Degradation of Phenol by Hydroxyl Radicals on Different Coating Lead Dioxide Electrodes

Lead dioxide electrodes on Ti substrates were prepared by thermal-deposition or electro-deposition. The amount of hydroxyl radicals generated at the electrodes prepared by the above-mentioned two methods was compared with that at the electrodes mingled with Bi or La prepared by electro-deposition. The experimental results indicate that the highest concentration of hydroxyl radicals generated by thermal-deposition, electro-deposition mingled with nothing, electro-deposition mingled with Bi or La was 0.781, 1.048, 1.838 or 2.044 μmol/L, respectively. When phenol was electrolyzed on the four electrodes at a current density of 30 mA/cm2, the removal efficiency of phenol after electrolysis for 1.5 h was 87.30%, 93.55%, 97.95% or 98.70%, TOC removal efficiency after electrolysis for 5 h was 86.76%, 94.26%, 98.53% or 99.60%, respectively. Through the degradation experiments of phenol, the amount of hydroxyl radicals was responsible for the removal efficiency of phenol. The electro-catalytic characteristics were investigated by SEM, the generation amount of hydroxyl radicals, the degradation degree of phenol and the stability and conductivity of the electrodes were also investigated. The experimental results indicate that the four electrodes all show good electro-catalytic characteristics; the electro-catalytic characteristics of the electrode mingled with La were superior to those of the other three ones, and the electrochemical degradation of phenol followed one-step reaction dynamics.     

Determination of the hydroxyl radical by its adduct formation with phenol and liquid chromatography/electrochemical detection

An HPLC-ECD method is described for the indirect determination of the hydroxyl (OH) radical. Fenton's reaction is used to produce OH, which simultaneously attacks phenols (phenol or pyrocatechol) to form the adducts, pyrocatechol or pyrogallic acid. Thus, [OH] quantification is based on the separation and detection of pyrogallic acid and/or pyrocatechol by an isocratic HPLC-ECD method. The quantification of OH is also performed alternatively by a chronoamperometric detection in an electrochemical cell, where simultaneously formed Fe^III (Fenton's reaction) combines [Fe^II(CN)₆]⁴⁻ to produce the Prussian blue (PB) molecules (Fe₄^III[Fe^II(CN)₆]₃). Newly formed PB molecules are then immediately converted to colorless Everitts salt (K₄Fe₄^II[Fe^II(CN)₆]₃) with the reduction of the high-spin Fe^III to Fe^II at the surface of a glassy carbon electrode at +0.150 V (versus Ag/AgCl). The calculated concentration of OH during incubation (0.626 ppm) can be detected with negative errors by the HPLC-ECD (0.595 and 0.615 ppm with the errors −5.2 and −1.8%, respectively) and by the chronoamperometric method (0.552 and 0.607 ppm with the errors −11.8 and −3.0%, respectively). For the comparison of the two sets of data, HPLC-ECD method is much more promising.     

A Simplified Method for Determination of Nifedipine in Human Plasma by High Performance Liquid Chromatography

Abstract

A simplified high performance liquid chromatographic method was developed to determine the levels of nifedipine in human plasma. Nifedipine and the internal standard, 11-ketoprogesterone, are extracted from alkalinized plasma into organic solvent. The organic solvent is then evaporated to total dryness and the analytes are reconstituted with mobile phase and chromatographed. The limit of quantitation is 10 ng/ml using a 1.0 ml plasma sample.     

Separation and Direct Chemical Determination of Nitrosamines by High Performance Liquid Chromatography (HPLC)

Abstract

Volatile and non-volatile nitrosamines are determined at subparts per million levels in a continuous, inexpensive, low-temperature procedure when samples are compatible with the aqueous-alcoholic solvents. Individual nitrosamines are resolved by gradient elution on appropriate HPLC columns, converted to nitrite ion by ultra-violet light, combined with modified Griess reagent and the red-colored product measured at 540 nanometers. Inorganic nitrite may be determined and two, organic compounds are known to interfere. The detection level for N-nitrosodimethyl amine is 0.1 parts per million.     

Micromethod for Determination of Thiopental in Biological Fluids by High Performance Liquid Chromatography. Application to Therapeutic Follow-Up and Pharmacokinetic Study

Abstract

Thiopental is an ultra-short acting barbiturate, used either to induce anesthesia, or to manage intracranial hypertension associated with head injuries. A high performance liquid chromatography method vas proposed for the rapid and easy determination of thiopental in biological fluids. After precipitation of proteins with acetonitrile the chromatographic separation vas performed onto a reversed-phase column with an acetonitrile-perchlorate buffer mixture as mobile phase. Compounds were analysed at 300nm and the detection limit vas about 0.1 mg/1. The analytical procedure vas applied to the therapeutic follow-up in patients (8 childrens. 4 adults) treated with long-term infusion of thiopental after head injury, and to a pharmacokinetic study in patients receiving a single 1Y bolus of thiopental to induce anesthesia.     

The effect of O2 and NO2 on the ring retaining products of the reaction of benzene with hydroxyl radicals

Summary The reaction of benzene with hydroxyl radicals affords phenol and 1,4-benzoquinone in 0.18±0.05 and 0.02±0.01 yield, respectively. The main reaction of the hydroxycyclohexadienyl radical with oxygen leads to the respective peroxy radical which in turn decomposes to ring cleavage products and phenol. In the presence of NO₂, nitrobenzene is also formed with yields depending linearly on the initial NO₂ concentration and vanishing as [NO₂] approaches zero. The amount of phenol formed in the presence of NO₂ is equal to that formed in the absence of NO₂ within experimental error.

---

Der Einfluß von O₂ und NO₂ auf die cyclischen Produkte der Reaktion von Benzol mit Hydroxylradikalen

Zusammenfassung Die Reaktion von Benzol mit Hydroxylradikalen liefert Phenol und 1,4-Benzochinon in Ausbeuten von 0.18 ± 0.05 und 0.02 ± 0.01. Die Hauptreaktion des Hydroxycyclohexadienylradikals mit Sauerstoff führt zum entsprechenden Peroxyradikal, das seinerseits zu offenkettigen Produkten und Phenol zerfällt. In Gegenwart von NO₂ entsteht Nitrobenzol; seine Ausbeute hängt linear von der Anfangskonzentration an NO₂ ab und läßt sich für verschwindende NO₂-Konzentrationen nach Null extrapolieren. Die Menge an gebildetem Phenol hängt nicht von der Anoder Abwesenheit von NO₂ ab.

     

菊花中活性成分的高效液相色谱测定与指纹图谱研究

采用高效液相色谱(HPLC)法测定了12个菊花样品中绿原酸、黄芩苷、槲皮素、木犀草素和柯因五种活性成分的含量。色谱柱为Nov-pak C18,以0.1%磷酸-甲醇为流动相,流速0.6 mL/min,梯度洗脱,检测波长为254 nm。该方法在10-3~10-5g/mL范围内线性关系良好,保留时间和峰面积相对标准偏差(RSD)分别在0.20%~0.96%、0.23%~0.77%之间,回收率在96.5%~104.0%之间。同时建立了菊花样品的指纹图谱,采用夹角余弦和相关系数法计算了12个菊花样品的相似度,并且运用MATLAB程序对相关系数法计算值进行聚类分析,结果与实际样品种属区分一致,为菊花的质量控制和种属的区分提供依据。     

生物技术培养银杏发根中的黄酮分析研究

本文研究了银杏发根中黄酮含量的高效液相色谱（ＨＰＬＣ）分析方法,改进了样品预处理过程,实行提取、水解同步进行,并与天然银杏树叶中的黄酮进行了对照,分析结果表明,采用生物技术培养的银杏发根中确实含有银杏黄酮。     

高效液相色谱共振瑞利散射联用方法检测大鼠血清中的西索米星

用高效液相色谱与共振瑞利散射方法联用对西索米星进行检测.采用滂胺天蓝(PSB)作为分子识别探针,C18反相色谱柱进行分离.流动相为含0.22％三氟乙酸的20 mmol/L醋酸钠和甲醇(92:8,V/V),流速为0.5 mL/min.柱后探针溶液流速为0.1 mL/min.共振瑞利散射(RRS)检测波长设为λex=λem...     

Determination of Cefmenoxime in Human Serum by Ion-Pair Reverse-Phase High Performance Liquid Chromatography

Abstract

A highly reproducible ion-pair reverse-phase high performance liquid chromatographic assay for cefmenoxime in human serum has been developed. A simple sample cleanup procedure is employed. Cefoxitin is the internal standard and separation is achieved using a C-18 μ-Bondapak column. The mobile phase consists of 20% acetonitrile and 80% 0.05 M ammonium acetate buffer containing 0.005 M tetrabutylammonium hydrogen sulphate as the ion-pair agent. Samples are quantitated by UV detector at 254 nm and 0.02 aufs with an assay sensitivity of 0.625 μg/ml. The method has been successfully applied in a clinical setting.     

分子印迹柱-高效液相色谱法测定猪肉中磺胺嘧啶(英文)

建立了分子印迹柱-高效液相色谱法检测猪肉中磺胺嘧啶残留方法。制备了磺胺嘧啶的分子印迹柱,并优化了分子印迹柱的萃取条件。研究结果表明,在最佳萃取条件下,分子印迹柱-高效液相色谱法的加标回收率≥75.6%,相对标准偏差≤6.1%。分子印迹柱为固相萃取柱可以预浓缩与纯化猪肉样品中磺胺嘧啶。与氧化铝萃取柱比,分子印迹柱具有较好的重复性和萃取效率。本方法已成功用于实际猪肉样品中磺胺嘧啶含量的检测,结果满意。     

Optimization of high-performance liquid chromatography and solid-phase extraction for determination of organophosphorus pesticide residues in environmental samples

High-performance liquid chromatography with solid-phase extraction (HPLC-SPE) was optimized for the analysis of three organophosphorus pesticide residues in water, apples and vegetable samples. Octadecylsilica disks (47-mm diameter) were used for solid-phase extraction. The parameters that affect both separation and extraction of methyl parathion, parathion and phoxim, such as mobile-phase composition, ionic strength, temperature, pH, and breakthrough volume, were investigated. The application of optimized HPLC-SPE to environmental samples gave reproducible results with low detection limits of 5 µg L^?1 for methyl parathion and parathion and 2.5 µgL^?1. Precisions of less than 8, 9 and 12% were obtained for water, spinach and apple samples, respectively.     

紫锥花种属中酚类化合物的HPLC分析

本文报道了一种测定紫锥花草药中咖啡酸、对羟基苯甲酸、对-香豆酸、原儿茶酸、丁香酸、阿魏酸、香草酸、咖啡奎尼酸、洋蓟酸、菊苣酸和紫锥花苷等11种酚类化合物的高效液相色谱分析方法。本法可应用于各种紫锥花草药中酚类化合物的测定。结果表明,在紫锥菊种属中含量最多的酚类化合物是菊苣酸、咖啡奎尼酸和紫锥花苷;在狭叶紫锥菊种属中含量较丰的是紫锥花苷和菊苣酸;而在白花紫锥菊种属中则以紫锥花苷以含量较多。     

Determination of the antioxidant capacity of different food natural products with a new developed flow injection spectrofluorimetry detecting hydroxyl radicals

This paper presents an automatic spectrofluorimetric method (flow injection analysis spectrofluorimetry) for detecting hydroxyl radicals. Based on H₂O₂ catalyzed by Co²⁺ yielding HO, the method utilized sodium terephthalate to trap hydroxyl radicals and obtained sodium 2-hydroxyterephthalate by aromatic hydroxylation, which resulted in an increase in the fluorescence intensity. The relative fluorescence intensity was proportional to the concentration of hydroxyl radicals. Hydroxyl radicals could be determined indirectly, based on the increase of fluorescence. It was a simple, rapid, precise, sensitive and automatic technique for the determination of HO. The relative standard deviation of 11 determinations was 0.57%. The method can be used to sieve antioxidant medicines and will have theoretical and practical guidance on the mechanism of hydroxyl radicals-damaging biology.     

Theoretical and experimental interpretations of phenol oxidation by the hydroxyl radical

Phenol oxidation by OH radicals produced by the Fenton reaction was studied and the oxidation process was monitored by the UV–visible, ¹³C NMR and LC techniques. The results show that benzoquinone is formed. In the NMR and LC experiments, since the peaks corresponding to isomers ortho and para- benzoquinones are unresolved, DFT was used to determine the branching ratios of the isomers formation that coincides with their ΔG values (ortho > para > meta): 72% for ortho, 23% for para and 5.0% for meta. Furthermore, the energy profile of the OH attack at ortho is quite similar to that at the para position while the meta position attack is less favored by 2.0 kcal/mol.     

高效液相色谱法测定原油脱钙工艺排水体系中NS-3缓蚀剂浓度

将反相高效液相色谱法用于原油脱钙工艺排水体系中缓蚀剂浓度测定研究,建立了缓蚀剂的快速分离检测方法.使用C18柱,以乙腈∶二氯甲烷=9∶1(V/V)混合溶剂为流动相,采用紫外检测器在300 nm处对排水体系中的缓蚀剂进行测定,外标法进行定性定量分析.测定结果表明缓蚀剂浓度在100~900 mg/kg时其峰面积与相应的质量浓度有良好的线性关系,其线性相关系数为0.999 9,相对标准偏差(RSD)和相对误差(RD%)都小于2.0%.用二氯甲烷为萃取剂对排水体系中的缓蚀剂进行萃取,其平均回收率为100%±2%.最低检测线为0.75mg/kg.该方法具有测定结果准确可靠,操作简便快速,重现性好等特点.     

Determination of Abnormal Hemoglobins by the Combined use of Reversed-Phase high Performance Liquid Chromatography and Fast Atom Bombardment Mass Spectrometry

Abstract

Separation by reversed-phase high performance liquid chromatography (RP-HPLC) of peptide mixtures obtained from tryptic digestion of abnormal human hemoglobins and subsequent analysis by fast atom bombardment mass spectrometry (FAB-MS) of selected peptides allow unambiguous, rapid identification of the hemoglobin variants. By this method two varied hemoglobins, Hb D Punjab and Hb J Sardegna, have been determined. The methodology described, which is simple and reliable, could be used for the detection and structural identification of known and unknown Hb variants, without amino acid (a.a.) or sequence analysis.     

Determination of Danazol in Plasma by High Performance Liquid Chromatography

Abstract

An HPLC method has been developed for the determination of danazol in human plasma. the chromatographic conditions consisted of an ODS column 80 × 7.0 mm, 3 μm; a mobile phase of 71:29, methanol:20 mM potassium dihydrogen phosphate. A UV-Visible detector was set at 288 nm to monitor the danazol peak. Danazol was extracted from plasma with acetonitrile which was salted out with potassium carbonate. Prior to salting out, cadmium sulfate was mixed with the acetonitrile-plasma mixture to remove any interfering constituents. the extracted acetonitrile layer was evaporated and the residue was reconstituted in the mobile phase before injection. the method was found to be reproducible with relative standard deviation (%rsd) from 2.3 to 7.2%. A number of clinically important drugs did not interfere with danazol determination.     

Separation and Detection of Arsenic and Selenium Species in Environmental Samples by HPLC-ICP-MS

A method is presented for arsenic speciation analysis of an oyster sample using ion chromatography coupled with an inductively coupled plasma mass spectrometry (ICP-MS) instrument. A strong anion exchange resin was employed with a step gradient elution of 0.1 mM/0.1 M K 2 SO 4 at pH 10.2. Arsenobetaine and dimethylarsinic acid were determined following extraction based on trypsin enzymolysis with 95-100% extraction efficiency. Limits of detection in the range 0.1-0.3 mg kg m 1 of arsenic were obtained for organic arsenic species. No inorganic arsenic was detected. Validation was performed using TORT-2 as a certified reference material. Although high performance liquid chromatography (HPLC) coupled to ICP-MS is an effective method for speciation analysis it is not always necessary to obtain such a detailed picture. A simple liquid chromatographic separation technique based upon mini-column technology is presented. It was developed to obtain a fast, efficient and reliable separation of inorganic from organic, i.e. assumed toxic from non-toxic, arsenic and selenium species suitable for use as an initial screening method for environmental analysis. Two types of strong anion exchange resin were tested. Excellent separation was obtained for both min-column resins and analysis times were within 7 min. Limits of detection obtained for inorganic arsenic, organic arsenic, selenomethionine, Se IV and Se VI were 1.6, 1.8, 66, 32 and 22 µg kg m 1 , respectively.     

High Performance Liquid Chromatographic Determination of Pirenzepine Dihydrochloride in Its Pharmaceutical Formulation

Abstract

A high-performance liquid chromatographic procedure for the determination of pirenzepine dihydrochloride as a bulk material and in its tablet dosage form (Gastrozepin^R) is presented. Normal phase liquid chromatography has been performed on a Micro-pack Si-10 column using ammonium hydroxide (28–30% NH₃) in methanol (0.75: 99.25% v/v) as mobile phase at a flow rate of 2 ml/min. Clobazam has been used as internal standard with retention times of 1.9 and 2.8 minutes for clobazam and pirenzepine dihydrochloride, respectively at 254 nm. Analytical calibration yields a linear relationship between 5 and 25 μg/ml, with correlation coefficient of 0.999. Tablets each labelled to contain 25 mg pirenzepine dihydrochloride give mean percentage found of 99.98 ± 0.4. A plot of logarithm of concentration against time for a solution in 6 N hydrochloric acid gives a straight line with a slope of - 0.197 day^?1. The proposed method is, therefore, a stability indicating method.