Identification of structures of nitrogen-containing compounds in crude oils in conjunction with chemometric resolution

A universal method was established for the systematically structural identification of nitrogen-containing compounds in crude oils. Pre-fractionation of the non-hydrocarbons in a crude oil sample into 7 fractions was performed by di-adsorption column chromatography using neutral aluminum oxide and silica gel; subsequent high-resolution separation of individual components was achieved by using capillary column gas chromatography, and compound types were detected by mass spectrometer. The two-dimensional data from the compounds in the fractions were further resolved by a chemometric method to obtained the deconvoluted chromatogram and mass spectrum of every compound, and then, the nitrogen-containing compounds were identified in combination with the retention indices. This method could relieve the difficulty of classical analysis in identifying those species with very low contents or incompletely separation, particularly in the cases where the authentic standards were not available for addition into the unknown samples in order to reveal what indeed existed in them. The structures of 168 nitrogen-containing compounds in a crude oil sample were determined by this method with satisfactory results.     

Systemic analysis of structures and contents of nitrogen-containing compounds and other non-hydrocarbons in crude oils in conjunction with chemometric resolution technique.

A method is described for the systemic identification and quantitative analysis of nitrogen-containing compounds and other non-hydrocarbons in crude oils. The pre-fractionation of a crude oil sample into 7 fractions was performed by di-adsorption column chromatography using neutral aluminum oxide and silica gel. A subsequent high-resolution separation of individual components was achieved by using capillary column gas chromatography, and compound types were detected by a mass spectrometer. In conjunction with a chemometric method, the compounds in the fractions were further resolved or separated, which made it possible to identify some nitrogen-containing compounds and other non-hydrocarbons in crude oils. To a certain extent, this method could relieve the difficulty of classical analysis in identifying those species with very low contents or incompletely separation, particularly in the cases where authentic standards were not available for addition into the unknown samples in order to reveal what indeed existed in them. The structures and contents of 168 nitrogen-containing compounds in one crude sample and 60 non-nitrogen-containing compounds in one of non-hydrocarbon fractions of this oil sample were determined, and the addition-recovery examination of some standard compounds showed that the analytical veracity was satisfactory.     

Ligand exchange chromatography: a vital dimension for the reliable characterization of heterocycles in crude oils and refined products

In the present study, we established a statistical distribution pattern of indigenous sulfur, nitrogen, and oxygen species in Arabian Heavy crude oil and its distilled fractions: naphtha, gas oil, and vacuum gas oil (VGO) using chemical derivatization with methyl iodide and subsequent characterization by positive electrospray Fourier transform mass spectrometry. It was observed that sulfur species for naphtha and gas oil were accumulated at lower double bond equivalent values and at lower carbon numbers compared to VGO, whereas crude oil encompassed a complete range of the sulfur species detected in all distilled fractions. Moreover, the use of alumina column chromatography and ligand exchange chromatography (LEC) on a palladium-bonded silica stationary phase revealed additional structural features of sulfur heterocycles in terms of condensed and non-condensed thiophenes. During LEC separation, in addition to sulfur heterocycles, interesting results were obtained for oxygen-containing compounds. Ortho-substituted alkyl phenols were separated from meta- and para-substituted alkyl phenols on a palladium-bonded silica stationary phase.     

宝明页岩柴油碱性氮化物的梯度富集及GC-MS分析

利用溶剂萃取和柱色谱等技术浓缩分离新疆宝明页岩油柴油馏分中的碱性氮化物。以宝明页岩柴油为原料,经糠醛溶剂精制,初步得到富集碱性氮化物的抽出油。以抽出油为深度富集碱性氮化物的原料,采用柱色谱等分离方法,从抽出油中分离得到碱性氮化物。利用傅立叶变换红外光谱仪(FT-IR)和气相色谱-质谱联用仪(GC-MS)分别对富集的碱性氮化物进行官能团检测和定性、定量分析。结果表明:新疆宝明页岩油柴油馏分中的碱性氮化物经溶剂精制和柱色谱等分离方法梯度富集后,碱性氮化物的质量分数由抽出油的12.08%提高到最终产物的69.48%,并在富集分离的产物中鉴定出60种碱性氮化物,其中主要为苯胺类、喹啉类和吡啶类化合物,各占25.85%,23.56%和16.52%。     

Normal phase high performance liquid chromatography for fractionation of organic acid mixtures extracted from crude oils

Crude oil contains such an extensive range of compounds that a complete analysis is impossible. Fractionation by chemical properties is often used to simplify analytical handling. This work presents a high performance liquid chromatography (HPLC) method using normal phase chromatography on a cyano-bonded phase column to separate acid extracts from crude oils into four fractions; non-polar compounds, saturated carboxylic acids, phenols and polyfunctional acids. The method has been developed both in analytical scale for characterisation of acid extracts, and in preparative scale to provide sufficient sample amounts for further analysis by complementary methods.     

Nitrogen speciation of polar petroleum compounds by compound class separation and on-line liquid chromatography – mass spectrometry (LC-MS)

Chromatography on Attapulgus clay and on silicic acid has been used to isolate ‘neutral’ and ‘basic’ nitrogen fractions from the 650–1050 °F distillate of an off-shore Californian crude oil. These polar compounds were subjected to on-line liquid chromatography – mass spectrometric (LC-MS) analysis using low voltage electron-impact ionization high resolution mass spectrometry (LVEI HRMS) and deuterated ammonia chemical ionization (ND₃ Cl) to determine the molecules' elemental composition and number of exchangeable hydrogen atoms. On-line separation of heavy oils into saturated, 1–4 ring aromatic, and polar compounds was performed by normal phase high performance liquid chromatography (HPLC) on a dinitroanilinopropyl (DNAP) silica column.     

原油非烃化合物结构与含量的馏分分离及联用色谱信息获取通用方法

用正己烷将沥青质从油样中分离,再根据类组分之间极性差别,用中性氧化铝-硅胶双层析柱将原油样其余部分分成脂肪烃、芳香烃和7个非烃馏分。各馏分回收完全。用色-质联用技术,将非烃馏分再分离并获取实验数据,为原油非烃结构和含量测定奠定有关的信息基础。不同油井样品研究和重复实验表明,方法对各种原油非烃化合物分离和信息测定有很好的重现性。     

Analysis of the chemical composition of the essential oil of Polygonum minus Huds. using two-dimensional gas chromatography-time-of-flight mass spectrometry (GC-TOF MS)

The essential oil in leaves of Polygonum minus Huds., a local aromatic plant, were identified by a pipeline of gas chromatography (GC) techniques coupled with mass-spectrometry (MS), flame ionization detector (FID) and two dimensional gas chromatography time of flight mass spectrometry (GC x GC-TOF MS). A total of 48 compounds with a good match and high probability values were identified using this technique. Meanwhile, 42 compounds were successfully identified in this study using GC-MS, a significantly larger number than in previous studies. GC-FID was used in determining the retention indices of chemical components in P. minus essential oil. The result also showed the efficiency and reliability were greatly improved when chemometric methods and retention indices were used in identification and quantification of chemical components in plant essential oil.     

Spectroscopic and Chromatographic Identification of Hydrocarbon Group Types in Pakistani Crude Oils

Two crude oil samples collected from Paniro and Tangri (Sindh) southern Pakistan. The distillate fractions of both crude oil samples were analysed by U.V‐visible spectrophotometer and column chromatography for hydrocarbon group types. It was found from the physico‐chemical study of these crude oils that Tangri crude oil contains mostly paraffinic contents while Paniro crude oil samples are rich in aromatics. It was concluded from all the experiments that Tangri crude oil is paraffinic in nature; while Paniro crude oil is naphthenic in nature, further it was observed that Tangri crude oil processing would be environmentally friendly compared to Paniro crude oil, because Paniro crude contains a high amount of polyaromatics.     

原油中芳香硫化合物形态分布的研究

建立了原油中多环芳香硫化合物形态分布的研究方法。采用氯化钯/硅胶配位交换色谱分离原油中的芳香硫化合物,并用气相色谱/质谱分析、气相色谱-硫化学发光检测法结合色谱保留指数,鉴定出原油中的100多个多环芳香硫化物,包括含烷基取代基的苯并噻吩和二苯并噻吩类硫化物。定量分析表明,二苯并噻吩类化合物的含量占芳香硫化合物总量的91%左右。该方法可用于不同来源的原油中芳香硫化合物的形态分布研究。     

Determination of petroleum sulfonates in crude oil by column-switching anion-exchange chromatography

A column-switching anion-exchange chromatography method was described for the separation and determination of petroleum monosulfonates （PMS） and petroleum disulfonates （PDS） in crude oil that was simply diluted with the dichloromethane/methanol （60/40）. The high performance liquid chromatography （HPLC） system consisted of a clean-up column and an analytical column, which were connected with two six-port switching valves. Detection of petroleum sulfonates was available and repeatable. This method has been successfully applied to determine PMS and PDS in crude oil samples from Shengli oil field.     

Determination of volatile and non-volatile nickel and vanadium compounds in crude oil using electrothermal atomic absorption spectrometry after oil fractionation into saturates, aromatics, resins and asphaltenes

In recent work, it has been shown that electrothermal atomic absorption spectrometry (ET AAS) can be used to differentiate between volatile and non-volatile nickel and vanadium compounds in crude oil. In the present work, the distribution of these two groups of compounds over different fractions of crude oil was investigated. For this purpose two crude oil samples were separated in two steps: firstly, the asphaltenes were precipitated with n-heptane, and secondly, the maltenes were loaded on a silica column and eluted with solvents of increasing polarity. The four fractions of maltenes eluted from silica column were: F1, saturated and light aromatics; F2, polyaromatics; F3, resins; and F4, polar compounds. Fractions F1 and F2 were further investigated using gas chromatography, and all fractions were characterized by CHN analysis, confirming the increase of aromatics in the fractions 2, 3, 4 and asphaltenes. For the determination of Ni and V by ET AAS, oil-in-water emulsions were prepared. The speciation analysis was carried out measuring without chemical modifier (stable compounds) and with 20 μg palladium (total Ni and V) and the volatile fraction was calculated by difference. The limits of detection were 0.02 μg g⁻¹ and 0.06 μg g⁻¹, for Ni and V, respectively, based on an emulsion of 2 g of oil in 10 mL. The volatile species of Ni and V were associated with fractions F3 and F4, while only thermally stable Ni and V was precipitated in part together with the asphaltenes.     

Analysis of sulfur-containing compounds in crude oils by comprehensive two-dimensional gas chromatography with sulfur chemiluminescence detection

This paper reports an analytical method for separating, identifying, and quantifying sulfur-containing compounds in crude oil fraction (IBP-360 degrees C) samples based on comprehensive two-dimensional gas chromatography coupled with a sulfur chemiluminescence detector. Various sulfur-containing compounds and their groups were analyzed with one direct injection. 3620 peaks were detected including 1722 thiols/thioethers/ disulfides/1-ring thiophenes, 953 benzothiophenes, 704 dibenzothiophenes, and 241 benzonaphthothiophenes. The target sulfur compounds and their groups were identified based on the group separation feature and structured retention of comprehensive two-dimensional gas chromatography as well as standard substances. The quantitative analysis of major sulfur-containing compounds and total sulfur was based on the linear response of the sulfur chemiluminescence detector using the internal standard method. The sulfur contents of target sulfur compounds and their groups in 4 crude oil fractions were also determined. The recoveries for standard sulfur-containing compounds were in the range of 90-102%. The quantitative result of total sulfur in the Oman crude oil fraction sample was compared with those from ASTM D 4294 standard method (total S by X-ray fluorescence spectrometry), the relative deviation (RD%) was 4.2% and the precision of the method satisfactory.     

High performance liquid chromatography-mass spectrometry based chemometric characterization of olive oils

In this study the effective discrimination of extra virgin olive oils is described using HPLC-MS, combined with chemometric evaluation. The presented method is simple since the diluted oil sample is directly injected into the system, without any preliminary chemical derivatization or purification step. Separation of diacylglycerols, triacylglycerols and sterols occurs within 20 min and is achieved using an octadecyl-silica column. Detection is performed by positive APCI mass spectrometry which provided sensitivity to detect over 50 compounds in the sample. After extraction of data, stepwise discriminant function analysis is used to select the variables with the highest discriminative power. These variables are used to perform linear discriminant analysis and classify/predict the samples. One-hundred per cent classification and 99% prediction rate was achieved for olive oils obtained from Nocellara, Biancolilla and Cerausola cultivars. Reliability of prediction was tested by cross validation.     

气相色谱/质谱结合化学计量学解析方法用于植物精油成分分析

使用气相色谱/质谱(GC-MS)法对缬草精油和含有缬草精油的混配精油的化学成分进行了分析.采用直观推导式演进特征投影法(HELP)对二维数据中的色谱重叠峰进行了解析,得到两种精油的各个物质的纯色谱和纯质谱,同时利用交互移动窗口因子分析法(AMWFA)直接比较两种精油中的共有组分,提取出共有组分的纯质谱,通过与HELP法解析出的质谱进行比较,发现AMWFA法比HELP法能更快速鉴别出混配精油中的缬草精油.     

结合直观推导式演进特征投影法分析原油中非烃结构和含量

提出一种分析原油非烃结构和含量的方法。用直观推导式演进特征投影法分辨有关二维数据以获得非烃的纯色谱和纯质谱,再将所获质谱在标准质谱库中检索,并结合色谱保留指数分析等来进行单个非烃化合物结构鉴定;利用实验数据,根据分辨获得的纯色谱峰面积所建立的规一化模型,进行非烃化合物定量分析。用本法确定了一原油样品中168个含氮化合物和该油样一个馏分中60个其它非烃化合物的结构和含量。本方法具有系统分析原油非烃结构和含量的通用性;标准化合物加标回收实验表明,其准确度很好。     

Quality assessment of traditional Chinese medicine herb couple by high‐performance liquid chromatography and mass spectrometry combined with chemometrics

This study was designed to develop a simple, specific and reliable method to overall analyze the chemical constituents in clematidis radix et rhizome/notopterygii rhizome et radix herb couple using high‐performance liquid chromatography coupled with tandem mass spectrometry and multiple chemometric analysis. First, the separation and qualitative analysis of herb couple was achieved on an Agilent Zorbax Eclipse Plus C₁₈ column (250 mm × 4.6 mm, 5 μm), and 69 compounds were unambiguously or tentatively identified. Moreover, in quantitative analysis, eight ingredients including six coumarins and two triterpenoid sapogenins were quantified by high‐performance liquid chromatography coupled with tandem mass spectrometry. In terms of good linearity (r² ≥ 0.9995) with a relatively wide concentration range, recovery (85.40–102.50%) and repeatability (0.99–4.45%), the validation results suggested the proposed method was reliable, and successfully used to analyze ten batches of herb couple samples. Then, hierarchical cluster analysis and principal component analysis were used to classify samples and search significant ingredients. The results showed that ten batches of herb couple samples were classified into three groups, and six compounds were found for its better quality control.     

Identification of nitriles in petroleum products : Complex formation as a method of isolation

Nitrogen compounds were completely removed from a hydrogenated furnace oil by shaking with a mixture of ferric chloride and zinc chloride. The resulting complexes were separated from the oil and thermally decomposed to liberate the nitrogen compounds. After removal of nitrogen bases with hydrochloric acid and indoles, carbazoles, and phenazines with perchloric acid, the nitrogen compounds remaining in the concentrate were separated by fractional clution from an aluminum oxide column and gas chromatography. The following compounds were identified or their presence was indicated in the resulting fractions by their ultraviolet and/or mass spectra: dicyanobenzene, dicyanocyclohexane, cyanoindene, cyano-2,3-dihydroindene, cyanonaphthalene, dicyanoindene, dicyano-2,3-dihydroindene, dicyanonaphthalene, cyanobiphenyl, dicyanooctahydronaphthalene, and/or several of their alkyl derivatives.     

顶空气相色谱-质谱测定橄榄调和油中橄榄油含量

建立了测定橄榄调和油中橄榄油含量的顶空气相色谱-质谱分析方法。对样品量、加热温度、加热时间、进样量、进样模式、色谱柱进行了优化。通过化学计量学方法发现了橄榄油的特征化合物。取1.0 g样品放置于20 m L顶空瓶中,在180℃加热振摇2 700 s,取1.0 m L顶空气体进样,通过HP-88色谱柱分离和质谱检测。结果表明,方法的线性范围为0~100%(橄榄油含量),线性相关系数(r2)大于0.995,检出限为1.26%~2.13%,模拟橄榄调和油中橄榄油含量测定的偏差为-0.65%~1.02%,相对偏差为-1.3%~6.8%,相对标准偏差为1.18%~4.26%(n=6)。该方法不使用任何溶剂,操作简单、快速、环保,灵敏度和准确度高,适用于橄榄调和油中橄榄油含量的测定。     

Discrimination of crude and processed rhubarb products using a chemometric approach based on ultra fast liquid chromatography with ion trap/time‐of‐flight mass spectrometry

Crude rhubarb subjected to different processing procedures will produce different therapeutic effects that are possibly due to processing‐induced variation in chemical composition. In this study, a chemometric approach based on ultra fast liquid chromatography with ion trap/time‐of‐flight mass spectrometry was established to systematically investigate the chemical variations of rhubarb induced by different processing methods. The approach was validated based on pooled quality‐control samples from two perspectives: the individual properties of variables and the bulk properties of samples. Orthogonal partial least squares discriminant analysis was introduced to compare the differences between crude and processed rhubarb products. A total of 20 significantly different markers were screened out and unambiguously/tentatively characterized. This research proved that a chemometric method based on ultra fast liquid chromatography with ion trap/time‐of‐flight mass spectrometry can comprehensively analyze the chemical variation of herbal medicine and provide evidence for a deeper understanding of the pharmacological activities of processed rhubarb products.