Creatinine sensor based on a molecularly imprinted polymer-modified hanging mercury drop electrode

Molecularly imprinted polymers (MIP) have been elucidated to work as artificial receptors. In our present study, a MIP was applied as a molecular recognition element to a chemical sensor. We have constructed a creatinine sensor based on a MIP layer selective for creatinine and its differential pulse, cathodic stripping voltammetric detection (DPCSV) on a hanging mercury drop electrode (HMDE). The creatinine sensor was fabricated by the drop coating of dimethylformamide (DMF) solution of a creatinine-imprinted polymer onto the surface of HMDE. The modified-HMDE, preanodised in neutral medium at +0.4 V versus Ag/AgCl for 120 s, exhibited a marked enhancement in DPCSV current in comparison to the less anodised (≤+0.3 V) HMDE. The creatinine was preconcentrated and instantaneously oxidised in MIP layer giving DPCSV response in the concentration range of 0.0025-84.0 μg mL⁻¹ [detection limit (3σ) 1.49 ng mL⁻¹]. The sensor was found to be highly selective for creatinine without any response of interferents viz., NaCl, urea, creatine, glucose, phenylalanine, tyrosine, histidine and cytosine. The non-imprinted polymer-modified electrode did not show linear response to creatinine. The imprinting factor as high as 9.4 implies that the imprinted polymer exclusively acts as a recognition element of creatinine sensor. The proposed procedure can be used to determine creatinine in human blood serum without any preliminary treatment of the sample in an accurate, rapid and simple way.     

Development of a Creatinine Sensor Based on a Molecularly Imprinted Polymer‐Modified Sol‐Gel Film on Graphite Electrode

An electrochemical creatinine sensor based on a molecularly imprinted polymer (MIP)‐modified sol‐gel film on graphite electrode was developed. The surface coating of MIP over sol‐gel was advantageous to obtain a porous film with outwardly exposed MIP cavities for unhindered selective rebinding of creatinine from aqueous and biological samples. A fast differential pulse, cathodic stripping voltammetric response of creatinine can be obtained after being preanodized the sensor in neutral medium containing appropriate amount of creatinine at +1.8 V versus SCE for 120 s. A linear response over creatinine concentration in the range of 1.23 to 100 μg mL^?1 was exhibited with a detection limit of 0.37 μg mL^?1 (S/N=3).     

Highly Selective Molecularly Imprinted Polymer Sensor for Indium Detection Based on Recognition of In‐Alizarin Complexes

A highly selective molecularly imprinted polymer electrochemical sensor for In³⁺ detection was proposed. In³⁺ ion was chelated with alizarin red S to form a complex In‐ARS. The complex was used as the template molecule to prepare a molecularly imprinted polymer (MIP) based sensor. The selectivity of the sensor was improved significantly due to the three‐dimensional specific structure of the complex, and the selective complexation of ligands for metal ions. Moreover, the sensitivity of the proposed sensor was improved by recording the reductive current of ligand in complex. This technique was highly sensitive for quantitative analysis of In³⁺ in the concentrations ranged from 1×10^?8 mol/L to 2.5×10^?7 mol/L with a detection limit of 4.7×10^?9 mol/L. The proposed sensor has been successfully used in detecting In³⁺ in real samples.     

Use of a bisphenol-A imprinted polymer as a selective sorbent for the determination of phenols and phenoxyacids in honey by liquid chromatography with diode array and tandem mass spectrometric detection

An extraction-preconcentration procedure based on the use of a molecularly imprinted polymer (MIP) as selective sorbent has been developed for the determination of several phenolic compounds (bisphenol-A, bisphenol-F and 4-nitrophenol) and phenoxyacid herbicides (2,4-D, 2,4,5-T and 2,4,5-TP) in honey samples. Liquid chromatography with diode array detection (LC-DAD) and electrospray ionisation-ion trap mass spectrometry (LC-IT-MS) were used for the separation, identification and quantification of these analytes.The molecularly imprinted polymer was obtained by precipitation polymerisation with bisphenol-A (BPA) as template and 4-vinylpyridine as the functional monomer. The behaviour of this sorbent was compared with those of other materials frequently used in SPE. The selectivity of the BPA-MIP for the target analytes was tested in samples containing other pesticides in common use. The recoveries achieved for all six compounds were in the 81-96% range.By applying the proposed procedure prior to LC-IT-MS, the limits of detection achieved in commercial honey samples were in the 0.1-3.8 ng g⁻¹ range, with relative standard deviations of 12-24%.     

Magnetic Molecularly Imprinted Polymers for the Rapid and Selective Extraction and Detection of Methotrexatein Serum by HPLC-UV Analysis

In this work, novel selective recognition materials, namely magnetic molecularly imprinted polymers (MMIPs), were prepared. The recognition materials were used as pretreatment materials for magnetic molecularly imprinted solid-phase extraction (MSPE) to achieve the efficient adsorption, selective recognition, and rapid magnetic separation of methotrexate (MTX) in the patients’ plasma. This method was combined with high-performance liquid chromatography–ultraviolet detection (HPLC–UV) to achieve accurate and rapid detection of the plasma MTX concentration, providing a new method for the clinical detection and monitoring of the MTX concentration. The MMIPs for the selective adsorption of MTX were prepared by the sol–gel method. The materials were characterized by transmission electron microscopy, Fourier transform-infrared spectrometry, X-ray diffractometry, and X-ray photoelectron spectrometry. The MTX adsorption properties of the MMIPs were evaluated using static, dynamic, and selective adsorption experiments. On this basis, the extraction conditions were optimized systematically. The adsorption capacity of MMIPs for MTX was 39.56 mgg⁻¹, the imprinting factor was 9.40, and the adsorption equilibrium time was 60 min. The optimal extraction conditions were as follows: the amount of MMIP was 100 mg, the loading time was 120 min, the leachate was 8:2 (v/v) water–methanol, the eluent was 4:1 (v/v) methanol–acetic acid, and the elution time was 60 min. MTX was linear in the range of 0.00005–0.25 mg mL⁻¹, and the detection limit was 12.51 ng mL⁻¹. The accuracy of the MSPE–HPLC–UV method for MTX detection was excellent, and the result was consistent with that of a drug concentration analyzer.     

识别三唑类农药的片段印迹聚合物的合成及在固相萃取中的应用

采用片段印迹技术, 合成了一系列对7种三唑类农药(三唑酮、烯唑醇、多效唑、烯效唑、戊唑醇、三唑醇和双苯三唑醇)具有识别能力的聚合物. 振荡平衡吸附实验表明, 以邻硝基苯酚为模板的聚合物(M1)对上述7种农药具有最佳的选择性吸附性能. 根据分析物结构对片段印迹聚合物吸附能力的影响, 提出了片段印迹聚合物的识别机理: 三唑类化合物的分子片段末端苯环进入片段印迹聚合物的孔穴中, 同时其羟基与聚合物孔穴外的功能单体4-乙烯基吡啶上的氮原子形成氢键, 二者的协同作用实现对目标分子的选择性识别, 其中分析物末端苯环和聚合物孔穴的匹配是影响片段聚合物识别能力的主要因素. 将基质固相分散(MSPD)与以M1为吸附剂的分子印迹固相萃取(MISPE)联用, 用于土壤样品的前处理. 在3种添加水平下, 各分析物的回收率均为75%~102%, 相对标准偏差为3%~9%(n=5), 方法检出限(信噪比等于3)0.9~15 μg/kg. 表明该分析方法结合了MSPD的快速提取和MISPE的高选择性的特点.     

Selective extraction of derivates of p-hydroxy-benzoic acid from plant material by using a molecularly imprinted polymer

Selective SPE of derivates of p-hydroxybenzoic acid (pHBA) from plant extract of Melissa officinalis is presented using a molecularly imprinted polymer (MIP) made with protocatechuic acid (PA) as template molecule. MIP was prepared with acrylamide as functional monomer, ethylene glycol dimethacrylate as crosslinking monomer and ACN as porogen. MIP was evaluated towards six phenolic acids: PA, gallic acid, pHBA, vanillic acid (VA), gentisic acid (GeA) and syringic acid (SyrA), and then steps of molecularly imprinted SPE (MISPE) procedure were optimized. The best specific binding capacity of MIP was obtained for PA in ACN (34.7 microg/g of MIP). Other tested acids were also bound on MIP if they were dissolved in this solvent. ACN was chosen as solvent for sample application. M. officinalis was extracted into methanol/water (4:1, v/v), the extract was then evaporated to dryness and dissolved in ACN before application on MIP. Water and ACN were used as washing solvents and elution of benzoic acids was performed by means of a mixture methanol/acetic acid (9:1, v/v). pHBA, GA, PA and VA were extracted with recoveries of 56.3-82.1% using this MISPE method. GeA was not determined in plant extract.     

Selective solid phase extraction of a drug lead compound using molecularly imprinted polymers prepared by the target analogue approach

Summary Molecularly imprinted polymers have been evaluated at the sample clean-up stage in the analysis of a drug lead compound. In order to circumvent quantification problems related to bleeding of the template, a structurally related analogue of the latter was used. This was selected based on criteria related to interaction site location, solubility, availability and stability of the analogue. Selection of suitable polymerisation conditions was then made using a small batch format (ca. 50 mg) and rapid assessment of binding in the equilibrium mode. It was found that the amount of template could be greatly reduced compared to the conventional protocol, requiring only 5 μmol of template per gram of polymer without seriously compromising the performance of the materials for chromatographic or SPE applications.     

A novel molecularly imprinted polymer for simultaneous extraction and determination of sudan dyes by on-line solid phase extraction and high performance liquid chromatography

A novel molecularly imprinted polymer was synthesized with attapulgite employed as matrix, which is simple and time-saving. In this method, sudan I was chosen as template molecule, 2-vinylpyridine as functional monomer and ethylene glycol dimethacrylate as cross-linking agent, respectively. The imprinted polymer was characterized by the infrared spectroscopy and transmission electron microscopy. Then the selectivity experiments were performed on sudan dyes and the recognition coefficients for sudan I, sudan II, sudan III and sudan IV were 2.9, 1.9, 1.9 and 2.3, respectively. As the packing material of solid-phase extraction, the imprinted polymer has been applied to on-line concentration of the four sudan dyes in samples from Yellow River water, tomato sauce and sausage. The corresponding analytical methods to determine these sudan dyes have been developed. The limits of detection for these sudan dyes were in the range of 0.01–0.05 ng mL⁻¹ for Yellow River water, 1.0–3.0 ng g⁻¹ for tomato sauce and 0.8–3.0 ng g⁻¹ for sausage.     

Selective solid-phase extraction of amoxicillin and cephalexin from urine samples using a molecularly imprinted polymer

In this paper we describe, for the first time, a molecularly imprinted polymer (MIP) for the antibiotic amoxicillin (AMX), synthesised by a noncovalent molecular imprinting approach and used to extract AMX selectively from urine samples. The MIP was applied as a molecularly selective sorbent in molecularly imprinted SPE (MISPE) in an off-line mode, where it showed useful cross-selectivity for a structurally related antibiotic, cephalexin (CPX). By using a MISPE protocol, the MIP was able to selectively extract both AMX and CFX from 5 mL of water spiked with 10 mg/L with recoveries of 75 and 78% for AMX and CFX, respectively. When applied to real samples (urine) at clinically relevant concentrations, recoveries from 2 mL of human urine spiked with 20 mg/L decreased slightly to 65 and 63% for AMX and CFX, respectively. To demonstrate further the selectivity of the MIP obtained, a comparison with commercially available SPE cartridges was performed. Improvements in the retention of both AMX and CFX on the MIP were obtained relative to the commercially available cartridges, and the MISPE extracts were considerably cleaner, due to molecularly selective analyte binding by the MIP.     

Selective enrichment of anti-inflammatory drugs from river water samples by solid-phase extraction with a molecularly imprinted polymer

A molecularly imprinted polymer (MIP) is synthesised by a noncovalent protocol in which ibuprofen was used as a template molecule. The polymer was evaluated chromatographically and it was seen that the MIP showed cross-reactivity. Subsequently, when this polymer was used as sorbent in SPE it was possible to selectively extract a mixture of nonsteroidal anti-inflammatory drugs from aqueous samples when a cleanup step with dichloromethane was performed. The performance of the MIP was evaluated with river water and water from a wastewater treatment plant, and compared with the performance of a commercial Isolute ENV+ sorbent.     

Selective solid phase extraction of trace cadmium(II) and lead(II) from biological and natural water samples by ofloxacin-modified-silica gel

Ofloxacin was successfully used as a chemical modifier to improve the reactivity of silica gel in terms of selective binding and extraction of heavy metal ions. This new functionalised silica gel (SG-ofloxacin) was as an effective sorbent for the solid-phase extraction (SPE) of Cd(II) and Pb(II) in biological and natural water samples and their determination by inductively coupled plasma optical emission spectrometry (ICP-OES). Experimental conditions for effective adsorption of trace levels of Cd(II) and Pb(II) were optimised with respect to different experimental parameters using the batch and column procedures. The time for 70% sorption for Cd(II) and Pb(II) was less than 2 min. Complete elution of the adsorbed metal ions from the SG-ofloxacin was carried out using 2.0 mL of 0.5 mol L^?1 of HCl. Common coexisting ions did not interfere with the separation and determination at pH 4.0. The maximum static adsorption capacity of the sorbent at optimum conditions was found to be 39.17 and 48.69 mg g^?1 for Cd(II) and Pb(II), respectively. The detection limits of the method were found to be 0.29 and 0.13 ng mL^?1 for Cd(II) and Pb(II), respectively. The relative standard deviation (RSD) of the method under optimum conditions was lower than 3.0% (n = 5). The method was applied to the recovery of Cd(II) and Pb(II) from the certified reference material (GBW 08301, river sediment) and to the simultaneous determination of these cations in different water and biological samples with satisfactory results and yielding 100-folds enrichment factor.     

Determination of Acrolein‐Derived 3‐Hydroxypropylmercapturic Acid in Human Urine Using Solid‐phase Extraction Combined with Molecularly Imprinted Mesoporous Silica and LC‐MS/MS Detection

A novel method for the analysis of (3‐hydroxypropyl)mercapturic acid (HPMA), a major acrolein metabolite in human urine incorporating a molecularly imprinted solid‐phase extraction (MISPE) process using N‐acetylcysteine ‐imprinted mesoporous silica particles coupled with LC‐MS/MS detection was developed. The molecularly imprinted mesoporous silica particles were synthesized based on the supported material of ordered mesoporous silica SBA‐15 with N‐acetylcysteine (NAC) as template using surface molecular imprinting technology. The condition of MISPE procedures was optimized. The use of MISPE improved the accuracy and precision of the LC‐MS method and lowered the limit of detection (0.23 ng/mL). The recoveries at three spiked levels ranged between 88.5% to 108.6%. The developed MISPE method enabled the selective extraction of HPMA successfully in human urine and could be used as an effective approach for the determination of ultra‐trace HPMA in complex biological matrices. The results in real samples showed that median levels of HPMA were significantly higher (1922.0 ng/mg of creatinine, N = 75) in smokers than in nonsmokers (759.1 ng/mg of creatinine, N = 5), demonstrating the higher acrolein uptake in smokers than in nonsmokers.     

Highly Sensitive and Selective Detection of 2,4-Dinitrophenol by a Fluorescent Amine-Functionalized Carbon Quantum Dot@Metal-Organic Framework

Russian Journal of Physical Chemistry A - Herein, we fabricate a composite fluorescence sensor by integrating amine-functionalized carbon quantum dots (amine-CQDs) and a zirconium-based...     

高灵敏选择性检测凝血酶的适体纳米银共振散射光谱探针

采用四氢硼钠制备了较稳定的纳米银,并用凝血酶(TB)适体修饰纳米银制各了识别凝血酶的适体纳米银探针.在pH 7.0的Tris-HCl缓冲溶液及KCl存在下,适体纳米银探针与凝血酶特异结合生成G-四分体和纳米银聚集体,导致体系在480 nm处的共振散射峰增强.随着凝血酶浓度的增大,生成的纳米银聚集体越多,共振散射强度线性...     

Study on an on-line molecularly imprinted solid-phase extraction coupled to high-performance liquid chromatography for separation and determination of trace estrone in environment

Estrone is one of the important potential endocrine-disrupting compounds, and the sensitive and reliable analytical methods for the determination of estrone are required for the assurance of human health. In this paper, using estrone as template molecule, 3-aminopropyltriethoxysilane as function monomer, and tetraethoxysilicane as cross-linker, a highly selective molecularly imprinted microsphere was synthesized by surface molecular imprinting technique combined with a sol–gel process. The imprinted material was characterized by the Fourier transform infrared and static adsorption experiments, and the results showed that it exhibited good recognition and selective ability for estrone. A novel method for separation and determination of trace estrone in environmental sample was developed using on-line molecularly imprinted solid-phase extraction coupled to high-performance liquid chromatography. With a sample loading flow rate of 2.6 mL min⁻¹ for a 9.6-min extraction, the enrichment factor obtained by the slopes of the linear portion in comparison with the direct injection of 10 μL standard sample solution was 1,045. The detection limit (S/N = 3) was 5.7 ng L⁻¹, and the relative standard deviations for nine replicate extractions of 5.0 μg L⁻¹ estrone was less than 10.0%. This method was evaluated for quantitative determination of estrone in well and lake water samples spiked at two levels (0.5 and 1.0 μg L⁻¹) with recoveries ranging from 86% to 95%.      

Selective recognition and discrimination of water‐soluble azo dyes by a seven‐channel molecularly imprinted polymer sensor array

A seven‐channel molecularly imprinted polymer sensor array was prepared and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, UV‐Vis spectroscopy, and nitrogen physisorption studies. The results revealed that the imprinted polymers have distinct‐binding affinities from those of structurally similar azo dyes. Analysis of the UV‐Vis spectral response patterns of the seven dye analytes against the imprinted polymer array suggested that the different selectivity patterns of the array were closely connected to the imprinting process. To evaluate the effectiveness of the array format, the binding of a series of analytes was individually measured for each of the seven polymers, made with different templates (including one control polymer synthesized without the use of a template). The response patterns of the array to the selected azo dyes were processed by canonical discriminant analysis. The results showed that the molecularly imprinted array was able to discriminate each analyte with 100% accuracy. Moreover, the azo dyes in two real samples, spiked chrysoidin in smoked bean curd extract and Fanta lime soda (containing tartrazine), were successfully classified by the array.     

Highly Selective and Sensitive Preconcentration of Mercury Ion and Determination by Cold Vapor Atomic Absorption Spectroscopy

Abstract

A simple and selective method based on a sodium dodecyl sulfate (SDS)–coated chromosorb P modified by 2‐mercaptobenzoxazole (MBO) has been developed to selectively separate and concentrate ultra trace amounts of mercury(II) ions for its highly sensitive measurement by cold vapor atomic absorption spectrometry (CVAAS).

The mercury ions were adsorbed quantitatively on SDS‐coated chromosorb due to its complexation with MBO, while the retained Hg²⁺ ions were then stripped from the column with minimal amounts of 2 M nitric acid in acetone. The eluting solution was sent to CV‐AAS for evaluating Hg²⁺ ion content and results indicate that the calibration curve was linear for Hg²⁺ ion in the range of 0.05–85.6 ng mL^?1 and 0.09–9.6 µg mL^?1 of Hg²⁺ ions. Maximum capacity of the SDS‐coated chromosorb modified with 40 mg of the ligand was found to be 498±30 µg of mercury(II), the limit of detection was 0.01 ng mL^?1, and enrichment factors were about 300, which make it suitable it for dilute solution analysis. The method was successfully applied to the determination of Hg²⁺ ion content in real samples.     

On-line solid-phase extraction using alizarin violet functionalized silica gel for determination of trace lead in environmental samples and wastewater by sequential injection spectrophotometry

Trace of Pb(Ⅱ) has been on-line separated and enriched from environmental samples and wastewater by using the self-made alizarin violet functionalized silica gel micro-column coupling with a sequential injection sampling technology. The determination is based on the color reaction of Pb(Ⅱ) with iodide and crystal violet to form an ionic association complex in the presence of polyvinyl alcohol and hydrochloric acid. The use of the microcolumn can prevent the interference of most familiar metal ions, and ther...     

Sensitive Analysis of Idarubicin in Human Urine and Plasma by Liquid Chromatography with Fluorescence Detection: An Application in Drug Monitoring

A new approach for the sensitive, robust and rapid determination of idarubicin (IDA) in human plasma and urine samples based on liquid chromatography with fluorescence detection (LC-FL) was developed. Satisfactory chromatographic separation of the analyte after solid-phase extraction (SPE) was performed on a Discovery HS C18 analytical column using a mixture of acetonitrile and 0.1% formic acid in water as the mobile phase in isocratic mode. IDA and daunorubicin hydrochloride used as an internal standard (I.S.) were monitored at the excitation and emission wavelengths of 487 and 547 nm, respectively. The method was validated according to the FDA and ICH guidelines. The linearity was confirmed in the range of 0.1–50 ng/mL and 0.25–200 ng/mL, while the limit of detection (LOD) was 0.05 and 0.125 ng/mL in plasma and urine samples, respectively. The developed LC-FL method was successfully applied for drug determinations in human plasma and urine after oral administration of IDA at a dose of 10 mg to a patient with highly advanced alveolar rhabdomyosarcoma (RMA). Moreover, the potential exposure to IDA present in both fluids for healthcare workers and the caregivers of patients has been evaluated. The present LC-FL method can be a useful tool in pharmacokinetic and clinical investigations, in the monitoring of chemotherapy containing IDA, as well as for sensitive and reliable IDA quantitation in biological fluids.