretical study of molecular ordering in liquid crystals with the help of intermolecular interaction energy calculations

A theoretical analysis has been carried out to determine the molecular alignment of some nematic liquid crystals like DPAB (4, 4'-di-n-propoxy-azoxybenzene), EPAB (ethyl para-azoxybenzoate) and PAA (para-azoxyanisole). CNDO/2 method has been employed to evaluate the net atomic charge and atomic dipole components at each atomic centre of the molecules. Configurational energy has been computed using a modified Rayleigh-Schrodinger perturbation method at an interval of 1 Å in translation and 10° in rotation between a pair of DPAB molecules. On the basis of stacking, in-plane and terminal interaction energy calculations, all possible geometrical arrangements between a molecular pair have been considered. A comparative picture of molecular parameters like total energy, binding energy, total dipole moment etc., has been obtained. An attempt has been made to explain the nematogenic behaviour of liquid crystal and thereby develop a molecular model for liquid crystallinity.     

在线流动注射液-液萃取非水介质汞还原原子荧光光谱法的研究及应用

提出了一种流动注射在线液－液萃取有机相汞还原原子荧光光谱法测定汞的新方法。该法以KI＋HNO3＋（NH2）2CS／TBP为萃取体系，将汞萃取到有机相中，汞还原反应是在金属络合萃取液与含NaBH4的N，N－二甲基甲酰铵（DMF）溶液和冰乙酸中发生。应用流动注射技术实现了液－液萃取非水介质汞还原反应原子荧光测定的在线分析。研究了反应的最佳条件和流动注射流路及运行程序。该法提高了测定灵敏度并消除了干扰。用于地质样品中汞的测定得到好的准确度和精密度。     

Determination of Trace Elements in Vegetable Oils and Biodiesel by Atomic Spectrometric Techniques—A Review

Abstract

The determination of trace elements in edible oils and biodiesel using atomic spectrometric methods is reviewed. Problems related to sample pretreatment for appropriate sample introduction and calibration are addressed as well as the strategies to overcome them. Recent trends aimed at simplifying sample manipulation are presented. The applications and scope of atomic absorption spectrometry (AAS), flame optical emission spectrometry (F-OES), inductively coupled plasma–optical emission spectrometry (ICP-OES), and inductively coupled plasma–mass spectrometry (ICP-MS) techniques for the determination of trace metals in edible oils and biodiesel are discussed, as well as some current instrumental new developments.     

Procedures of Separation and Pre‐concentration for Molybdenum Determination Using Atomic Spectrometry—a Review

Abstract

The literature concerning the improvement of atomic and ionic procedures for molybdenum determination through separation and pre‐concentration were updated. Analytical procedures based on flame atomic absorption spectrometry (AAAS), electrothermal or graphite furnace atomic absorption spectrometry (GFAAS), inductively coupled plasma optical emission spectrometry (ICP‐OES), and inductively coupled plasma mass spectrometry were reviewed taking into consideration the preliminary steps, which can enhance the selectivity and sensitivity based on co‐precipitation, solvent extraction, and solid‐phase extraction. Both in‐batch and on‐line procedures were considered.     

砷和汞的顺序注射-蒸气发生原子吸收光谱测定

本文建立了砷和汞的顺序注射 蒸气发生原子吸收光谱测定方法。在流动注射蒸气发生原子吸收光谱测定方法的基础上 ,采用汇流技术 ,通过两个微量注射泵和一个多位选择阀的计算机程控操作 ,实现待测组分与硼氢化钠间的强氧化还原反应及其气 液分离过程。与流动注射方法相比 ,进一步大幅度节省试剂消耗 ,显著提高分析的精度及长期稳定性。在 1 2 0·h- 1 的采样频率下汞和砷的测定精度RSD分别为 2 2 %和 1 4%,检出限分别为 0 1 5和 0 0 7μg·L- 1 。方法用于地球化学标准样品的分析 ,取得满意结果。     

甲氧氯普胺和盐酸普鲁卡因顺序注射光谱研究和测定

在酸性介质中,铈(Ⅳ)与甲氧氯普胺和盐酸普鲁卡因反应生成不稳定的红色产物,研究了不同条件下的光谱吸收曲线,初步探讨了反应机理,并据此建立了顺序注射光度法测定甲氧氯普胺和盐酸普鲁卡因的新方法。测定甲氧氯普胺方法的线性范围9.71～116.6 μg·mL-1,检出限6.5 μg·mL-1,进样频率45 h-1。测定盐酸普鲁卡因的方法的线性范围10.0～130.0 μg·mL-1,检出限7.4 μg·mL-1,进样频率45 h-1。用于针剂和胃复安药片中甲氧氯普胺的含量以及针剂中盐酸普鲁卡因含量的测定,并与标准测定方法对照,经统计学处理无显著性差异,结果满意。     

Spectrophotometric Determination of Ammonia in Estuarine Waters by Hybrid Reagent‐Injection Gas‐Diffusion Flow Analysis

Abstract

A flow‐injection gas‐diffusion technique is described for the online determination of ammonia in estuarine waters covering a salinity range of S=0 to 36. The flow analysis system, which is a hybrid of reagent injection and conventional sample‐injection flow systems, avoids the need for a rotary injection valve. Whereas gas‐diffusion techniques have been widely applied in conventional sample‐injection flow analysis, reagent‐injection flow analysis involving gas diffusion has been little used because it is susceptible to interference from dissolved gaseous species such as carbon dioxide coexisting with ammonia in the sample. This source of interference has been overcome by online adjustment of sample to pH 8.4 prior to the injection of the base that initiates gas diffusion of ammonia. The pore sizes of hydrophobic membranes used in gas diffusion were characterized by a bubble‐point test prior to use in the flow analysis system. These showed wide variation in pore size, and grading and careful selection was necessary in order to obtain reliable gas diffusion measurements of ammonia. The proposed flow‐injection system can be operated in a continuous flow mode, at a sample throughput of 135 measurements hr^?1 with a typical limit of detection (LOD) of 9 µg N L^?1, or in stopped‐flow mode at 60 measurements hr^?1 with a LOD of 3 µg N L^?1. The technique was validated using water samples containing a wide range of dissolved carbon dioxide concentrations, salinity, and pH. Excellent agreement (r=0.999) was observed between results obtained using the reagent‐injection system and an approved reference method.