A New Molecularly Imprinted Polymer for Solid-phase Extraction of Cotinine from Human Urine

A molecularly imprinted polymer （MIP）, prepared around a cotinine template, has been synthesized. The feasibility of using the polymer for solid-phase extraction （SPE） of cotinine from biological samples has been investigated. The results show that cotinine can be quantitatively retained and eluted from the polymer. Experiments with human urine samples indicate that clean target analyte is obtained for HPLC with UV detection using the protocol.     

Determination of Cotinine in Urine by Molecularly Imprinted Polymer Solid Phase and Liquid–Liquid Extraction Coupled with Gas Chromatography

A comparison between molecularly imprinted solid phase extraction (MISPE) and liquid–liquid extraction (LLE) was performed for cotinine in human urine followed by gas chromatography analysis. The molecularly imprinted polymer (MIP) was synthesized via bulk methodology employing cotinine, methacrylic acid, and ethylene glycol dimethacrylate as template, functional monomer, and cross-linker, respectively. Both methods were validated with good precision and accuracy. The LLE method (limit of quantification = 10 nanograms per milliliter) was slightly more sensitive than the MISPE (limit of quantification = 15 nanograms per milliliter) procedure, but both methods were able to determine cotinine at typical concentrations in urine. An important advantage of the molecularly imprinted polymer approach was its ability to be reused up to at least 100 times. Other advantages of the MISPE include simple manipulation, low solvent consumption, and low worker exposure.     

The Half-Life of 11α-Hydroxy-9, 15-Dioxo-2,3,4,5,20-Pentanor-19-Carboxyprostanoic Acid (PGE-M) in Human Urine

Abstract

A GC-MS-SIM assay for PGE-M recently developed by us (Analyt. Biochem. 128:351–358, 1983) is based on the use of the diethyl ester of the analyte as the Internal standard (IS). Because the decay rate of this is and that of the underivatized metabolite cannot be assumed to be Identical, we determined the half-lives of both species so that data can be adjusted accordingly when the urine specimens are stored for a prolonged time. At -22°C the first-order rate constant of PGE-M decomposition and that of its diethyl ester are 3.120 × 10^?3 day^?1 (t_1/2 222 days) and 2.422 × 10^?3 day^?1 (t_1/2 286 days), respectively. Thus, if the storage time is less than 60 days data adjustment can be omitted, the consequent error being less than 4.3%.     

Determination of β2-Agonists in Porcine Urine by Molecularly Imprinted Solid Phase Extraction Followed Ultra-Performance Liquid Chromatography–Tandem Mass Spectrometry Detection

A novel, sensitive, and robust method has been developed to detect 9 β₂-agonists in porcine urine to monitor illegal use of β₂-agonists in swine rearing. The method based on the molecular imprinted polymer (MIP) rapid extraction followed ultra-performance liquid chromatography coupled tandem mass spectrometry (UPLC-MS/MS) detection. The cleaning efficiency of MIP cartridges was demonstrated by comparing with common ion exchange solid phase extraction. The presented method was validated in accordance with the European Commission Decision 2002/657/EC. The linearity, decision limit (CCα), detection capability (CCβ), recovery, precision, robustness, and stability were studied in detail. CCα and CCβ values were from 0.006 ng/mL to 0.03 ng/mL and from 0.02 ng/mL to 0.08 ng/mL, respectively. The mean recoveries and repeatability varied from 68.8% to 94.2% and from 2.8% to 10.1%. The proposed method was applied to test 170 porcine urine samples from the Shaanxi province in China and two urine samples were confirmed as clenbuterol positive and the concentrations of clenbuterol in positive urine samples were about 0.08 ng/mL and 0.1 ng/mL, respectively. The developed method was demonstrated to be more sensitive and robust for the determination of 9 β₂-agonists in porcine urine. The method was proven to be simple and easy in operation with high selectivity and good reproducibility.     

A Simple Procedure for the Preparation of 4-(α-Mercaptobenzyl)Phenoxyacetic Acid,A Thiol Linker Unit Used in Solid Phase Synthesis of Peptide-α-Thioacids

A convenient procedure for the preparation of the title compound via direct thionation of its alcohol precursor by Lawesson's reagent is described.     

Simultaneous Determination of Fluvoxamine and Its Metabolites in Human Liver Microsomes by High‐Performance Liquid Chromatography with Solid‐Phase Extraction

Abstract

A simple and sensitive high‐performance liquid chromatography method was developed for the simultaneous quantitative determination of fluvoxamine and its two metabolites, fluvoxamino alcohol and fluvoxamino acid, in human liver microsomes. Chromatographic separation was achieved with a Grand‐pak C4‐5 column using a mobile phase at pH 2.5 of 0.5% KH₂PO₄‐acetonitrile (75:25, v/v). Analysis involved a solid‐phase extraction with an Oasis HLB cartridge, which gave high extraction recovery (>92.8%) with good selectivity. The lower limit of quantification of this assay was 78.6 nM for fluvoxamine and fluvoxamino acid, and 82.2 nM for fluvoxamino alcohol, respectively. The coefficient of variation of intra‐ and interday assays was less than 5.8% and accuracy was within 5.3% for all analytes (concentration range 78.6 nM–2.36 µM for fluvoxamine and fluvoxamino acid, and 82.2 nM–2.47 µM for fluvoxamino alcohol, respectively). This method is applicable for accurate and simultaneous determination of oxidative metabolites of fluvoxamine by human liver microsomes.     

Headspace Solid Phase Microextraction for Terpenes and Volatile Compounds Determination in Mastic Gum Extracts,Mastic Oil and Human Urine by GC– MS

A reliable analytical method was developed, which is based on Headspace Solid Phase Microextraction (HS-SPME) and Gas Chromatography–Mass Spectrometry (GC-MS) for the detection of volatile components of the gum and the essential oil of Pistacia lentiscus var. chia, commonly known as mastic gum and mastic oil respectively. The conditions of the HS-SPME were optimized and aqueous-ethanolic extracts of mastic gum and solutions of mastic oil in ethanol-water were analyzed by GC-MS. Almost 26 volatile components in mastic gum and 34 in mastic oil were identified in the gum and the oil respectively. The major constituents of the mastic gum and the mastic oil were α-pinene (63% and 76%, respectively), β-myrcene (15% and 14%), β-pinene (4% and 4%), limonene (2.5% and 1.5%), and caryophyllene (5% and 1%). The quantitative determination of six of the aforementioned substances in multi-analyte standard solutions was achieved with good performance features. The repeatability (RSD%) was <4.2% and the limits of detection were 1.2 µg/L for α-pinene, 0.09 µg/L for β-pinene, 0.7 µg/L for β-myrcene, 0.02 µg/L for camphene, 0.02 µg/L for p-cymene, and 0.07 µg/L for α-terpineol. The HS-SPME/GC-MS procedure was successfully applied to samples of human urine samples after dietetic use of various mastic products such as mastic gum, mastic oil and Greek traditional highly viscous white mastic sweet. Traces of several constituents of mastic, such as α-pinene, β-myrcene, limonene, p-methyl anisole, terpinene, carveol, myrtenol, caryophyllene, α-caryophyllene, and so forth, were detected in the collected urine samples.     

The Simultaneous Determination of Δ9-Tetrahydrocanna-Binol and 11-Hydroxy -Δ9 -Tetrahydrocannabinol in Plasma

Abstract

A technique capable of determining both Δ⁹-tetrahydrocannabinol and 11-hydroxy-Δ⁹-tetrahydrocannabinol is described. The method is based on the reactivity of the phenolic functionality common to both compounds, and is sensitive to 5 ng of Δ⁹-tetrahydrocannabinol and 1 ng of 11-hydroxy-Δ⁹-tetrahydrocannabinol per ml of plasma.     

Determination of Phthalate Esters in Textiles by Solid Phase Extraction and Gas Chromatography–Mass Spectrometry

A sensitive and rapid method was developed for the determination of seven phthalate esters in baby waterproof fabrics, decorated waterproof tarpaulins, and printed textiles by solid phase extraction followed by gas chromatography–mass spectrometry. The method showed good linearity with correlation coefficients between 0.9958 and 0.9999 and limits of quantification and detection from 23 to 274 micrograms per liter and 7 to 82 micrograms per liter, respectively. The maximum recoveries were between 96.2 and 100.9 percent with relative standard deviations from 1.06 to 6.87 percent. The protocol was applied to the determination of phthalate esters in textiles: the samples contained more than 0.1 percent phthalate esters, which exceed relevant standards.     

Determination of BTEX Compounds in Solid–Liquid Mixing Paint Using the Combination of Solid Phase Extraction,Thermal Desorption and GC-FID

A novel method was developed and validated for determination of benzene, toluene, p-xylene, m-xylene, o-xylene (BTEX) in a solid–liquid mixing matrix. It makes use of solid phase extraction and thermal desorption (SPE-TD), followed by gas chromatographic flame ionization detector analysis (GC-FID). The trapped BTEX can be measured directly after thermal desorption onto the stainless-steel packed chromatographic column. The effect of tailing area of solvent was removed with the use of SPE-TD technique, and the result shows good reproducibility with very little matrix dependency. The study also supports that the lifetime of the Tenax adsorption tube could be extended over 150 desorption operation at 200 °C, which enables performing excellent stability and reproducibility of BTEX analysis.

     

A Novel Derivatization Method for Separation of Sarcosine from Isobaric l-Alanine in Human Urine by GC–MS

Sarcosine, an isomer of l-alanine, has been recently proposed as a potential biomarker for prostate cancer risk and aggressiveness, while some studies debated its importance. As both sarcosine and l-alanine are present in human urine, it is a great challenge to separate and accurately quantify these isobaric (i.e., same m/z) compounds by chromatographic separation and mass spectrometric detection. In this study, we developed a novel 1,3-dipolar cycloaddition derivatization method that resolves sarcosine from l-alanine and allows accurate quantification of sarcosine in human urine by gas chromatography–mass spectrometry (GC–MS). This novel derivatization approach was specific to sarcosine only, while the common silylanization method resulted in overlapped derivates of both sarcosine and l-alanine. The derivatization conditions, including reagent amount, reaction temperature and time, were optimized. The method developed here has excellent precision (relative standard deviation <4.7 %, n = 5), good linearity (slope = 0.2408; r ² = 0.9996, 0.1–100 μg mL^?1), and a low limit of detection in human urine (0.15 ng mL^?1). Application of this analytical method to urine samples spiked with standard sarcosine indicates that it is a robust and powerful alternative for resolving and quantifying sarcosine from l-alanine isomer in human urine by GC–MS.     

Comparison of Modifiers for Mercury Speciation in Water by Solid Phase Extraction and High Performance Liquid Chromatography–Atomic Fluorescence Spectrometry

Diethyldithiocarbamate and 2-mercaptoethanol modifiers were compared for the preconcentration of mercury species in water by C₁₈ solid phase extraction (SPE). The recovery values of mercury species were determined by high performance liquid chromatography–atomic fluorescence spectrometry. The eluent type, pH, chloride ion concentration, humic acid concentration, and storage time were evaluated to compare the preconcentration efficiency. L-cysteine was employed to elute the mercury compounds. Less eluent was needed for 2-mercaptoethanol modified SPE than for diethyldithiocarbamate modified SPE at an L-cysteine concentration of 0.12%. Diethyldithiocarbamate modified SPE could be used over a wider pH range and higher humic acid concentrations, whereas 2-mercaptoethanol modified SPE was less affected by the chloride concentration. Both modified SPE systems stored mercury species for 5 days, but diethyldithiocarbamate modified SPE could be stored longer. Diethyldithiocarbamate SPE provided limits of detections of 3.5, 2.5, and 4 ng · L^?1 and average recoveries of 90.78 ± 3.37%, 96.79 ± 5.12%, and 84.88 ± 5.37% for mercury(II), methylmercury, and ethylmercury, respectively. The relative standard deviation was less 6.5%. For 2-mercaptoethanol modified SPE, the limits of detection were 1.4, 1, and 1.6 ng · L^?1 and the recoveries were of 87.66 ± 8.45%, 86.70 ± 2.61%, and 91.31 ± 6.98% for mercury(II), methylmercury, and ethylmercury, respectively, with a relative standard deviation below 9.7%. Water should be characterized for its physical and chemical characteristics before mercury preconcentration to choose the most suitable method.     

Polythiophene–Chitosan Magnetic Nanocomposite as a Novel Sorbent for Disperse Magnetic Solid Phase Extraction of Triazine Herbicides in Aquatic Media

In this paper, polythiophene/chitosan magnetic nanocomposite as a novel adsorbent is proposed for the preconcentration of triazines in aqueous samples prior to gas chromatography. The synthesized nanoparticles, magnetic chitosan and polythiophene–chitosan magnetic nanocomposite were characterized by scanning electron microscopy. The magnetic polythiophene–chitosan nanocomposite containing analytes could be removed from the sample solution by applying a permanent magnet. The major factors influencing the extraction efficiency including desorption conditions, nanocomposite components ratio, sorbent amount, extraction time, ionic strength and sample pH were optimized. The developed method proved to be rather convenient and offers sufficient sensitivity and good reproducibility. The limit of detection (S/N = 3) and limit of quantification (S/N = 10) of the method under optimized conditions were 10–30 and 100 ng L⁻¹, respectively. Under the optimum conditions, good linearity was obtained within the range of 100–5000 ng L⁻¹ for all triazines with correlation coefficients >0.9994. The relative standard deviation at a concentration level of 150 ng L⁻¹ was 7–12 %. Furthermore, the method was successfully applied to the determination of triazines in real samples, where relative recovery percentages of 96–102 % were obtained. Compared with other methods, the current method is characterized by easy, fast separation and low detection limits.

     

A Silica Monolithic Column with Chemically Bonded l-Pipecolic Acid as Chiral Stationary Phase for Enantiomeric Separation of Dansyl Amino Acids by CEC–MS

A silica monolithic column chemically modified with l-pipecolic acid as chiral stationary phase has been developed for chiral separation of dansyl amino acids by capillary electrochromatography–mass spectrometry (CEC–MS). The monolithic column was prepared by a sol–gel process and subsequent chemical modification by l-pipecolic acid as chiral selector with 3-glycidoxypropyltrimethoxysilane as spacer. Interestingly, it was found that the l-pipecolic acid-modified monolithic column can hold copper(II) ions tightly after loading Cu(II) ions during column preparation and conditioning and allows CEC separation to be conducted based on chiral ligand exchange with MS detection by a mobile phase without copper ions. It has been demonstrated that the chiral monolithic column operates well for enantioseparation of several dansyl amino acids by CEC–MS.

     

Box–Behnken Experimental Design for the Synthesis of Magnetite–Polypyrrole Composite for the Magnetic Solid Phase Extraction of Non-steroidal Anti-inflammatory Drug Residues

A magnetite–polypyrrole composite adsorbent was synthesized and applied for the magnetic solid phase extraction of three non-steroidal anti-inflammatory drugs in aqueous solution and systematically investigated using Box–Behnken design. The synthesized composite adsorbent was characterized using Fourier-transform infrared spectroscopy, transmission electron microscopy, the Brunauer–Emmett–Teller method, vibrating sample magnetometry, and X-ray diffraction. The material was successfully modeled by Box–Behnken design (R²?=?0.94–0.98, p value: <0.001%) by monitoring the extraction efficiencies of naproxen, diclofenac sodium, and mefenamic acid. The analytes were determined using high-performance liquid chromatography with ultraviolet detection. The polymerization time was found to be the most significant factor, followed by amount of oxidant and monomer in the synthesis of the composite with a fixed Fe₃O₄ mass. Box–Behnken design was employed for the optimization of four parameters affecting the magnetic solid phase extraction: sample pH, salt addition, adsorption, and desorption time (R²?=?0.88–0.94). The optimized conditions for the procedure were validated, providing low detection limits (0.9–3.5?µg?L^?1) with good reproducibility (<7.16% relative standard deviation) and excellent recoveries (97.87–100.49%) for tap, river, and wastewater samples. The synthesized adsorbent demonstrated good adsorption efficiency for the simultaneous determination of the non-steroidal anti-inflammatory drug residues.     

Fabrication of CeO2 Nanoparticle Modified Glassy Carbon Electrode for Ultrasensitive Determination of Trace Amounts of Uric Acid in Urine

The preparation of a glassy carbon electrode modified by CeO2 nanoparticles was described, which was characterized by cyclic voltammetry and electrochemical impedance spectroscopy. In pH 6.0 buffer, the CeO2 nanoparticle modified electrode （CeO2 NP/GC） gave an excellent electrocatalytic activity for the oxidation of uric acid （UA）. The catalytic current of UA versus its concentration had a good linear relation in the range of 2.0 × 10^-7-5.0 × 10^- 4 mol/L, with the correlation coefficient of 0.9986 and detection limit of 1.0 ×10^-7 mol/L. The modified electrode can be used for the determination of UA in urine, which can tolerate the interference of ascorbic acid up to 1000-fold. The method was simple, quick and sensitive.