Determination of free formaldehyde in nail varnish by HPLC

Summary Free formaldehyde in cosmetic samples can be determined by HPLC and post-column derivatisation as a lutidine derivative. Applying this method to nail varnishes results in poor reproducibility. It is demonstrated that most of the formaldehyde determined is generated by hydrolysis of the resin in aqueous solution during sample clean-up, extraction and determination procedures. The hydrolysis is slowest in acidic solution at low temperature. The formaldehyde concentration is thus a function of the method of determination. Kinetic evaluation of its formation by hydrolysis shows that the initial concentration of free formaldehyde in the resin is below 100 ppm.     

Selective response mechanism of a platinum disk electrode modified with polyacrylamide membrane conjugated with gallium(III) phthalocyaninate

A non-plasticized polyacrylamide polymer (PAA) coupled with (phthalocyaninato) gallium(III) ([Ga(pc)]⁺), PAA-[Ga(pc)], was first synthesized, and the potentiometric response behavior of this PAA-[Ga(pc)] modified platinum electrode to certain ions was examined in the non-aqueous solvents acetonitrile (AN), dimethylacetamide (DMA), and N-methylpyrrolidinone (NMP). The electrode showed a Nernstian or near-Nernstian response to CN⁻ and F⁻ in AN, DMA, and NMP, but it showed a non-thermodynamic response to Cl⁻and Br⁻ in all the above solvents. Both spectrophotometric and cyclic voltammetric methods were used to investigation the reaction of [Ga(pc)]⁺ with the ions in the solvents. The results revealed that the special selective response phenomena were due to the complex formation reactions of the ions with [Ga(pc)]⁺. The reaction mechanisms were determined on the basis of the shift of the maximum absorption peaks, the appearance of the new peaks on UV-vis spectra for [Ga(pc)]⁺ in the presence of CN⁻ and F⁻ and the clear difference in the redox voltammogram for [Ga(pc)]⁺ at the platinum electrode between the addition of F⁻ and Br⁻ in DMA. There were no obvious differences between the three solvents in terms of their influence on the complexing. It was concluded that the electrode might have applications in obtaining the solubility product of NaF in AN.     

SPE/LC/ESI/MS with phthalic anhydride derivatisation for the determination of alcohol ethoxylate surfactants in sewage influent and effluent samples

A new method for the analysis of alcohol ethoxylates (AEs) using electrospray ionisation liquid chromatography/mass spectrometry (ESI LC/MS) is described. The procedure incorporates a novel derivatisation step with phthalic anhydride for the analysis of EO0-20 ethoxylates in a single analysis. The derivatives obtained have proved to be very stable and the negative ion spectra show reduced background ions and competing adduct formation as compared to positive ion spectra. An automated solid phase extraction (SPE) step is used to allow both pre-concentration and clean-up of the environmental samples. The method provides more efficient recovery of AEs across the C12-C18 range than previously reported in the literature. Recoveries from final effluent spiked at 100 microg/L total AE, for the 126 species analysed, were found to be in the range 55-117%, with approximately 100 of the individual analytes having recoveries of 90-105%. An LOD of 0.02 microg/L for individual ethoxylate components is reported with the instrument operated in scan mode over the range m/z 300-1300. The method was applied to sewage effluent and influent samples, with AEs determined at approximately 7 and 5000 microg/L, respectively.     

非水体系中磷酸钴大单晶的合成与结构

非水体系中磷酸钴大单晶的合成与结构徐家宁，袁宏明，卜卫名，邵一鸣，宋天佑，樊玉国，徐如人（吉林大学化学系超分子结构与谱学开放实验室，长春，１３００２３）关键词磷酸钴，大单晶，非水体系，晶体结构近年来的研究结果表明，非水合成技术对合成具有开放骨架结构的...     

非水毛细管电泳法测定芬布芬含量的研究

本文建立了非水体系高效毛细管电泳法测定芬布芬的新方法。考察了运行电压、非水介质和电解质等因素的影响。选择15 mmol/LNaAc-25 mmol/L十六烷基三甲基溴化铵(CTAB)为电泳介质,甲醇为溶剂,紫外检测波长281 nm,分离电压-25 kV,13 min内可以实现芬布芬的分离检测。在优化条件下,药物中辅料不干扰芬布芬的测定,加标回收率为98.2%~103.1%。方法简便、快速,可用于芬布芬片中芬布芬含量的测定。     

有机质子溶剂和有机-水溶液中质子浓度的精确测定

用水标准溶液标定的玻璃电极可用来测定有机质子溶剂和有机-水溶液中质子的水标准活度pHm质子的浓度可用-og[H2S^ ]=pHm-(-logγ-D)来精确测定。(-logγ-D)是一个常数，可以通过对有机质子溶剂和有机-水溶液中强酸-强碱滴定曲线的数学模拟后求得。因此避免了玻璃电极在有机溶剂中标定的困难。     

Separation of Nile Blue-labelled fatty acids by CE with absorbance detection using a red light-emitting diode

The separation of fatty acids derivatised with Nile Blue (NB) by CE with detection using a red light-emitting diode (LED) was examined. NB was selected as the derivatisation agent due to its high molar absorption coefficient of 76,000 M(-1) cm(-1) at 633 nm, making it well suited for sensitive absorbance detection using a red 635 nm LED. NB-labelled fatty acids were separated by both MEKC using SDS micelles, i-PrOH and n-BuOH and by NACE in a number of solvents including MeOH, EtOH and ACN. The sensitivity of NACE was superior to MEKC, with detection limits of 5x10(-7)-7x10(-7) M obtained for each acid, approximately 20 times lower than the MEKC method. The NACE detection limits are approximately 100 times lower than previous reports on the separation of fatty acids by CE using indirect absorbance detection, ten times lower than using indirect fluorescence detection and are inferior only to those obtained using precapillary derivatisation and direct fluorescence detection. The efficiency of the NACE method was also superior to MEKC and allowed the separation of unsaturated fatty acids to be examined, although it was not possible to baseline-resolve linoleic (C18:2) and linolenic (C18:3) acids in a reasonable time. The method was used to analyse the fatty acid profile of two edible oils, namely sunflower and sesame oils, after alkali hydrolysis, where it was possible to identify both the saturated and unsaturated fatty acids in each sample.     

Development of a chemometric correlation technique to estimate acid-base descriptors for cationic acids in non-aqueous media

We propose a procedure for estimating acid-base constants in organic solvents or mixture of solvents from the corresponding pK_a values in aqueous medium and from certain properties of the organic solvents that characterize them. To accomplish this, we developed and validated a chemometric correlation for the calculation of the acid-base constants of different cationic acids in a broad variety of non-aqueous solvents. The parameters chosen for building the model were as follows: the acid-base constant of the compound in aqueous medium and those corresponding to the polarity-polarizability, basicity and acidity scales of the solvent. The results of the fitting were significant (p < 0.01), with a root mean error in cross-validation of 18%, with no overfitting. The prediction of the acid-base constants for an external set of compounds had a mean absolute prediction error value of less than 0.8 pK_a units.