Preparative isolation and characterization of zinc dialkyldithiophosphates from commercial antiwear additives

An automated HPLC separation methodology was developed for the preparative separation of ZnDTP components from commercial lubricant antiwear additives. Using silica columns that can be reactivated by elution with appropriate solvents, gram quantities of additives can be isolated. The isolated materials are useful for carrying out further mechanistic and synthetic studies. Preliminary estimations suggest that separation repeatability and fraction recoveries have acceptable levels. Qualitative characterization of isolated ZnDTP mixtures was achieved by IR, TLC‐FID, and RP‐HPLC. IR is useful for assessing the nature of ZnDTP alcoholic moieties. TLC‐FID provides a check on the preparative HPLC separation efficiency. RP‐HPLC on octadecylsil‐silica columns provides fingerprints for isolated commercial ZnDTP active concentrates. Fingerprinting on small bore HPLC columns proved advantageous compared with conventional columns.     

Chromatographic performance of deuterated solvents in reversed phase micro high performance liquid chromatography

The chromatographic performance of the deuterated solvents, CD₃OD and D₂O, has been investigated in reversed-phase micro high performance liquid chromatography. The chromatographic performance of CD₃OD is only slightly superior to that of CH₃OH. However, the performance of D₂ is significantly superior to that of H₂O, separation of aromatics being improved by about 30%. D₂ is a particularly powerful solvent for the separation iof deuterated and non-deuterated compounds.     

HPLC isolation and NMR structure elucidation of the most prominent octabromo isomer in technical octabromo diphenyl ether

The major octabromo isomer of technical octabromo diphenyl ether mixture (technical octaBDE) DE-79 was isolated by RP-HPLC. Three serially coupled columns (each 250 mm long) enabled a good separation of the target compound from other congeners using 100% ACN as eluent. Approximately 100 microg of the target compound was isolated with a purity of >90% and investigated by MS for confirmation of the degree of bromination. 1H-NMR and 2-D 1H-13C correlation NMR spectra unequivocally clarified that the octaBDE in question is 2,2',3,3',4,4',6,6'-octabromodiphenyl ether (BDE 197). Based on annual production rates of technical BDE products (1999/2001), approximately 380 tons of BDE 197 were annually produced which, on the long term, may enter the environment. Compared with other individual BDE congeners, BDE 197 has the seventh highest application rate. Reductive debromination of BDE 197 can lead to four hepta-, 15 hexa-, 23 penta-, and 28 tetra-BDE isomers, respectively. This variety includes all known major BDEs of environmental concern (BDE 47, 85, 99, 100, 153, 154, and 183). The identification of BDE 197 in technical octaBDE DE-79 strongly suggests that research on the environmental fate of BDEs should include this key-BDE congener.     

Reaction des lithiens avec les organophosphores. Reaction d'addition du t-butyllithium sur le noyau benzenique des sels de phenylphosphoniums

A new reaction of organolithium compounds with phosphonium salts is described; reaction of t-butyllithium with dibenzylaminophosphonium or tetraphenylphosphonium bromides takes place through addition of the t-butyl group on a benzene ring at the position para to the phosphorus atom, the ylid formed reacts in a characteristic Wittig reaction with p-tolylaldehyde.     

An optimized method for determination of intracellular glutathione in mouse macrophage cultures by fluorimetric high-performance liquid chromatography

We have optimized a method for the determination of intracellular glutathione by high-performance liquid chromatography, using fluorimetric detection. To minimize artifacts and provide an accurate determination of intracellular glutathione, cell extracts were prepared using extraction conditions specifically designed to inhibit autoxidation and enzymatic degradation of glutathione. The sensitivity of the method was enhanced by adjusting the dansyl chloride derivatization reaction with regard to parameters such as pH, reaction time and dansyl chloride concentration. Both oxidized and reduced forms of glutathione were quantified using the refined method in extracts of oxidatively stressed J774A.1 mouse macrophage cells and reflected an expected shift in cellular redox status.     

Development of new solid-phase microextraction fibers by sol-gel technology for the determination of organophosphorus pesticide multiresidues in food

Allyloxy bisbenzo 16-crown-5 trimethoxysilane was first used as precursor to prepare the sol-gel-derived bisbenzo crown ether/hydroxyl-terminated silicone oil (OH-TSO) SPME coating. The coating procedure involving sol solution composition and conditioning process was presented. Compared with commercial SPME stationary phases, the new coatings showed higher extraction efficiency and therefore could provide higher sensitivity for organphosphorous pesticides (OPs). Limits of detection (LODs) were in the range of 0.003-1.0 ng/g for these OPs in food samples (honey, juice, orange and pakchoi). The optimal extraction conditions of the new coatings to OPs in these samples were investigated by adjusting extraction time, salt addition, extraction temperature, and dilution ratios of samples with distilled water by using SPME coupled with gas chromatography (GC)-flame photometric detection (FPD). The method was applied to determine the concentrations of OPs in real samples.     

Identification of radicals spin-trapped in autoxidized linoleic acids: A high performance liquid chromatography and electron spin resonance study

Radicals generated in linoleic acid and deuterated linoleic acid have been trapped by the spin trap 2-methyl-2-nitroso-propane (MNP) and identified by electron spin resonance (ESR) and ENDOR spectroscopy. The formation of two distinct secondary alkyl radical adducts (one conjugated, the other non-conjugated, as shown by their UV absorption spectra) was demonstrated by 11, 11-dideuterio-9-cis-12-cis-linoleic acid using HPLC and ESR spectroscopy.     

Fluorinated lignands in HPLC

Summary The chromatographic behaviour of C₆F₅(CH₂)₃SiCl₃, C₆H₅(CH₂)₃SiCl₃, CF₃(CF₂)₇CH₂CH₂SiCl₃ and n-C₁₀H₂₁SiCl₃ as well as the bonding of these ligands to silica is described. Phases with partially fluorinated ligands show entirely different chromatographic characteristics to analogous phases, where hydrogen replaces fluorine. The silica with the pentafluorophenyl-3-n-propyl-C₆F₅(CH₂)₃-ligand has higher k-values and a better selectivity for aromatic hydrocarbons than that with phenyl-3-n-propyl C₆H₅(CH₂)₃-groups, whereas the phase with the fluorinated carbon chain is less useful than the silica modified with n-decyltrichlorosilane n-C₁₀H₂₁SiCl₃. The first effect can be explained by complex formation, and the second may be due to a different contact area between the ligand and the solute. The normal hydrocarbon chains hinder each other sterically and expose many adsorption sites, in contrast the perfluorinated chains are sterically fixed and are the first example of real brushes in HPLC.     

用高效液相色谱手性固定相法拆分芳香仲醇及芳香乙二 醇类手性化合物

在ChiralcelOD和ChiralcelOJ两支多糖类手性固定相上，以各种不同配比的正己烷-异丙醇为洗脱剂对38种带有不同取代基的芳香仲醇及芳香乙二醇类手性化合物的对映体进行拆分，考察了这些外消旋体在这两支手性柱上的色谱行为。结果表明，扬长避短一柱对这些化合物的拆分能力与化合物取代基的性质和位置有关，这些化合物与手性固定相之间的氢键作用和π-π作用是影响手性拆分的重要原因。拆分方法已应用于潜手性酮不对称还原产物的光学纯度的鉴定，并取得了很好的效果。     

高效液相色谱检测Zn（Ⅱ）、Cd（Ⅱ）、Co（Ⅱ）、Pb（Ⅱ）、Ni（Ⅱ）、Cu（Ⅱ）、Hg（Ⅱ）

用双-(2-羟乙基)二硫代甲酸铵(HEDC)在反相液相色谱中作检测某些金属离子的衍生化试剂，HEDC的金属螯合物微溶于水，可直接水样注射于C18柱中进行检测，范围为0．006～10mg／L相对偏差1％～2％，检测波长254nm，金属汞的整合物在HPLC分析前进行浓缩富集检测限可低至0．06～25μg／L，相对偏差小于2％。