Rapid analysis of lubricants by atmospheric solid analysis probe–ion mobility mass spectrometry

Formulated lubricants are complex mixtures composed of base oil(s) and additives with various functions (detergents, corrosion inhibiter, antioxidant, viscosity modifiers, etc.). Because of the aliphatic nature of base oil and the chemical diversity of additives, the characterization of lubricant is currently a long and complex process. The comprehensive analysis of lubricant samples involves several techniques such as nuclear magnetic resonance, mass spectrometry, chromatography and infrared spectroscopy. The coupling of atmospheric solid analysis probe (ASAP) with ion mobility‐mass spectrometry (IM‐MS) has been shown to be an efficient tool for the characterization of complex mixture containing vaporizable polar to non‐polar compounds. This approach affords the coupling of a direct ionization technique that does not require sample preparation, with a bi‐dimensional separation method with high peak capacity. In this work, we show that ASAP‐IM‐MS is a suitable method for rapid and direct characterization of lubricant samples. Indeed, base oil and additives yielded, by ASAP, ions series which could be separated by IM‐MS. Molecular additives such as Zn‐dithiocarbamate, phosphite, thiophosphate and Alkyl diphenylamine were ionized as molecular ions [M]^+? or protonated molecules [M + H]⁺, depending of their polarity. In some cases, fragment ions were observed, confirming the additive identification. In addition, high molecular weight polymeric additives such as poly(alkyl methacrylate) (PAM) were pyrolized in the ASAP source leading to characteristic fragment ions. ASAP‐IM‐MS is shown to be a powerful tool for studying complex mixtures, allowing the first comprehensive analysis of lubricants in just a few minutes. Copyright © 2014 John Wiley & Sons, Ltd.     

The use of ATR-IR to identify the components separated by paper chromatography

Summary A modified procedure for the identification of separated components in paper chromatography using attenuated total reflection infrared spectroscopy is described. This combined method, though inferior in sensitivity and resolution to the modern separation systems interfaced with sophisticated analytical instruments, is simple, relatively less expensive and suitable for routine analysis of components like polymer additives.     

On the variation of the stability constants of EuCl2+ in the mixed system of dimethyl sulfoxide and water

The effect of water-miscible alcohols and acetone on the extraction and separation of Cd and Zn chlorides by TOPO was systematically investigated. The maximum extraction of Zn chloride with 0.1 M TOPO decreases in the order: acetone>methanol>ethanol>2-propanol>2-butanol. For alcohols, the sequence of decreasing extractability is thus parallel to the order of their dielectric constants. This can be explained by the increase of HCl extraction by TOPO in the same direction. The presence of additives in the polar phase prevents the formation of a bulky white precipitate encountered during extraction of ZnCl₂ from pure aqueous solutions. A decrease of Cd chloride extraction was generally noticed in presence of additives; this is more noticeable for the longer chain alcohols. The highest separation factor (E for ZnCl₂ and CdCl₂ in 0.48M HCl is obtained from 30% methanol (13.8 compared to about 3.8 in absence of methanol) and from 10–20% acetone where it reaches 30.     

Synthesis Characterization and Application of Polyglycerol Esters of Fatty Acids: Biodegradable Surfactants

Surfactant-based separations are attracting interest due to simple operations and viable economics. The present work focuses on the synthesis of two nonionic surfactants, polyglycerol fatty acid esters of cotton seed oil and castor seed oil, its characterization using Fourier transform infrared spectroscopy and liquid spectroscopy-mass spectroscopy. The synthesized surfactant is used in breaking azeotropic composition of n-propanol–water mixture via cloud point separation. The separation obtained from the synthesized surfactants is compared with the separation obtained from Tween 20 and it is found that both the synthesized surfactants are capable of breaking the azeotrope of n-propanol–water mixture.     

An infrared spectroscopic method for quantitative analysis of fatty alcohols and fatty acid esters in machinery oils

A new infrared spectroscopic method suitable for determining total fatty alcohol and fatty acid ester concentrations in industrial oils has been developed. Oil samples were diluted with toluene (1:3 w/w), the toxicity and volatility of which are relatively low compared with more commonly used IR solvents, like carbon tetrachloride or carbon disulfide. Mixture standards were prepared from dodecanol, tetradecanol, octadecanol, methyl stearate and methyl palmitate. Some analytical and statistical tests were performed on the developed method. The recoveries and the repeatability of the method proved to be sufficient for the quantitative determination of fatty alcohol and fatty acid ester additives in industrial oils. Reproducibility testing in another laboratory also produced satisfactory results. The developed method also proved to be relatively quick and simple. This method was developed to satisfy industry’s need to determine the concentrations of these oil additives, and it has already been applied successfully in machinery oil analysis.     

Implications of on-line FTIR detection in the separation of coal-derived products via HPLC with polar modifiers

Summary Fourier-transform infrared spectrometry (FTIR) was utilized as a detection system for high-performance liquid chromatography of polar compounds on a normal bonded-phase system. In addition to FTIR, UV (254 nm) and refractive index detection were employed in the separation of model compounds containing oxygen and nitrogen atoms in their molecules (phenols, alcohols, neutral and weakly basic nitrogen compounds). A polar amino-cyano (PAC) bonded-phase column was employed with a binary mobile phase (98:2 CDCl₃:CH₃CN). The separations and the information gained from each detector is discussed, including interactions between sample material and mobile phase. A polar fraction of a coal-derived product is also chromatographed under identical conditions. The results based on FTIR detection and chromatographic retention behavior suggest the exclusive presence of hindered and unhindered phenols.     

Quantitation of Serotonin in Human Plasma,Serum and Cerebrospinal Fluid Samples by HPLC-EC Using 6-Hydroxytryptamine as an Internal Standard

Abstract

A simple method for sample clean up and concentration of serotonin (5-HT) in biological samples, such as human cerebro-spinal fluid and serum, is described. To the sample 6-hydroxy-tryptamine (6-HT) is added as an internal standard and it is then absorbed either on C₁₈ SEP-PAK cartridge or Biorex-70 short column. 5-HT and 6-HT are then eluted from the column with methanolic formic acid. After evaporation, the residue is dissolved in the mobile phase and an aliquot is used for LC-EC quantitation.     

SEP-PAK Preparative Chromatography: Use in Radiopharmaceutical Synthesis

Abstract

The use of SEP-PAK^R C₁₈ cartridges for the isolation and purification of radiopharmaceuticals, labeled with the 20.4 minute half-life radionuclide carbon-11, is reported. Synthesis and SEP-PAK preparative chrotmatographic purification of [1-¹¹C]palmitic acid, [¹¹C-methyl]benzyl methyl ether, [1-¹¹C]butan-1-ol, and [1-¹¹C]pyruvic acid are described. The use of SEP-PAK C₁₈ cartridges has allowed development of rapid and remote methods for handling of high amounts (> 100 mCi) of radioactive products.     

大黄素键合硅胶高效液相色谱柱的制备和应用

采用中间体法,先将大黄素配体与γ-[（2,3）-环氧丙氧]丙基三甲氧基硅烷（KH-560）偶联剂反应制备含配体的硅氧烷试剂,然后再与硅胶键合,最终制得大黄素键合硅胶液相色谱固定相（以下简称ESP）。通过红外光谱、元素分析和热重分析表征固定相的结构。以萘作为溶质探针,甲醇-水（60：40,v/v）为流动相,流速为0.8 mL/min,测得ESP柱的柱效。采用传统的反相C₁₈和苯基柱作参比,将ESP应用于系列中性、碱性和酸性芳香族化合物以及实际样品风油精的分离分析,并探讨相关的色谱分离机理。结果表明,配体大黄素被成功地键合到球形硅胶表面,测得配体键合量为0.23 mmol/g,ESP柱理论塔板数约为19874 N/m。ESP的偶联剂链和蒽醌环提供了疏水性的结构基础,大黄素配体还能为溶质提供π-π或p-π、电荷转移、氢键、偶极-偶极等作用点。多位点的协同作用使得ESP柱具有独特和优秀的色谱分离选择性,并且无需调节pH值,采用简单而廉价的甲醇-水流动相就能实现胺类、酚类等极性样品的基线分离,实验条件简单、方便。     

Use of zwitterionic buffer additives to improve the separation of proteins in capillary zone electrophoresis

In CZE, the adsorption of the proteins on the capillary wall is a common problem. This paper describes the simple method of utilizing zwitterionic buffer additives to improve the separation of proteins in untreated fused silica capillaries at neutral pH. Three kinds of zwitterion are evaluated in the separation of acidic, neutral, and basic proteins, including their effect on protein efficiency, mobility, separation, and resolution; the difference between the effects of the different additives are also highlighted. The method has proved to be a possible means of reducing protein adsorption, especially for basic proteins.     

Preparation and Evaluation of Some Terpolymers as Lube Oil Additives

In the present work, some polymeric additives were prepared to use as viscosity index improvers and pour point depressants for lube oil via copolymerization of hexadecylacrylate and dodecylacrylate with styrene. Structure of the prepared compounds was confirmed by infrared spectroscopy and nuclear magnetic resonance. The molecular weights of the prepared copolymers were determined by using gel permeation chromatograph. The efficiency of the prepared terpolymers as viscosity index improvers and pour point depressants for lube oil was investigation. It was found that all the prepared terpolymers are effective as viscosity index improvers and pour point depressants. The viscosity index of the prepared terpolymers increases with increasing the concentration of the additives and increases by increasing the percentage of hexadecylacrylate until 70%. The best result for viscosity index of the prepared terpolymers is when the percentage of styrene is 10%. The pour point of the prepared compound decreases with decreasing concentration of additive used.     

Silica modified with a thiourea derivative as a new stationary phase for hydrophilic interaction liquid chromatography

Nowadays there are limited types of commercially available stationary phases for hydrophilic interaction liquid chromatography and therefore new ones with unique selectivity are urgently in demand to meet the need of separations of various polar and hydrophilic analytes. The present study describes the preparation and evaluation of a new stationary phase based on thiourea derivative modified silica for hydrophilic interaction liquid chromatography. Thiourea derivative was bonded onto the surface of silica particles via a mild addition reaction between –NH₂ and –SCN, and the result of elemental analysis together with infrared analysis and solid‐state NMR spectroscopy proved that the synthesis method was feasible. The new stationary phase succeeded in fast separations of a wide range of polar and hydrophilic analytes and exhibited excellent separation performance, especially unique selectivity. Furthermore, the effects of water content, buffer pH, and salt concentration on retention indicated that a complicated separation mechanism rather than partitioning was involved in the stationary phase and hydrogen bonding interaction between analytes and thiourea functional group could play a very important role in its selectivity. For sure, the new stationary phase is of a great potential as a new type of hydrophilic interaction liquid chromatographic stationary phase.     

High Performance Liquid Chromatography Analysis of Sugar Cane Bagasse Hydrogenation Products. I. Group-Type Separation

Abstract

An HPLC Group-Type Separation was developed for the analysis of the liquefaction product of sugar cane wood fibers (bagasse). First, a liquid-liquid extraction technique was applied to separate the highly polar and polymerized aqueous fraction from the less polar organic fraction. This last fraction was then separated by HPLC into four classification groups: three hydrocarbons (saturates, olefins and aromatics) and a combination of polar compounds.

The application of these extraction and separation methods to the analysis of Brazilian sugar cane residue liquefaction products was very promising since the major group present in the extract is the aromatic hydrocarbons, suggesting its potential use as chemical feedstock, as well as a possible renewable source of energy. In addition, the method generates discrete and “clean” fractions for further detailed characterization when desired.     

RP-LC for Determination of Plastochromanol, Tocotrienols and Tocopherols in Plant Oils

An isocratic high performance liquid chromatographic method, with the application of C₁₈ and C₃₀ reverse-phase column and fluorescence detection, is described for the analysis of plastochromanol, tocotrienols and tocopherols in plant seed oils. The solvent systems have been optimized to obtain high resolution for all tocochromanols and relatively short analysis time. The use of reverse-phase columns for plastochromanol analysis, previously not reported, enables very sensitive and selective detection of plastochromanol which under the described separation conditions did not interfere with tocochromanols or any other compounds. The sample extraction method is fast, simple and highly efficient. The obtained results show that plastochromanol was present in most of the investigated seed oils. Its level was the highest in flax (17–30 mg/100 g oil), rape (8.5–9), camelina (4.3), peanut (1.95), corn (1.69) and grape (1.31) seed oils. Its level in the other investigated oils was below 1 mg/100 g oil, and only in sesame and coconut oils it was not detected. Tocotrienols were found in most of the oils but their content was usually very low (<<1 mg/100 g oil) with the exception of grape, milk thistle and corn oils where it reached >1 mg/100 g oil. Tocopherol content and isomer composition was within the earlier reported literature values for the investigated oils.     

Polymers-Copolymer as Flow Improvers for Fuel Oils and Their Electrical Conductivity

In order to find efficient cold flow improvers for fuel oil, polymethylmethacrylate (PMMA), polystyrene (PS), and a copolymer [styrene (S)–methylmethacrylate (MMA) were prepared. The structure of these polymers and the copolymer were characterized by infrared spectral analysis and their molecular weights were measured. These polymers-copolymer were used as additives for fuel oils in order to lower their pour point. Accordingly, they were evaluated as flow improvers for fuel oil. The results indicated that PMMA possesses less performance as pour point depressant. While the addition of PS and the copolymer (S–MMA) yield excellent pour point depressants for fuel oil. Upon studying the prepared additives and their properties, it was found that the electrical properties of the copolymer were changed due to the presence of polar ion in MMA effect on the electrical properties. The highest electrical conductivity was found when styrene:MMA molar ratio was 1:1.     

Recent advances in microemulsion electrokinetic chromatography

Microemulsion electrokinetic chromatography (MEEKC) is an electrodriven separation technique. Separations are typically achieved using oil-in-water microemulsions, which are composed of nanometre-sized droplets of oil suspended in aqueous buffer. The oil droplets are coated in surfactant molecules and the system is stabilised by the addition of a short-chain alcohol cosurfactant. The novel use of water-in-oil microemulsions for MEEKC separations has also been investigated recently. This report summarises the different microemulsion types and compositions used to-date and their applications with a focus on recent papers (2002-2004). The effects of key operating variables (pH, surfactant, cosurfactant, oil phase, buffer, additives, temperature, organic modifier) and methodology techniques are described.     

The dispersion of natural oils in de-gassed water

Recent studies have demonstrated that pure hydrocarbon oils can be dispersed in water as fine droplets without the use of additives. The high interfacial tension between hydrocarbons and water is expected to cause cavitation between oil droplets during separation. This cavitation is aided by dissolved atmospheric gases present in both the oil and water. Their removal allows oil droplets to be readily dispersed in water. In this paper we report on the effect of the de-gassing process on the dispersion of several natural, water immiscible oils. These natural, mixed oils are eucalyptus, lavender and tea tree oil. Although these oils are mixtures and in some cases not as hydrophobic as those used in the earlier studies, the effect of de-gassing substantially enhances their dispersion, producing micron-sized droplets without the need for additives. Dispersions of these natural oils in pure water have a wide range of uses where purity is an advantage, for example, in skin cleaning products and oral sprays.     

Poly(dimethylsiloxane) networks modified with poly(phenylsilsesquioxane)s: Synthesis, structural characterisation and evaluation of the thermal stability and gas permeability

Self-supported translucent films constituted of semi-inorganic polymeric materials were prepared by sol-gel process from poly(phenylsilsesquioxane) (PPSQ) and poly(dimethylsiloxane) (PDMS), modified by diphenylsilanediol (DPS), phenyltriethoxysilane (PTES) and/or tetraethoxysilane (TEOS). These materials were characterized by infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermo-gravimetric analysis (TGA). Permeability to N₂, O₂, CH₄ and CO₂ and selectivity for a specific gas pair were investigated using the time-lag method. In the gas separation process high permeability and selectivity coefficients were observed, particularly for the membrane containing DPS and PTES as additives, which presented potential applications in the separation of CO₂/CH₄ and CO₂/N₂. The materials also showed good thermal stability, which could be correlated to the relative amounts between di-functional (D), tri-functional (T) and tetra-functional (Q) silicon units.     

Novel additives for the separation of organic acids by ion-pair chromatography

<正>This paper proposes the use of novel surfactant additives for the separation of organic acids by ion-pair chromatography and studies the influences of surfactants on the chromatographic separation behaviors.Researches have been carried out on both silica gel matrix and polymer supporters in order to compare the two ordinary kinds of stationary phases,and the phenomenon is similar. Separation is based on differences in the stabilities of analyte-additive complexes in solution.Retention times of analytes can be varied over a large range by varying the additive concentration.The results indicate that the additives of proper concentrations can reduce the retention times of different organic acids while the resolution remains the same.The larger the molecular weight is,the greater the shift of the retention time is.This greatly expands the scope of macromolecular polar compounds that can be separated by ion-pair chromatography with the advantages of retention times being greatly reduced.     

Comparison of various types of stationary phases in non-aqueous reversed-phase high-performance liquid chromatography–mass spectrometry of glycerolipids in blackcurrant oil and its enzymatic hydrolysis mixture

The selection of column packing during the development of high-performance liquid chromatography method is a crucial step to achieve sufficient chromatographic resolution of analyzed species in complex mixtures. Various stationary phases are tested in this paper for the analysis of complex mixture of triacylglycerols (TGs) in blackcurrant oil using non-aqueous reversed-phase (NARP) system with acetonitrile–2-propanol mobile phase. Conventional C₁₈ column in the total length of 45 cm is used for the separation of TGs according to their equivalent carbon number, the number and positions of double bonds and acyl chain lengths. The separation of TGs and their more polar hydrolysis products after the partial enzymatic hydrolysis of blackcurrant oil in one chromatographic run is achieved using conventional C₁₈ column. Retention times of TGs are reduced almost 10 times without the loss of the chromatographic resolution using ultra high-performance liquid chromatography with 1.7 μm C₁₈ particles. The separation in NARP system on C₃₀ column shows an unusual phenomenon, because the retention order of TGs changes depending on the column temperature, which is reported for the first time. The commercial monolithic column modified with C₁₈ is used for the fast analysis of TGs to increase the sample throughput but at cost of low resolution.