高效液相色谱-二极管阵列检测法测定护发产品中肌酸

建立了护发产品中肌酸的高效液相色谱(HPLC)测定方法.样品经流动相溶解并提取,采用偏磷酸溶液为流动相,流速为1.0 mL/min,以C8色谱柱(250 mm×4.6 mm 5μm)进行分离,二极管阵列检测器进行检测,检测波长为210 nm.在上述条件下,目标物质与样品的杂质获得有效分离,在2～100 mg/L范围内,质量浓度与峰面积呈良好的线性关系.对护发产品进行添加回收,回收率为92.5%～101.6%,RSD为2.0%～3.7%.已用于护发产品中肌酸含量的分析.     

Determination of novobiocin by a kinetic spectrophotometric method in milk and biological samples

A new, simple, inexpensive, and fast kinetic spectrophotometric method was developed for the determination of trace amounts of antibiotic drug novobiocin sodium over the range of 4?32 ng/mL. The method is based on the inhibitory effect of novobiocinon the reaction of Amido Black and periodate in the acidic micellar mediums. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance at 627 nm and fixed-time 6 min from initiation of the reaction. The detection limit is 3 ng/mL, and relative standard deviation for 4.8 and 12 ng/mL novobiocin were 0.52 and 0.65%, respectively, for six replicate measurements. The method was applied to the determination of novobiocin in human and dog serum, urine, and milk samples.     

Determination of rare-earth elements in rock samples by neutron activation analysis with a lithium-drifted germanium detector after chemical group-separation

A lithium-drifted germanium detector combined with chemical group-separation has been utilized for the determination of rare-earth elements (La, Ce, Nd, Sm, Eu, Gd, Tb, Tm, Yb and Lu) in rock samples by neutron activation. This procedure has the advantage of a low background level which cannot be attained in the non-destructive method. The combination of the Ge(Li) detector and chemical group-separation also offers a distinct simplification in the correction of contributions from other nuclides. For optimum utility of a Ge(Li) detector in neutron activation analysis, chemical group-separations are recommended.     

Determination of parabens in cosmetic products by solid-phase microextraction of poly(ethylene glycol) diacrylate thin film on fibers and ultra high-speed liquid chromatography with diode array detector

The fabrication of a solid-phase microextraction (SPME) fiber through UV-induced polymerization of poly(ethylene glycol) diacrylate (PEG-DA) for determination of parabens in cosmetic products is presented in this work. The PEG-DA polymer coating was covalently attached to the fiber by introducing a surface modification with 3-(trichlorosilyl)propyl methacrylate (TPM). The PEG-DA polymer thin film coated on the fiber was homogeneous and wrinkled, which led to an increase of the surface area and high extraction efficiency. The extraction performances of the prepared SPME fibers were assessed by preconcentration of parabens including methylparaben, ethylparaben, propylparaben and benzylparaben from cosmetic products. The analysis was performed on an ultra high-speed liquid chromatography with diode array detector. The prepared SPME fibers exhibited good repeatability (for one fiber) and reproducibility (fiber-to-fiber) with RSDs of 5.4 and 6.9%, respectively. The optimized SPME method supported a wide linear range of 0.50-160 μg/mL and the detection limits for parabens were in the range of 0.12-0.15 μg/mL (S/N=3). The developed method was successfully applied for determination of parabens in cosmetic products with different natures.     

Determination of alkyl methylphosphonates and methylphosphonic acid by capillary electrophoresis with a diode-array spectrophotometric detector

Method of capillary electrophoresis with a diode-array detector was used to study the conditions of the separation of three alkyl methylphosphonates and methylphosphonic acid, hydrolysis products of nerve agents. The optimal conditions providing their separation and determination are reported (background electrolyte based on 100 mM boric acid with the addition of 10 mM of phenylphosphonic acid (pH 6.0); voltage +30 kV, detection wavelength 210 nm, electrokinetic introduction of the sample (10 kV, 10 sec), separation time below 10 min). Calibration curve for all the compounds was linear in the concentration range 0.05–1.0 mg/mL, the correlation coefficient was 0.999 in all cases. The procedure was tested for river and ground waters containing a mixture of isopropyl, isobutyl, pinacolyl methylphosphonates and methylphosphonic acid. Relative standard deviations of the migration times under the conditions of the repeatability of the results lie in the range 1.9–2.7% (n = 5), the relative standard deviation of the reduced peak areas vary from 1.2 to 7.0%.     

利用凝胶渗透色谱示差-紫外检测器联用测定丁苯共聚物的组成分布

将凝胶渗透色谱(GPC)中的示差与紫外检测器联用,测定了无规共聚丁苯橡胶和SBS三元嵌段共聚物中各级分的组成变化.实验方法选择中对比了两种浓度参数的确定方法,发现通过改变注射量来实现浓度变化的方法优于使用系列浓度样品的方法.分别测定标准样品在紫外和示差检测器上信号产生的时间间隔可以确定两个检测器上信号的时间差.根据紫外-示差检测器联用可以看到SBR无规共聚物和三嵌段SBS共聚物样品中每一个级分中随着相对分子质量的变化,苯乙烯含量的变化.     

Determining the purity of samples from natural products by coupling HPLC and CCD spectrometry

Isolation and identification of natural products is a very important and active research field. However, establishing the purity of the samples during the isolation process is quite difficult, especially when the retention times are similar for two desired components in HPLC. Although some technologies, e.g. MS and NMR, offer effective ways of obtaining purity information about the samples, the expensive instrumentation required or the off-line nature of coupling (generally speaking) make purity analysis somewhat inconvenient. In this paper, an on-line analytical system coupling HPLC and a CCD spectrometer for determination of purity for each eluate was developed in a thin layer spectrometric cell. The effectiveness of the system was demonstrated by differentiating Tanshinone I, Tanshinone IIA, and their mixture. The time-resolved UV-Vis spectra promptly revealed significant differences between the three samples while conventional single wavelength detection (CSWLD) could not. The system was then used to distinguish two steroid compounds which behaved as a single component in CSWLD. The compounds were isolated from a Chinese marine invertebrate animal, a marine annelid, Arenicola cristata, referred to here as Stimpson. The method reported here provided an efficient, convenient, fast, and inexpensive approach holding promise for on-line determination of the purity of samples isolated from natural products.     

Automated determination of carboxylic acids in biological and geochemical samples by means of a chemical reaction detector

Rapid evaluation of carboxylic acids by means of an automated spectrophotometric determination in a continuous-flow system is described. The system was applied to food and soil extracts either as a stand-alone device or as a chemical reaction detector coupled to a chromatographic separation column. Calibration in the automated system was performed with citric acid as a reference standard in the concentration range 4.76 × 10^?5?4.76 × 10^?3 mol l^?1. The molar calibration equation was A=64x ? 6.7 × 10^?5 (x=concentration ) with a correlation coefficient of 0.9997 ( six points). The sample volume was 0.5 ml. In addition to the semi-quantitative evaluation of carboxylic groups, it is shown that the system is also applicable to species analyses.     

Determination of copper and zinc in metallurgical products by automatic derivative spectrophotometric titrations

Direct automatic derivative spectrophotometric titration procedures for copper and zinc in brasses and bronzes are described. Copper reacts with excess iodide and the liberated iodine is automatically titrated with thiosulfate using the UV absorption band of iodine for end-point detection. Total copper and zinc is automatically titrated with EDTA using PAN as indicator, and zinc is found by difference. 'I'he automatic termination of the titrations eliminates the subjective evaluation of the end-points, and the entire procedure is simple, precise and accurate. The total time required for determining copper and zinc in brass or bronze is about twenty minutes.     

Determination of nitrite in food samples by second-order calibration of kinetic spectrophotometric data

A method for the determination of nitrite in soil and vegetable samples by UV-Vis spectroscopy was proposed. The kinetic UV-Vis data were collected during the reaction between nitrite and 4-amino-3-hydroxynaphthalene-1-sulfonic acid with concentration of 0.001 M and pH 1.6. Data were collected by standard addition method. Multivariate curve resolution-alternating least squares was employed to analyze data with non-negativity and three-way data structure constraints. The method can be used to solve matrix effect and unknown interferents in the determination of nitrite in complex samples. The proposed method was used to determine nitrite at low mg/L levels with satisfactory results in soil, lettuce, cabbage and cucumber samples.     

顺序注射光度滴定法测定食醋和饮料的总酸度

以溴百里酚蓝(BTB)为指示剂,NaOH溶液(含指示剂)为滴定剂,应用顺序注射光度滴定法测定了食醋和饮料的总酸度。乙酸在0.20～2.00mol/L、柠檬酸在3.29×10-3～1.67×10-2mol/L范围内其浓度的对数分别与(未反应碱区带的)吸收信号的峰面积成反比例关系,测定方法的相对标准偏差(RSD)分别为HAc<3.0%、柠檬酸<1.3%,采样频率为30样/h,对市售食醋及饮料样品检测的结果与国家标准方法(酸碱滴定法)一致。     

Determination of nimesulide in pharmaceutical and biological samples by a spectrophotometric method assisted with the partial least square method

A simple and sensitive spectrophotometric method for the determination of nimesulide in bulk, in pharmaceutical dosage form, and in biological fluids was developed. The method is based on the reduction of the nitro group of nimesulide by zinc and hydrochloric acid followed by diazotization, and coupling with orcinol in basic medium to form a stable chromophore, which absorbs at 465 nm. The method showed a good linearity in the range 0.4–4.0 μg mL^?1. Partial least square modeling as a powerful multivariate statistical tool is also applied, compiled, and compared for determination of nimesulide. The experimental matrix for the partial least square calibration method was designed with 24 samples. The cross-validation was used for selecting the number of factors. The root mean square error prediction (RMSEP) and the relative error of prediction (REP %) were 0.089 and 3.95, respectively. The developed method is free from the interference of common excipients used in pharmaceutical dosages. The method was also used for the determination of nimesulide in pharmaceutical dosages as well as in human serum and urine samples.     

Determination of ametoctradin in plant residues and environmental samples by HPLC with an UV detector

The study deals with the development of a method for the determination of ametoctradin by HPLC with UV detection. Samples were extracted with aqueous acetone and then purified by distribution between immiscible solvents and also on solid-phase extraction cartridges. The procedure was tested in the determination of ametoctradin in water in the range 0.001–0.01 mg/L, in soil, potato vine and potato tubers, salad, onion, cucumber, tomatoes, carrots, grapes, and grape juice in the range from 0.005 to 0.1 mg/kg, depending on the matrix. The average recoveries were 78?92% with RSD < 0.08%. The proposed procedure is applicable to the determination of ametoctradin in environmental samples and plant residues.     

浊点萃取光度法测定水样中亚硝酸根

A new method for the determination of trace nitrite by spectrophotometric after cloud point extraction was proposed.The effects of experimental conditions such as acidity,concentration of chromogenic reagent and surfactant,equilibration temperature and time on cloud point extraction were discussed.Under the optimum conditions,a good linear relationship was obtained in the range of 4.0～200 μg/L of the nitrite(r=0.9998),the detection limits of 0.43 μg/L.The recoveries fell in the range from 97.7% to 102.4% an...     

Determination of synthetic acaricides residues in beeswax by high-performance liquid chromatography with photodiode array detector

A multiresidue HPLC method for identification and quantification of the synthetic acaricides fluvalinate, coumaphos, bromopropylate and its metabolite 4,4′-dibromobenzophenone in beeswax has been developed. Different techniques were tested and modified. The method consists of a sample preparation with isooctane followed by solid phase extraction using Florisil columns. Determination of the synthetic acaricides is achieved by HPLC with a photodiode array detector. Analytical performance of the proposed method, including sensitivity, accuracy and precision was satisfactory. The LOD for the analytes varied between 0.1 and 0.2 μg g⁻¹ wax and the recoveries between 70 and 110%. Relative standard deviation of the repeatability of the method is <15% and reproducibility is <31%.     

Determination of optical purity in partially racemized samples of l-aspartic acid by means of liquid crystals

A method for the determination of the optical purity of partially racemized samples of l-aspartic acid, based on the measurement of the pitch and handedness of cholesteric mesophases induced in MBBA (p-methoxybenzylidene-p'-n-butylaniline), is described. The minimum quantity of aspartic acid required varies with the optical purity of the sample (from 50 mug for an enantiomeric purity of 10-20% down to 5 mug for purities around 90%).