Variable selection in near-infrared spectroscopy: benchmarking of feature selection methods on biodiesel data

In the present work, microwave heating initiated precipitation polymerization was developed to prepare podophyllotoxin (PPT) molecularly imprinted polymers (MIPs), resulting in much shorter polymerization time and better particle morphology. Prior to the polymerization, ultraviolet and FTIR spectroscopy were used to study the interactions between PPT and the functional monomers. The synthesized parameters were respectively optimized and the optimal conditions for the efficient adsorption property were template: PPT, 1 mmol; functional monomer: acrylamide, 6 mmol; bi-crosslinker: ethylene glycol dimethacrylate, 20 mmol and divinylbenzene, 20 mmol; porogen: acetonitrile, 40 mL; initiator: azobisisobutyronitrile, 0.01mol L?1; polymerization temperature: 60°C. FTIR spectroscopy, SEM and thermal analysis were used to characterize the MIPs. The results of the equilibrium rebinding experiments and the competitive adsorption experiments showed that these imprinted polymers exhibited good adsorption ability for the PPT. Scatchard analysis illustrated that two and one types of binding sites were generated in the MIPs and non-imprinted polymers (NIPs), respectively. Using the prepared MIPs as the solid phase extraction (SPE) sorbent, PPT was extracted selectively and efficiently from Dysosma versipellis, Sinopodophyllum hexandrum and Diphylleia sinensis. The regression equation was y=5.873×10?x+17075.659 with the correlation coefficient of 0.9994 in the concentration range of 0.005-0.4 mg mL?1. After washing and eluting the SPE column with methanol and MeOH/acetic acid solution (v/v, 9:1), the limits of detection were 0.12-0.18 μg mL?1 and their recoveries were in the range of 89.5-91.1% with all RSDs lower than 3.7.     

Molecularly imprinted solid-phase extraction of matrine from radix Sophorae tonkinensis

In the study, molecularly imprinted polymers (MIPs) with special molecular recognition properties of matrine (MAT) were prepared in our lab, using melamine-urea-formaldehyde (MUF) as the functional monomer and matrine as the template. An equilibrium binding experiment was performed to investigate the binding ability of the MIPs, and indicated that the MIPs had a high adsorption and good elution ability to the target molecule MAT, when the template/functional monomer ratio (T/M) was 5 mg g(-1). Scatchard analysis and isothermal equilibrium adsorption indicated that only one kind of binding site had existed in the MAT-imprinted polymers with its dissociation constants estimated to be 3.31 × 10(-4) mol L(-1) (200-400 mesh (inch(-1))) and 6.83 × 10(-4) mol L(-1) (over 400 mesh (inch(-1))) depending on the mesh of the MIPs. MAT purification and elution experiments were carried out using MIPs as the solid-phase extraction (MISPE) sorbent, and acetone, water, and chloroform as the elution solvents. The results demonstrated that MIPs achieved their highest adsorption capability after treatment with alkaline solution, while acetone was the most efficient elution solvent. Then, a crude extraction of matrine in radix Sophorae tonkinensis was performed using these MIPs as the separation medium. The results showed that MIPs had a high MAT selectivity, and the amount of matrine content obtained by MISPE was 1.4-fold to that obtained by liquid-liquid extraction.     

Construction and analytical application of a biosensor based on stearic acid-graphite powder modified with sweet potato tissue in organic solvents

A biosensor based on stearic acid-graphite powder modified with sweet potato (Ipomoea batatas (L.) Lam.) tissue as peroxidase source was constructed and applied in organic solvents. Several parameters were studied to evaluate the performance of this biosensor such as stearic acid-graphite powder and tissue composition, type and concentration of supporting electrolyte, organic solvents, water/organic solvent ratio (% v/v) and hydrogen peroxide concentration. After selection of the best conditions, the biosensor was applied for the determination of hydroquinone in cosmetic creams in methanol. At the peroxidase electrode hydroquinone is oxidized in the presence of hydrogen peroxide and the radical formed was reduced back electrochemically at -180 mV vs Ag/AgCl (3.0 mol L(-1) KCl). The reduction current obtained was proportional to the concentration of hydroquinone from 6.2 x 10(-5) to 1.5 x 10(-3) mol L(-1) (r = 0.9990) with a detection limit of 8.5 x 10(-6) mol L(-1). The recovery of hydroquinone from two samples ranged from 98.8 to 104.1% and an RSD lower than 1.0% for a solution containing 7.3 x 10(-4) mol L(-1) hydroquinone and 1.0 x 10(-3) mol L(-1) hydrogen peroxide in 0.10 mol L(-1) tetrabutylammonium bromide methanol-phosphate buffer solution (95:5% v/v) (n = 10) was obtained.     

利巴韦林原位聚合分子印迹电化学传感器的研制

利用原位聚合分子印迹技术,以3-氨基苯硼酸(3-ABBA)为功能单体,利巴韦林(RIB)为目标分子,以硼酸和顺式二醇在不同酸碱度条件下可逆形成环内酯键为原理,在玻碳电极表面原位聚合形成利巴韦林分子印迹膜,研制了测定利巴韦林的分子印迹电化学传感器。采用循环伏安法(CV)和差分脉冲法(DPV)对印迹膜性能进行研究。DPV测试表明:在最优实验条件下,利巴韦林的浓度在5.0×10~(-8)~1.0×10~(-5)mol/L范围内与峰电流呈良好的线性关系,相关系数(r~2)为0.995 3,检出限(S/N=3)为1.5×10~(-8)mol/L。特异性实验表明制备的传感器对利巴韦林的选择性良好。该分子印迹电化学传感器可用于食品中利巴韦林的检测。     

Flow injection chemiluminescence sensor using core-shell molecularly imprinted polymers as recognition element for determination of dapsone

This paper reports the preparation of dapsone (DDS) imprinted polymer layer-coated silica submicron particles (SiO(2)) combined with chemiluminescence (CL) toward analysis of tracing DDS in practical samples. To induce the selective occurrence of surface polymerization, the amino groups were first grafted at the surface of SiO(2) by the (3-aminopropyl)triethoxysilane (APTES). The molecularly imprinted polymers (MIP) were coated at the surface of modified SiO(2) by the graft copolymerization. After the removal of templates, recognition sites of DDS were exposed in the polymer layers. The DDS-imprinted products were characterized by FT-IR, SEM, TEM, dynamic adsorption, and static adsorption tests. The proximity between the thickness of MIP layer and the spatial size of DDS indicated that the imprinted sites almost situated at the surface of MIP, leading to rapid adsorption saturation within 90 min. The apparent maximum binding amount of MIP toward DDS was evaluated as 14.98 mg·g(-1), which was much higher than that of non-molecularly imprinted polymers. The CL sensor provided a wide linear range for DDS within 1.0 × 10(-6) to 1.0 × 10(-4) mol·L(-1) with a detection limit of 5.27 × 10(-7) mol·L(-1) and the relative standard deviation of 1.8 % (n = 11) by determinations of 5.0 × 10(-6) mol·L(-1) DDS. This method was applied to determine DDS in urine samples and satisfactory results were obtained.     

石杉碱甲分子印迹聚合物的制备、表征及其吸附性能

以硅胶为牺牲载体,石杉碱甲为模板分子,甲基丙烯酸为功能单体,二乙烯基苯为交联剂,偶氮二异丁腈为引发剂,首次制备了石杉碱甲分子印迹聚合物,并用红外光谱、扫描电子显微镜和热重分析研究了印迹聚合物的结构特征,用静态吸附法和Scatchard分析法研究了印迹聚合物的识别效能和表面位点分布特征。 结果表明,石杉碱甲印迹聚合物对模板分子具有较好的选择吸附性能,选择系数为1.399。Scatchard分析表明,印迹聚合物基体中主要存有两类吸附位点,对高亲和位点：平衡离解常数Kd1=0.776 g/L,最大表观结合量Qmax1=0.213 mg/g;对低亲和位点：平衡离解常数Kd2=0.169 g/L,最大表观结合量Qmax2=0.832 mg/g。 当该聚合物用于微固相萃取蛇足石杉粗提液中的石杉碱甲时,石杉碱甲回收率为93.5%,显示了较好的富集效果。     

对羟基苯甲酸酯分子印迹电化学传感器的研制

利用分子印迹技术,以对羟基苯甲酸乙酯为模板分子,甲基丙烯酸为单体,在玻碳电极表面原位聚合分子印迹聚合物敏感膜.采用方波伏安法对对羟基苯甲酸乙酯在该印迹电极上的电化学行为进行了研究,当响应时间为15 min时,0.95 V(vs SCE)处的峰电流与对羟基苯甲酸乙酯的浓度在2.0×10-6 ～2.0×10-4 mol/L范围内呈线性关系,检出限(S/N=3)为1.0 μmol/L,而相同条件下,对羟基苯甲酸乙酯在控制电极上的响应非常小并对浓度变化不灵敏;同时在印迹电极上氧化峰电位较在裸电极上发生了微弱正移.同一支印迹电极对对羟基苯甲酸乙酯响应值的RSD为4.3%(n=10).该印迹电极对尼泊金酯类具有良好的选择性,对对羟基苯甲酸甲酯、丙酯以及丁酯的选择性系数分别为1.89、1.70和2.01;对结构相似的苯酚、对羟基苯甲酸、对氨基苯甲酸等响应不灵敏,对结构差异较大的如维生素C等几乎无响应.用该分子印迹电极对实际样品进行分析,加标回收率大于90%.     

High sensitivity voltammetric determination of sodium nitroprusside at acetylene black electrode in the presence of CTAB

A sensitive electroanalytical method for detection of sodium nitroprusside (SNP) was investigated, on the basis of the enhanced electrochemical response of SNP at an acetylene black electrode (ABE) in the presence of cetyltrimethylammonium bromide (CTAB). Voltammetric studies showed that SNP exhibited a pair of quasi-reversible redox peaks at ABE in the presence of CTAB while no any redox peak was observed in the absence of CTAB. This was attributed to the enhanced adsorption of SNP at AB through electrostatic interactions between SNP and CTAB as well as hydrophobic adsorption of CTAB at the hydrophobic surface of ABE. Under optimal working conditions, the reduction current was proportional to the concentration of SNP in the range of 1.0x10(-7) to 1.0x10(-5) mol/L and 1.0x10(-5) to 1.0x10(-2) mol/L. A low detection limit of 5.0x10(-9) mol/L was obtained for 2 min accumulation at open circuit (S/N=3). The proposed method was successfully applied to the determination of SNP in pharmaceutical dosage forms.     

酚酞分子印迹聚合物的制备及特异吸附性能

以泻药酚酞为模板分子,4-乙烯基吡啶为功能单体制备了模板分子和功能单体不同比例的一系列酚酞分子印迹聚合物。利用扫描电镜对聚合物进行了表面形态分析,采用静态平衡实验法研究了聚合物对模板分子及其类似物的吸附行为和选择性识别能力。实验结果表明,所制备的分子印迹聚合物,吸附 3 h 后基本接近最大吸附量,其中模板分子、4-乙烯基吡啶和交联剂的摩尔比为 1∶6∶20的MIP2的印迹因子为 2.30,效果最佳。Scatchard 分析表明, 在所研究的浓度范围内,吸附过程存在两类结合位点,一类高亲和力结合位点的离解常数为Kd1= 0.63 mmol/L,最大表观结合量 Qmax1 = 25.4 umol/g,另一类低亲和力结合位点的离解常数为 Kd2 =3.5 mmol/L,最大表观结合量 Qmax2 = 61.9 umol/g,通过与酚酞类似物质在酚酞分子印迹聚合物上的吸附行为比较,表明对酚酞具有很好的选择性吸附。     

多壁碳纳米管表面过氧化苯甲酰印迹复合材料的制备及固相萃取应用

以过氧化苯甲酰(BOP)为模板分子,甲基丙烯酸(MAA)为功能单体,乙二醇二甲基丙烯酸酯(EGDMA)为交联剂,偶氮二异丁腈(AIBN)为引发剂,采用热聚合法在多壁碳纳米管(MWNTs)表面制备印迹聚合物(MWNTs-MIPs)。采用红外和热重分析等技术对聚合物结构进行表征。采用液相色谱考察该分子印迹聚合物对过氧化苯甲酰的吸附特性。结果表明该印迹聚合物对过氧化苯甲酰表现出特异性吸附,该印迹聚合物对模板分子存在一种结合位点,其最大表观结合量为56.20 µmol/g。该印迹聚合物成功应用于固相萃取富集面粉中微量过氧化苯甲酰,浓度富集因子为526。     

以马来松香丙烯酸乙二醇酯为交联剂的茶碱分子印迹膜电化学传感器的研究

利用分子印迹技术, 以马来松香丙烯酸乙二醇酯为交联剂, 丙烯酸为功能单体研制了测定茶碱的新型电化学传感器. 以自由基热聚合的方式于玻碳电极表面制备茶碱分子印迹聚合物膜. 通过循环伏安法、电化学交流阻抗法及计时电流法研究了传感器对茶碱的响应特性. 结果表明, 在最佳的实验条件下, 传感器的峰电流与茶碱浓度在2.00×10^-7～3.45×10^-4 mol/L 范围内呈现出良好的线性关系(线性相关系数为0.9961), 检出限(S/N＝3)为1.00×10^-7 mol/L;该传感器的选择性高, 稳定性和重现性好, 将此传感器用于茶碱缓释片中茶碱的含量测定, 回收率为95.6%～103.8%.关键词 马来松香丙烯酸乙二醇酯; 茶碱; 分子印迹聚合物; 电化学传感器     

Synthesis and evaluation of molecularly imprinted core-shell carbon nanotubes for the determination of triclosan in environmental water samples

Synthetic core-shell molecularly imprinted polymers (MIPs) were prepared for the extraction of trace triclosan in environmental water samples. The synthesis process combined a surface molecular imprinting technique with a sol-gel process based on carbon nanotubes (CNTs) coated with silica. The morphology and structure of the products were characterized by transmission electron microscopy and Fourier transform infrared spectroscopy. The adsorption properties of the polymers were demonstrated by equilibrium rebinding experiments and Scatchard analysis. The prepared imprinted materials exhibited fast kinetics, high capacity and favorable selectivity. The process of synthesis was quite simple and different batches of MIPs and non-imprinted polymers (NIPs) showed good reproducibility in the template binding. The feasibility of determination of triclosan from real samples was testified using spiked river and lake water samples. The recoveries of river water and lake water samples were ranged from 92.1 to 95.3% and 90.7 to 93.6%, respectively, when the environmental water samples were spiked with 0.1, 0.3, and 0.5 μg L(-1) of TCS. In addition, the reusability of MIPs and NIPs without any deterioration in capacity was demonstrated for at least 10 repeated cycles.     

多巴胺有序介孔硅表面分子印迹传感器的研制

以多巴胺(DA)为模板,氨基修饰的介孔硅为载体,制得对多巴胺具有特异选择性的表面分子印迹聚合物(MIP)。将所得的MIP制成碳糊电极,用循环伏安法对多巴胺进行检测。在优化实验条件下,传感器的氧化峰电流与多巴胺浓度在1.0×10-7～2.0×10-6mol/L和2.0×10-6～1.0×10-4mol/L范围内呈良好的线性关系,相关系数分别为0.992 5和0.996 9,检出限为1.3×10-9mol/L。该传感器对DA具有较高的灵敏度和选择性,将其用于实际样品检测,结果满意。     

基于分子印迹电聚合膜的褪黑素传感器的研究

在弱酸条件下,以邻苯二胺为功能单体,褪黑素为模板,以电化学聚合物法在铂电极表面合成了性能稳定的褪黑素分子印迹聚合物膜.采用循环伏安法(CV)和差分脉冲法(DPV)对分子印迹传感器的识别性能进行了研究.结果表明:此传感器对褪黑素具有快的响应、良好的选择性和高的灵敏度.以K3Fe(CN)6为电子传递媒介,建立了一种差分脉冲伏安法(DPV)间接检测褪黑素的分析方法.在1×10-10～1×10-8 moL/L范围内,褪黑素的浓度与K3Fe(CN)6的相对峰电流变化呈良好的线性关系;检出限为1×10-11 mol/L(S/N=3).将此传感器应用于复合褪黑素及尿样中褪黑素含量的测定,加标平均回收率大于94％.     

芦丁-槲皮素双模板印迹聚合物的制备、表征及识别

以芦丁(RT)-槲皮素(QT)为混合模板分子制备了芦丁-槲皮素复合模板分子印迹聚合物。 优化了制备条件,研究了模板用量比、功能单体及交联剂用量对印迹聚合物吸附性能的影响。 用傅里叶红外光谱和扫描电镜对分子印迹聚合物进行结构表征。 探讨了分子印迹聚合物的吸附动力学、等温吸附及键合位点特征,考察了其选择识别性能,并以分子印迹聚合物为吸附介质,萃取分离芦丁粗提液中的目标化合物。 结果表明,当槲皮素与芦丁的摩尔比为3:2,且模板总量与功能单体及交联剂用量摩尔比为1:8:10时,所得分子印迹聚合物的吸附性能最好,对槲皮素和芦丁的吸附量分别达47.86和60.97 mg/g。 吸附可在3.5 h内达到平衡,显示了较快的吸附动力学。 Scatchard分析表明,分子印迹聚合物基体中存在四类不同性能的键合位点,分别为芦丁和槲皮素的高亲和键合位点及非选择键合位点。 相对分布系数(k=K_d(RT)/K_d(QT),K_d=q_e/ρ_e,K_d为分布系数,q_e为平衡吸附量,ρ_e为平衡质量浓度)大于1,表明了分子印迹聚合物对芦丁具有更高的选择键合作用,当模拟混合物中芦丁和槲皮素浓度分别为0.07和0.03 mmol/L时,相对分布系数和分离因子(α=q_e(RT)/q_e(QT))分别达6.669和25.02。 另外,以乙腈、甲醇及甲醇-醋酸混合物依次为洗脱剂,通过分子印迹固相萃取可从槐米提取物中分离芦丁和槲皮素两种黄酮类化合物,总回收率分别为96.70%和94.67%。     

Quantum dot nanocrystals having guanosine imprinted nanoshell for DNA recognition

Molecular imprinted polymers (MIPs) as a recognition element for sensors are increasingly of interest and MIP nanoparticles have started to appear in the literature. In this study, we have proposed a novel thiol ligand-capping method with polymerizable methacryloylamido-cysteine (MAC) attached to CdS quantum dots (QDs), reminiscent of a self-assembled monolayer and have reconstructed surface shell by synthetic host polymers based on molecular imprinting method for DNA recognition. In this method, methacryloylamidohistidine-platinium (MAH-Pt(II)) is used as a new metal-chelating monomer via metal coordination-chelation interactions and guanosine templates of DNA. Nanoshell sensors with guanosine templates give a cavity that is selective for guanosine and its analogues. The guanosine can simultaneously chelate to Pt(II) metal ion and fit into the shape-selective cavity. Thus, the interaction between Pt(II) ion and free coordination spheres has an effect on the binding ability of the CdS QD nanosensor. The binding affinity of the guanosine imprinted nanocrystals has investigated by using the Langmuir and Scatchard methods, and experiments have shown the shape-selective cavity formation with O6 and N7 of a guanosine nucleotide (K(a) = 4.841x10(6) mol L(-1)) and a free guanine base (K(a) = 0.894x10(6) mol L(-1)). Additionally, the guanosine template of the nanocrystals is more favored for single stranded DNA compared to double stranded DNA.     

A NOVEL MOLECULARLY IMPRINTED POLYMER： SYNTHESIS AND ADSORPTION BEHAVIOR OF GATIFLOXACIN

A kind of molecularly imprinted polymer （MIPs） with high selectivity was prepared using methacrylic acid （MAA） as functional monomer, ethylene glycol dimethacrylate （EDMA） as crosslinker and Gatifloxacin as template. The effect of various parameters such as volume of solvent, functional monomer dosage, crosslinker dosage and polymerization time were investigated. The selective binding experiment for substrates show that the affinity and selectivity for Gatifloxacin were higher than that for blank polymer. Scatchard analysis show that the MIPs recognized template with two kinds of binding sites. The dissociation constant Kd and maximum adsorption quantity Qmax of these two kinds of binding sites were calculated： Kd1 and Qmax1 of the binding sites with high affinity were 8.67×10^-4 mol/L and 28.19μmol/g, while Kd2 and Qmax2 of the binding sites with low affinity were 1.05×10^-3 mol/L and 33.20μmol/g respectively.     

聚吡咯/STAB-NaMMT/GC电极对苯二酚的电化学行为研究

利用十八烷基三甲基溴化氨（STAB）和聚吡咯（PPy）钠基蒙脱土制备了PPy/STAB钠基蒙脱土/GC电极（PPy/STAB-NaMMT/GC）.用循环伏安法和方波溶出伏安法（SWSV）研究了对苯二酚在该电极上的电化学行为.实验表明,在pH 6.0 PBS电解液中,对苯二酚在该电极的电极反应受扩散控制,转移的电子数与质...     

Sensitive and selective molecularly imprinted electrochemical sensor based on multi-walled carbon nanotubes for doxycycline hyclate determination

An electrochemical sensor for doxycycline hyclate(DC)detection with high sensitivity and good selectivity is reported.The sensor was fabricated by electro-polymerization of molecularly imprinted polymers(MIPs)in the presence of DC onto multi-walled carbon nanotubes modified glassy carbon electrode(MWCNTs/GCE).The MWCNTs can significantly increase the current response of the sensor,leading to enhanced sensitivity.The MIPs provide selective recognition sites for DC detection.The experimental parameters,such as the polymer monomer concentration,supporting electrolyte pH,the time for electro-polymerization and the incubation time of the sensor with DC were optimized.Under optimized experimental conditions,the sensor displayed a linear range of 0.05μmol/L-0.5μmol/L towards DC detection,with the detection limit of 1.3×10^-2μmol/L.The sensor was successfully applied for recovery test of DC in human serum samples.     

A molecularly imprinted polymer based on functionalized multiwalled carbon nanotubes for the electrochemical detection of parathion-methyl

A novel composite of vinyl group functionalized multiwalled carbon nanotubes (MWCNTs) molecularly imprinted polymer (MIP) was synthesized and applied as a molecular recognition element to construct an electrochemical sensor for parathion-methyl in this paper. The special molecular recognition properties of parathion-methyl mainly dominated by π-π, p-π interaction and hydrogen bonding formed among functional monomer, template and matrix. A series of electrochemical experiment results proved that the prepared material had good adsorption capacity and fast mass transfer rate to parathion-methyl. The good selectivity of the sensor allowed fine discrimination between parathion and paraoxon, which had similar structures to parathion-methyl. The response of the MIPs was linearly proportional to the concentration of parathion-methyl over the range of 2.0 × 10(-7) to 1.0 × 10(-5) mol L(-1) with a lower detection limit of 6.7 × 10(-8) mol L(-1) (S/N = 3). This sensor was also applied in the detection of parathion-methyl in pear and cucumber with average recoveries of between 94.9% and 106.2% (RSD < 5%) being obtained. The results mentioned above show that the novel electrochemical sensor is an ideal device for the real-time determination of parathion-methyl in real samples.