Separation of polycyclic aromatic hydrocarbons with a C60 bonded silica phase in microcolumn liquid chromatography

A chemically bonded C₆₀ silica phase was synthesized as a stationary phase for liquid chromatography (LC) and its retention behavior evaluated for various polycyclic aromatic hydrocarbons (PAHs) using microcolumn LC. The results indicate that the C₆₀ bonded phase offers selectivity different from that of octadecylsilica (ODS) bonded phases in the separation of isomeric PAHs. With the C₆₀ phase, PAH molecules having a partial structure similar to that of the C₆₀ molecule, e.g. triphenylene and perylene, were retained longer than with ordinary ODS stationary phases. The results also show that good correlation exists between the retention data with this C₆₀ bonded phase and with C₆₀ itself as the stationary phase.     

Retention behavior of polycyclic aromatic hydrocarbons in microcolumn liquid chromatography with acridine derivative as stationary phase

Retention behavior of polycyclic aromatic hydrocarbons (PAHs) on an acridine derivative stationary phase was examined in microcolumn liquid chromatography. 3,6-Bis(dimethylamino)-10-dodecylacridinium was electrostatically introduced into a cation-exchanger, and its selectivity was compared with that of octadecylsilyl-bonded silica gel. The former stationary phase provided smaller retention for non-planar PAHs than that achieved by the latter stationary phase. The results suggest that interaction between PAHs and the acridinyl ring dominates the retention of PAHs, and preferential retention of planar PAHs is attributed to the fact that they have more chance to interact with the acridinyl ring of the stationary phase than non-planar PAHs.     

Retention prediction of large and condensed polycyclic aromatic hydrocarbons in reversed-phase microcolumn liquid chromatography with diphenylsilica stationary phase

The retention behavior of condensed large polycyclic aromatic hydrocarbons has been investigated with diphenylsilica stationary phases in reversed-phase microcolumn liquid chromatography. The results were correlated with two parameters which indicate size and shape of the molecules. Since the resulting equation can be used for retention prediction of large polycyclic aromatic hydrocarbons, computer-assisted “standardless” identification is accomplished for “unknown” compounds contained in the standard.     

Microcolumn liquid chromatography of polycyclic aromatic hydrocarbons and some isomeric compounds on cyclodextrin stationary phases

Preparative-grade bonded β- and γ-cyclodextrin stationary phases were used as the packing material of liquid chromato-graphic analytical microcolumns. Although the resulting columns are characterized by relatively low efficiency, the high selectivity of the cyclodextrin phases nevertheless allows their successful use for the separation of different classes of isomeric compounds that are difficult to resolve on conventional LC stationary phases. Examples of baseline (or almost baseline) separations of a number of isomeric compounds, including isomeric polycyclic aromatic hydrocarbons, are presented to demonstrate the analytical potential of such columns. Retention behavior of the separated isomers is discussed based on the structure of the solute molecule and the possibility of its inclusion into the molecular cavity of cyclodextrin stationary phases.     

Retention characteristics of alkylated polycyclic aromatic hydrocarbons in normal phase liquid chromatography

Summary Retention characteristics of series of polymethyl and mono-n-alkyl derivatives of benzene and pyrene, and also of parent polycyclic aromatic hydrocarbons (PAH), were studied using silica and aminopropyl- and cyanopropyl-modified silica. Differences in the selectivities for the studied compound groups were found between the three phases. Deviations from linear behaviour in plots of log (k′)vs. carbon number were observed for the methyl series. These are explained in terms of differences in π-electron delocalisation within the aromatic ring systems. Further, the effect of methyl substitution on selectivity decreased with an increasing number of aromatic rings. Results were obtained which indicated that the primary adsorption site in a cyano column used in normal phase mode, at least for PAH molecules, is the cyano group.     

Computer interactive identification system for polycyclic aromatic hydrocarbons in reversed-phase microcolumn liquid chromatography

Summary A computer interactive identification system is proposed which is based on the relationship between retention and molecular properties such as the size and shape of polycyclic aromatic hydrocarbons (PAHs). This system offers an automatic analytical process for liquid chromatography, providing a reliable identification of the separated components. The identification can be further enhanced by the use of multiple detectors such as a multichannel UV detector. The system can be used for optimization procedures, resulting in a highly automatic complex analytical system.     

Retention prediction of polycyclic aromatic hydrocarbons in reversed phase liquid chromatography with various mobile phase compositions and column temperatures

Summary The relationship between the logarithmic capacity factor measured in reversed-phase liquid chromatography and the operating conditions including the mobile phase composition and the column temperature is investigated. The strategy described herein can offer the possibility to predict the retention of polycyclic aromatic hydrocarbons without any experiments and standard materials, by utilizing equations describing the relationships between retention, temperature, mobile phase composition and physicochemical properties of the solutes previously stored in the program of the microcomputer-assisted retention prediction system.This concept is one of the most promising techniques for the optimization of the separation conditions in reversed-phase liquid chromatography.     

HPLC analysis of the large polycyclic aromatic hydrocarbons in a diesel particulate

Summary High performace liquid chromatography (HPLC) was used to separate the large polycyclic aromatic hydrocarbons in a diesel particulate extract. Identification of individual peaks was made using a photodiode array UV/visible detector to collect their absorbance spectra. Comparisons between standard compounds and the peaks were made using both retention times and spectra. Compounds of up to 10 rings were identified.     

Retention characteristics of chlorinated polycyclic aromatic hydrocarbons in normal phase HPLC. I. Chloro-added PAHs

Summary Retention characteristics in normal phase HPLC of highly biologically active chloro-added polycyclic aromatic hydrocarbons (PAHs) were studied. Silica, cyanopropyldimethylsilyl- and aminopropylsilyl- modified stationary phases were investigated. Retention properties of chloroadded PAHs on these phases were shown to be strongly influenced by the number of chloro-additions. This is due to the strong polarity of the methylene carbon at the chloro-addition site. Active silica had a strongly degrading effect on the unstable chloro-added PAHs during separation. Aminopropylsilica did not exhibit sufficient selectivity towards chloro-added PAHs when compared to chlorosubstituted PAHs. Cyanopropyldimethylsilica was shown to be applicable to a group separation of chloro-added and chloro-substituted PAHs. A fast clean-up procedure for chloro-added PAHs in complex samplesis outlined. It involves an initial elimination of more polar substances on a short open column with strongly deactivated silica and a subsequent separation on a cyanopropyldimethylsilyl HPLC column in normal phase mode.     

超高效液相色谱法检测土壤中的多环芳烃

采用二极管阵列(PDA)检测器,建立了超高效液相色谱(UPLC)定性定量分析土壤中16种多环芳烃(PAHs)的方法。并将该方法与传统高效液相色谱(HPLC)的分析性能进行了详细的比较。研究结果表明,采用UPLC法分析16种PAHs具有分析速度快(13.5 min)、检出限低(2～20 pg)、灵敏度高等优点。     

Retention characteristics of chlorinated polycyclic aromatic hydrocarbons in normal phase HPLC. II. Chloro-substituted PAHs

Summary The retention behaviour of chloro-substituted PAHs on several commercial normal bonded phase HPLC columns has been investigated. Chloro-substitution was shown to generally decrease the retention on stationary phases like amino-, diol- and nitrophenylpropyl-modified silica. Dimethylaminosilica exhibited more complex retention characteristics towards chloro-substituted PAHs. On this stationary phase, the position of the chlorine substituents on the aromatic solute seemed to be of greater importance for retention than on the amino-, nitro- and diolsilica. For some chloro-PAHs, the retention was shown to increase with the number of chloro-substitutions, probably due to the large affinity of the electron-rich nitrogen in the stationary phase for the electron deficient -system of the chloro-PAHs. Chloro-substituted PAHs were strongly retarded on the electron donating 2-(1-pyrenyl)-ethylsilica (PYE) stationary phase. However, the molecular shape of the chloro-derivatives had a large influence on retention, which was considerably decreased for some nonplanar chloro-derivatives of chrysene and benz(a)anthracene. A two-dimensional back-flush HPLC method, consisting of a combination of a nitrophenylsilica column and a PYE column of matched lengths, was shown to be useful for clean-up of chloro-substituted PAHs in environmental samples.     

微波提取-高效液相色谱法测定大气颗粒物中的多环芳烃

建立了一种微波提取-高效液相色谱法测定大气颗粒物中多环芳烃的方法。吸附有颗粒物的超细玻璃纤维/石英纤维滤膜用正己烷/丙酮(1∶1,v/v)混合溶剂经微波提取,提取液用弗罗里硅土柱净化,经浓缩定容后,采用液相色谱法-二极管阵列(PDA)-荧光双检测器测定。目标化合物在20.0~500μg/L范围内线性良好,相关系数不小于0.996 0。空白膜加标结果显示,目标化合物的回收率在56.3%~101%之间。该法已运用于南京市大气颗粒物中多环芳烃分布的调查研究。     

Retention behavior of polycyclic aromatic hydrocarbons in supercritical fluid chromatography on a chemically bonded stationary phases based upon liquid-crystalline polymer

Summary The retention behavior of a set of polycyclic aromatic hydrocarbons in supercritical fluid chromatography have been studied on a chemically bonded stationary phase based upon a side chain liquid crystalline polymer (LCP) with carbon dioxide-based mobile phase. The effects of the mobile phase pressure, column temperature and amount of mobile phase organic modifier have been investigated in order to detect a possible structural change in the liquid crystal polymer linked to the silica support. The influence of these factors on the selectivity coefficients has also been studied. Two distinctive behaviors with temperature are noted at low pressure on the one hand and at higher pressure on the other. This change in behavior is based on the density of the supercritical CO₂ and the PAH volatility rather than on any specific stationary phase structural change. Both lower mobile phase pressure and amount of mobile phase modifier are required to obtain better selectivities. Better planarity recognition is observed in SFC than in HPLC with these new bonded liquid crystal stationary phases. The bonded liquid crystal phase is only weakly affected by the addition of organic modifier in the supercritical CO₂.     

On-line preconcentration of trace carcinogenic polycyclic aromatic hydrocarbons (PAHs) in microcolumn liquid chromatography via large volume injection

The ability and efficiency of micro precolumns made of C30 particles, monolithic silica C18 stationary phase and quartz wool coated with C30, which act as novel solid phase absorbing materials, for the on-line enrichment of aqueous polycyclic aromatic hydrocarbons (PAHs) in microcolumn liquid chromatography (LC) was investigated. The enrichment unit was designed in such a way that micro precolumns were directly connected to a 6-port micro injection valve via fused-silica tubing (0.05 mm I.D.) in order to minimize band broadening of the samples, and the enrichment efficiency of the three materials was tested using 14 PAHs, which are selected by the US Environmental Protection Agency (US EPA), as the analytes. The separation of PAHs was evaluated by using laboratory-made C30 or ODS capillary columns and the results were compared. There were no significant differences showed from the separation of PAHs in terms of peak signal between the C30 and ODS capillary columns, but the C30 capillary column was chosen for the following experiment due to its ability to produce better repeatability than the ODS column. By using the three kinds of precolumn materials, results showed that the precolumn packed with C30 particles as well as the capillary monolithic C18 precolumns (0.1 or 0.2 mm I.D.) provided better recovery than those of the quartz wool's. As long as the recovery and separation of the PAHs were concerned, 0.1 mm I.D. monolithic C18 precolumn showed the best results and the R.S.D.s (N = 7) for the retention time, peak area and peak height were between 0.70-1.5, 2.3-5.8 and 2.4-6.6%, respectively. Large volume injection up to 0.5 mL, i.e. 2500-fold enrichment, was possible and no negative effect on the separation profile was found. The LOD (S/N = 3) were between 0.10 and 4.6 pg mL⁻¹, while the LOQ (S/N = 10) were in the range of 0.32-15 pg mL⁻¹, which showed that the system is comparable to many major analytical techniques and is sensitive enough for the trace analysis of PAHs in environmental samples. The system was then applied to the determination of trace PAHs present in soil sample which was randomly taken from a nearby highway.     

石墨烯层层键合固相微萃取纤维的制备及对多环芳烃的检测

通过3-巯基丙基三甲氧基硅烷处理银层包裹的不锈钢纤维,得到Si-OH功能化的纤维,氧化石墨烯被层层键合到Si-OH功能化的纤维上,还原氧化石墨烯得到石墨烯层层键合的固相微萃取纤维。该方法制备的新型石墨烯层层键合的固相微萃取纤维具有制备简单,机械性能强,萃取涂层牢固,萃取能力强等优势。建立具有较宽线性范围(5~200μg/L)、较低检测限(0.007~0.09μg/L)的固相微萃取-气相色谱分析方法,用该方法测定河水和雨水中多环芳烃的含量。所制备的新型纤维重现性好、稳定性高、萃取能力强,可实现对多环芳烃的痕量检测。     

Graphene oxide bonded fused-silica fiber for solid-phase microextraction-gas chromatography of polycyclic aromatic hydrocarbons in water

A novel chemically bonded graphene oxide/fused-silica fiber was prepared and applied in solid-phase microextraction of six polycyclic aromatic hydrocarbons from water samples coupled with gas chromatography. It exhibited high extraction efficiency and excellent stability. Effects of extraction time, extraction temperature, ionic strength, stirring rate and desorption conditions were investigated and optimized in our work. Detection limits to the six polycyclic aromatic hydrocarbons were less than 0.08 μg/L, and their calibration curves were all linear (R(2)≥0.9954) in the range from 0.05 to 200 μg/L. Single fiber repeatability and fiber-to-fiber reproducibility were less than 6.13 and 15.87%, respectively. This novel fiber was then utilized to analyze two real water samples from the Yellow River and local waterworks, and the recoveries of samples spiked at 1 and 10 μg/L ranged from 84.48 to 118.24%. Compared with other coating materials, this graphene oxide-coated fiber showed many advantages: wide linear range, low detection limit, and good stability in acid, alkali, organic solutions and at high temperature.