Determination of urinary arsenic species using an on-line nano-TiO2 photooxidation device coupled with microbore LC and hydride generation-ICP-MS system

We have developed an on-line digestion device-based on the nano-TiO₂-catalyzed photooxidation of arsenic species—for coupling between microbore anion-exchange chromatography (μ-LC) and hydride generation (HG)-inductively coupled plasma mass spectrometry (ICP-MS) systems that can be used for the determination of urinary arsenic species. To maximize the signal intensities of the desired arsenic species, we optimized the photocatalytic oxidation efficiency of the analyte species and developed a rapid on-line pre-reduction process for converting the oxidized species into As(III) prior to HG-ICP-MS determination. Under the optimized conditions for the nano-TiO₂-catalyzed photooxidation-i.e., using 1 g of nano-TiO₂ per-liter, at pH 5.2, and illuminating for 3 min- As(III), monomethylarsenoic acid (MMA), and dimethylarseinic acid (DMA) can be converted quantitatively into As(V). To attain maximal hydride generation efficiency, 0.5% Na₂S₂O₄ solution, which can reduce As(V) to As(III) virtually instantaneously upon on-line mixing, was added as a pre-reductant prior to performing the HG step. In light of all the HG efficiency of tested arsenicals were improved and a segmented-flow technique was employed to avoid the loss of peak resolution when using our proposed on-line μ-LC-UV/nano-TiO₂/HG-ICP-MS, the detection limits for As(III), MMA, DMA, and As(V) were all in the range of sub-microgram-per-liter (based on 3 sigma). A series of validation experiments-analysis of neat and spiked urine samples-indicated that our proposed methods can be applied satisfactorily to the determination of As(III), MMA, DMA, and As(V) in urine samples.     

Speciation determination of arsenic in urine by high-performance liquid chromatography-hydride generation atomic absorption spectrometry with on-line ultraviolet photooxidation

A coupled system for arsenic speciation determination based on high-performance liquid chromatography (HPLC), on-line UV photooxidation and continuous-flow hydride generation atomic absorption spectrometry (HGAAS) was built from commercially available modules with minor modifications to the electronic interface, the software and the gas-liquid separator. The best results were obtained with strong anion-exchange columns, Hamilton PRP X-100 and Supelcosil SAX 1, and gradient elution with phosphate buffers containing KH2PO4-K2HPO4. The on-line UV photooxidation with alkaline peroxodisulfate, 4% m/v K2S2O8-1 mol l-1 NaOH, in a PTFE knotted reactor for 93 s ensures the transformation of inorganic AsIII, monomethylarsonate, dimethylarsinate, arsenobetaine, arsenocholine, trimethylarsine oxide and tetramethylarsonium ion to arsenate. About 32-36 HPLC-UV-HGAAS runs could be performed within 8 h, with limits of detection between 2 and 6 micrograms l-1 As, depending on the species. The method was applied to the analysis of spot urine samples and certified urine reference materials (CRMs). Upon storage at 4 degrees C, reconstituted CRMs are stable for at least 2 weeks with respect to both their total arsenic content and the individual species distribution.     

Determination of bismuth in biological samples using on-line flow-injection microwave-assisted mineralization and precipitation/dissolution for electrothermal atomic absorption spectrometry

An on-line automated flow injection system with microwave-assisted sample digestion for the electrothermal atomic absorption spectrometric determination of bismuth in biological materials is described. After the exposure of the sample to microwave radiation, the analyte was subject to a precipitation/dissolution process. Bismuth was precipitated with the stannite ion in basic medium and collected on the walls of a knotted coil, while the other matrix components flowed downstream to waste. The precipitate was dissolved with nitric acid and a sub-sample was collected in a capillary of a sampling arm assembly, to introduce 20 mul volumes into the graphite tube by means of positive displacement with air through a time-based injector. The analytical figures of merit were first evaluated by filling the sampling arm with a standard solution of bismuth and thereafter injecting aliquots of this solution into the atomizer. The calibration graph was linear from the detection limit (8 pg) to 1.2 ng of bismuth. The sensitivity was of 26.8 mug l(-1) for 0.2 A-s and the characteristic mass (m(o)) was of 11.8 pg/0.0044 A-s. The precision of the method, evaluated by replicate analyses of solutions containing 20 and 200 pg of bismuth, were 5.5 and 3.0% (n=10), respectively. When solutions were introduced in the flow system here described, the calibration graph was linear in the range 0.04-6.0 mug l(-1), which means that a preconcentration factor of 10 was obtained for bismuth. The precision slightly deteriorated, e.g. the replicate analysis of solutions containing 1 and 10 pg of bismuth were 7.1 and 5.3% (n=10), respectively. However, the recoveries values obtained with urine and whole blood bismuth spiked samples were over 96.5% and the agreement between observed and certified values was good.     

Determination of trace metals in urine with an on-line ultrasound-assisted digestion system combined with a flow-injection preconcentration manifold coupled to flame atomic absorption spectrometry

A flow analysis method with on-line sample digestion/minicolumn preconcentration/flame atomic absorption spectrometry is described for the determination of trace metals in urine. First, urine sample was on-line ultrasound-assisted digested exploiting the stopped-flow mode, and then the metals were preconcentrated passing the pre-treated sample through a minicolumn containing a chelating resin. A home-made minicolumn of commercially available imminodiacetic functional group resin, Chelite Che was used to preconcentrate trace metals (Cu, Fe, Mn and Ni) from urine. The proposed procedure allowed the determination of the metals with detection limits of 0.5, 1.1, 0.8 and 0.8 μg L⁻¹, for Cu, Fe, Mn and Ni, respectively. The precision based on replicate analysis was less than ±10.0%, and the enrichment factor obtained was between 21.3 (Mn) and 44.1 (Ni), for sample volumes between 2.5 and 5.0 mL, and an eluent volume of 110 μL. This procedure was applied for determination of metals in urine of workers exposed to welding fumes and urine of unexposed persons (urine control).     

Determination of phenol at ng l-1 level by flow-injection chemiluminescence combined with on-line solid-phase extraction

In this paper, a simple flow-injection chemiluminescence (CL) system combined with on-line solid-phase extraction is presented to determine phenol. This method is based on the enhancement effect of phenol on the luminol-K3Fe(CN)6 CL system. The solid-phase extraction promised the high sensitivity and improved selectivity of CL detection. With the calibration range from 4.7 ng l-1 to 470 ng l-1 phenol concentration, the proposed method was applied to analyzing phenol in water samples and the obtained results were validated by the standard method. The detection limit was determined as 0.66 ng l-1. The relative standard deviation was 1.5% for determining 4.7 ng l-1 phenol standard (n=7).     

Determination of total cationic and total anionic arsenic species in oyster tissue using microwave-assisted extraction followed by HPLC-ICP-MS

A microwave-assisted digestion procedure was developed in presence of concentrated nitric acid (2.0 ml) and 30% hydrogen peroxide (0.20 ml) using a closed pressurized microwave digestion system for the determination of total anionic and total cationic arsenic compounds reside in oyster tissue. At 450 W for 15 min digestion, 74% of anionic arsenic, and 31% of cationic arsenic (105% total arsenic) were retrieved. At 300 W microwave power, 68% of anionic and 30.5% of cationic arsenic (98.5% total arsenic), and 100 W, 63% of anionic and 31% of cationic arsenic (94% total arsenic) were extracted out. The methanol water mixture (9:1) was cull out, exclusively 31.6% of anionic and 29% of cationic arsenic compounds (60.6% total). The dimethylarsinoylriboside (phosphate-arsenosugar) was the predominant arsenic species, along with arsenobetaine (AB), dimethylarsinic acid (DMA), inorganic arsenic, methylarsonic acid (MA), arsenocholine (AC), trimethylarsineoxide (TMAO) and tetramethylarsonium ion (TMI). Some other arsenic compounds, those were not matched with the retention time of the available standards, were also detected. Arsenosugar was fragile and adequately transmuted to DMA (100%), AB and AC to TMAO (100%) when 450 W microwave power was applied for 15 min. The separation and quantification of arsenic compounds in the microwave digests and extracts, were carried out in anion (PRP-X100) and cation (LC-SCX) exchange columns using ICP-MS as arsenic specific detector. The procedure was also validated by determining the total cationic and total anionic arsenic compounds present in DORM 1.     

Determination of ambroxol hydrochloride in tablets using flow-injection UV spectrophotometry and HPLC

A flow-injection UV spectrophotometric method was developed for the determination of ambroxol hydrochloride in tablets. The quantitative determination of ambroxol was performed at 245 nm using distilled water as the carrier solvent. In this study, the flow rate, loop volume, and the number of injections per hour were 15 mL/min, 193 μL, and 100, respectively. The analytical signal of ambroxol was linear in the concentration range of 40–200 μg/mL. The detection limit and limit of quantification were found as 11.55 and 38.49 μg/mL, respectively. The results for the determination of ambroxol in tablets, 29.99 ± 0.23 mg (mean ± SD), were in good agreement with the labeled quantities (30 mg/tablet). A relatively high recovery value (100.4%) shows the accuracy of the proposed method. Furthermore, the results obtained were in accordance with those obtained by the HPLC method, which were used as a comparison method for the determination of ambroxol HCl, as far as the Student’s t-test and Fisher test results were concerned. It was concluded that the proposed flow-injection UV spectrophotometric method was fast, accurate, precise, and suitable for automation in the determination of ambroxol. The text was submitted by the authors in English.     

氧弹燃烧-氢化物发生-原子吸收法测定硫磺中砷

研究了氧弹燃烧、NaOH溶液吸收预处理硫磺样品的方法,优化了HG-AAS法测定砷的最佳条件。     

Determination of nitrate by flow-injection analysis with an on-line anion-exchange column

Nitrate (? 6 × 10^-4 M) is determined by displacing thiocyanate froman anion-exchange mini-column and determining it spectrophotometrically after reaction with iron (III). The efficiency of lead- and silver-loaded ion-exchange columns in removing anionic interferences is investigated. It is found necessary to incorporate a copperized cadmium reductor to reduce lead or silver ions released by these columns, which otherwise depress the nitrate response. Incorporation of a lead/silver ion-exchange column allows the determination of nitrate in tap water.     

Determination of ultra-trace amounts of arsenic(III) by flow-injection hydride generation atomic absorption spectrometry with on-line preconcentration by coprecipitation with lanthanum hydroxide or hafnium hydroxide

A time-based flow-injection (FI) procedure for the determination of ultra-trace amounts of inorganic arsenic(III) is described, which combines hydride generation atomic absorption spectrometry (HG-AAS) with on-line preconcentration of the analyte by inorganic coprecipitation-dissolution in a filterless knotted Microline reactor. The sample and coprecipitating agent are mixed on-line and merged with an ammonium buffer solution, which promotes a controllable and quantitative collection of the generated hydroxide on the inner walls of the knotted reactor incorporated into the FI-HG-AAS system. Subsequently the precipitate is eluted with 1 mol 1(-1) hydrochloric acid, allowing ensuing determination of the analyte via hydride generation. The preconcentration of As(III) was tested by coprecipitation with two different inorganic coprecipitating agents namely La(III) and Hf(IV). It was shown that As(III) is more effectively collected by lanthanum hydroxide than by hafnium hydroxide, the sensitivity achieved by the former being approximately 25% better. With optimal experimental conditions and with a sample consumption of 6.7 ml per assay, an enrichment factor of 32 was obtained at a sample frequency of 33 samples h(-1). The limit of detection (3sigma) was 0.003 microg 1(-1) and the precision (relative standard deviation) was 1.0% (n = 11) at the 0.1 microg 1(-1) level.     

Methods for the separation and quantification of arsenic species in SRM 2669: arsenic species in frozen human urine

Two independent liquid chromatography inductively coupled plasma-mass spectrometry (LC/ICP-MS) methods for the separation of arsenic species in urine have been developed with quantification by standard additions. Seven arsenic species have been quantified in a new NIST frozen human urine Standard Reference Material (SRM) 2669 Arsenic Species in Frozen Human Urine, Levels 1 and 2. The species measured were: arsenite (As(III)), arsenate (As(V)), monomethylarsonate (MMA), dimethylarsinate (DMA), arsenobetaine (AB), arsenocholine (AC), and trimethylarsine oxide (TMAO). The purity of each arsenic standard used for quantification was measured as well as the arsenic species impurities determined in each standard. Analytical method limits of detection (L _D) for the various species in both methods ranged from 0.2 to 0.8 μg L⁻¹ as arsenic. The results demonstrate that LC/ICP-MS is a sensitive, reproducible, and accurate technique for the determination of low-level arsenic species in urine. Measurements of the arsenic species 3 years after initial production of the SRM demonstrate the stability of the arsenic species in the urine reference material.     

Determination of gatifloxacin in drug formulations,human urine,and serum samples using energy transfer chemiluminescence coupled with flow-injection analysis

A simple and sensitive method for the determination of gatifloxacin (GFLX) is developed by using flow injection analysis with potassium permanganate-sodium sulfite chemiluminescence (CL) detection based on the energy transfer from GFLX to terbium(III). Intense signal instead of the weak CL produced by potassium permanganate-sulfite-GFLX system can be observed when Tb(III) is added to the system. A narrow and intense emission band at 545 nm arising from the excited-state Tb(III) was obtained. Under the optimum conditions, a linear range was 5.0 × 10^?8 to 8.0 × 10^?6 M and the detection limit was 3.2 × 10^?9 M. The method has been successfully applied to the determination of gatifloxacin in drug formulations, urine and serum samples. There was no interference from some common excipients used in pharmaceutical preparations. The possible energy transfer mechanisms in the lanthanide complexes were discussed.     

氢化物发生电加热石英管原子吸收法测定包头铁矿中的砷、锑、铋

研究了氢化物发生原子吸收法测定包头矿中痕量砷、锑、铋的分析方法,试验确立了反应条件,建立了以KI、抗坏血酸、硫脲为还原体系,消除试样中共存元素的干扰,利用KMnO4消除锑对砷的干扰.砷、锑、铋的检出限可分别达到:0.15,0.28,0.15 ng/mL.方法已用于包头矿分析.     

高效液相色谱法测定生物样品中多种蝶呤类化合物

建立了一种同时分离测定人体尿液中4种蝶呤类化合物(新蝶呤、异黄蝶呤、蝶呤和生物蝶呤)的高效液相色谱法。采用SHIMADZU Shim-pack:Vp-ODS(250 mm×4.6 mm×5μm)色谱柱结合荧光检测器,在流动相为甲醇-水(10+90),流速1.0mL/min,荧光检测波长Ex390 nm,Em450 nm,柱温为室温的色谱条件下,4种蝶呤类化合物分离效果良好。尿液经0.45μm的一次性滤膜过滤,取10μL滤液直接进样测定。结果表明,各组分的线性范围为:新蝶呤0.05～1.20μg/mL,异黄蝶呤0.05～0.80μg/mL,蝶呤0.05～1.00μg/mL,生物蝶呤0.05～1.00μg/mL。4种组分的检测限均为0.01μg/mL。该方法可应用于临床癌症病人和健康人尿样中4种蝶呤类化合物的检测。     

Continuous solid-phase extraction method for the determination of amines in human urine following on-line microwave-assisted acid hydrolysis

Humans are exposed to endogenous or exogenous formation of aromatic amines (AAs) and N-nitrosamines (NAms), which are considered to be potent carcinogens. The objective of this study was to monitor AAs and NAms in human urine to obtain a way to assess exposure. However, while NAms can be directly detected in urine samples, AAs require hydrolysis to convert their conjugates into free amines. A semiautomatic flow-base method is proposed for the simultaneous determination of aliphatic and aromatic NAms, anilines and chloroanilines in human urine in one analytical run. Conjugated AAs are released from urine by on-line microwave-assisted acid hydrolysis without degradation of NAms; all amines were then preconcentrated using solid-phase extraction. Separation/determinations are carried out by gas chromatography and mass spectrometry operating in selected ion monitoring mode. The method is fast (∼15 min for 25 mL of sample) and provides low limits of detection (from 2 to 26 ng/L) with good precision (relative standard deviation within and between days less than 7%). Finally, the proposed method was successfully applied to check AAs and NAms in the human urine of exposed and unexposed researchers. The kinetics of amine excretion in the urine of the researchers exposed is calculated after termination of the exposure and shows half-life times between 1.3 and 2.1 h, and that the dosage absorbed was eliminated within 6 h after exposure.     

Chemiluminescence assay for uric acid in human serum and urine using flow-injection with immobilized reagents technology

A novel chemiluminescence (CL) flow sensor for the determination of uric acid in human urine and serum has been developed by using controlled-reagent-release technology. The reagents involved in the chemiluminescence (CL) reaction, luminol and periodate, are immobilized on anion-exchange resin packed in a column. After injection of water, chemiluminescence generated by released luminol and periodate in alkaline media is inhibited in presence of uric acid. By measuring the decreased chemiluminescence (CL) intensity the uric acid is sensed. The decreased response is linear in the 5.0-500.0 ng mL(-1) range, with a detection limit of 1.8 ng mL(-1). The flow sensor showed remarkable operational stability and could be easily reused for over 80 h with sampling frequency of 100 h(-1). The proposed sensor was applied to the determination of uric acid in human urine and serum, and monitoring metabolic uric acid in human urine with RSD less than 3.0%.     

Determination of nitrate with a flow-injection system combining square-wave polarographic detection with on-line deaeration

The combination of a flow-injection system with square-wave polarography and on-line deaeration is applied to the determination of nitrate, utilizing the catalytic reaction between nitrate and uranyl ion. The method is simple, rapid (60 samples h^?1), sensitive and accurate, with a detection limit of 2 μM nitrate. The method has been applied to the determination of nitrate in drinking and river waters.     

Determination of arsenic in the presence of high copper concentrations using flow-injection analysis-hydride atomic absorption spectrometry

Summary Arsenic is determined in environmental samples containing metal ions up to 10,000 mg/l copper, 200 mg/l lead, 200 mg/l iron and 200 mg/l nickel by using the FIA-hydride-AAS technique. In the presented sample preparation method arsenic is prereduced and the interfering metal ions are precipitated. As signal depressions from metal ions are excluded, a detection limit of 1 g/l arsenic is achieved.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday     

Determination of Meldonium in human urine by HPLC with tandem mass spectrometric detection

A procedure is proposed for determining Meldonium in human urine, including sample preparation to analysis and analyte determination by HPLC with tandem mass spectrometric detection. For sample preparation, the procedure of “dilute-and-shoot” was used. The lower limit of the analytical range is 10 ng/mL; the limit of detection is 7.5 ng/mL; and the linearity range is 10–250 ng/mL. The proposed procedure is tested on real samples obtained from volunteers. A possibility of the direct analysis of urine samples after dilution is demonstrated; the limit of detection is 20 ng/mL. The high sensitivity of the procedure ensures its use for the determination of Meldonium in clinical diagnosis and doping control.