Rapid determination of Δ-Tetrahydrocannabinol in saliva by polymer monolith microextraction combined with gas chromatography-mass spectrometry

A method was developed for the determination of Δ⁹-Tetrahydrocannabinol (THC) in saliva by polymer monolith microextraction (PMME) combined with gas chromatography-mass spectrometry. The poly(methacrylic acid-co-ethylene glycol dimethacrylate) (p(MAA-co-EGDMA)) monolithic capillary column was selected as the extraction medium of PMME, which showed high extraction capacity towards THC in saliva. To reach optimum PMME extraction performance, several PMME parameters were investigated, including matrix pH, flow rate for extraction, sampling volume and elution solvent. Under the optimal conditions, good extraction efficiency was obtained with no matrix interference in the process of extraction and the subsequent GC-MS analysis. In the selected-ion monitoring (SIM) mode, the limit of detection (LOD) for THC was 0.68 ng/mL. The linearity range of the method was 3-300 ng/mL. Excellent reproducibility of the method was exhibited by intra- and inter-day precisions, yielding the relative standard deviations (R.S.D.s) less than 12%; recoveries higher than 89%. The proposed method was proved to be rapid, sensitive, and competently applied to the determination of THC in saliva samples.     

Influence of the polymerisation time on the porous and chromatographic properties of monolithic poly(1,2-bis(p-vinylphenyl))ethane capillary columns

In order to elucidate the effect of the polymerisation time on the morphology of styrene based monolithic support materials, continuous poly(1,2-bis(p-vinylphenyl))ethane (BVPE) rods were synthesised in 1.0 ml glass vials by thermally initiated free radical polymerisations of BVPE in the presence of porogens (toluene, decanol) and a,a′-azoisobutyronitrile (AIBN) as initiator at 65 °C for different polymerisation times (60, 90, 150, 300 and 600 min). Porosity parameters like pore-size-distribution and total porosity were investigated by mercury intrusion porosimetry, while the specific surface area of the BVPE monolithic supports was determined by N₂-adsorption (BET) measurements. An untypical bimodal pore-size-distribution comprising a high fraction of both mesopores (2–50 nm) and macropores (mainly flow-channels in the micrometer range) was observed as a result of the stepwise decrease of the polymerisation time. In consequence of the significant changes of the pore-size-profile, shortening the polymerisation time also resulted in enhanced total porosity due to enlarged flow-channel diameters and increased surface area according to the presence of a considerable amount of mesopores. Results upon the porosity profile of the support are further confirmed by SEM images of monoliths polymerised for different time periods. Since mesoporosity and high surface area of the chromatographic support material play key roles in the interaction and thus retention of low-molecular-weight compounds, polymerisation time should also affect the chromatographic properties and applicability of these polymers. To study the influence of the polymerisation time towards the separation efficiency of small molecules on BVPE capillary columns (200 μm I.D., 8 cm), a mixture of homologous alkylbenzenes was chosen for column evaluation. In accordance with the observations of the porous properties of BVPE stationary phases, the rapid and high resolution separation of a range of low-molecular-weight compounds on monolithic BVPE supports were successfully realised. The methodical reduction of the polymerisation time has been demonstrated to be a simple and effective tool to tailor the porous properties of organic monoliths to provide novel polymer-based stationary phases with porous properties adequate for the rapid and high resolution chromatography of small organic molecules.     

Preparation and characterisation of silica monoliths using a triblock copolymer (F68) as porogen

Silica-based monoliths with co-continuous structure were successfully prepared through a sol–gel process in the presence of a poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (F68). The triblock copolymer was compared to the classical PEG, in the formation of silica monoliths and was demonstrated to lead to co-continuous structures in a wider composition range, presenting smaller through pores. Moreover, mesoporous structures templated at the sol–gel transition were assumed to occur at the surface of the silica skeleton while PEG exhibited no mesopore templating.     

In‐situ photopolymerized polyhedral oligomeric silsesquioxane‐derived monolithic capillary columns with quinidine functionality for enantioseparation by nano‐liquid chromatography

The successful fabrication of monolithic capillary columns for enantiomer separations was achieved within vinylized fused silica capillaries via fast “one‐pot” photo‐initiated free radical polymerization reaction. A mixture consisting of polyhedral oligomeric silsesquioxane, O‐[2‐(methacryloyloxy)ethylcarbamoyl]‐10,11‐dihydroquinidine was copolymerized in the presence of n‐butanol, ethylene glycol and photo‐initiator 2,2‐dimethoxy‐2‐phenylacetophenone. The morphology of the resultant polymeric hybrid inorganic‐organic material and its permeability as well as porosity can be controlled by adjusting the composition of the monomers and binary porogenic solvent. The chromatographic characteristics of the columns have been investigated. Separation factors of N‐acetyl‐phenylalanine (Ac‐Phe) and dichlorprop dropped with decrease of chiral functional monomer. Permeability was better when the macroporogen ethyleneglycol was present at higher concentrations during the polymerization. In general, the chiral compounds were well separated (dichlorprop: α = 1.53, R_s up to 4.14; Ac‐Phe: α = 1.36, R_s up to 2.69) by nano‐HPLC with an optimized enantioselective monolithic capillary column which can be prepared within a few minutes.     

CeO2-ZrO2复合氧化物对金属蜂窝整体催化剂性能的影响

 用浸渍法制备了不同比例的CeO2－ZrO2复合氧化物，并用XRD，H2－TPR和BET等研究了复合氧化物的晶相、还原性能及热稳定性．结果表明，所制备的CeO2－ZrO2复合氧化物形成了固溶体，Ce0．6Zr0．4O2比Ce0．90Zr0．10O2更容易被H2还原；1100℃老化后，晶胞参数无明显变化，比表面积仍有11．8m2／g．模拟二冲程摩托车尾气组成，对用贵金属Pt，Pd，Rh与CeO2及CeO2－ZrO2固溶体所制备的催化剂进行了活性评价．结果显示，1100℃老化后，催化剂仍具有很高的氧化活性．在贫氧区，Pt－Pd－Rh／Ce0．6Zr0．4O2－Al2O3对碳氢化合物氧化的催化活性则有一定的优势，是一种具有较高热稳定性的催化剂．     

原位合成的活性脲醛树脂作为模板剂制备二氧化硅介孔材料

利用酸性条件下正硅酸乙酯的水解和脲醛树脂的聚合反应同时一步原位进行的方法合成了二氧化硅复合粉体(包括核壳微球结构和网状结构)和块体凝胶材料. 液氮吸附BET分析结果证明复合材料焙烧后得到的二氧化硅孔径分布均匀, 大小在介孔范围内. 改变反应性单体尿素. 甲醛及正硅酸乙酯等的初始浓度可对二氧化硅块体材料的孔径大小进行调节. 扫描电子显微镜观测结果显示, 随着原料单体初始浓度的变化复合粉体材料的微米级形貌可以是多孔网状结构或核壳结构. 从红外光谱和差热分析的结果推测, 高甲醛/尿素摩尔比[n(甲醛)∶n(尿素)≥2]条件下形成的支链脲醛树脂可作为块体二氧化硅理想的孔结构导向剂.     

Monolithic silica columns with chemically bonded β-cyclodextrin as a stationary phase for enantiomer separations of chiral pharmaceuticals

An enantioselective silica rod type chiral stationary phase (CSP) is presented; a novel combination of the well known enantiomer separation properties of -cyclodextrin and the unique properties concerning the flow behavior of silica monoliths. Two different synthesis routes are described, and it was found that the in situ modification of a plain silica rod column turned out to be the best. The chromatographic behaviour of the -cyclodextrin silica rod was studied and compared with a very similar commercially available -cyclodextrin bonded particulate material (ChiraDex^®). Even if the amount of -cyclodextrin bound to the silica rod was only about half of the amount of -cyclodextrin bound to ChiraDex^® particles, good resolutions were achieved for a set of chiral test components like Chromakalin, Prominal, Oxazepam, Methadone and some other drugs. By taking advantage of the unique features of the silica rods relating to their flat H/u (Van Deemter) curves, fast enantiomer separations could be demonstrated.     

基于硅胶整体材料研磨颗粒的多功能聚乙二醇键合固定相的制备及其在高效液相色谱多模式分离中的应用

研究通过对溶胶-凝胶法制备的硅胶整体材料进行研磨、浮选、假晶相转换和水热处理，最终获得了粒径为2~5 μm、孔径为20~60 nm的硅胶颗粒。利用部分含氟的阴离子表面活性剂Capstone FS-66和常用的阳离子表面活性剂十六烷基三甲基溴化铵（CTAB）组成的双胶束模板体系对硅胶基质进行假晶相转换处理；再采用碳酸钠溶液水热处理的方式，进一步扩大孔径。用扫描电镜（SEM）和N₂吸附-解吸等温线测量对扩孔处理前后的硅胶整体材料研磨颗粒进行表征，结果清楚地显示了处理前后的形貌变化和差异。随后将含有长链聚乙二醇（PEG）的硅烷键合到扩孔后的硅胶颗粒表面，分别利用元素分析、红外光谱以及热重分析对固定相进行表征，并对固定相进行色谱性能评价。对键合固定相的元素分析和热重分析数据进行分析表明，硅胶表面键合PEG的含量约为8%。研究揭示了利用假晶相转换法与碳酸钠溶液水热处理和长链PEG硅烷修饰的硅胶整体材料颗粒在尺寸排阻色谱分离蛋白质方面的良好分离效果。同时进一步的高效液相色谱评价结果表明，该键合固定相还可用于疏水作用色谱模式分离核糖核酸酶A和溶菌酶，以及可用于亲水作用色谱模式分离吡啶甲酸、左旋多巴、三聚氰胺和邻苯二酚等极性比较强的化合物。研究显示了PEG键合固定相具有多功能性，及其在多模式高效液相色谱分离中的应用潜力。     

前沿分析法研究对-羟基苯甲酸印迹整体柱的热力学行为

采用矩形前沿分析法对原位聚合的对-羟基苯甲酸印迹整体柱的热力学吸附等温线进行了测定. 印迹整体柱的吸附等温线是分别以乙腈、甲醇、 四氢呋喃和含有体积分数分别为1%, 3%, 5%和7%乙酸的乙腈为流动相以及在以甲醇为流动相时柱温分别为20, 40和50 ℃的条件下测定的. 吸附等温线表明, 印迹整体柱对模板分子的吸附能力比其结构类似物(邻-羟基苯甲酸)的吸附能力强. 用双Langmuir方程对不同条件下得到的实验数据进行拟合, 得到模板分子和邻-羟基苯甲酸在印迹整体柱各种吸附位点上的饱和吸附量和键合常数, 结果表明, 流动相中乙酸含量、有机溶剂的性质和柱温对模板分子容量因子的影响比对邻-羟基苯甲酸的大, 造成印迹聚合物的选择性随条件的变化而发生了明显的改变.     

Determination of fluoroquinolones in environmental water and milk samples treated with stir cake sorptive extraction based on a boron‐rich monolith

In this study, a new stir cake sorptive extraction using a boron‐rich monolith as the adsorbent was prepared by the in situ copolymerization of vinylboronic anhydride pyridine complex and divinylbenzene. The effect of preparation parameters, including the ratio of vinylboronic anhydride pyridine complex and divinylbenzene, monomer mixture, and porogen solvent, on extraction performance was investigated thoroughly. The physicochemical properties of the adsorbent were characterized by infrared spectroscopy, scanning electron microscopy, and mercury intrusion porosimetry. Several conditions affecting the extraction efficiency were investigated in detail. Under the optimized conditions, a convenient and sensitive method for the determination of trace fluoroquinolones residues in water and milk samples was established by coupling stir cake sorptive extraction with high‐performance liquid chromatography and diode array detection. The limits of detection for the target compounds were 0.10–0.26 and 0.11–0.22 μg/L for water and milk samples, respectively. In addition, the developed method showed good linearity, repeatability, and precision. Finally, the proposed method was successfully applied for the detection of trace fluoroquinolones residues in environmental water and milk samples. Satisfactory recoveries were obtained for the determination of fluoroquinolones in spiking samples that ranged from 68.8 to 120%, with relative standard deviations below 10% in all cases.