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.     

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 behavior of large polycyclic aromatic hydrocarbons on cholesteryl 10-undecenoate bonded phase in microcolumn liquid chromatography

Summary The retention behavior of large polycyclic aromatic hydrocarbons (PAH) in reversed-phase microcolumn liquid chromatography has been found to depend primarily on the inherent planarity of the molecules, the degree of orderliness of the bonded phase, and the concentration of solvent. The planarity recognition capability of cholesteryl 10-undecenoate bonded phase for large PAH is comparable with that of monomeric ODS phases. During solvation, however, the phase characteristics seemed to suggest a fairly rigid structure (an ordered phase), i.e. increased selectivity for non-planar molecules which approaches that of polymeric ODS rather than that of other phases with similarly bulky groups, e.g. naphthylethyl and pyrenylethyl bonded phases.     

Compatibility and universality of the retention prediction system for polycyclic aromatic hydrocarbons in reversed-phase liquid chromatography

Summary System-compatibility and universality of the retention prediction concept has been investigated for polycyclic aromatic hydrocarbons in reversed-phase liquid chromatography. The results clearly indicate that the retention prediction approach has a very high potential for optimization of separation conditions in almost all reversed-phase systems, and allows more precise and rapid analysis. This approach may be one of the best optimization techniques, because the system does not require any standard materials.     

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.     

Retention prediction of small peptides in reversed-phase liquid chromatography

Summary Retention prediction of small peptides (up to four residues) in reversed-phase liquid chromatography has been investigated, considering the contributions of side chains in each position to the peptide retention. In isocratic elution the retention of peptides could be predicted within about 8% relative error.     

Retention prediction of o-phthalaldehyde amino acid derivatives in reversed-phase liquid chromatography

Summary Retention prediction of o-phthalaldehyde amino acid derivatives in reversed-phase liquid chromatography has been investigated. The retention of all derivatives could be predicted within about 10% relative error under the appropriate separation conditions in both isocratic and gradient-elution modes.     

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.     

Retention prediction of phenylthiohydantoin amino acid derivatives in reversed-phase liquid chromatography

Summary The concept of retention prediction for the separation of phenylthiohydatoin-amino acid derivatives in isocratic reversed-phase liquid chromatography is described. A novel retention-solubility parameter, R, is defined, for the retention prediction strategy and the performance of this R value is evaluated by comparing measured and predicted retention data. Excellent agreement between these values were observed. It is concluded that the R value has a very high potential in describing the retention of phenylthiohydantopinamino acid derivatives withdifferent types of separation systems consisting of C-18, C-8 and phenethyl bonded stationary phases and various mobile phases.     

Retention behavior of aromatic hydrocarbons and dansylamino acids in reversed-phase liquid chromatography with cation-exchange-induced stationary phases

The retention behavior of aromatic hydrocarbons and dansylamino acids on cation-exchangers modified with alkylammonium ions has been examined by microcolumn liquid chromatography. Several parameters affected the retention of analytes, involving concentration of the modifier in the mobile phase, its alkyl chain length and mobile phase composition. Stationary phases modified with a reagent having longer alkyl chains achieved better column efficiency.     

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.     

Chitosan-based stationary phases in microcolumn liquid chromatography

Two kinds of cross-linked chitosan beads were evaluated as the stationary phase for microcolumn liquid chromatography. The phase with aminoalkyl substituent can be expected to function similarly to commonly known aminopropyl bonded phases. Separation of PAH with the chitosan phase bearing phenyl group substituents has been accomplished in the gradientelution mode with acetonitrile-water as the mobile phase. Planarity recognition capability comparable with that of monomeric octadecylsilica phase was observed.     

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.     

Retention of polycyclic aromatic hydrocarbons on propyl-phenyl stationary phases in reversed-phase high performance liquid chromatography

A study on the retention of PAHs on three Propyl-phenyl stationary phases was conducted, assessing absolute retention, selectivity, retention correlation and thermodynamic behaviour. The chromatographic retention data revealed that each of the three Propyl-phenyl columns exhibited differences in absolute retention, however, comparison of the compensation temperatures derived from enthalpy-entropy compensation plots showed that the underlying processes responsible for the retention on these columns were the same.     

Study on retention behavior of peropyrene-type polycyclic aromatic hydroccrbons with various bonded stationary phases in reversed-phase liquid chromatography

Summary The retention behavior of 15 peropyrene-type polycyclic aromatic hydrocarbons was investigated on various bonded stationary phases in reversed-phase liquid chromatography. On diphenyl and naphthylethyl bonded phases, high correlations were obtained between the molecular polarizability of solutes and their retention. However, very low or no correlations were found on various octadecyl bonded phases. These facts are discussed by using the electrostatic interaction concept between the solutes and the stationary phase. We conclude that these observations are due to two reasons: the difference in the degree of planarity of polycyclic aromatic hydrocarbons and the high ability of planarity recognition of octadecyl bonded phases.     

稠环芳烃在烷基膦酸改性锆镁复合氧化物固定相上的反相液相色谱保留行为

 以稠环芳烃为探针,考察了烷基膦酸改性锆镁复合氧化物材料的反相色谱性能。研究了稠环芳烃类化合物的结构与其保留值的关系,比较了烷基膦酸改性锆镁复合氧化物固定相和十八烷基键合硅胶ZorbaxODS对稠环芳烃异构体的选择性,并对可能的保留机理进行了讨论。以甲醇-水(体积比为75∶25)为流动相,在烷基膦酸改性锆镁复合氧化物固定相上分离了8种稠环芳烃类化合物。     

Retention behavior of aromatic hydrocarbons in reversed-phase liquid chromatography with ion-exchange-induced stationary phases

Chromatographia - The retention behavior of aromatic hydrocarbons on anion-exchangers modified with alkylsulfate or alkanesulfonate has been examined by column liquid chromatography. Several...     

Cellulose acetate as stationary phase in microcolumn LC

The retention characteristics of alkylbenzenes and polycyclic aromatic hydrocarbons (PAHs) have been examined in liquid chromatography on a microcapillary column packed with cellulose acetate. Particulate and fibrous cellulose acetate were used as the stationary phase. Fibrous cellulose diacetate was found to be of use as an alternative stationary phase for liquid chromatography, although the separation efficiency was low. The retention characteristics for planar PAHs were linearly correlated with the size of the molecules, but the retention behavior for alkylbenzenes and nonplanar PAHs was affected by exclusion. The retention order was strongly influenced by the addition of dimethylformamide or water to methanol in the mobile phase. The results suggested that the retention behavior is influenced by a slight change in the polymer matrix of cellulose acetate.