Multimode Retention Behavior of Azaarenes in Size Exclusion Chromatography with Poly(Divinylbenzene)

Abstract

The size exclusion retention behavior of azaarenes on poly(divinylbenzene) is described. With dichloromethane as the mobile phase a strong nonsize effect was evident and retention was found to be governed by the pK_a of the eluate. By changing the mobile phase to N-methylpyrrolidinone, retention became independent of pK_a and components eluted in order of decreasing molecular weight. Some degree of nonsize behavior was still evident and separation proceeded through a multimode mechanism. LogMW for both the azaarenes and PAH. However, in the case of the azaarenes, a less than ideal correlation coefficient (-.705) suggests that retention is not purely size-dependent.     

超声萃取-高效液相色谱法测定沉积物中多环芳烃

提出了高效液相色谱法测定沉积物中多环芳烃(PAH′s)含量的方法。样品中多环芳烃用正己烷-丙酮(1+1)混合溶液超声提取,离心分离后,所得萃取液经蒸发浓缩,然后过装有1g无水硫酸钠和2g硅胶的层析柱净化。以Varian PAHs色谱柱为分离柱,不同比例配成的甲醇和水为流动相梯度洗脱,用荧光检测器检测。方法的检出限(3S/N)在0.34～1.52ng.g-1之间。方法用于沉积物中多环芳烃的测定,测定结果的相对标准偏差(n=5)在3.2%～10.6%之间。用标准加入法测定方法的回收率,结果在57.1%～103.4%之间     

An assessment of the retention behaviour of polycyclic aromatic hydrocarbons on reversed phase stationary phases--thermodynamic behaviour on C18 and phenyl-type surfaces

The thermodynamic retention behaviour of a linear series of polycyclic aromatic hydrocarbons (PAHs) was investigated on C18 and selected phenyl-type reversed-phase stationary phases, namely C18, C18 Aqua, Propyl-phenyl and Synergi polar-RP stationary phases, using methanol mobile phases. The Propyl-phenyl stationary phase, despite having the lowest surface coverage, was found to exhibit significantly larger enthalpic interactions to the other Phenyl-type phase (Synergi polar-RP) even though this had a much higher surface coverage. This indicated that stronger interactions between the PAHs and the stationary phase ligands were occurring on the Propyl-phenyl phase. Evaluation of the elution band profile of the PAHs in the aqueous methanol mobile phase revealed fairly symmetrical bands for the C18, C18 Aqua and Synergi polar-RP, but severe peak tailing on the Propyl-phenyl phase. A change in mobile phase from methanol to acetonitrile improved the peak shape of the PAHs on the Propyl-phenyl phase, leading to the assumption that unfavourable pi-pi interactions were occurring between the electron-rich PAHs and the electron-rich phenyl rings of the Propyl-phenyl phase.     

Influence of Physicochemical Parameters of Some Ring-Substituted Phenol Derivatives on Their Retention on a Porous Graphitized Carbon Column

Abstract

The retention characteristics of 29 phenol derivatives were determined on a porous graphitized carbon column in unbuffered acetonitrile—water and methanol—water eluent mixtures at various organic phase concentrations. Each phenol derivative showed symmetric peaks in each eluent without buffers. Good linear correlations were found between the log k' value and the organic mobile phase concentration in the eluent. Principal component analysis indicated that methanol and acetonitrile expose different selectivities. Stepwise regression analysis proved that the retention of ring—substituted phenol derivatives is mainly governed by the sterical parameters, electron-withdrawing power and hydrogen donor capacity of substituents. According to the results of Free-Wilson analysis, the substituents with large steric parameters, strong electron-withdrawing power and hydrogen donor capacity have the highest impact on the retention. The lipophilicity of phenol derivatives did not affect significantly the retention, although the eluents were typical reversed-phase eluents.     

Polycyclic aromatic hydrocarbons as test probes to investigate the retention behavior of 1,3‐alternate calix[4]arene silica‐bonded stationary phases

A series of polycyclic aromatic hydrocarbons (PAHs) of different size and shape has been used to characterize the chromatographic behavior of five calix[4]arene stationary phases in 1,3‐alternate conformation synthesized in our laboratory. The selection of linear, four‐ring nonlinear, and five‐ring PAHs gave data on selectivity changes across range of the calix[4]arene columns. Retention of the 12 aromatic solutes has been evaluated at various methanol contents in the mobile phase (70–100% v/v) and column temperatures (20–45°C). The thermodynamic parameters underlying the retention mechanisms revealed that each of the five calix[4]arene columns exhibited variation in selectivity and retention of PAHs caused by enthalpy and entropy effects. The calixarene stationary phases substituted with electron‐withdrawing groups exhibit enhanced selectivity toward PAHs in comparison to the rest of the investigated columns. The observed divergences are due to differences in solute–stationary phase interactions and originate in π–π and π‐electron transfer specific to the analytes and the type of calix[4]arene functionalization at the upper rim, as well as steric and sorption phenomena.     

高效液相色谱β-环糊精键合固定相直接拆分硫代和硒代缩水甘油醚对映异构体

 用两种不同的方法合成了β-环糊精键合固定相。通过对硝基苯胺异物体的拆分,对键合相进行了评价。拆分了3种硫代缩水甘油醚和2种未见文献报道的硒代缩水甘油醚。     

HPLC retention behaviors of pi-electron rich compounds on Ni2+- and Cu2+-phthalocyanine derivatives bound to silica gels in polar eluents.

The effect of the central metal of columns packed with silica gels binding Ni(2+)- and Cu(2+)-phthalocyanine derivatives (Ni-and Cu-PCS(D)s) on the retention behavior of poly-aromatic-hydrocarbons (PAHs) thereof in a polar eluent was examined. The retention factors of PAHs on the Ni- and Cu-PCS(D)s in 80% methanol showed a good linear correlation. The Cu-PCS(D) column exhibited the pi-pi interactions for PAHs, while the Ni-PCS(D) column exhibited the pi-d interactions for PAHs in addition to the pi-pi interaction for PAHs. Further, an investigation of the retention behavior of anthracene derivatives having different substituents revealed that the Ni- and Cu-PCS(D) columns could recognize the differences of substituents only in a polar eluent.     

Column selectivity in reversed-phase liquid chromatography III. The physico-chemical basis of selectivity

Reversed-phase liquid chromatography (RP-LC) retention data for 23 additional solutes have been acquired to further test and evaluate a general relationship from part I: log alpha = log (k/kref) = eta'H(i) + sigma'S(ii) beta'S(iii) + alpha'B(iv) +kappa'C(v) The physico-chemical origin of terms i-v above is examined here by comparing values of (a) the solute parameters of Eq. (1) (eta', sigma', etc.) vs. solute molecular structure, and (b) the column parameters (H, S, etc.) vs. column properties (ligand length and concentration, pore diameter, end-capping). We conclude that terms i-v correspond, respectively, to hydrophobic (i), steric (ii), hydrogen bonding (iii, iv) and ionic (v) interactions between solute and stationary phase. While steric interaction (term ii) is superficially similar to what previously has been defined as "shape selectivity", the role of the solute and column in determining steric selectivity (term ii) appears more complex than previously proposed for "shape selectivity". Similarly, what has previously been called hydrogen bonding between donor solutes and an acceptor group in the stationary phase (term iv) is very likely an oversimplification.     

New on-line concentrator for LC-GC: Analysis of PAHs with LC-GC

A new, versatile, and low cost on-line LC-GC interface has been devloped for the fast and reliable introduction of large volume samples into a cappillary GC column without using the conventional retention gap. PAHs in soot were analyzed by on-line normal phase HPLC-capillary GC. A glass, vial-shaped on-line concentrator provides a zone for solvent evaporation and sample concentration. Large volumes of HPLC eluate can be concentrated with the on-line concentrator and then transferred directly into the cappillary column. Trace levels (< 10 ppb) of PAH compounds can be efficiently concentrated with the on-line concentrator and determined without loss or contamination.     

Structure-activity relationships for flow cytometric data of smaller polycyclic aromatic hydrocarbons

Using flow cytometry, select polycyclic aromatic hydrocarbons (PAHs) were evaluated for induction of apoptosis in human monocytic THP-1 cells. Based on structure, the PAHs were divided into linear and bay-region-containing compounds. Except for fluorene, the linear PAHs failed to induce apoptosis; all of the bay-region-containing PAHs induce apoptosis. The relationship that a bay-region is required to induce apoptosis is supported by results for benzo[a]pyrene (positive) and 2-methylanthracene (negative). The data for bay-region containing, four-ringed PAH compounds reveal that possessing a linear-region of more than two rings diminishes the ability of a PAH to induce apoptosis. Owing to the steric interactions of the hydrogen atoms of the methyl group and those on the ring carbons, 1-methylanthracene does not have a true bay-region. However, the methyl group substituted in the 1-position does confer a bay-like conformation, which may explain its activity in contrast to its parent derivative anthracene and its 2-postion homologue.     

Determination of polycyclic aromatic hydrocarbons in food samples by automated on-line in-tube solid-phase microextraction coupled with high-performance liquid chromatography-fluorescence detection

A simple and sensitive automated method, consisting of in-tube solid-phase microextraction (SPME) coupled with high-performance liquid chromatography-fluorescence detection (HPLC-FLD), was developed for the determination of 15 polycyclic aromatic hydrocarbons (PAHs) in food samples. PAHs were separated within 15 min by HPLC using a Zorbax Eclipse PAH column with a water/acetonitrile gradient elution program as the mobile phase. The optimum in-tube SPME conditions were 20 draw/eject cycles of 40 μL of sample using a CP-Sil 19CB capillary column as an extraction device. Low- and high-molecular weight PAHs were extracted effectively onto the capillary coating from 5% and 30% methanol solutions, respectively. The extracted PAHs were readily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. Using the in-tube SPME HPLC-FLD method, good linearity of the calibration curve (r > 0.9972) was obtained in the concentration range of 0.05–2.0 ng/mL, and the detection limits (S/N = 3) of PAHs were 0.32–4.63 pg/mL. The in-tube SPME method showed 18–47 fold higher sensitivity than the direct injection method. The intra-day and inter-day precision (relative standard deviations) for a 1 ng/mL PAH mixture were below 5.1% and 7.6% (n = 5), respectively. This method was applied successfully to the analysis of tea products and dried food samples without interference peaks, and the recoveries of PAHs spiked into the tea samples were >70%. Low-molecular weight PAHs such as naphthalene and pyrene were detected in many foods, and carcinogenic benzo[a]pyrene, at relatively high concentrations, was also detected in some black tea samples. This method was also utilized to assess the release of PAHs from tea leaves into the liquor.     

Versatile synthesis of small NLO-active molecules forming amorphous materials with spontaneous second-order NLO response

A novel synthetic approach to a series of bulky triarylamines substituted by various electron-withdrawing groups and forming amorphous materials is presented. Under vacuum evaporation, thin films with high optical quality are obtained and exhibit spontaneous second-order nonlinear optical activity. This unprecedented result is likely due to subtle balance between strong dipole-dipole interactions and steric crowding causing self-assembly and noncentrosymmetric local ordering, stable up to one year.     

Acceptor modulation for improving thermally activated delayed fluorescence emitter in through-space charge transfer on spiroskeletons

Through-space charge transfer (TSCT) is regarded as an effective way to develop thermally activated delayed fluorescence (TADF) emitters. Based on this strategy, many molecular frameworks have been proposed, among which spirobased scaffolds have been extensively studied due to their unique advantages. In this work, we developed three emitters SPS, SPO, and SPON, which were constructed with the same donor and various acceptors to explore the influence of acceptor modulation at the C9 position of fluorene for spirostructure TSCT emitters. The results show that the acceptor with too weak electron-withdrawing ability will cause the emitter to not have TADF properties, while the acceptor with too much steric hindrance will weaken the face-to-face π-π stacking interaction between donor/acceptor (D/A). Since SPO balances the electron-withdrawing strength and steric hindrance of the acceptor, it achieves the highest external quantum efficiency (EQE) of 17.75%. This work shows that appropriate acceptor selection is essential for the TADF properties and high efficiency of the spirobased scaffold TSCT emitter     

Preparation and characterization of six calixarene bonded stationary phases for high performance liquid chromatography

Six calixarene bonded silica gel stationary phases were prepared and characterized by elemental analysis, infrared spectroscopy and thermal analysis. Their chromatographic performance was investigated by using PAHs, aromatic positional isomers and E- and Z-ethyl 3-(4-acetylphenyl) acrylate isomers as probes. Separation mechanism based on the different interactions between calixarenes and analytes were discussed. The chromatographic behaviors of those analytes on the calixarene columns were influenced by the supramolecular interaction including pi-pi interaction, space steric hindrance and hydrogen bonding interaction between calixarenes and analytes. Notably, the presence of polar groups (-OH, -NO(2) and -NH(2)) in the aromatic isomers could improve their separation selectivity on calixarene phase columns. The results from quantum chemistry calculation using DFT-B3LYP/STO-3G* base group were consistent with the retention behaviors of PHAs on calix[4]arene column.     

超高效液相色谱-串联质谱法同时测定水体中莠去津和呋喃丹的含量

水样中莠去津和呋喃丹通过C18固相萃取柱使之分离并富集。用氮气将固相萃取柱吹干后,用二氯甲烷淋洗使被测组分洗脱,所得洗脱液用氮气吹至尽干,用混合溶剂[甲醇与甲酸-水(0.1+99.9)溶液按40比60的比例混合]1 mL溶解残渣,所得溶液供超高效液相色谱-串联质谱法(UPLC-MS/MS)分析用。用Waters BEH C18色谱柱作分离柱,用不同比例的甲醇和甲酸-水(0.1+99.9)溶液的混合液作流动相进行梯度淋洗,使上述两种农药分离后进行串联质谱测定,所用质谱条件为电喷雾离子源,正离子扫描和多反应监测模式。两种农药质量浓度均在0.10~10.00μg.L-1范围内与相应的峰面积值呈线性关系,检出限(3S/N)均为0.15 ng.L-1。在3个浓度水平上(0.10,0.50,5.00μg.L-1)加入两种农药的标准溶液进行回收试验,测得其平均回收率在77.0%~102.2%之间,相对标准偏差(n=5)在2.9%~7.6%之间。     

超高效合相色谱快速分析塑料制品中的18种多环芳烃

建立了一种超高效合相色谱-二极管阵列检测器快速分析塑料制品中萘、苊烯、苊、芴、菲、蒽、荧蒽、芘、苯并(a)蒽、(屈艹) 、苯并(b)荧蒽、苯并(k)荧蒽、苯并(j)荧蒽、苯并(e)芘、苯并(a)芘、茚并(1,2,3-cd)芘、二苯并(a,h)蒽、苯并(g,h,i)苝(二萘嵌苯)的方法。以甲苯为溶剂,超声萃取实际塑料制品中的多环芳烃,经超高效合相色谱分析。采用Daicel IB-3手性色谱柱,以CO₂为流动相,甲醇/乙腈(25:75, v/v)为流动相助溶剂,在柱温为40 ℃,背压为15.17 MPa的条件下,18种多环芳烃在8.5 min之内实现基线分离。18种多环芳烃的线性范围为0.05~50 mg/L(r≥0.9995),定量限(S/N> 10)为0.05 mg/L。加标回收率为78.3%~117.6%,相对标准偏差(RSD, n=5)小于5%。该方法具有分析速度快、分离效率高、节约有机溶剂的优点。     

Application of High-Performance Liquid Chromatography on Short Narrow-bore Columns to the Determination of Priority Polycyclic Aromatic Hydrocarbons in Environmental Samples

Conditions were optimized for the separation of priority polycyclic aromatic hydrocarbons (PAHs) by high-performance liquid chromatography on short narrow-bore columns (2 × 75 mm). Twelve PAHs were determined by the direct injection of preconcentrated extracts from highly contaminated soil, solid phase of snow water, an aerosol, and surface water. PAH peaks were identified using retention times and spectral ratios (R). In the case of the detection of nonhomogeneous peaks (by the R value), the repeated separation of the sample was proposed with a change in the selectivity of the mobile phase, detection wavelength, and column temperature. The spread of the results of measurements of the PAH mass was estimated at different deviations of R from the standard value.     

Selectivity Factors for Several Pah Pairs on C18 Bonded Phase Columns

Abstract

The selectivity factors for four pairs of polycyclic aromatic hydrocarbons (PAHs) have been found to be very different on the HC-ODS column in comparison to most other C₁₈ bonded-phase columns. The selectivity factors for these PAH pairs varied slightly with different manufacturing lots of the HC-ODS material, the selectivity variations for each PAH pair being linearly correlated with those for the other pairs.     

High-performance liquid chromatography on silica modified with temperature-responsive polymers

Summary The separation selectivity of temperature-responsive poly(N-isopropylacrylamide)-modified silica as a packing material for high performance liquid chromatography was investigated with steroids, alkaloids, and substituted anilines as solutes. The elution profiles of the solutes depended on the temperature of the column and the methanol content of the mobile phase, indicating that the separation selectivity could be controlled by the column temperature or the mobile phase composition.     

紫外检测器-荧光检测器串联的HPLC法测定火力发电厂环境中的多环芳烃

 建立了一种紫外检测器(UVD)与荧光检测器(FLD)串联的HPLC法,检测了火力发电厂环境中的多环芳烃（PAH）化合物。在所选择的色谱条件下12个PAH可得到完全分离,其中萘等8个PAH用UVD检测,苯并〔a〕芘等4个PAH用FLD检测。应用该方法对湖南省内几家火力发电厂的废水、烟道气、粉煤灰中的12个PAH进行了实测,效果良好。