Parameter optimization of an improved two-jet plasmatron for analyzing powder samples

The effect of operation parameters on an analytical signal in the jet of an improved two-jet plasmatron was studied. It was found that the analysis can be performed at lower current intensities and smaller gas flow rates on approaching the plasma-jet merging zone and choosing an analytical zone 3 to 2 mm ahead the site of plasma-jet merging. The detection limits of many elements in the direct analysis of graphite powders were 10^?8–10^?6 wt % against 10^?6–10^?4 on a previous plasmatron.     

Investigation of a “Plasmatron” as a tool for spectrochemical analysis of powdered samples of complex composition

A plasma jet produced by a plasmatron with non-consumed electrodes has been developed into a promising analytical tool. The temperature of the plasma does not depend on the chemical composition of the sample. The presence of an excess of an easily ionized element in the plasma results in the intensification of the lines of analyte elements. The main cause of the effect of sample composition on the intensity of spectral lines is a change in the electron pressure.The evaporation conditions were optimized. Analysis of samples of widely varying composition may be performed using a single set of reference samples with an accuracy meeting the requirements of quantitative analysis. The errors caused by the grain size of the samples are eliminated by grinding the samples to a particle size of 0·01 mm.Under optimum conditions of excitation the detection limits of elements are in a range between 10^?5 and 10^?7%. Many elements may be determined simultaneously.     

Atomic emission spectrographic determination of trace elements in environmental objects using a two-jet argon arc plasmatron

The effect of the main components (K, Na, Ca, Mg, Fe) on the atomic and ionic emission of trace elements Sr, Lu, V, Sc, Ti, Cr, Pb, Sn, Ni, Co, Bi, Mn, Pd, Zn, Be, Ba, Zr, Y, and La in atomic emission spectrometry with a two-jet argon arc plasmatron was studied to improve the accuracy of the quantitative multielement analysis of natural objects. It was shown that all of the studied macro elements to a certain extent enhance the analytical signal. The maximum enhancement was 2.5-fold. The effect of the matrix composition of the material is not strong and can easily be controlled by properly selecting the operational conditions of the formation of a plasma jet and bufferation, and also samples and reference elements. It was shown that a wide spectrum of trace elements can be quantitatively determined in various rocks, soils, and plant ashes with a relative standard deviation of 6–15% and detection limit of n × 10^?4 to n × 10^?6% using unified reference samples prepared synthetically.     

Theory of trace element detection from a static thermal induction plasma

Emission spectroscopy of small samples sealed into high-pressure electrodeless lamps greatly reduces the complexity of conditions commonly encountered in open excitation sources and facilitates theoretical treatment. In this paper, analytical curves and detection limits are calculated for such a closed system. A radio frequency (rf) induction discharge maintained in argon at atmospheric pressure in a cylindrical quartz vessel is considered as the excitation source. It is assumed that the plasma has a known temperature distribution, is in local thermal equilibrium (LTE) and will undergo complete mixing with the vapors of trace elements. Charts and relationships are presented for convenient determination of the maximum number of atoms of an analyte element that the plasma can hold for a given container volume, minimum temperature at the plasma-wall interface and a suitably defined average plasma temperature. Local concentrations of electrons, atoms and ions are calculated for additions of magnesium, antimony or mercury to the discharge plasma in amounts of 10^?6, 10^?9 and 10^?12 g each from Saha equilibrium, charge neutrality and space charge conservation. Detailed results are given for the magnesium—argon system which, in the considered temperature and concentration ranges, passes through a transition from metal-dominated to fill-gas dominated ionization. This transition causes the singularities in the emission coefficients of Mg atomic lines known as norm temperature effects. Measurement of the norm temperature at the location of an aureole in a contained plasma provides a means for determining the total amount of an element. Plots of line intensities against mass for Mg and the other elements show only insignificant deviations from linearity. They indicate that, with a typical spectrometric arrangement, an element is easily detectable without causing a noticeable disturbance in the plasma energy balance and that, from a practical standpoint, linear relationships ranging over several orders of magnitude can be expected. Less than 10^?15 g Mg are needed for the Mg(II) 279.6nm line to cause a signal power of 10^?15 W at the detector. This power is taken as equal to the shot noise level of the photodetector. The noise level of the source, due to fluctuations in continuum emissions, is still lower by an order of magnitude. The practical detection limit may be set by impurities released from the hot wall or by its permeability to analyte materials.     

Determination of Se(IV) in On‐Line System by Cathodic Stripping Voltammetry

A sensitive and selective on‐line voltammetric procedure for determination of traces of Se(IV) is presented. The pulsed potential accumulation was proposed for minimization of interferences of surface active substances and foreign ions. The calibration plot was linear from 1×10^?9 mol L^?1 to 4×10^?8 mol L^?1 for accumulation time of 180 s. The relative standard deviation was 6.1% (n=5) for a Se(IV) concentration of 1×10^?8 mol L^?1. The detection limit estimated from (3 σ) for an accumulation time of 180 s was about 4×10^?10 mol L^?1. The validation of the procedure proposed was made by a recovery tests for tap and river water samples.     

Cadmium Determination in Sedimented Dust by Atomic Emission Spectrometry With a New Radiofrequency Capacitively Coupled Plasma Source

ABSTRACT

A new radiofrequency capacitively coupled plasma source (r.f.CCP) was used for Cd determination in dust samples by atomic emission spectrometry. The plasma torch consists of a molybdenum tube electrode and one or two ring electrodes situated outside the quartz tube. Plasma was operated at 27.12 MHz, at low power (275 W) and low gas consumption (0.4 1 min^? argon flow). The choice of the optimum operating conditions for Cd determination in dust samples dissolved in acids and pneumatically nebulized is presented. The results obtained in such samples were compared with those obtained by flame atomic absorption spectrometry (FAAS). The matrix effect of NaCl and CaCl₂ on Cd emission was also studied depending of the plasma coupling system. The true limit of detection for Cd in dust sample by r.f.CCP-AES is 3 μg g^?1. Concentration of Cd higher than 10 μg g^?1 can be determined by the proposed method with a relative standard deviation within the range 5 - 10%. The recovery is 100 ± 10%.     

Determination of Iodine in Cereal Grains and Standard Reference Materials by Neutron Activation Anaylsis

Abstract

Trace amounts of iodine in thirty-eight cereal grain samples cultivated at different locations in Austria were determined for the first time in this study by radiochemical neutron activation analysis. For the dissolution of cereal grain samples and standard reference materials, two different procedures, alkaline and acidic dissolution, were applied in the presence of an iodine carrier. Rapid and simple dissolution procedure with acidic solution was demonstrated in this study. The analytical values in the cereal grain as well as in the standard reference materials obtained by the different dissolution procedures were in good agreement within one standard deviation. The iodine in cereal grains and the standard reference materials ranged from 0.002 to 0.03 μg g^?-1 and 0.0015 to 0.30 μg g^?-1, respectively. The distribution of relative standard deviation (RSD) for iodine concentration below 0.01 μg g^?-1 were 21% and 24% of all data for the range 1–10% RSD and 11–20% RSD, respectively. The RSD for 0.1 μg g^?1 of iodine concentrations were around 10%     

Sequential Voltammetric Determination of Ultratrace Osmium,Ruthenium and Iridium. Application to Superficial Water

The present work, regarding the determination of ultratrace Os(VIII), Ru(III) and Ir(III) in superficial waters is an interesting example of the possibility to simultaneously, or better sequentially determine each single element in real samples by voltammetry. The method is based on the catalytic current of the Os(VIII)‐ and Ru(III)‐bromate systems by square wave voltammetry and on the Ir(III) determination by square wave catalytic adsorptive stripping voltammetry. 0.5 mol L^?1 acetate buffer pH 4.9+7.7×10^?2 mol L^?1 NaBrO₃ and 0.5 mol L^?1 acetate buffer pH 4.9+7.7×10^?2 mol L^?1 NaBrO₃+2.3×10^?5 mol L^?1 cetyltrimethylammonium bromide (CTAB) +0.2 mol L^?1 KCl were employed as the supporting electrolytes. The analytical procedure was verified by the analysis of the standard reference materials: Sea Water BCR‐CRM 403 and Fresh Water NIST‐SRM 1643d. For all the elements, the accuracy, expressed as relative error e (%), was satisfactory, being lower than 6 %, while precision as repeatability, expressed as relative standard deviation, s_r (%), was generally lower than 5 %. Once set up on the standard reference materials, the analytical procedure was transferred and applied to superficial water sampled in proximity to superhighway and in the Po river mouth area.     

Spectrophotometric determination of magnesium through adsorption of its oxinate complex on microcrystalline naphthalene

An analytical procedure for spectrophotometric determination of magnesium has been developed. The method is based on adsorption of its oxinate complex under controlled experimental conditions on microcrystalline naphthalene at room temperature. The adsorbed species is then dissolved in dimethylformamide and magnesium is quantified spectrophotometrically at 382 nm. The oxine complex in DMFO has molar absorptivity of 4.1 × 10³ liter mol^?1 cm^?1, while its sensitivity is 5.9 × 10^?3 μg/cm² for 0.001 absorbance. The analytical precision is good, since for 10 replicate analyses at 30 μg of Mg, the relative standard deviation did not exceed 2.5%. The method has been applied toward Mg analysis in reference materials and environmental samples.     

Automated method for the determination of boron in water by flow-injection analysis with in-line preconcentration and spectrophotometric detection

A sensitive, automated method for the determination of boron in water samples is described, involving flow injection with on-line ion-exchange preconcentration and spectrophotometric detection of the azomethine-H—boron complex. The method is applicable to various water samples and is free from interferences, even in coloured samples. Detection limits of 5 μg l^?1 at 20 samples h^?1 and 1 μg l^?1 at 10 samples h^?1 with relative standard deviations of < 10% at 1–10 μg l^?1 and < 5%at 10–200 μg l^?1 levels of boron were achieved. The recoveries for spiked natural water samples ranged from 96 to 101%. The method compares favourably with inductively coupled plasma atomic emission spectrometry.     

Fast Determination of Ciprofloxacin by Batch Injection Analysis with Amperometric Detection and Capillary Electrophoresis with Capacitively Coupled Contactless Conductivity Detection

We report fast, precise, selective, and sensitive electroanalytical methods for the determination of ciprofloxacin in milk and pharmaceutical samples by batch‐injection analysis with amperometric detection (BIA‐AMP) and by capillary electrophoresis with capacitively‐coupled contactless conductivity detection (CE‐C⁴D). Both methods required simple sample preparation protocols before analysis (milk samples were just diluted and tablets powdered and dissolved in electrolyte/water). The analytical features of BIA‐AMP and CE‐C⁴D methods include, respectively, low relative standard deviation values for repetitive measurements (2.8 % and 1.7 %, n=10), low detection limits (0.3 and 5.0 µmol L^?1), elevated analytical frequency (80 and 120 h^?1) and satisfactory accuracy (based on comparative determinations by HPLC and recovery values for spiked samples).     

Ultrasensitive Assay of Gatifloxacin at Picogram Level Based on its Enhancing Effect on the Myoglobin‐Luminol Chemiluminescence Reaction

Abstract

Picogram‐level gatifloxacin was determined based on its significantly catalyzed effect on myoglobin‐luminol chemiluminescence (CL) reaction in the flow injection system. The enhanced chemiluminescence intensity was linear with gatifloxacin concentration in the range from 50 ngl^?1–10 µg l^?1 (r²=0.9995), and the detection limit was 20 ng l^?1 (3σ). At a flow rate of 2.0 ml min^?1 for each line, a complete analytical process could be performed within 0.5 min, including sampling and washing, with a relative standard deviation of less than 4.0% (n=7). The proposed method was applied successfully in the determination of gatifloxacin in tablets, human serum and urine samples with the recovery from 97.4–104.5%.     

Evaluation and Application of the Internal Standard Technique for the Direct Determination of Copper in Fruit Juices Employing Fast Sequential Flame Atomic Absorption Spectrometry

Abstract

The present paper describes the evaluation and application of internal standard for the determination of copper in fruit juices, employing Fast Sequential Flame Atomic Absorption Spectrometry (FS FAAS). The internal standards tested were indium, cobalt, and nickel using correlation graphs. However, indium was used, considering the composition of the samples. After this step, copper was determined in fruit juices using indium as internal standard. This method allows the determination of copper with a limit of quantification of 0.011 mg L^?1. The fruit juice samples selected for analysis were of grape, orange, pineapple, peach, cashew, and strawberry. The contents of copper in these samples varied from 0.02 to 0.42 mg L^?1. The analytical results were compared with the results obtained by analysis of these samples after complete mineralization using acid digestion and determination employing FS FAAS. The statistical comparison by a t-test (95% confidence level) showed no significant difference between the results. The relative standard deviations (RSD) with and without the use of the internal standard for a copper solution containing 0.4 mg L^?1 were of 0.62 and 1.94%, respectively. The use of indium as internal standard provided more accurate analytical results, as well as better analytical performance for the determination of copper in juice samples.     

Validation of QuEChERS-based UPLC-MS/MS method for determination of quinoid niclosamide (LDS) residue in water,soil and rice samples

A sensitive, rapid and easy analytical method was validated for the determination of quinoid niclosamide (LDS) molluscicide in water, rice and soil using a QuEChERS extraction procedure and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) detection. The LDS was extracted by using acetonitrile and then cleaned up by using dispersive solid-phase extraction with florisil and C18 sorbents. The determination of the target compound was achieved in less than 3 min using an electrospray ionisation source in negative mode. The overall average recoveries for this method in water, rice and soil matrix at three fortified levels ranged from 82.54 to 99.9%, with relative standard deviations in the range of 1.51 to 4.86% (n = 5). The calculated limits of detection were lower than 0.1 µg kg^?1 and quantification was 5 µg kg^?1; these values were much lower than the maximum residue levels established by the Australian standard (0.01 mg kg^?1). The results of the method validation confirmed that this proposed method is convenient and reliable for the determination of LDS molluscicide in water, rice and soil samples.     

Multi‐responses Methodology Applied in the Electroanalytical Determination of Hair Dye by Using Printed Carbon Electrode Modified with Graphene

This paper describes a rapid and sensitive method for determination of the hair dye Basic Blue 41 in wastewater samples using screen‐printed carbon electrodes modified with graphene (SPCE/Gr). The method is based on the reversible reduction of azo groups of the dye at potential of ?0.23 V/?0.26 V, where both the anodic and cathodic currents increased 1,300 % when compared to screen‐printed carbon (SPCE) and glassy carbon electrodes (GCE). The optimization of a square wave voltammetric method was performed by means of 2³ factorial design, Doehlert matrix and multi‐response assays, and the best parameters were: frequency (54.8 Hz), step potential (6 mV), pulse amplitude (43.7 mV) and pH 4.5. The analytical curve was constructed from 3.00×10^?8 to 2.01×10^?6 mol L^?1, with detection and quantification limits of 5.00×10^?9 and 1.70×10^?8 mol L^?1, respectively. The repeatability of the method evaluated for 10 consecutive measurements at concentrations of 1.70×10^?7 mol L^?1 and 1.70×10^?6 mol L^?1, showed relative standard deviation of 3.56 and 0.57 %, respectively. The sensor based in SPCE/Gr was successfully applied in wastewater samples collected from a drinking water treatment plant and validated by comparison with HPLC‐DAD method with good accuracy.     

Simultaneous determination of fluoroquinolone and tetracycline antibacterials in sewage sludge using ultrasonic-assisted extraction and HPLC-MS/MS

A reliable method was proposed for the simultaneous determination of five fluoroquinolones (FQs) and two tetracyclines (TCs) in sewage sludge using ultrasonic-assisted extraction (USE) followed by SPE cleanup and high-performance liquid chromatography-mass spectrometry (HPLC-MS)/MS analysis with electrospray ionisation (ESI) in a positive mode. The USE conditions (e.g. extraction solvent, pH, and extraction cycles) and high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) parameters were optimised. Quantification was performed by internal standard calibration in multiple reaction monitoring mode. Recoveries of the antibacterials ranged from 41 to 123%, with relative standard deviations within 17%. The sample-based limits of quantification were 10–63?ng?g^?1 dry weight (dw) for FQs (ciprofloxacin, enrofloxacin, lomefloxacin, norfloxacin, and ofloxacin) and 250–500?ng?g^?1 dw for TCs (tetracycline and oxytetracycline). The method was applied to determine the antibacterials in sewage sludge and sediment samples were collected from the Pearl River Delta, China. Ciprofloxacin, norfloxacin, and ofloxacin were frequently detected, ranging from 1052 to 17740?ng?g^?1 dw in dewatered sludge samples, 585–3545?ng?g^?1 dw in untreated solids, and 98–258?ng?g^?1 dw in an urban stream sediment sample, respectively. Lomefloxacin and enrofloxacin were also occasionally detected.     

Indirect determination of fluoride in waters with lanthanum alizarin complexone and inductively-coupled plasma emission spectrometry

Fluoride is determined indirectly by measurement of the La II 333.75-nm line in the lanthanum/alizarin complexone/fluoride complex. The ternary complex is extracted into hexanol containing N,N-diethylaniline and the extract is introduced directly into the plasma. Related to water samples, the detection limit (3σ, concentration factor 5) is 0.59 ng ml^?1 fluoride, calibration is linear up to 1.2 μg ml^?1 and the relative standard deviation for 0.04 μg ml^?1 is 2.6%. Alkali, alkali elements and most anions do not interfere. The method is applied in the analysis of river water, coastal seawater and drinking water.     

Simultaneous Quantitation of Paracetamol, Pseudoephedrine and Chlorpheniramine in Dog Plasma by LC-MS-MS

A simple, rapid and sensitive liquid chromatography/electrospray tandem mass spectrometry quantitative detection method, using amantadine as internal standard, was developed for the simultaneous analysis of paracetamol, pseudoephedrine and chlorpheniramine concentrations. Analytes were extracted from plasma samples by liquid–liquid extraction with n-hexane–dichloromethane–2-propanol (2:1:0.1, v/v), separated on a C18 reversed-phase column with 0.1% formic acid–methanol (40:60, v/v) and detected by electrospray ionization mass spectrometry in positive multiple reaction monitoring mode. Calibration curves for plasma were linear over the concentration range 10–10,000 ng mL^?1 of paracetamol, 2–2,000 ng mL^?1 of pseudoephedrine and 0.2–200 ng mL^?1 of chlorpheniramine. The method has a lower limit of quantitation of 10 ng mL^?1 for paracetamol, 2.0 ng mL^?1 for pseudoephedrine and 0.2 ng mL^?1 for chlorpheniramine. Recoveries, precision and accuracy results indicate that the method was reliable within the analytical range, and the use of the internal standard was very effective for reproducibility by LC-MS-MS. This method is feasible for the evaluation of pharmacokinetic profiles of a novel multicomponent sustained release formulation containing 325 mg of paracetamol, 30 mg of pseudoephedrine hydrochloride and 2 mg of chlorpheniramine maleate. It is the first time the pharmacokinetic evaluation of a novel sustained-action formulation containing paracetamol, pseudoephedrine and chlorpheniramine has been elucidated in vivo using LC-MS-MS.     

Size Exclusion Chromatographic Determination of PEG 3350 in Human Plasma and Urine

Abstract

A size exclusion chromatographic method is reported that quantitated PEG 3350 in human plasma and urine to a concentration of 10 μg/ml in plasma, or urine. The chromatographic system consisted of a 500 A gel permeation analytical column, a differential refractometer detector, and chloroform as the eluting solvent. Organic extraction was used as an initial separation technique. PEG 400 was used as the internal standard for PEG 3350, and showed similar extraction properties. Spiked plasma standards yielded standard calibration curves with correlation coefficients of greater than 0.99, and relative standard deviations (n=3) of 2.19% (500 μg/ml) and 6.97% (20 μg/ml). The analytical technique was used to estimate the elimination rate constant of PEG 3350 from 5 normal human subjects after oral administration of 240 grams of PEG 3350. K_E was found to be 0.1079 hr^?1 0.03781^?1 hr (mean s.d.) using the Sigma-minus data analysis method on total urines collected from the 5 subjects at varying intervals.     

Cross-validation and evaluation of the performance of methods for the elemental analysis of forensic glass by μ-XRF, ICP-MS, and LA-ICP-MS

Elemental analysis of glass was conducted by 16 forensic science laboratories, providing a direct comparison between three analytical methods [micro-x-ray fluorescence spectroscopy (μ-XRF), solution analysis using inductively coupled plasma mass spectrometry (ICP-MS), and laser ablation inductively coupled plasma mass spectrometry]. Interlaboratory studies using glass standard reference materials and other glass samples were designed to (a) evaluate the analytical performance between different laboratories using the same method, (b) evaluate the analytical performance of the different methods, (c) evaluate the capabilities of the methods to correctly associate glass that originated from the same source and to correctly discriminate glass samples that do not share the same source, and (d) standardize the methods of analysis and interpretation of results. Reference materials NIST 612, NIST 1831, FGS 1, and FGS 2 were employed to cross-validate these sensitive techniques and to optimize and standardize the analytical protocols. The resulting figures of merit for the ICP-MS methods include repeatability better than 5 % RSD, reproducibility between laboratories better than 10 % RSD, bias better than 10 %, and limits of detection between 0.03 and 9 μg g^?1 for the majority of the elements monitored. The figures of merit for the μ-XRF methods include repeatability better than 11 % RSD, reproducibility between laboratories after normalization of the data better than 16 % RSD, and limits of detection between 5.8 and 7,400 μg g^?1. The results from this study also compare the analytical performance of different forensic science laboratories conducting elemental analysis of glass evidence fragments using the three analytical methods.