氢化物—原子荧光光谱法联合测定水中的砷和汞

本文利用氢化物原子荧光光谱法(HG-AFS)联合测定水中的砷和汞,对灯电流、原子化器高度、载气流量、干扰离子、酸介质以及酸度等一系列测定条件进行了研究。实验结果表明:该法具有操作简单、快速,干扰少、灵活度高等优点,在最优测定条件下,本法砷、汞检出限分别为0.07μg·L^-1和0.009μg·L^-1,线性范围为0～80.0μg·L^-1及0～8.00μg·L^-1。     

Decarbonylation of As2Co2(CO)6, a binuclear cobalt carbonyl derivative of diarsenic

The structures and relative energies of the As₂Co₂(CO)_n (n = 6, 5, 4) derivatives are predicted by density functional theory to be analogous to those of the corresponding H₂C₂Co₂(CO)_n derivatives. Thus As₂Co₂(CO)₆ is predicted to have three carbonyls on one cobalt atom eclipsed relative to the three carbonyls on the other cobalt atom. The corresponding As₂Co₂(CO)₆ structure with a staggered rather than eclipsed arrangement of the Co(CO)₃ units is a transition state rather than a genuine minimum. For As₂Co₂(CO)₅ the structure in which an equatorial group is removed from the As₂Co₂(CO)₆ structure and a singly bridged As₂Co₂(CO)₄(μ-CO) structure are predicted to have essentially the same energies, within <2 kcal/mol. A higher energy As₂Co₂(CO)₅ structure by 9 ± 2 kcal/mol is derived from the As₂Co₂(CO)₆ structure by removal of an axial carbonyl group. The two unbridged As₂Co₂(CO)₅ structures correspond to those observed experimentally in the photolysis of As₂Co₂(CO)₆ in Nujol matrices at low temperatures. In such photolysis experiments the higher energy isomer is produced initially and then converted to the lower energy isomer upon annealing. A singly bridged structure was found for As₂Co₂(CO)₄. The analogous structure was not observed in the previous work with H₂C₂Co₂(CO)₄. However, such a H₂C₂Co(CO)₃(μ-CO) structure is found here for the acetylene complex. This singly bridged structure is predicted to lie 1.9 kcal/mol below the H₂C₂Co₂(CO)₄4-1S structure by the BP86 method but 3.5 kcal/mol above the latter by the B3LYP method. In addition to the singly bridged As₂Co₂(CO)₄ structure, the same six unbridged structures were located for As₂Co₂(CO)₄ that were previously found for H₂C₂Co₂(CO)₆.     

Screening of eltanolone metabolites in dog urine by anion-exchange/reversed-phase liquid chromatography and mass spectrometry

Strong anion-exchange (SAX) chromatography and reversed-phase liquid chromatography (RPLC) followed by different mass spectrometric techniques for the separation and identification of conjugated and unconjugated ¹⁴C-labelled eltanolone (5β-Pregnan-3α-ol-20-one) metabolites in biological fluids are presented. Conjugates of estradiol were used as model compounds for the development of a SAX based group separation of neutral steroids, glucuronides, sulfates and di-conjugated steroids. The usefulness of the technique is demonstrated by the analysis of ¹⁴C-labelled eltanolone metabolites in dog urine. The analytical SAX column used prior to RPLC improved the capacity to separate the metabolites from each other and from endogenous components, compared to a single reversed-phase system. Liquid chromatography negative ion electrospray-mass spectrometry (LC–ESI-MS) was used for the molecular mass determination of conjugated eltanolone metabolites. Unconjugated metabolites and hydrolysed conjugates were identified using gas chromatography–mass spectrometry with an electron impact ion source (GC–MS) after trimethylsilyl (TMS) derivatization. An unexpected finding in dog urine was the diglucuronide formation of eltanolone (presumably after enolisation of its carbonyl group).     

Determination of 25-hydroxyvitamin D3 in human plasma by reversed-phase high-performance liquid chromatography with ultraviolet detection

A method for the determination of 25-hydroxyvitamin D₃, the major metabolite of vitamin D₃ in human plasma, using a non-radioactive internal standard and reversed-phase high-performance liquid chromatography with UV detection (265 nm) has been developed. The method was applied to the determination of the metabolite in plasma from healthy subjects (n=25) and from patients with chronic renal failure (n=12). 25-Hydroxyvitamin D₃ 3-sulfate, a major conjugated metabolite of 25-hyroxyvitamin D₃, was also determined and the correlation between the concentrations of these metabolites was examined. The study showed that almost equal amounts of both compounds were detected in the plasma of healthy subjects, however, in two subjects, the amount of sulfate in the free form was found to be about twice as high as normally detected. In contrast, the free form was predominant in the plasma of patients with chronic renal failure and the sulfate was not detected in four patients.     

Chemical speciation of arsenic in urine of patients with blackfoot disease

Blackfoot disease is a peripheral vascular disease resulting in gangrene of the lower extremities. Although extensive epidemiological study has implicated high arsenic content in artesian well water of the endemic area bears some important connection with the disease, the etiology of the disease is still not clarified. In this study, attention is paid to chemical speciation of arsenic in order to find out whether the concentrations of arsenic species in urine of Blackfoot disease patients are different from those of controls. Experimental results indicate that the total arsenic, inorganic arsenic, monomethylarsonic acid, and other forms of arsenic in the urine of patients are significantly higher than those of the contols. The possible connection of those arsenic species with the etiology of the disease is discussed.     

Quantification of corticosteroids in bovine urine using selective solid phase extraction and reversed-phase liquid chromatography/tandem mass spectrometry

This paper presents the development of a simple liquid chromatography–tandem mass spectrometry (LC–MS/MS) method to determine corticosteroids in bovine urine sample matrices. This method uses a single phase extraction (SPE) for cleaning of the sample with an Oasis MAX cartridge at pH 9.0–9.5 and elution by a neutral organic solvent (acetonitrile/dichloromethane), followed by separation on a GEMINI C18 column in the gradient mode with acetate buffer (pH 4.1)/methanol. A triple quadrupole mass spectrometer equipped with a multimode ion source, set to negative atmospheric pressure chemical ionization (APCI) in the multiple reaction monitoring mode was used for detection. The main advantage of this method over other commonly used methods includes the use of SPE with a low volume cartridge for sample preparation and no ion suppression effects from matrix components of the urine samples in the LC–MS/MS analysis. This allowed a reduction the quantification limits (decision limits, CCα) for the first time to 0.1 μg/L (1 and 0.2 μg/L for triamcinolone and flumethasone, respectively). The developed method was validated in accordance with the European Union Commission Decision 2002/657 EC. The recoveries and within-laboratory reproducibility varied from 77% to 115% and 87% to 107.5%, respectively, at 2, 3, and 4 μg/L levels of corticosteroids. The relative standard deviation (RSD) of the measurements was lower than 30%. The decision limit was calculated by multiplying the signal-to-noise ratio by 3 and the obtained values were in the range of 0.1–1.0 μg/L, confirmed by the analysis of twenty blank samples, which were spiked at the desired concentrations. The detection capability was calculated by the addition of the decision limit and the standard deviation followed by multiplication by 1.64 of the within-laboratory reproducibility at 2 μg/L of corticosteroids. The method was applied to four urine samples, giving concentrations of prednisolone (PRED) residues in the range from 0.3 to 0.9 μg/L.     

Thermochemotherapy effect of nanosized As2O3/Fe3O4 complex on experimental mouse tumors and its influence on the expression of CD44v6, VEGF-C and MMP-9

Background  

Both thermotherapy and arsenic have been shown to be active against a broad spectrum of cancers. To reduce the limitations of conventional thermotherapy, improve therapeutic anticancer activity, reduce the toxicity of arsenic on normal tissue, and increase tissue-specific delivery, we prepared a nanosized As₂O₃/Fe₃O₄ complex (Fe₃O₄ magnetic nanoparticles encapsulated in As₂O₃). We assessed the thermodynamic characteristics of this complex and validated the hyperthermia effect, when combined with magnetic fluid hyperthermia (MFH), on xenograft HeLa cells (human cervical cancer cell line) in nude mice. We also measured the effect on the expression of CD44v6, VEGF-C, and MMP-9 which were related to cancer and/or metastasis.     

On-line EPR study of free radicals induced by peroxidase/H2O2 in human low-density lipoprotein

The aim of this study was to use direct electron paramagnetic resonance (EPR) spectroscopy at 37 °C and spin trapping techniques to study radical species formed during horseradish peroxidase/H₂O₂-initiated low-density lipoprotein (LDL) oxidation. Using direct EPR, we obtained evidence for the formation not only of the α-tocopheroxyl radical but also of a protein radical(s), assigned to a tyrosyl radical(s) of apolipoprotein B-100 (apo B-100). Spin trapping with 2-methyl-2-nitrosopropane revealed (i) the formation of a mobile adduct with β-hydrogen coupling assigned to a lipid radical and (ii) a partially immobilised adduct detected in LDL as well as in apo B-100, assigned after proteolytic digestion to the trapping of a radical centred on a tertiary carbon atom of an aromatic residue, probably tyrosine. Our results support the hypothesis that radicals are initiators of the oxidative process, and show that their formation is an early event in peroxidase-mediated oxidation. We also tested the effects of resveratrol (RSV), a polyphenolic antioxidant present in red wine. Our data indicate that 1–10 μM RSV is able to accelerate α-tocopherol consumption, conjugated dienes formation and the decay kinetics of LDL-centred radicals. Since phenols are substrates for peroxidases, this result may be ascribed to a RSV-mediated catalysis of peroxidase activity.     

Separation and quantification of the B6 vitamers in plasma and 4-pyridoxic acid in urine of adolescent girls by reversed-phase high-performance liquid chromatography

The vitamin B₆ status of seemingly healthy adolescent girls was determined using several accepted and proposed parameters in an effort to establish guidelines for status evaluation. High-performance liquid chromatography-derived plasma B₆ vitamers (pyridoxal phosphate, PLP; pyridoxine phosphate, PNP; pyridoxamine phosphate, PMP; pyridoxal, PL; pyridoxine, PN; and pyridoxamine, PM) and 4-pyridoxic acid (4-PA) concentrations and urinary 4-PA levels of 28 white adolescent females, 12–15 years, having radiomonitored plasma PLP concentrations and coenzyme stimulation of erythrocyte alanine aminotransferase activities indicative of adequate status were determined. Mean vitamin B₆ and protein intakes were 1.48 mg and 78.3 g. Ranges for plasma B₆ vitamer and 4-PA concentrations (nmol/1) were: PLP, 40.9–122.2; PNP, non-detectable (ND)—16.1; PMP, ND—8.1; PL, ND—15; PN, ND—21.9; PM, ND—17.8; and 4-PA, ND—55.7. PLP was the only vitamer found in plasma of all subjects. Urinary 4-PA concentrations ranged from 0.11 to 2.50 μmol/mmol of creatinine. B₆ vitamer values of these girls should be of use in the establishment of normal ranges for vitamin B₆ status parameters.     

Analysis of plant galactolipids by reversed-phase high-performance liquid chromatography/mass spectrometry with accurate mass measurement

The composition of plant membrane lipids was investigated by reversed-phase high performance liquid chromatography mass spectrometry with accurate mass measurement. The data dependent methods for the analysis of monogalactosyldiacylglycerols (MGDGs) and digalactosyldiacylglycerols (DGDGs) have been developed. The optimised chromatographic systems were based on a 2.0mm i.d. Nucleosil C18 column with methanol/water (MGDGs) or acetonitrile/methanol/water (DGDGs) gradients. The galactolipids were ionised by electrospray operated in the positive ion mode and identified based on their MS/MS spectra. High resolution spectra with accurate masses were found to be essential for correct interpretation of the MS data. The elution order of non-oxidised MGDGs and DGDGs followed the equivalent carbon numbers. The methods were applied for detailed characterisation of the MGDGs and DGDGs in the leaves of Arabidopsis thaliana and Melissa officinalis.     

Transesterification of sunflower oil to biodiesel on ZrO2 supported La2O3 catalyst

ZrO₂ supported La₂O₃ catalyst prepared by impregnation method was examined in the transesterification reaction of sunflower oil with methanol to produce biodiesel. It was found that the catalyst with 21 wt% loaded La₂O₃ and calcined at 600 °C showed the optimum activity. The basic property of the catalyst was studied by CO₂-TPD, and the results showed that the fatty acid methyl ester (FAME) yield was related to their basicity. The catalyst was also characterized by TG–DTA, XRD, FTIR, SEM and TEM, and the mechanism for the formation of basic sites was discussed. It was also found that the crystallite size of support ZrO₂ decreased by loading of La₂O₃, and the model of the solid-state reaction on the surface of La₂O₃/ZrO₂ catalyst was proposed. Besides, the influence of various reaction variables on the conversion was investigated.     

Studies of the reaction products of adenosine with [Pt(NH3)3Cl]Cl and cis-Pt(NH3)2Cl2 by high performance liquid chromatography

The reaction products of adenosine with [Pt(NH₃)₃Cl]Cl or cis-Pt(NH₃)₂Cl₂ have been studied using high performance liquid chromatography and uv spectroscopy. The reaction of [Pt(NH₃)₃Cl]Cl with adenosine (pH = 7.0, Pt/base = 0.5) gives four products. Two of them, mononuclear complexes in which platinum is bound to adenosine through N(7) or N(1), comprise more than 90% of all the products. The N(1) and N(7) sites on adenosine indicate almost equal binding affinity for [Pt(NH₃)₃Cl]Cl. The reaction of cis-Pt(NH₃)₂Cl₂ with adenosine has been studied in the presence of a large excess of adenosine (Pt/base ? 0.05). The reaction gives four products. One is the monomeric 2:1 complex with cis-Pt(NH₃)₂²⁺ bound to two adenosine molecules through the N(7) site and the N(1) site, and another is the monomeric 2:1 complex with cis-Pt(NH₃)₂²⁺ bound to two adenosine molecules through the N(7) sites. cis-Pt(NH₃)₂Cl₂ is stronger affinity to the N(7) site than of adenosine to the N(1) site.     

Determination of 3-methoxy-4-hydroxyphenylethylene glycol in urine using reversed-phase liquid chromatography with column switching and electrochemical detection

A column-switching method was developed for the determination of total 3-methoxy-4-hydroxy-phenylethyleneglycol (MHPG) in urine. This was performed by first treating samples with β-glucuronidase, followed by extraction with ethyl acetate. The reconstituted extracts with injected onto an HPLC system containing an amperometric detector and tandem Nucleosil C₁₈ and C₈ reversed-phase columns connected by a switching valve. The total analysis time for MHPG was 12 min. The limit of detection was 0.18 ng, or 9 μg/l for 20-μl injections of a 1.0-ml reconstituted extract prepared from 1.0 ml of urine. The linear range extended up to 80 mg/l. The within-day precision for a urine sample containing 170 μg/l total MHPG was ±6% and the day-to-day precision was ±15%. The average levels determined by this method for total MHPG in normal subjects showed good agreement with previous literature values. This approach could be modified for the determination of free MHPG by using only ethyl acetate extraction for sample pretreatment.     

H2O2 generation during the redox cycle of mitomycin C and DNA-bound mitomycin C

Reduction of mitomycin C by NaBH₄ or by NADPH in the presence of a cell extract followed by exposure to air results in the generation of H₂O₂. This phenomenon occurs not only with free mitomycin but also with mitomycin irreversibly bound to DNA. In view of these findings, the antibiotic activity of mitomycin was tested in two bacterial systems: a facultative aerobic bacterium grown in the presence or absence of oxygen and an obligate anaerobic bacterium. No oxygen effect could be demonstrated in either case in the growth-inhibitory and bactericidal activity of the drug. Nevertheless, the H₂O₂ generating capacity of mitomycin-DNA complexes inside the nucleus may play a role in the drug-induced biological damage to the genetic material of cells.     

A novel large heteropolytungstate constructed from two types of lacunary Keggin anions: K7Na13[(PW11O39)2(PW9O34)2(W2O3)2] · 25H2O

A novel crown-shaped heteropolytungstate is formed by covalently linking two [PW₁₁O₃₉]⁷⁻ and two [PW₉O₃₄]⁹⁻ fragments with four WO₆ octahedra, which represents not only the largest tungstophosphate constructed from two types of building blocks without considering the 4f lanthanide or other 3d transition metal ion linkers but also the highest degree of aggregation known in the large clusters incorporating monovacant lacunary anions.     

Study on the heterogeneous degradation of chitosan with H2O2 catalyzed by a new supermolecular assembly crystal: [C6H8N2]6H3[PW12O40]·2H2O

A new supermolecular assembly crystal, [C₆H₈N₂]₆H₃[PW₁₂O₄₀]·2H₂O (DMB-PWA), was synthesized with phosphotungstic acid (PWA) and 1,2-diaminobenzene (DMB) under hydrothermal conditions and was characterized by Fourier-transform infrared spectra (FTIR) and single-crystal X-ray diffraction analysis. DMB-PWA could effectively catalyze oxidative degradation of chitosan with H₂O₂ in the heterogeneous phase. The optimum degradation conditions were determined by orthogonal tests as follows: amount of chitosan 1.00 g, 30% (wt %); H₂O₂, 3.0 mL; dosage of catalyst, 0.06 g; reaction temperature, 85 °C; and reaction time, 30 min. The water-soluble chitosan with a viscosity-average molecular weight (M_v) of 4900 was obtained under the optimum degradation conditions and was characterized by FTIR, ultraviolet-visible diffuse reflection spectra (UV-vis DRS), and X-ray powder diffraction analysis.     

Determination of iodide in serum and urine by ion-pair reversed-phase high-performance liquid chromatography with coulometric detection

An HPLC method is described for the determination of iodide in serum and urine using ion-pair chromatography with coulometric detection. After adding hexadecyltrimethylammonium chloride, the ions pairs formed with the iodide in the sample are extracted using an organic solvent. The solvent is then evaporated and the dry residue obtained is mixed with an appropriate volume of mobile phase so as to concentrate the sample prior to injection into the chromatograph. For a sample of 0.5 ml of serum, the method features a limit of detection (signal-to-noise ratio of 3) of 0.2 μgl⁻¹, sufficient to be applied in paediatric assays for the diagnosis of both iodide deficiency and excess.     

Determination of leukotriene E4 in human urine using liquid chromatography–tandem mass spectrometry

A liquid chromatographic–tandem mass spectrometric (LC–MS–MS) method was developed for the quantitation of urinary leukotriene E₄ (LTE₄). LTE₄ and its internal standard were extracted by solid-phase extraction and analysed using LC–MS–MS in the selected reaction monitoring (SRM) mode. A good linear response over the range of 10 pg to 10 ng was demonstrated. The accuracy of added LTE₄ ranged from 97.0% to 108.0% with a mean and SD of 100.6±2.4%. We detected LTE₄ (63.1±18.7 pg/mg creatinine, n=10) in healthy human urine. This method can be used to determine LTE₄ in biological samples.