Assessment of Inorganic Fibre Burden in Biological Samples by Scanning Electron Microscopy – Energy Dispersive Spectroscopy

A method based on cloud point extraction (CPE) separation/preconcentration of trace cadmium as a prior step to its determination by graphite furnace atomic absorption spectrometry (GFAAS) has been developed. If the system temperature is higher than the cloud point temperature (CPT) of the nonionic surfactant of p-octyl polyethyleneglycolphenyether (Triton X-100), the complex of Cd²⁺ with 1-(2-pyridylazo)-2-naphthol (PAN) could be extracted into surfactant-rich phase. The chemical variables affecting CPE were evaluated and optimized. Under the optimum conditions, preconcentrating 10.0 mL of water samples permitted a limit of detection of 5.9 ng · L⁻¹ (3σ) for cadmium with an enhancement factor of 50 and a relative standard deviation of 2.1% (n = 11, c = 2.0 ng · mL⁻¹). The method was applied to the determination of cadmium in reference material and water samples with satisfactory results.     

Catalytic Determination of Vanadium Based on the Bromate Oxidative-C oupling Reaction of Metol with Phloroglucinol

 A selective, sensitive and simple catalytic method is developed for the determination of vanadium in natural and highly polluted waste waters. The method is based on the catalytic effect of V^V and/or V^IV on the bromate oxidative-coupling reaction of metol with phloroglucinol (PG). The reaction is followed spectrophotometrically by tracing the oxidation product at 464 nm after 10 minutes of mixing the reagents. The optimum reaction conditions are metol (8.0×10⁻³ M), PG (4.0×10⁻³ M) and bromate (2×10⁻² M) at 35°C and in presence of an activator-b uffer mixture of 5×10⁻² M of each of citric and monochloroacetic acids (pH 2.40). Following the recommended procedure, vanadium can be determined with a linear calibration graph up to 8.0 ng mL⁻¹ and a detection limit, based on the 3s_b criterion, of 0.1 ng mL⁻¹. Spectrophotometric determination of as little as 1.0 ng mL⁻¹ of V^V or V^IV in aqueous solutions gave an average recovery of 98% with relative standard deviations of ?1.8% (n = 5). The proposed method was directly applied to the determination of vanadium in Nile river water and highly polluted industrial wastes. Statistical treatments of analytical results could not detect any systematic error and showed the high accuracy and precision of the developed method. Received November 25, 1999. Revision March 10, 2000.     

Adsorptive anodic stripping voltammetry of zirconium(IV)-alizarin red S complex at a carbon paste electrode

A sensitive adsorptive anodic stripping procedure for the determination of trace zirconium at a carbon paste electrode (CPE) has been developed. The method is based on adsorptive accumulation of the Zr(IV)-alizarin red S(ARS) complex onto the surface of the CPE, followed by oxidation of adsorbed species. The optimal experimental conditions include the use of 0.10 mol · L⁻¹ ammonium acetate buffer (pH 4.3), ARS, an accumulation potential of 0.20 V (versus SCE), an accumulation time of 2 min, a scan rate of 200 mV · s⁻¹ and a second-order derivative linear scan mode. The oxidation peak for the complex appears at 0.69 V. The peak current is proportional to the concentration of Zr(IV) over the range of 1.0 × 10⁻⁹–2.0 × 10⁻⁷ mol · L⁻¹, and the detection limit is 3 × 10⁻¹⁰ mol · L⁻¹ for a 2 min adsorption time. The relative standard deviations (n = 8) for 5.0 × 10⁻⁸ and 5.0 × 10⁻⁹ mol · L⁻¹ Zr(IV) are 3.3 and 4.8%, respectively. The proposed method was applied to the determination of zirconium in ore samples with satisfactory results.     

Flow Injection Chemiluminescence for the Determination of Estriol via a Noncompetitive Enzyme Immunoassay

A novel approach to the detection of estriol using a flow injection system coupled to enhanced chemiluminescent immunoassay was developed based on noncompetitive immunoassay formats. A conjugated estriol-ovalbumin immobilized immunoaffinity column was inserted into the flow system to trap the unbound horseradish peroxidase (HRP)-labeled antibody after an off-line incubation of estriol and HRP-labeled anti-estriol antibody. The trapped enzyme conjugate was detected by the injection of chemiluminescent substrates to produce enhanced chemiluminescence. The linear range for the determination of estriol is 10.0 to 400 ng · mL⁻¹ with a correlation coefficient of 0.996 and a detection limit of 5.0 ng · mL⁻¹. The total time for sampling and chemiluminescent detection of one sample is 400 seconds after 30 min of pre-incubation. The results for pregnancy serum samples obtained by this method are in good agreement with those obtained using ELISA.     

Application of chitosan functionalized with 3,4-dihydroxy benzoic acid moiety for on-line preconcentration and determination of trace elements in water samples

Chitosan resin functionalized with 3,4-dihydroxy benzoic acid (CCTS-DHBA resin) was used as a packing material for flow injection (FI) on-line mini-column preconcentration in combination with inductively coupled plasma-atomic emission spectrometry (ICP-AES) for the determination of trace elements such as silver, bismuth, copper, gallium, indium, molybdenum, nickel, uranium, and vanadium in environmental waters. A 5-mL aliquot of sample (pH 5.5) was introduced to the minicolumn for the adsorption/preconcentration of the metal ions, and the collected analytes on the mini-column were eluted with 2 M HNO₃, and the eluates was subsequently transported via direct injection to the nebulizer of ICP-AES for quantification. The parameters affecting on the sensitivity, such as sample pH, sample flow rate, eluent concentration, and eluent flow rate, were carefully examined. Alkali and alkaline earth metal ions commonly existing in river water and seawater did not affect the analysis of metals. Under the optimum conditions, the method allowed the determination of metal ions with detection limits of 0.08 ng mL⁻¹ (Ag), 0.9 ng mL⁻¹ (Bi), 0.07 ng mL⁻¹ (Cu), 0.9 ng mL⁻¹ (Ga), 0.9 ng mL⁻¹ (In), 0.08 ng mL⁻¹ (Mo), 0.09 ng mL⁻¹ (Ni), 0.9 ng mL⁻¹ (U), and 0.08 ng mL⁻¹ (V). By using 5 mL of sample solution, the enrichment factor and collection efficiency were 8–12 fold and 96–102%, respectively, whereas the sample throughput was 7 samples/hour. The method was validated by determining metal ions in certified reference material of river water (SLRS-4) and nearshore seawater (CASS-4), and its applicability was further demonstrated to river water and seawater samples.     

Voltammetric study of the interaction of the ofloxacin–copper complex with DNA, and its analytical application

The electrochemical behavior of the ofloxacin–copper complex, Cu(II)L₂, at a mercury electrode, and the interaction of DNA with the complex have been investigated. The experiments indicate that the electrode reaction of Cu(II)L₂ is an irreversible surface electrochemical reaction and that the reactant is of adsorbed character. In the presence of DNA, the formation of the electrochemically non-active complexes Cu(II)L₂-DNA, results in the decrease of the peak current of Cu(II)L₂. Based on the electrochemical behavior of the Cu(II)L₂ with DNA, binding by electrostatic interaction is suggested and a new method for determining nucleic acid is proposed. Under the optimum conditions, the decrease of the peak current is in proportional to the concentration of nucleic acids in the range from 3 × 10⁻⁸ to 3 × 10⁻⁶ g · mL⁻¹ for calf thymus DNA, from 1.6 × 10⁻⁸ to 9.0 × 10⁻⁷ g · mL⁻¹ for fish sperm DNA, and from 3.3 × 10⁻⁸ to 5.5 × 10⁻⁷ g · mL⁻¹ for yeast RNA. The detection limits are 3.3 × 10⁻⁹, 6.7 × 10⁻⁹ and 8.0 × 10⁻⁹ g · mL⁻¹, respectively. The method exhibits good recovery and high sensitivity in synthetic samples and in real samples.     

Electrochemical determination of lead(II) using a montmorillonite calcium-modified carbon paste electrode

Utilizing the fascinating properties of montmorillonite calcium (MMT-Ca), such as huge cationic exchange capacity, strong adsorptive ability, high chemical and mechanical stability, an MMT-Ca modified carbon paste electrode (CPE) was constructed for the sensitive determination of Pb²⁺. In 0.01 mol·L⁻¹ HCl, Pb²⁺ was firstly exchanged and accumulated on an MMT-Ca modified CPE surface and secondly reduced to Pb at −0.90 V. In the following potential sweep from −0.90 to −0.50 V, reduced Pb was oxidized, resulting in an obvious stripping peak at −0.58 V. After optimizing the parameters, such as determining medium, content of MMT-Ca, accumulation potential and time, an electrochemical method was developed for the analysis of Pb²⁺. Compared with bare CPE, the MMT-Ca modified CPE significantly enhances the sensitivity of Pb²⁺ analysis. The limit of detection is evaluated to be 6.0 × 10⁻⁹ mol L⁻¹ Pb²⁺. Finally, this method was successfully employed to determine trace levels of Pb²⁺ in water samples. The first two authors contribute equally do this work     

Electrochemical behavior of lead(II) at poly(phenol red) modified glassy carbon electrode, and its trace determination by differential pulse anodic stripping voltammetry

Poly(phenol red) (denoted as PPR) films were electrochemically synthesized on the surface of a glassy carbon electrode (GCE) by cyclic voltammetry to obtain a chemically modified electrode (denoted as PPR-GCE). The growth mechanism of PPR films was studied by attenuated total reflection spectroscopy. This PPR-GCE was used to develop a novel and reliable method for the determination of trace Pb²⁺ by anodic stripping differential pulse voltammetry. At optimum conditions, the anodic peak exhibits a good linear concentration dependence in the range from 5.0 × 10⁻⁹ to 5.0 × 10⁻⁷ mol L⁻¹ (r = 0.9989). The detection limit is 2.0 × 10⁻⁹ mol L⁻¹ (S/N = 3). The method was employed to determine trace levels of Pb²⁺ in industrial waste water samples. Correspondence: Gongjun Yang, Ming Shen, College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, P.R. China     

Development of a liquid chromatography-mass spectrometry method for the determination of ursolic acid in rat plasma and tissue: application to the pharmacokinetic and tissue distribution study

A fast and sensitive liquid chromatography–mass spectrometry method was developed for the determination of ursolic acid (UA) in rat plasma and tissues. Glycyrrhetinic acid was used as the internal standard (IS). Chromatographic separation was performed on a 3.5 μm Zorbax SB-C18 column (30 mm × 2.1 mm) with a mobile phase consisting of methanol and aqueous 10 mM ammonium acetate using gradient elution. Quantification was performed by selected ion monitoring with (m/z)⁻ 455 for UA and (m/z)⁻ 469 for the IS. The method was validated in the concentration range of 2.5 − 1470 ng mL⁻¹ for plasma samples and 20 − 11760 ng g⁻¹ for tissue homogenates. The intra- and inter-day assay of precision in plasma and tissues ranged from 1.6% to 7.1% and 3.7% to 9.0%, respectively, and the intra- and inter-day assay accuracy was 84.2 − 106.9% and 82.1 − 108.1%, respectively. Recoveries in plasma and tissues ranged from 83.2% to 106.2%. The limits of detections were 0.5 ng mL⁻¹ or 4.0 ng g⁻¹. The recoveries for all samples were >90%, except for liver, which indicated that ursolic acid may metabolize in liver. The main pharmacokinetic parameters obtained were T _max = 0.42 ± 0.11 h, C _max = 1.10 ± 0.31 μg mL⁻¹, AUC = 1.45 ± 0.21 μg h mL⁻¹ and K _a = 5.64 ± 1.89 h⁻¹. The concentrations of UA in rat lung, spleen, liver, heart, and cerebellum were studied for the first time. This method is validated and could be applicable to the investigation of the pharmacokinetics and tissue distribution of UA in rats.     

Development of a highly precise ID-ICP-SFMS method for analysis of low concentrations of lead in rice flour reference materials

Microwave digestion and isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-SFMS) has been applied to the determination of Pb in rice flour. In order to achieve highly precise determination of low concentrations of Pb, the digestion blank for Pb was reduced to 0.21 ng g⁻¹ after optimization of the digestion conditions, in which 20 mL analysis solution was obtained after digestion of 0.5 g rice flour. The observed value of Pb in a non-fat milk powder certified reference material (CRM), NIST SRM 1549, was 16.8 ± 0.8 ng g⁻¹ (mean ± expanded uncertainty, k = 2; n = 5), which agreed with the certified value of 19 ± 3 ng g⁻¹ and indicated the effectiveness of the method. Analytical results for Pb in three brown rice flour CRMs, NIST SRM 1568a, NIES CRM 10-a, and NIES CRM 10-b, were 7.32 ± 0.24 ng g⁻¹ (n = 5), 1010 ± 10 ng g⁻¹ (n = 5), and 1250 ± 20 ng g⁻¹ (n = 5), respectively. The concentration of Pb in a candidate white rice flour reference material (RM) sample prepared by the National Metrology Institute of Japan (NMIJ) was observed to be 4.36 ± 0.28 ng g⁻¹ (n = 10 bottles). Figure Digestion blank of Pb was carefully reduced to approximately 0.2 ng g^-1 which permitted the highly precise determination of Pb at low ng g^-1 level in foodstuff samples by ID-SFMS     

Ammonium pyrrolidinedithiocarbamate-modified activated carbon micro-column extraction for the determination of As(III) in water by graphite furnace atomic absorption spectrometry

A simple and selective method using ammonium pyrrolidinedithiocarbamate modified activated carbon (APDC-AC) as solid phase extractant has been developed for speciation of As(III) in water samples. At pH 1.8–3.0, As(III) could be adsorbed quantitatively by APDC-AC, and then eluted completely with 2.0 mL of 0.1 mol L⁻¹ HNO₃, while As(V) could almost not be retained at pH 1–7. Effects of acidity, sample flow rate, concentration of elution solution and interfering ions on the recovery of As(III) have been systematically investigated. Under the optimal conditions, the adsorption capacity of APDC-AC for As(III) is 7.3 mg g⁻¹. The detection limit (3σ) of As(III) is 0.05 ng mL⁻¹ for graphite furnace atomic absorption spectrometry (GFAAS) with enrichment factor of 50, and the relative standard deviation (RSD) is 4.1% (n = 9, C = 5 ng mL⁻¹). The method has been applied to the determination of trace As(III) in water, and the recoveries of As(III) are 100 ± 10%. Correspondence: Yiwei Wu, Department of Chemistry and Environmental Engineering, Hubei Normal University, Huangshi 435002, P.R. China     

Study on the Catalytic Determination of Vanadium (V) Using the Rhodamine 6G-Periodate Redox Reaction and its Analytical Application

 A fluorescence quenching method for the determination of vanadium (V) based on the vanadium- catalyzed oxidation of rhodamine 6G (R6G) with periodate in the presence of ethylenediaminetetraacetic acid disodium salt (EDTA) in sulfuric acid medium is described. The fluorescence was measured with excitation and emission wavelengths of 525 and 555 nm, respectively. The calibration graph for vanadium (V) had linear ranges of 3.0 × 10⁻⁹–1.5 × 10⁻⁸ mol/l and 1.5 × 10⁻⁸–4.0 × 10⁻⁸ mol/l, respectively. The detection limit was 1.7 × 10⁻⁹ mol/l. The proposed method was successfully applied to the determination of vanadium (V) in river water, rain water and cast iron samples. Received June 29, 2001 Revision October 9, 2001     

Growth and characterization of Mn- and Co-doped ZnO nanowires

A flow injection chemiluminescence method is proposed for the determination of cobalt, based on the strong catalytic effect of Cobalt(II) (1,10-phenanthroline)₃ complex on the lucigenin-periodate reaction in alkaline medium. Under the optimum experimental conditions, the chemiluminescence signal responded linearly to the concentration of cobalt(II) in the 1.0 × 10⁻⁹–3.0 × 10⁻⁷ g mL⁻¹ range with a detection limit of 4.4 × 10⁻¹⁰ g mL⁻¹ cobalt(II). The relative standard deviation for the determination of 5.0 × 10⁻⁸ g mL⁻¹ of cobalt was 2.3% in eleven replicated measurements. The method was successfully applied to the determination of cobalt(II) in pharmaceutical preparations.     

Determination of trace Cd and Pb in natural waters by direct single drop microextraction combined with electrothermal atomic absorption spectrometry

A new method of direct single-drop microextraction combined with electrothermal atomic absorption spectrometry (ETAAS) is presented for the determination of trace Cd and Pb with dithizone (H₂DZ) as chelating reagent. Factors influencing the microextraction efficiency and determination, such as pH, microdrop volume, stirring rate, extraction time were evaluated. Under the optimized experimental conditions, the detection limits of the method are 2 and 90 pg mL⁻¹ for Cd and Pb, and the relative standards deviations for 0.5 ng mL⁻¹ Cd and 10 ng mL⁻¹ Pb are 11 and 12.8%. After 10 min of extraction, the enrichment factors for Cd and Pb are 118 and 90, respectively. The results for the determination of Cd and Pb in tap water, spring water, river water, pond water, lake water and spiked water samples demonstrate the accuracy, recovery and applicability of the method. An environmental water certified reference material (GSBZ 50009-88) was analyzed, and the determined values are in a good agreement with the certified values. Correspondence: Bin Hu, Department of Chemistry, Wuhan University, Wuhan 430072, P.R. China     

Trace analysis of triasulfuron and bensulfuron-methyl in water samples using a carbon nanotubes packed cartridge in combination with high-performance liquid chromatography

This paper describes a simple, rapid and sensitive method for the determination of triasulfuron and bensulfuron-methyl using a multi-walled carbon nanotube-packed cartridge as the preconcentration step prior to analysis by high-performance liquid chromatography. The experimental results indicate an excellent linear correlation between the peak area and the concentration for triasulfuron and bensulfuron-methyl over the concentration range of 0.08–80 and 0.04–40 ng · mL⁻¹, and the correlation coefficients are 99.93 and 99.38%, respectively. The detection limits are 22.4 and 2.9 ng · L⁻¹ based on the signal being three times the baseline noise (S/N = 3). The precision of the method is satisfactory at a very low level, and the relative standard deviations (RSD) are 2.6 and 4.8% (n = 6), respectively. Satisfactory recoveries were achieved with spiked real water samples, inferring that the established method can be applied to real sample analysis.     

Determination of Yttrium by Resonance Light Scattering Technique

 Yttrium was determined by means of the resonance light scattering (RLS) technique. The characteristics of resonance light scattering spectra of yttrium-1, 6-bi(1′-phenyl-3′-methyl-5′-pyrazolone-4′-) hexanedione (BPMPHD), the effective factors and optimum conditions were studied. In the pH range of 5.0–6.1, yttrium-BPMPHD complex produces three characteristic peaks of RLS at 365, 402 and 467 nm. The enhanced intensity of RLS is proportional to the concentration of yttrium in the range of 1.0×10⁻⁸ to 1.0×10⁻⁵ mol · L⁻¹. The limit of detection is 5.9×10⁻⁹ mol · L⁻¹. The method has been used for the determination of Y³⁺ in mixed rare earths. Correspondence: Key Lab for Colloid and Interface Chemistry of Education Ministry, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, People’s Republic of China. e-mail: wux@sdu.edu.cn Received July 3, 2002; accepted October 20, 2002     

Speciation Analysis of Antimony (III) and Antimony (V) by Flame Atomic Absorption Spectrometry After Separation/Preconcentration With Cloud Point Extraction

A sensitive and simple method for flame atomic absorption spectrometry (FAAS) determination of antimony species after separation/preconcentration by cloud point extraction (CPE) has been developed. When the system temperature is higher than the cloud point extraction temperature, the complex of antimony (III) with N-benzoyl-N-phenyhydroxylamine (BPHA) can enter the surfactant-rich phase, whereas the antimony (V) remains in the aqueous phase. Antimony (III) in surfactant-rich phase was analyzed by FAAS and antimony (V) was calculated by subtracting of antimony (III) from the total antimony after reducing antimony (V) to antimony (III) by L-cysteine. The main factors affecting the cloud point extraction, such as pH, concentration of BPHA and Triton X-114, equilibration temperature and time, were investigated systematically. Under optimized conditions, the detection limits (3σ) were 1.82 ng mL⁻¹ for Sb(III) and 2.08 ng mL⁻¹ for Sb(total), and the relative standard deviations (RSDs) were 2.6% for Sb(III) and 2.2% for Sb(total). The proposed method was applied to the speciation of antimony species in artificial seawater and wastewater, and recoveries in the range of 95.3–106% were obtained by spiking real samples. This technique was validated by means of reference water materials and gave good agreement with certified values.     

Molecularly imprinted on-line solid-phase extraction combined with chemiluminescence for the determination of pazufloxacin mesilate

A novel molecularly imprinted polymer solid-phase extraction (MISPE) with flow-injection chemiluminescence (CL) was developed for the determination of pazufloxacin mesilate (PZFX). The molecularly imprinted polymer (MIP) was synthesized by using PZFX as the imprinting molecule. A glass tube packed the particles of the MIP was employed as MISPE micro-column, which was connected into the sampling loop of the eight-way injection valve for on-line selective preconcentration and extraction of PZFX. The eluent of acetonitrile:acetic acid (9:1, v:v) was used as carrier for eluting the adsorbed PZFX to react with the mixture of cerium(IV) and sodium sulfite in the flow cell to produce strong CL. The relative intensity of CL was linear to PZFX concentration in the range from 2.5 × 10⁻⁹ to 2.5 × 10⁻⁷ g mL⁻¹. The limit of detection was 7 × 10⁻¹⁰ g mL⁻¹ (3 σ) and the relative standard deviation for 5 × 10⁻⁸ g mL⁻¹of PZFX solution was 3.7% (n = 7). This method has been applied to the determination of PZFX in human urine.     

HPLC determination of cefotaxime and cephalexine residues in milk and cephalexine in veterinary formulation

An HPLC method was developed and validated for the determination of the cephalosporins cefotaxime and cephalexine in skimmed bovine milk. The analytical column, Kromasil C₁₈ (250 mm × 4.0 mm, 5 μm) was operated at ambient temperature. Mobile phase consisted of CH₃OH-acetate buffer (pH = 4.0) and it was delivered isocratically at a flow rate of 1.0 mL · min⁻¹. Total analysis time was less than 5 min. Caffeine was used as internal standard (5 ng · μL⁻¹). UV detection was performed at 265 nm. Method validation was performed by means of intra-day (n = 5) and inter-day accuracy and precision (n = 8), sensitivity and linearity. Limits of detection (LOD) and limits of quantification (LOQ) were 0.1 and 0.3 ng · μL⁻¹, respectively. The method was applied to the analysis of a veterinary drug (CEPOREX) containing cephalexine. The results were quite accurate with the relative error varying from −8.0 to −3.5%. Solid-phase extraction was applied to remove all matrix interference from milk samples. High extraction recoveries (average 84–121%) were achieved by using Abselut NEXUS cartridges with acetonitrile as eluent and a rinsing step with water and n-butanol. A pre-concentration step was necessary in a 1/10 level to reach the EU MRL concentration level (100 μg · kg⁻¹). RSD values were less than 7% for both cephalosporins. Correspondence: Ioannis N. Papadoyannis, Laboratory of Analytical Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece     

Analysis of phosphate rock samples for vanadium using accelerator-based thermal neutrons

Extensive sedimentary phosphate deposits exist in the Sirhan-Turayf basin in northwestern Saudi Arabia containing significant amounts of uranium, thorium, vanadium and rare earth elements. The determination of the concentration and pattern of distribution of some of these elements is essential for economic aspects. This study reports the analysis of vanadium in selected phosphate rock samples from the basin using accelerator-based thermal neutrons activation analysis (TNAA). Samples were irradiated in a thermal neutron flux of 2.5·10⁶ n·cm⁻²·s⁻¹. The induced activity was measured with a HP-GMX detector coupled to a PC-based data acquisition and analysis system. The facility was calibrated using certified standards of vanadium. The minimum detection limit of vanadium was about 1 mg. Three independent measurements on each sample yielded comparable results indicating the reliability of the technique. The vanadium concentrations in the samples vary from 23 to 457 ppm. This revised version was published online in July 2006 with corrections to the Cover Date.