Electrospray mass spectrometry of zinc dithiophosphate derivatives and its application to the analysis of engine oil antiwear additives

Electrospray mass spectrometry (ES-MS) has been applied to a variety of zinc O,O′-dialkyldithiophosphate (DTP) derivatives. The neutral Zn(DTP)₂ compounds were converted to the [Zn(DTP)₃]⁻ anions by reaction with excess DTP⁻ and these principal anions are readily observed by ES-MS. Exchange reactions between two different zinc tris(DTP) anions leads to the simultaneous observation of zinc anions containing all possible combinations of ligands even though the species in solution are exchanging rapidly on the NMR timescale. Similar mass spectra are observed upon mixing Zn(DTP)₂ with a different DTP⁻ anion. Reaction of Zn(DTP)₂ with dimethylsulfoxide (DMSO) in methanol solution gives [Zn(DTP)(DMSO)_1,2]⁺ and free DTP⁻ ions which are observed in the positive ion and negative ion ES mass spectra respectively. This latter reaction provides a convenient method for the characterisation and qualitative analysis of engine oil inhibitor and antiwear additives, which contain zinc dithiophosphates with alkyl and aryl substituents.     

Determination of zinc in lubricating oil by polarography of emulsified samples

Summary A new polarographic determination of zinc in lubricating oils is based on the formation of an oil/toluene-water emulsion and bubbling nitrogen through the emulsion. A well developed peak appears at –1440 mV. The precision is ±3% for a sample with 382 mg Zn/kg.     

毛细管区带电泳法同时测定饮料中16种食品添加剂

建立了毛细管区带电泳法测定饮料中酸性红92、专利蓝V、荧光素二钠、酸性红1、靛蓝胭脂红、亮黑、丽春红6R、日落黄、苋菜红、柠檬黄等10种人工合成色素和苯甲酸、山梨酸、对羟基苯甲酸甲酯、对羟基苯甲酸乙酯、对羟基苯甲酸丙酯、对羟基苯甲酸丁酯等6种防腐剂的分析方法。考察了缓冲溶液种类、浓度、pH值及运行电压、温度等对分离的影响,确定最佳电泳条件为: 未涂层弹性石英毛细管柱(46 cm×50 μm),缓冲溶液为70 mmol/L硼酸(pH=9.5)(含体积分数为4%的乙腈),检测波长220 nm,电泳电压30 kV,进样时间5 s,电泳温度25 ℃。该法用于测定市售饮料样品得到满意结果: 在1～250 mg/L范围内线性关系良好,相关系数不小于0.9938,回收率在95.8%与108.7%之间。该法简便、准确,能够满足食品添加剂的常规检测要求。     

新型汽车发动机油用添加剂的研究进展

本文介绍了汽车发动机油用添加剂尤其是多功能添加剂的发展概况、作用机理、种类、结构及应用效果，并对未来润滑油添加剂的发展方向提供了一些参考，为我国润滑油品的高档化发展提出了几点想法。     

Characterization of the transmembrane serine receptor by capillary zone electrophoresis

Summary Capillary zone electrophoresis (CZE) was applied to the characterization of the transmembrane serine receptor in biosynthetic samples. The serine receptor, otherwise known as Tsr (taxis to serine and repellents), is a ∼ 60,000 Dalton intrinsic membrane protein whose periplasmic domain (ligand binding domain) reversibly binds the amino acid serine. In general, the electrophoresis of intrinsic membrane proteins is difficult due to severe solubility problems and adsorption which occurs during the electrophoretic run. This is due to the tendency of these types of proteins to undergo aggregation, self-aggregation and precipitation in aqueous environments. The addition of percentage levels of the surfactant, sodium dodecyl sulfate (SDS), to a tetraborate run buffer was shown to be effective both in enhancing the solubility of intact Tsr and in preventing the adsorption of intact Tsr to the fused-silica capillary wall during electrophoretic analysis. Critical separation parameters such as run buffer concentration, surfactant concentration and surfactant type were optimized to give the best separation profiles.     

Determination of recombinant hirudin structural deviants by capillary zone electrophoresis augmented with buffer additives

The polypeptide hirudin is a potent and specific thrombin inhibitor used in anticoagulant therapy and naturally occurring in medicinal leech. Using gene-technology methods, recombinant (r) hirudin can be produced on a large scale. Purity evaluation of the synthesized r-hirudin is essential to monitor co-expressed structural deviants and degradation products before therapeutic use. Although the well established RP-HPLC analysis appears to be the method of choice, in the case of r-hirudin baseline separation of the structural deviants is not necessarily achieved. Capillary zone electrophoresis augmented with buffer additives was used as a complementary technique to separate r-hirudin successfully from several similar species, in order to provide characterization information, as well as performing purity control and stability studies.     

Characterization of quantum dots using capillary zone electrophoresis

Commercially available quantum dots (QDs) were characterized using CE. The CE instruments were laboratory-built, each being capable of both electrokinetic and hydrodynamic injection. Modes of detection include UV absorption and LIF. The CE-LIF system was further modified to handle microliter sample volumes during injection. Sodium phosphate (5-25 mM, pH 7.5-11) was found to be a good buffer electrolyte. Sodium mercaptoproprionate CdTe/CdS (ADS620) QDs and carboxylic acid CdSe/ZnS (T2-Evitag) QDs yielded high separation efficiencies of N = 1.5x10(6) plates at t(M) = 10 min and N = 1.0x10(5) plates at t(M) = 3.8 min, respectively. Apparently the EDC/sulfo-NHS bioconjugation chemistry worked well with the neutral T2-Evitag QDs, but not so well with the negatively charged ADS620 QDs. This preliminary knowledge will serve as a basis for new CE immunoassay studies of QD-biomolecule conjugates and their immunocomplexes with target analytes.     

The analysis of lubricating oil additives by supercritical fluid chromatography with packed and open tubular capillary columns

Lubricating oil additives have been analyzed by supercritical fluid chromatography on open tubular and packed capillary columns. Carbon dioxide and modified carbon dioxide were used as mobile phases and detection was accomplished by flame ionization and micro UV. Rapid and efficient analysis of the lubricating oil additives was demonstrated.     

The application of mycelial wastes from microbiological production of antibacterial antibiotics as lubricating oil additives

The antiwear and antitear properties of mycelial wastes from production of antibacterial antibiotics have been studied. The waste mycelium from fucidin production has been shown to exhibit the best antiwear and antitear performance due to a higher percentage content of phosphorus and sulfur as compared to the mycelial wastes from production of other antibacterial antibiotics.     

Synthesis of ricinoleate anion based ionic liquids and their application as green lubricating oil additives

Ricinoleate anion based ionic liquids (ILs) were synthesized from four different nitrogen containing cationic counterparts such as tetrabutylammonium, tetrapropylammonium, cetyltrimethylammonium, imidazolium. Tribological performance of synthesized ILs were evaluated using four ball tribo tester by blending with two lubricant base oils namely epoxy2-ethylhexyl esters of karanja fatty acids (EKE) and dioctyl sebacate (DOS). Antiwear behaviour was explored by varying different factors including concentration, applied load and rotation speed. It was found that the synthesized ILs in base oil significantly reduced the wear scar diameter by 17–25% at 0.8 wt% and a remarkable reduction in wear scar diameter was observed for all the tested applied load (40 to 80 kg) and rotation speed (1200 to 1742 rpm). Further, the load carrying capacity of base oil was improved by 25–43% at 1.25 wt% of IL dosage. The imidazolium cation containing IL outperform tribological performance among all the ILs being studied. The morphology of worn surface after the wear tests and deposition of elementals on the worn surface lubricated with neat base oil and IL blended base oil was studied by scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX).     

Piperazine quaternary diammonium salts as additives to background electrolytes in capillary zone electrophoresis

The differential behavior of five different quaternary mono- and diammonium salts, among the 18 investigated, in modulating the electroendoosmotic flow (EOF) and analyte separations in capillary zone electrophoresis is evaluated. It is found that quaternary diammonium salts with positive charges separated by more than four carbon atoms, while exhibiting a very strong affinity for chromatographic silica beads, to the point of exhibiting Rf values close to zero, display, on the contrary, a very poor affinity for the silica wall of capillaries. Compounds separated only by a C2 unit (i.e., 1,4-dialkyl-1,4-diazoniabicyclo[2,2,2,]octane, salts 17 and 18) show high Rf values due to strong ion pair association. The unique behavior of quaternary monoammonium salts possessing an iodinated alkyl (butyl or octyl) tail (i.e., 1, 6, and 7) is attributed to their ability to be covalently affixed to the silica wall via alkylation of ionized silanols at alkaline pH values. They thus strongly modulate and typically invert the EOF, even when not present in the background electrolyte. On the contrary, all diammonium salts, devoid of such alkyl tails, are unable to modulate the EOF and to prevent analyte binding to the silica wall, since they are rapidly removed from the wall by the voltage gradient. However, if added in small amount to the background electrolyte, they offer excellent separations of mixtures of very similar organic acids and prevent any interaction with the capillary wall.     

Determination of additives in food by capillary electrophoresis

The application of capillary electrophoresis (CE) to the analysis of additives in food has been reviewed. Additives included in the review are preservatives, antioxidants, sweeteners, colourings, caffeine, niacin, choline, nitrate, and nitrite. The review highlights the versatility of CE in separating this often widely disparate group of compounds. The application of the methods to real food samples is also discussed.     

Characterization of calcium hydroxyapatite polycrystalline nanoparticles by capillary zone electrophoresis and scanning electron microscopy

A systematic study of factors affecting the parameters of the electrophoretic separation of synthetic nanocrystals of calcium hydroxyapatite is performed. Data of capillary zone electrophoresis and scanning electron microscopy are compared. Optimal conditions for the determination of calcium hydroxyapatite by capillary zone electrophoresis are selected. It is shown that calcium hydroxyapatite nanoparticles are polydisperse; the nanostructures exist in a variety of clusters and floccules with characteristic sizes, which is confirmed by the coinciding data of capillary zone electrophoresis and scanning electron microscopy. A linear dependence of the normalized total area of calcium hydroxyapatite nanoparticles on their concentration in suspension is obtained.     

A versatile kit of additives to lubricating oils

Various mixtures of imidazolines, copolymers of methacrylic acid esters, and trithiolanes were examined as additives to motor oils for diesel fuels or to cutting fluids.     

Synthesis of new polyfunctional additives to lubricating oils

Possibility of synthesizing new polyfunctional sulfur-, phosphorus-, and zinc-containing compounds with anti-wear and anti-scuff properties, promising as high-efficiency additives to lubricating oils, was studied.