自行配制的系列标准样品应用于刚玉质耐火材料的X射线荧光光谱分析

用矾土标准物质、白云石标准样品、基准氧化铝及优级纯氯化钾和氯化钠作为基本材料,并应用Excel公式算法求得上述各物质的准确质量,配制成一组包括各被测组分的质量分数呈梯度分布的12种混合物,分别将上述各混合物置于铂-金坩埚中与无水四硼酸锂熔融,所得玻璃状熔块即为自制的一组供X射线荧光光谱分析刚玉质耐火材料用的系列标准样品。按所给的各分析通道的参数,测定了此类耐火材料中8项组分(即SiO2、Al2O3、MgO、Na2O、K2O、Fe2O3、CaO及TiO2)。另取基准氧化铝一份,按试验方法作空白试验,从而消除其中可能存在的痕量杂质的干扰。将所配制的系列标准样品应用于实样分析,所得8项组分的测定结果与用化学分析法所测得结果相符,其测定值的相对标准偏差(n=10)均小于12%。     

Determination of Particulate Atomospheric Benzoic Acid by Ion Chromatography with Ultraviolet Detection

Abstract

A simple method involving ion chromatography with ultraviolet detection (IC-UV) is applied to the determination of benzoic acid in atmospheric samples. The detection limit is 10 nanograms. Validation and interference studies are described. The application of the IC-UV method to other aromatic acids including nitrophenols is briefly discussed.     

Analyses of Chloramphenicol in Biological Samples by HPLC

Abstract

Chloramphenicol (CAP) is the drug of choice for the treatment of typhoid fever and other diseases and is consumed by millions of people. Chloramphenicol is a broad-spectrum antibiotic, but it has serious side effects and high risk of anemia if taken continuously. The drug persists for a long time in the human body and is likely to damage to the liver, kidneys, and red blood cells, even at low concentrations. From the human health point of view, analysis of low levels of this drug in biological samples is important. This article present an overview of the analysis of CAP in biological samples by high-performance liquid chromatography (HPLC). In addition, the available methods are compared in terms of their applications, efficiencies, and effectiveness.     

A Fluorescence Spot Test for Salicylate Determination

Abstract

A procedure based on a spot test for salicylate is presented. The method is simple, rugged and is based on the salycilate native fluorescence measurement on the surface of a filter paper by using optical fibers for light conduction. The fluorescence was linear at concentration range of 0.01–0.4 mmol l^?1. The relative standard deviation of 5% (n=10) was observed. Detection and quantification limits were 4 and 14 µmol l^?1, respectively. The results obtained in pharmaceutical salicylate determinations showed that practically no statistical difference existed with the pharmacopeical method (95% confidence level). The recovery studies in biological samples spiked with salicylic acid at overdose concentration levels showed that the matrix sample did not interfere in the method.     

Liquid Chromatographic Residue Analysis of Carbaryl Based on a Post-Column Catalytic Reactor Principle and Fluorigenic Labelling

Abstract

A method is described for the residue analysis of carbaryl in polluted water samples. The technique is based on catalytic hydrolysis of the carbaryl on anion exchangers followed by fluorescence detection of the α-naphthol or the OPA derivative of the methyl amine. A low cost 200 mesh Amberlite strong anion exchanger can be used for this purpose when coupled to the OPA reaction detector. Combining this approach with on-line preconcentration and clean-up on an 3P-18 loaded precolumn can provide a powerful tool for automated residue analysis of carbaryl (and other N-methyl carbamates) in polluted water sources. Recoveries in the order of 100% are reported. The reproducibility of the technique is better than 2% rel. st. dev. Detection limits are 0.4–2 ng per injection for carbaryl depending on the system and linearity of response is more than two orders of magnitude with r = 0.9998. The selectivity and sensitivity of this method permits residue analysis at the sub ppb concentration level in heavily polluted water samples. Data on hydrolysis yields and band broadening as a function of residence time and temperature in the reactor are given.     

Determination of Nickel in Biological Samples by Electrothermal Atomization-Atomic Absorption Spectrometry Involving a Prior Extraction with 1,5-Bis (Di-2-Pyridylmethylene) Thiocarbono-Hydrazide

Abstract

The use of 1,5-bis(di-2-pyridylmethylene) thiocarbono-hydrazide as a reagent for the extraction of Ni(II), Co(II), Zn(II), Fe(II), Cd(II) and Cu(II) into methyl isobutyl ketone has been studied, and a method for the determination of nickel at ultra-trace (ng/ml) level has been developed, by using electrothermal-atomization (graphite furnace) atomic absorption spectrometry involving a prior extraction with the cited extracting reagent. The chief advantage of the proposed method lies in its maximum allowed aqueous-to-organic phase volume ratio of 15. It has been successfully applied to the determination of nickel substrates in various biological samples.     

Trace determination of dichlorodiphenyltrichloroethane and its main metabolites in environmental water samples with dispersive liquid–liquid microextraction in combination with high performance liquid chromatography and ultraviolet detector

Dichlorodiphenyltrichloroethane,1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and its main metabolites have been paid much more attention, and present paper describes a new process for the rapid determination of such pollutants in environmental water samples based on dispersive liquid–liquid microextraction (DLLME) and high performance liquid chromatography with ultraviolet detector, which has merits such as high enrichment factor and sensitivity, low cost and easy to operate. Significant parameters such as extraction solvent and dispersive solvent type and volume, pH, extraction time and centrifuging time, which would have important impact on the enrichment of target pollutants, have been investigated in detail. The results exhibited that excellent performance could be achieved with carbon tetrachloride and acetonitrile as the extraction solvent and dispersive solvent, respectively. Under the optimal conditions, excellent linear relationship was gained in the range of 1.0–50 μg L⁻¹, and detection limits were in the range of 0.32–0.51 μg L⁻¹. The precisions of the proposed method were in the range of 2.80–7.50% (RSD). The proposed method was validated with real water samples, and the results indicated the spiked recoveries were in the range of 85.58–119.6% and the established method was very good and competitive in the determination of DDT and its metabolites.     

Determination of alkenylbenzenes and related flavour compounds in food samples by on-column preconcentration-capillary liquid chromatography

A new, simple and versatile method is presented for the determination of different concentration levels of alkenylbenzenes (eugenol, isoeugenol, eugenol methyl ether, myristicin, anethole and estragole) and the related flavour compounds (coumarin and pulegone) in food samples. The method involves the use of a stationary phase (capillary column) for the enrichment with appropriate elution. After the sample had completely passed through the capillary column the eluent was changed and the separation/detection was achieved. Excellent linearity was obtained under the proposed conditions for a direct determination method and a method including on-line preconcentration. The limits of detection were in the ranges 97–148 and 9.5–14.2 ng/mL, respectively. Evidence for a matrix effect was not found and recoveries between 92 and 110% were obtained. The precision of the method, expressed as relative standard deviation values, was below 5% in all cases. The applicability of this methodology was tested by analyzing synthetic and real food samples.     

Phase equilibria for salt-induced lysozyme precipitation: Effect of salt type and temperature

The salt-induced precipitation of lysozyme from aqueous solutions was studied through precipitation assays in which the equilibrium compositions of the coexisting phases were determined. Lysozyme precipitation experiments were carried out at 5, 15 and 25 °C and pH 7.0 with ammonium sulfate, sodium sulfate and sodium chloride as precipitating agents. In these experiments a complete separation of the coexisting phases (liquid and solid) could not be achieved. Nevertheless it was possible to determine the composition of the precipitate. The enzymatic activity of lysozyme in the supernatant phase as well as in the precipitate phase was also determined. The activity balance suggests that there is a relationship between the composition of the true precipitate and the total activity recovery.     

Determination of chlorinated hydrocarbons in milk samples using sol-gel based polymer coated silica sorbent for stir-bar supported micro-solid-phase extraction coupled with gas chromatography mass-spectrometry

In this work, sol-gel reaction chemistry was utilized to create 3-(trimethoxysilyl)propyl methacrylate-poly (propylene glycol) polymer coating on amorphous silica. The synthesized sorbent was characterized using energy dispersive X-ray spectrometry, field emission scanning electron microscopy, and thermogravimetric analysis. The sorbent was then used for membrane protected stir-bar supported micro-solid-phase extraction (SB-µ-SPE) of chlorinated hydrocarbons (CHCs) in milk samples and analyzed using gas chromatography mass spectrometry. Sorbent suitability, sorbent quantity, solvent for desorption, solvent volume, time for extraction, time for desorption, and ionic strength were all optimized for extraction. This method resulted in a wide linear range for all tested CHCs with an r² up to 0.9992. The lower limits of detection ranged between 0.2 and 2.8 ng mL^?1. Reproducibility of the method was also determined at three different concentrations ranging between 3.8 and 7.3%. The relative recoveries in milk samples were found to be between 85.1 and 104.3%.