溶剂及电解质盐对氧在有机电解液体系中电化学还原的影响

应用线性循环伏安(CV)法研究了氧在几种有机电解液体系中的电化学还原过程.实验表明,氧在四丁基六氟磷酸铵(TBAPF6)/乙腈(MeCN)或TBAPF6/丙烯碳酸酯(PC)电解液中,均首先发生1电子还原生成O2-的过程,但电位回扫还原过程的可逆性却表现出很大差异:在乙腈溶液中反应可逆性较好,CV曲线表现出一对可逆的氧化还原峰,而在丙烯碳酸酯为溶剂的电解液中,氧还原过程可逆性差,不仅初始氧还原电流显著减小,而且表征O2-氧化的电流峰几乎消失.此外,电解质盐对氧还原过程也具有很大影响,在六氟磷酸锂(LiPF6)/乙腈电解液中,氧的还原可逆性较差.     

多壁碳纳米管固相微萃取纤维制备及其在海水中多溴联苯测定中的应用

通过以Nation为黏合剂、不锈钢丝为涂层载体,制备了多壁碳纳米管固相微萃取纤维．该纤维的制备方法快速、简便、成本低,并具有热稳定性好（300℃）、使用寿命长（〉100次）、对多溴联苯萃取效率高等特点．研究优化了影响萃取及分离效率的解吸温度和时间、萃取时间、搅拌速度、盐度等实验条件,进行了海水中多溴联苯的测定．对一溴联苯的线性范围为0．1-5．0ng／mL,而二溴联苯、三溴联苯、四溴联苯和五溴联苯的线性范围均为0．01～5．0ng／mL．方法的检测限为0．1～0．8ng／L．在优化的条件下分别测定了0．1和1ng／mL多溴联苯的海水加标样品,回收率在91．1％～107.3％之间,相对标准偏差小于12％．该方法分析时间短、灵敏度高、操作简便,适用于水样中多溴联苯的痕量分析．     

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.     

Simple solvent extraction technique for elimination of matrix interferences in the determination of methylmercury in environmental and biological samples by ethylation-gas chromatography-cold vapor atomic fluorescence spectrometry

A solvent extraction technique involving no critical clean-up steps was developed for the determination of methylmercury (MeHg) in environmental and biological samples by aqueous phase ethylation, room temperature precollection, gas chromatographic separation and cold vapor atomic fluorescence spectrometric detection. Samples were first digested with KOH-methanol. then acidified prior to extraction with methylene chloride. MeHg was back-extracted from the solvent phase into water prior to aqueous phase ethylation. Recoveries close to 100% were obtained with RSDs less than 5% for all samples analyzed, making direct standardization possible. The detection limits were about 0.08 ng g(-1) when analyzing 0.1 g of dry sea plant homogenate and 0.02 ng g when analyzing 0.5 g of wet sediment samples. Various certified reference materials and intercomparison samples, including sediments, sea plants and tissues, were analyzed, and the results were in good agreement with the certified values. The technique was applied to the determination of MeHg in both sea plants from the Atlantic and the red blood protein of dolphins from the Mediteranean Sea. in sediments from the Mediterranean Sea and Minnesota rivers and in soils from different origins. Concentrations of MeHg in dolphin red blood protein samples were as high as 300 ng g(-1).     

Sensitive derivatizatton reagents for the resolution of carboxylic acid enantiomers by high-performance liquid chromatography

Two highly sensitive, chiral derivatization reagents, D- and L-1-aminoethyl-4-dimethyl-aminonaphthalene, were synthesized from 1-dimethylaminonaphthalene. Condensation of carboxylic acids with the chiral reagent was readily effected in the presence of a watersoluble carbodiimide. The diastereoisomeric amides formed from N-acetylamino acid and α-arylpropionic acid enantiomers were efficiently resolved by normal phase chromatography (μPorasil column) -with hexane/ethyl acetate or hexane/tetrahydrofuran as a mobile phase. With a fluorescence detector (excitation 320 nm, emission 395 nm), the detection limit was 0.1 ng.     

Sensitive determination of fenpropathrin, cyhalothrin and deltamethrin in environmental water samples using multiwalled carbon nanotubes cartridge prior to HPLC

This paper described a new method for the trace determination of fenpropathrin, cyhalothrin and deltamethrin using multiwalled carbon nanotubes （MWCNTs） cartridge. Important parameters, such as the sample pH, eluent and its volume, sample flow rate and sample volume were investigated in detail. The linear ranges, the detection limits, and precisions （R.S.D.） were in the range of 0.1- 40 μg L^-11, 1.34.3 ng L^-1 and 2.3-2.8%, respectively. The performance of the proposed method was validated with real water samples, and the spiked recoveries were in the range of 91.7-117.8%, respectively. The experimental results demonstrated that the proposed method was an excellent alternative for the routine analysis of such pollutants in environmental samples. 2007 Qing Xiang Zhou. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.     

Fast determination of synthetic polycyclic musks in sewage sludge and sediments by microwave-assisted headspace solid-phase microextraction and gas chromatography–mass spectrometry

One-step in situ microwave-assisted headspace solid-phase microextraction (MA-HS-SPME) followed by gas chromatography–mass spectrometry (GC–MS) analysis is presented as a fast and solvent-free technique to determine synthetic polycyclic musks in sewage sludge and sediment samples. Six synthetic polycyclic musks (galaxolide (HHCB), tonalide (AHTN), celestolide (ADBI), traseolide (ATII), cashmeran (DPMI) and phantolide (AHMI)) were selected in the method development and validation. The effects of extraction parameters for the quantitative extraction of these analytes by one-step MA-HS-SPME were systematically investigated. The dewatered solid sample mixed with 20-mL deionized water (containing 3 g of NaCl in a 40-mL sample-vial) was efficiently extracted by a polydimethylsiloxane-divinylbenzene (PDMS-DVB) fiber placed in the headspace when the extraction slurry was microwave irradiated at 80 W for 5 min. The limits of detection (LODs) ranged from 0.04 to 0.1 ng/g, and the limits of quantification (LOQs) ranged from 0.1 to 0.3 ng/g (fresh weight). A preliminary analysis of sludge and sediment samples revealed that HHCB and AHTN were the two most commonly detected synthetic polycyclic musks; using a standard addition method, their total concentrations were determined to range from 0.3 to 10.9 ng/g (fresh weight) with relative standard deviation (RSD) ranging from 4% to 10%.     

Solid-phase extraction of triazole fungicides from water samples using disks impregnated with carbon nanotubes followed by GC-MS analysis

Triazole fungicides are pesticides widely employed in the cultivation of fruits, vegetables and grains. However, their ability to change the steroid hormone biosynthesis may result in endocrine complications for mammals, as well as changes in cholesterol and triglyceride levels and hepatotoxicity. The analysis of the triazole fungicides in superficial waters is important in order to monitor the risk for the biota. However, the use of efficient extraction procedures has been necessary in order to concentrate these pesticides before the analysis. In-disk solid-phase extraction (SPE) can be highlighted as a potential pre-concentration technique, mainly because the possibility to extract the analytes from a large sample volume, increasing the method detectability. Carbon nanotubes (CNTs) have been often used as solid extraction phase due to their high sorption capacity, surface area and internal volume, as well as mechanical, chemical and thermal stability. In this paper, we proposed the preparation of a new SPE disk impregnated with CNTs for the extraction of triazole fungicides from environmental water samples. The disks were obtained by acid corrosion of a cellulose membrane followed by its impregnation with CNTs. The developed method was validated for the analysis of triadimenol, tebuconazole and epoxiconazole, according to international validation protocols. The limits of quantification obtained for triadimenol, tebuconazole and epoxiconazole were 0.1, 0.1 and 0.05 µg L^?1, respectively. The linearity ranged from 0.05 to 10.00 µg L^?1 for epoxiconazole and from 0.1 to 10.00 µg L^?1 for triadimenol and tebuconazole, with correlation coefficients higher than 0.999 for all of them. The precisions, expressed as relative standard deviation, were lower than 12%. The accuracies were within ?12.07% to 17.7% (expressed as relative error).     

Development and validation of an HPLC-DAD method for the simultaneous determination of most common rice pesticides in paddy water systems

Rice crop is mainly cultivated in large river basins which constitute unique ecosystems and their ecological quality is invaluable. However, the high loads of pesticides used in rice cultivation contribute to the contamination of the water resources in such rice-cultivated regions. To regularly monitor the quality of such water resources there is a need for a rapid and sensitive multi-residue analytical method. This study presents the development and validation of a new analytical method for the simultaneous determination of most rice pesticides including penoxsulam, tricyclazole, propanil and its main metabolite 3,4-dichloroaniline, azoxystrobin, molinate, profoxydim and deltamethrin. A solid-phase extraction (SPE) procedure followed by high performance liquid chromatography (HPLC) with diode array detection (DAD) was used. A C₁₈ RP column operated at 30°C was utilised and the analytes were separated with a mobile phase of acetonitrile/water mixture in a linear gradient. Clean-up of water samples and isolation of pesticides was performed on SPE Bakerbond octadecyl cartridges and an ethyl acetate-dichlomethane mixture (9?:?1 v/v, 2?mL) was used for elution. Method validation was performed by means of intra-day (n?=?5) and inter-day accuracy and precision (n?=?8), sensitivity and linearity. The relative recoveries of the pesticides in paddy water samples were acceptable (80.6–110.2%) and the relative standard deviation (RSD%) ranged from 1.9 to 7.6%. Limits of detection (LOD) and limits of quantification (LOQ) varied from 0.1 to 0.8?ng?mL^?1 and 0.25 to 2.0?ng?mL^?1 respectively, depending on the analyte. The method was subsequently applied for the determination of pesticide residues in paddy and canal water samples. Tricyclazole was the most frequently detected pesticide at the highest concentrations, while herbicides were less frequently detected and at lower concentrations. The method described could be a valuable tool for regular monitoring of surface water systems in rice-cultivated basins.     

Determination of phosphate in urine by sequential injection analysis

Two simple turbidimetric methods for the determination of phosphate in urine are presented and compared. One method is based on the calcium phosphate crystallisation, and the other one on the inhibitory action of phosphate on the calcium carbonate crystallisation. The analytical features of both methods were: linear range = 0.2-1.5 g L-1, LOD = 14 mg L-1 and RSD 1.1-2.0% for the calcium phosphate method, linear range = 0.1-1.8 mg L-1, LOD = 0.01 mg L-1 and RSD 0.97-1.90% for the inhibitory method. Urines with high calcium content (> or = 400 mg L-1) can interfere the method based on the crystallisation of calcium phosphate. This interference was solved using a cation exchange resin as a part of the manifold. Considering the low toxicity of used reagents, these methods can be considered as a contribution to Green Analytical Chemistry.     

On-Line Solid Phase Extraction–Gas Chromatography–Cryotrapping–Infrared Spectrometry for the Trace-Level Determination of Microcontaminants in Aqueous Samples

A large-volume on-column GC–cryotrapping–IR system was developed for injections of up to 100 μl of organic extracts. Considerable reduction of the solvent-and-water background and enhanced analyte detectability was achieved by using an open-split interface between the GC column and the IR detector and improving the leak-tightness of the system. The system was combined with solid-phase extraction to yield on-line SPE–GC–IR. With this set-up, sample volumes of only 20 ml sufficed to detect, and identify, microcontaminants in tap and surface water at the 0.1–1 μg/L level. Detection limits were on the order of 15 ng/L for tap water when using appropriate functional-group chromatograms. Or, in other words, SPE–GC–IR is a suitable technique for the screening of environmental water samples for functional groups, i.e. classes of compounds, of interest.     

Determination of trace PAHs in seawater and sediment pore-water by solid-phase microextraction (SPME) coupled with GC/MS

A fast and reliable method for the determination of trace PAHs (polynuclear aromatic hydrocarbons) in seawater by solid-phase microextraction (SPME) followed by gas chromatographic (GC) analysis has been developed. The SPME operational parameters have been optimized, and the effects of salinity and dissolved organic matter (DOM) on PAHs recoveries have been investigated. SPME measures only the portion of PAHs which are water soluble, and can be used to quantify PAH partition coefficient between water and DOM phases. The detection limits of the overall method for the measurement of sixteen PAHs range from 0.1 to 3.5 ng/g, and the precisions of individual PAH measurements range from 4% to 23% RSD. The average recovery for PAHs is 88.2±20.4%. The method has been applied to the determination of PAHs in seawater and sediment porewater samples collected in Jiaozhou Bay and Laizhou Bay in Shandong Peninsula, China. The overall levels of PAHs in these samples reflect moderate pollution compared to seawater samples reported elsewhere. The PAH distribution pattern shows that the soluble PAHs in seawater and porewater samples are dominated by naphthalenes and 3 ring PAHs. This is in direct contrast to those of the sediment samples reported earlier, in which both light and heavy PAHs are present at comparable concentrations. The absence of heavy PAHs in soluble forms (<0.1-3.5 ng/L) is indicative of the strong binding of these PAHs to the dissolved or solid matters and their low seawater solubility.     

Sensitive Analysis of Idarubicin in Human Urine and Plasma by Liquid Chromatography with Fluorescence Detection: An Application in Drug Monitoring

A new approach for the sensitive, robust and rapid determination of idarubicin (IDA) in human plasma and urine samples based on liquid chromatography with fluorescence detection (LC-FL) was developed. Satisfactory chromatographic separation of the analyte after solid-phase extraction (SPE) was performed on a Discovery HS C18 analytical column using a mixture of acetonitrile and 0.1% formic acid in water as the mobile phase in isocratic mode. IDA and daunorubicin hydrochloride used as an internal standard (I.S.) were monitored at the excitation and emission wavelengths of 487 and 547 nm, respectively. The method was validated according to the FDA and ICH guidelines. The linearity was confirmed in the range of 0.1–50 ng/mL and 0.25–200 ng/mL, while the limit of detection (LOD) was 0.05 and 0.125 ng/mL in plasma and urine samples, respectively. The developed LC-FL method was successfully applied for drug determinations in human plasma and urine after oral administration of IDA at a dose of 10 mg to a patient with highly advanced alveolar rhabdomyosarcoma (RMA). Moreover, the potential exposure to IDA present in both fluids for healthcare workers and the caregivers of patients has been evaluated. The present LC-FL method can be a useful tool in pharmacokinetic and clinical investigations, in the monitoring of chemotherapy containing IDA, as well as for sensitive and reliable IDA quantitation in biological fluids.     

Rapid Screening and Determination of Residual Veterinary Drugs in Milk by Ultrahigh Performance Liquid Chromatography–High-Resolution Quadrupole Time-of-Flight Mass Spectrometry

A rapid screening and determination of 150 veterinary drugs of various classes in milk by UHPLC–high-resolution quadrupole time-of-flight mass spectrometry is proposed. One gram of milk was used for the analysis; the precipitation of proteins and extraction were performed with acetonitrile; the extract was analyzed without purification or preconcentration. Veterinary drugs were identified by accurate masses of analyte ions produced by electrospray ionization, their retention time, and the pattern of ion isotope distribution (mSigma). The quantitative analysis of the detected analytes was carried out by the standard addition method. The limits of detection were 0.1–0.5 ng/g; the analytical ranges were (0.1)1–500 ng/g; the duration of screening was 20–30 min; and the analysis time was 30–40 min. The relative standard deviation of the results for all analytes did not exceed 15%.     

Trace analysis of sulfonylurea herbicides and their metabolites in water using a combination of off-line or on-line solid-phase extraction and liquid chromatography–tandem mass spectrometry

Two alternatives for the rapid simultaneous quantification of six sulfonylurea herbicides and five of their main degradation products in natural water are proposed. For concentration, the compounds were extracted on a polystyrene–divinylbenzene solid phase under pH and elution conditions that suppressed any hydrolysis. The eluates were analysed by liquid chromatography coupled to electrospray tandem mass spectrometry within 20 min. The whole method was validated and shown to give no hydrolysis artefacts. The application of off-line and on-line SPE of sulfonylureas enabled the 0.1 μg L⁻¹ and 1 ng L⁻¹ LOQ levels to be reached, respectively. The on-line SPE–LC–MS–MS method allowed the accurate quantitation of all sulfonylureas and three degradation products at 0.1 μg L⁻¹ or below in natural water, with an average repeatability of 8%.     

Determination of pyrene and benzo(a)pyrene residues in water by derivative synchronous solid-phase spectrofluorimetry

Benzo(a)pyrene (BaP) and pyrene (Pyr) are two polycyclic aromatic hydrocarbons (PAHs) showing native fluorescence in solution. Both compounds have been determined in water at trace levels by solid-phase spectrofluorimetry, in which BaP and Pyr are fixed on Sephadex G-25 gel and the relative fluorescence intensity is measured after the system is packed in a 1-mm silica cell. First-derivative synchronous spectra obtained at =38 nm were used to determine BaP and Pyr in the presence of other potentially interferent PAHs. The spectral characteristics of the PAHs-gel system are described, the applicable concentration ranges being 0.4–2.5 ng/ml for BaP and 0.7–4.5 ng/ml for Pyr. The relative standard deviations were 1.1% and 1.4% for BaP and Pyr respectively. The detection limits were 0.04 ng/ml for BaP and 0.1 ng/ml for Pyr. The method was applied to the analysis of both compounds in water at trace levels and a recovery study on tap, natural and sea waters was carried out.     

Determination of synthetic polycyclic musks in water by microwave-assisted headspace solid-phase microextraction and gas chromatography-mass spectrometry

This paper describes a rapid and solvent-free method, microwave-assisted headspace solid-phase microextraction (MA-HS-SPME), for the extraction of six commonly used synthetic polycyclic musks: galaxolide (HHCB), tonalide (AHTN), celestolide (ADBI), traseolide (ATII), cashmeran (DPMI) and phantolide (AHMI) from water samples prior to their determination using gas chromatography-mass spectrometry (GC-MS). The effects of various extraction parameters for the quantitative extraction of these analytes by MA-HS-SPME were systematically investigated and optimized. The analytes in a 20-mL water sample (in a 40-mL sample-vial containing 4 g of NaCl) were efficiently extracted by a polydimethylsiloxane-divinylbenzene (PDMS-DVB) fiber placed in the headspace when the system was microwave irradiated at 180 W for less than 4 min. The limits of detection (LODs) ranged from 0.05 to 0.1 ng/L, and the limits of quantification (LOQs) were less than 0.2 ng/L. A preliminary analysis of wastewater samples revealed that HHCB and AHTN were the two most commonly detected synthetic polycyclic musks; using a standard addition method, their concentration were determined to range from 1.2 to 37.3 ng/L with relative standard deviation (RSD) ranging from 2 to 6%. The results obtained using this approach are better than those from the conventional oil-bath HS-SPME.     

Application of microcrystalline cellulose as an efficient and cheap sorbent for the extraction of metoprolol from plasma and wastewater before HPLC–MS/MS determination

A dispersive solid-phase extraction method based on a new sorbent has been performed on plasma and wastewater samples to determine metoprolol by high-performance liquid chromatography–tandem mass spectrometry. In this study, the analyte was adsorbed from the samples onto microcrystalline cellulose as a green and efficient sorbent and then eluted for use in the determination step. In the mass spectrometer, the analyte was detected in the positive mode and selectivity of the analysis was increased by sequential mass analysis through multiple reaction monitoring. All of the effective parameters in the extraction of metoprolol from plasma and wastewater were optimized. Under optimal conditions the method was linear in the ranges of 1–1,000 and 0.1–1,000 ng/ml in plasma and wastewater samples, respectively. The detection limits of the method were 0.30 and 0.03 ng/ml in plasma and wastewater samples, respectively. The data showed that the method provides low detection limit, wide linear range, good precision and high extraction recovery. Finally several plasma and wastewater samples were successfully analyzed using the method. The use of a small amount of a green and inexpensive sorbent and a low volume of plasma without the need for further pretreatment steps are the main advantages of the method.     

超高效液相色谱-串联质谱法同时测定浓缩果汁中的18种多酚物质

建立了浓缩果汁中18种多酚物质的超高效液相色谱(UPLC)-串联质谱(MS/MS)检测方法.样品经水稀释,HLB固相萃取净化,浓缩蒸干后用甲醇和0.1%甲酸定容.采用Acquity UPLC BEH C18 (1.7μm ×2.1 mm ×50 mm)色谱柱分离,以甲醇和0.1%甲酸为流动相,在0.3 ml,·min-...     

Comprehensive-trace level determination of methyltin compounds in aqueous samples by cryogenic purge-and-trap gas chromatography with flame photometric detection.

A comprehensive method was developed for the sensitive and fast determination of trace levels of methyltin compounds in aqueous samples. Tin compounds in aqueous solution at pH 5 were converted to the corresponding volatile hydrides: CH3SnH3, (CH3)2SnH2, and (CH3)3SnH, by reaction with potassium borohydride. A CP-4010 purge and trap injector (PTI) was used to purge analyte species from water directly. The volatile derivatives were base-line separated on a capillary column in an Angilent-6890 gas chromatograph by a suitable temperature program and were detected by a flame photometric detector (FPD). The detection limits were 18 ng L-1 for monomethyltin, 12 ng L-1 for dimethyltin, and 3 ng L-1 for trimethyltin, respectively. This method was successfully applied to the determination of methyltin compounds in different aqueous samples.