GC-MS Assay For 9α, 15(S)-Dihydroxy-11-Oxo-thromba-5(Z), 13(E)-Dien-1-oic Acid

Abstract

The title compound (TXB₂?M) is a quantitative index of thromboxane A₂ synthesis in the human. We developed a method for its determination in urine based on the use of the ¹³C-labeled methyl ester derivative of the analyte as internal standard and GC-EIMS. the interassay coefficient of variation (CV) was 5.3% (N=4) and the intraassay CV ranged from 2.6 to 8.2% (N=3). the equation of the regression curve correlating the amounts added and recovered was Y=0.932X+3.99 (R=0.9947). the relative recovery of TXB₂?M from nine urine specimens was 99.8 ± 2.8% (mean ± SEM). the mean (±SD) 24-hr output in six healthy male subjects was 1371 ± 307 ng, and in six females it was 1176 ± 418 ng. Concentrations as low as 200 pg/ml of urine can easily be measured with this procedure if one uses 50 ml of urine for the analysis.     

Coupled liquid-liquid extraction and column switching LC for the determination of a new antihistaminic H1 drug in human urine

Summary Mizolastine (SL 85.0324) is a new antihistaminic H₁ benzimidazole derivative which is excreted into urine almost completely metabolized; about 2% of the unchanged drug is excreted as conjugated compound which requires enzymatic deconjugation before analysis. Since the existing methods for plasma samples do not work on deconjugated human urine due to interferences, a new method was developed. The method is based on a diethyl-ether extraction of mizolastine and an internal standard from alkalinized urine. The ether extract is back-extracted with an aqueous buffer (pH=2.6), this extract is neutralized (pH=6.5) and an aliquot injected into a C₁₈ pre-column where clean up and preconcentration take place. The analytes are then desorbed from the pre-column and transferred to the analytical column. The analytical column is a C₁₈ type specially seactivated for basic compounds with an eluent of acetonitrile/phosphate solution (pH=4.5), 40/60, v/v, at a flow rate of 1 ml min^–1. Detection is at 285 nm. The method is linear in the range 10–500 ng ml^–1 with a lower limit of detection of 10 ng ml^–1. The precision and accuracy, evaluated during intra-day and inter-day assays, are satisfactory for pharmacokinetic investigations.     

In-tube magnetic solid phase microextraction of some fluoroquinolones based on the use of sodium dodecyl sulfate coated Fe3O4 nanoparticles packed tube

In-tube magnetic solid phase microextraction (in-tube MSPME) of fluoroquinolones from water and urine samples based on the use of sodium dodecyl sulfate (SDS) coated Fe₃O₄ nanoparticles packed tube has been reported. After the preparation of Fe₃O₄ nanoparticles (NPs) by a batch synthesis, these NPs were introduced into a stainless steel tube by a syringe and then a strong magnet was placed around the tube, so that the Fe₃O₄ NPs were remained in the tube and the tube was used in the in-tube SPME-HPLC/UV for the analysis of fluoroquinolones in water and urine samples. Plackett–Burman design was employed for screening the variables significantly affecting the extraction efficiency. Then, the significant factors were more investigated by Box–Behnken design. Calibration curves were linear (R² > 0.990) in the range of 0.1–1000 μg L⁻¹ for ciprofloxacin (CIP) and 0.5–500 μg L⁻¹ for enrofloxacin (ENR) and ofloxacin (OFL), respectively. LODs for all studied fluoroquinolones ranged from 0.01 to 0.05 μg L⁻¹. The main advantages of this method were rapid and easy automation and analysis, short extraction time, high sensitivity, possibility of fully sorbent collection after analysis, wide linear range and no need to organic solvents in extraction.     

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.     

Development of an on-line preconcentration system for zinc determination in biological samples

An on-line preconcentration system for zinc determination in 24-h urine, blood plasma and erythrocyte matrices by flame atomic absorption spectrometry (FAAS) was used. This procedure was based on adsorption of Zn(II) ions onto a minicolumn filled with silica gel, chemically modified with niobium(V) oxide (Nb₂O₅-SiO₂). The determination of the optimum conditions for Zn(II) preconcentration was done using two-level full factorial and Doehlert designs. In the optimization procedure, four variables (sample pH, eluent concentration, sample flow rate and eluent flow rate) were investigated. The results obtained from the full factorial design demonstrated that the sample pH and sample flow rate variables, and their interactions, were statistically significant. A Doehlert matrix was used in order to determine the optimum conditions for the sample pH and sample flow rate. The optimized conditions for sample pH and flow rate sampling were 6.6 and 7.1 ml min⁻¹, respectively, to obtain the maximum Zn(II) preconcentration and determination in the biological samples studied. Parameters of analytical curve, precision, effect of other ions in the proposed system and accuracy were achieved to assess the proposed method. The accuracy was confirmed by analysis of certified reference materials (urine Seronorm™ Trace Elements) and recovery tests in blood plasma and erythrocyte samples. Detection limit (3σ/S) of 0.77 μg l⁻¹, precision (calculated as relative standard deviation) of 1.5% for Zn(II) concentration of 10 μg l⁻¹ (n = 7) and a sampling frequency of 27 samples/h were obtained from the proposed system.     

Reprint of: Extraction of fluoxetine from aquatic and urine samples using sodium dodecyl sulfate-coated iron oxide magnetic nanoparticles followed by spectrofluorimetric determination

A new method based on the combination of magnetic solid phase extraction (MSPE) and spectrofluorimetric determination was developed for isolation and preconcentration of fluoxetine form aquatic and biological samples using sodium dodecyl sulfate (SDS) coated Fe₃O₄ nanoparticles (NPs) as a sorbent. The unique properties of Fe₃O₄ NPs including high surface area and strong magnetism were utilized effectively in the MSPE process. Effect of different parameters influencing the extraction efficiency of fluoxetine including the amount of Fe₃O₄ and SDS, pH value, sample volume, extraction time, desorption solvent and time were optimized. Under optimized condition, the method was successfully applied to the extraction of fluoxetine from water and urine samples and absolute recovery amount of 85%, detection limit of 20 μg L⁻¹ and a relative standard deviation (RSD) of 1.4% were obtained. The method linear response was over a range of 50–1000 μg L⁻¹ with R² = 0.9968. The relative recovery in different aquatic and urine matrices were investigated and values of 80% to 104% were obtained. The whole procedure showed to be conveniently fast, efficient and economical for extraction of fluoxetine from environmental and biological samples.     

Determination of thiamine in blood serum and urine by high-performance liquid chromatography with direct injection and post-column derivatization

Thiamine (vitamin B₁) was determined in human serum and urine by HPLC with fluorimetric detection of its oxidation product, thiochrome. The samples were injected directly into the chromatographic system without previous treatment or dilution. A column filled with an ultra-high molecular weight surface-modified polyethylene (PE) was able to separate matrix components from analyte and also to allow a good chromatographic resolution of thiamine. The interaction of thiamine, thiocrome and both matrices (serum and urine) with PE was studied off- and on-line to determine the optimal procedure for vitamin B₁ determination. When carried off-line, matrix adsorption yield was 49 mg serum proteins/g polymer and components of 1000 μl urine/g polymer. In an on-line arrangement, the yield dropped to 10 mg/g and 150 μl/g, respectively. The matrix/analyte separation was carried out in an on-line procedure on a 50×4.6-mm, 25-μm PE column, using a water-sodium phosphate-methanol gradient elution. Part of the matrix was eluted within the first 2 min and thiamine after 3.8 min. The rest of the matrix retained on the column was eluted after thiamine at the last step of the gradient elution. Analysis time was 12 min. The within-day and day-to-day precision gave C.V. varying from 3.6% to 14.5% and recoveries from spiked samples were in the range of 84.8-98.8%.     

Highly sensitive determination of atropine using cobalt oxide nanostructures: Influence of functional groups on the signal sensitivity

This study describes sensitive determination of atropine using glassy carbon electrodes (GCE) modified with Co₃O₄ nanostructures. The as-synthesised nanostructures were grown using cysteine (CYS), glutathione (GSH) and histidine (HYS) as effective templates under hydrothermal action. The obtained morphologies revealed interesting structural features, including both cavity-based and flower-shaped structures. The as-synthesised morphologies were noted to actively participate in electro-catalysis of atropine (AT) drug where GSH-assisted structures exhibited the best signal response in terms of current density and over-potential value. The study also discusses the influence of functional groups on the signal sensitivity of atropine electro-oxidation. The functionalisation was carried with the amino acids originally used as effective templates for the growth of Co₃O₄ nanostructures. The highest increment was obtained when GSH was used as the surface functionalising agent. The GSH-functionalised Co₃O₄-modified electrode was utilised for the electro-chemical sensing of AT in a concentration range of 0.01–0.46 μM. The developed sensor exhibited excellent working linearity (R² = 0.999) and signal sensitivity up to 0.001 μM of AT. The noted high sensitivity of the sensor is associated with the synergy of superb surface architectures and favourable interaction facilitating the electron transfer kinetics for the electro-catalytic oxidation of AT. Significantly, the developed sensor demonstrated excellent working capability when used for AT detection in human urine samples with strong anti-interference potential against common co-existing species, such as glucose, fructose, cysteine, uric acid, dopamine and ascorbic acid.     

Amperometric biosensor based on reductive H2O2 detection using pentacyanoferrate-bound polymer for creatinine determination

Pentacyanoferrate-bound poly(1-vinylimidazole) (PVI[Fe(CN)₅]) was selected as a mediator for amperometric creatinine determination based on the reductive H₂O₂ detection. Creatinine amidohydrolase (CNH), creatine amidohydrolase (CRH), sarcosine oxidase (SOD), peroxidase (POD), and PVI[Fe(CN)₅] were crosslinked with poly(ethylene glycol) diglycidyl ether (PEGDGE) on a glassy carbon (GC) electrode for a creatinine biosensor fabrication. Reduction current was monitored at −0.1 V in the presence of creatinine and O₂. It is revealed that PVI[Fe(CN)₅] is suitable as a mediator for a bioelectrocatalytic reaction of POD, since PVI[Fe(CN)₅] neither reacts with reactants nor works as an electron acceptor of SOD. The amounts of PVI[Fe(CN)₅], PEGDGE, and enzymes were optimized toward creatinine detection. Nafion as a protecting film successfully prevented the enzyme layer from interferences. The detection limit and linear range in creatinine determination were 12 μM and 12–500 μM (R² = 0.993), respectively, and the sensitivity was 11 mA cm⁻² M⁻¹, which is applicable for urine creatinine tests. The results of the creatinine determination for four urine samples measured with this proposed method were compared with Jaffe method, and a good correlation was obtained between the results.     

On-line preconcentration and separation of Co, Ni and Cd via capillary microextraction on ordered mesoporous alumina coating and determination by inductively plasma mass spectrometry (ICP-MS)

In this paper, an ordered mesoporous alumina coating was prepared and applied to capillary microextraction (CME) of trace Co, Ni and Cd for the first time. The coated capillary was used for on-line coupling CME with inductively plasma mass spectrometry (ICP-MS) for the determination of trace metals of Co, Ni and Cd. The porous structure of Al₂O₃ coating was examined by SEM and TEM. The effects of the extraction parameters including pH, sample flow rate and volume, elution solution and interfering ions on the recovery of analytes have been investigated and optimized. Under the optimized conditions, the limits of detection were 0.33, 1.5 and 1.4 ng L⁻¹ for Co, Ni and Cd, respectively, with a preconcentration factor of 10 times. The precisions for all investigated elements were 2.7, 4.1 and 2.5% (c = 0.05 ng L⁻¹, n = 7), for Co, Ni and Cd, respectively, and the sample frequency was 8 h⁻¹.The proposed method was successfully applied for the analysis of trace metals in water, rice and urine samples with the recovery of 94-105%. In order to validate the proposed method, two certified reference materials of GBW 0913 human urine and NIES No.10-b rice flour were analyzed, and the determination values are in good agreement with the certified values. The ordered mesoporous Al₂O₃ coated capillary can be used more than 20 times without decreasing the extraction efficiency.     

Determination of urinary arsenic species using an on-line nano-TiO2 photooxidation device coupled with microbore LC and hydride generation-ICP-MS system

We have developed an on-line digestion device-based on the nano-TiO₂-catalyzed photooxidation of arsenic species—for coupling between microbore anion-exchange chromatography (μ-LC) and hydride generation (HG)-inductively coupled plasma mass spectrometry (ICP-MS) systems that can be used for the determination of urinary arsenic species. To maximize the signal intensities of the desired arsenic species, we optimized the photocatalytic oxidation efficiency of the analyte species and developed a rapid on-line pre-reduction process for converting the oxidized species into As(III) prior to HG-ICP-MS determination. Under the optimized conditions for the nano-TiO₂-catalyzed photooxidation-i.e., using 1 g of nano-TiO₂ per-liter, at pH 5.2, and illuminating for 3 min- As(III), monomethylarsenoic acid (MMA), and dimethylarseinic acid (DMA) can be converted quantitatively into As(V). To attain maximal hydride generation efficiency, 0.5% Na₂S₂O₄ solution, which can reduce As(V) to As(III) virtually instantaneously upon on-line mixing, was added as a pre-reductant prior to performing the HG step. In light of all the HG efficiency of tested arsenicals were improved and a segmented-flow technique was employed to avoid the loss of peak resolution when using our proposed on-line μ-LC-UV/nano-TiO₂/HG-ICP-MS, the detection limits for As(III), MMA, DMA, and As(V) were all in the range of sub-microgram-per-liter (based on 3 sigma). A series of validation experiments-analysis of neat and spiked urine samples-indicated that our proposed methods can be applied satisfactorily to the determination of As(III), MMA, DMA, and As(V) in urine samples.     

Quantitative determination of ginsenoside Rh2 in rat biosamples by liquid chromatography electrospray ionization mass spectrometry

Ginsenoside Rh₂ is a “hot” natural compound with great potential as a new anti-cancer drug based on abundant pharmacological experiments. However, no systemic pharmacokinetic study of Rh₂ was reported because current analysis methods could not fully meet the requirements. Thus, we developed a simple LC/MS method with highly improved sensitivities for the determination of Rh₂ in rat plasma, bile, urine, feces and most tissues. The tissues and feces were firstly homogenized mechanically using buffer and methanol as the media, respectively. Plasma, bile, urine and tissue homogenates were extracted with diethyl ether for sample preparation. Feces homogenates were directly deproteinized with acetonitrile. The subsequent analysis procedures were performed on a Shimadzu LCMS2010A system (electrospray ionization single quadrupole mass analyzer), with an ODS column (150 mm × 2.0-mm i.d., 5 μm) plus a C18 guard column for separation and ammonium chloride (500 μmol) as mobile phase additive. The proportions of mobile phase were changed timely according to gradient programs. Chlorinated adducts of molecular ions [M + Cl]⁻ of Rh₂ at m/z 657.35 and internal standard digitoxin at m/z 799.55 were monitored in selective ion monitoring mode of negative ions. The method was validated to be accurate, precise and rugged with good linearity in all matrices, according to the FDA guidelines. The lower limits of quantitation in rat plasma, urine and feces were 0.2, 0.2 and 20 ng/mL respectively. Stability studies were also performed, indicating that there were no stability-related problems in the analytical procedure of Rh₂. The proposed method was successfully applied to the preclinical pharmacokinetic research of Rh₂ in rats, including plasma kinetics, tissue distribution and excretion studies.     

Indirect determination of perchlorate by atomic absorption spectrometry

A liquid-liquid extraction and determination of perchlorate by atomic absorption spectrometry is described. The method involves extraction of perchlorate with the Schiffs base complex [Co(BPTC)₂]⁺, where BPTC = 2-benzoyl pyridine thiosemicarbazone, in methyl isobutyl ketone in acidic medium and subsequent analysis of cobalt in flame AAS, hence indirectly for perchlorate. The extraction efficiency is 98%. The calibration graph was found to be linear for 1.0–11.4 g ClO ₄ ^– per ml of solvent, and the limit of detection is 30 ng ml^–1. The present method is free from interference of large number of foreign ions. The method has been applied for determination of perchlorate in human blood serum samples spiked with perchlorate, urine and commercial potassium chlorate sample.     

Highly sensitive multianalyte immunochromatographic test strip for rapid chemiluminescent detection of ractopamine and salbutamol

A novel immunochromatographic assay (ICA) was proposed for rapid and multiple assay of β₂-agonists, by utilizing ractopamine (RAC) and salbutamol (SAL) as the models. Owing to the introduction of chemiluminescent (CL) approach, the proposed protocol shows much higher sensitivity. In this work, the described ICA was based on a competitive format, and horseradish peroxidase-tagged antibodies were used as highly sensitive CL probes. Quantitative analysis of β₂-agonists was achieved by recording the CL signals of the probes captured on the two test zones of the nitrocellulose membrane. Under the optimum conditions, RAC and SAL could be detected within the linear ranges of 0.50–40 and 0.10–50 ng mL⁻¹, with the detection limits of 0.20 and 0.040 ng mL⁻¹ (S/N = 3), respectively. The whole process for multianalyte immunoassay of RAC and SAL can be completed within 20 min. Furthermore, the test strip was validated with spiked swine urine samples and the results showed that this method was reliable in measuring β₂-agonists in swine urine. This CL-based multianalyte test strip shows a series of advantages such as high sensitivity, ideal selectivity, simple manipulation, high assay efficiency and low cost. Thus, it opens up new pathway for rapid screening and field analysis, and shows a promising prospect in food safety.     

Quantification of 1-hydroxypyrene in undiluted human urine samples using magnetic solid-phase extraction coupled with internal extractive electrospray ionization mass spectrometry

Polycyclic aromatic hydrocarbons (PAHs) are a group of ubiquitous environmental contaminants raising worldwide concerns due to their carcinogenic effects. In this study, 1-hydroxypyrene (1-OHP, the most widely used biomarker of internal dose of PAHs exposure) in undiluted human urine samples (10 mL) was selectively enriched by polypyrrole-coated Fe₃O₄ magnetite nanocomposites (termed as Fe₃O₄@Ppy, 1 mg) and then directly eluted by the electrospraying solvent (acetone/benzene/acetic acid (v/v/v, 90/10/1); 100 uL) biased with −3.5 kV to produce the deprotonated 1-OHP anions for mass spectrometric analysis. The method established here significantly improved the current performance for detection of urinary 1-OHP, providing the speed for a single sample analysis within 4 min, the limits of detection (LOD) of 0.0001 μg L⁻¹, the linear response range of 0.001–5.000 μg L⁻¹ (R² = 0.9994), recovery rates of 90.6–96.1%, and relative standard deviation (RSD, n = 6) values between 2.9% and 8.0%. Human samples including raw human urine collected from 10 healthy volunteers (5 smokers and 5 nonsmokers) and 7 lung cancer patients have been successfully analyzed, showing that magnetic solid-phase extraction (MSPE) coupled with internal extractive electrospray ionization mass spectrometry (iEESI-MS) is an alternative strategy for high throughput quantitative detection of urinary 1-OHP for health risk assessment of PAHs exposure.     

Purification of clenbuterol-like beta2-agonist drugs of new generation from bovine urine and hair by alpha1-acid glycoprotein affinity chromatography and determination by gas chromatography-mass spectrometry

The control of illegal use of clenbuterol and other β₂-agonist drugs as growth promoters in the European Union countries has led to outlaw practices for synthesizing new concept molecules, showing similar biological activity but not detectable by test methods usually employed to perform the official monitoring programmes. The synthesis schemes of some β₂-agonist compounds, formally derived from clenbuterol, were found out by Italian detective authorities. These compounds were synthesised ex novo in our laboratories: then, both their molecular structures and biological activities were characterised. In this paper, we describe different strategies for purifying some β₂-agonist drugs of new concept, more hydrophobic than clenbuterol. A two-step clean up procedure, prior to gas chromatography-mass spectrometry analysis, was developed for the multi-residue determination of these β₂-agonists from bovine hair and urine. The purification strategy we chose was based on adsorption solid phase extraction and, subsequently, on specific molecular recognition by affinity chromatography. The affinity columns were homemade by coupling bovine α₁-acid glycoprotein, a plasmatic acceptor for basic drugs, to a chromatographic support; their effectiveness for purifying new β₂-agonists was discussed. The data about method recoveries and repeatability were also reported.     

Dispersive micro-solid-phase extraction of benzodiazepines from biological fluids based on polyaniline/magnetic nanoparticles composite

In this study, diverse types of Fe₃O₄ nanocomposites modified by polyaniline, polypyrrole, and aniline–pyrrole copolymer were synthesized through chemical oxidative polymerization process for dispersive-μ-solid phase extraction (D-μ-SPE) in the presence of various dopants. The results showed that the nanocomposite modified by polyaniline with p-toluene sulfonic acid as a dopant demonstrated higher extraction efficiency for lorazepam (LRZ) and nitrazepam (NRZ). Also the synthesized magnetic sorbents were characterized. The nanocomposite sorbent in combination with high performance liquid chromatography–UV detection was applied for the extraction, preconcentration and determination of lorazepam and nitrazepam in urine and plasma samples. Different parameters influencing the extraction efficiency including: sample pH, amount of sorbent, sorption time, elution solvent and its volume, salt content, and elution time were optimized. The obtained optimal conditions were: sample pH, 6; amount of sorbent, 5 mg; sorption time, 5.0 min; elution solvent and its volume, 0.5 mM cethyltrimethyl ammonium bromide in acetonitrile, 150 μL; elution time, 2.0 min and without addition of NaCl. The calibration curves were linear in the concentration range of 1–2000 μg L⁻¹. The limits of detection (LODs) were achieved in the range of 0.5–1.8 μg L⁻¹ for NRZ and 0.2–2.0 μg L⁻¹ for LRZ, respectively. The percent of extraction recoveries and relative standard deviations (n = 5) were in the range of 84.0–99.0, 6.1–7.8 for NRZ and 90.0–99.0, 4.1–7.0 for LRZ, respectively. Ultimately, the applicability of the method was successfully confirmed by the extraction and determination of NRZ and LRZ in human urine and plasma samples.     

Voltammetric determination of atenolol at C(60)-modified glassy carbon electrodes

C₆₀-modified glassy carbon electrode has been found to exhibit excellent electrocatalytic activity towards atenolol oxidation for its voltammetric determination at physiological pH. Lowering of overpotential associated with atenolol oxidation indicates electrocatalytic nature of electrode. Determination of atenolol was carried out at pH 7.2 at modified electrode and a well-defined oxidation peak has been observed ∼1040 mV versus Ag/AgCl electrode for atenolol oxidation. Calibration plot having good co-linearity with a correlation coefficient 0.997 was obtained in the concentration range of 0.25-1.5 mM atenolol and the sensitivity of the method has been found to be 8.58 μA mM⁻¹. The detection limit is found to be 0.16 mM. The method developed is applicable for atenolol determination in pharmaceutical preparations and urine samples. The modified electrode showed a good surface coverage (∼85%) with C₆₀.     

Facile synthesis of a boronate affinity sorbent from mesoporous nanomagnetic polyhedral oligomeric silsesquioxanes composite and its application for enrichment of catecholamines in human urine

A boronate-decorated nanomagnetic organic-inorganic hybrid material was facilely synthesized by utilizing the nanomagnetic polyhedral oligomeric silsesquioxanes (POSS) composite (Fe₃O₄@POSS) as the base platform. A simple copolymerization occurred between 3-acrylamidophenylboronic acid (AAPBA) and the residual end vinyl groups supplied by the substrate. Here the special emphasis was placed on the octavinyl POSS, which not only acted as the building blocks for a hybrid architecture but also facilitated the process of grafting boronate groups onto the surface of POSS based nanomagnetic composite (Fe₃O₄@POSS). The successful immobilization of affinity ligand-AAPBA on the Fe₃O₄@POSS was confirmed by Fourier transform infrared (FT-IR), elemental analysis, inductively coupled plasma atomic emission spectrometer (ICP-AES), field emission scanning electron microscope. A magnetic solid-phase extraction (MSPE) for cis-diols enrichment was developed using the as-prepared Fe₃O₄@POSS-AAPBA material as an affinity sorbent and three catecholamines (CAs), namely noradrenaline, epinephrine and isoprenaline, as model analytes. Under the optimal extraction conditions, sensitive and simultaneous analysis of three CAs from the urine sample was achieved by high-performance liquid chromatography with UV detection (HPLC-UV). The limits of detection (LOD, S/N = 3) and the limits of quantitation (LOQ, S/N = 10) for the target analytes were 0.81–1.32 ng mL⁻¹ and 2.70–4.40 ng mL⁻¹, respectively. Also good recoveries (85.5–101.7%) and repeatability (RSD≤10.1%) were obtained by this method. This work not only showed a facility for the utilization of Fe₃O₄@POSS as a substrate for constructing a boronate functionalized nanomagnetic sorbent, but also demonstrated the capability of the derived material for recognition of trace amount of cis-diols biomolecules presented in complicated biological matrices.     

Influence of the Lanthanide Ion and Solution Conditions on Formation of Lanthanide Wells–Dawson Polyoxotungstates

Lanthanide complexes of polyoxometalates, including the α₂-P₂W₁₇O₆₁ ¹⁰⁻ ligand, have been pioneered by Michael T. Pope, to whom this paper is dedicated. Examination of the solid-state and solution behavior of lanthanide complexes of the α₂-P₂W₁₇O₆₁ ¹⁰⁻ ligand are reported here to identify trends that will facilitate rational synthesis of hybrid organic lanthanide polyoxometalate complexes. Therefore, combining our data with that obtained by Pope and others a number of trends come into view. It is clear that there are two structural types for the 1:1 or 2:2 [Ln(H₂O)_X(α₂-P₂W₁₇O₆₁)]₂ ¹⁴⁻ species. The early lanthanides show a “cap to cap” structure that allows the Ln ion to be 9 coordinate and accommodates the longer bond lengths. The mid-late lanthanides show a “cap to belt” structure that allows the lanthanides to be 8 coordinate; this structural type is appropriate for the shorter bond lengths of the later lanthanides. The 1:1⇌1:2 equilibrium, that was observed by Pope for the Ce(III) analog is prevalent for the early- mid lanthanides. This equilibrium is slightly dependent on pH; however, cations have a major influence on this equilibrium. Larger, poorly hydrated cations appear to favor the 1:2 species for the early to mid lanthanides. Cations do not appear to influence the equilibrium for the later lanthanides; for all counterions, the 1:1 species was stable with no trace of the 1:2 species. Stability constants, K1 and K2, for the early to mid lanthanides were measured in this study by a competitive method and compared well with other published stability constant determinations. We suggest that the stability constants are not only dependent on the strength of interaction of the Ln with the α₂-P₂W₁₇O₆₁ ¹⁰⁻ ligand, but are also significantly influenced by the medium. The medium may bias the equilibria of the early-mid lanthanides and later lanthanides. The log K₁/log K₂ ratios are very close, suggesting that it is difficult to separate the 1:1 and 1:2 Ln: α₂-P₂W₁₇O₆₁ ¹⁰⁻ species.Electronic Supplementary Material Supplementary material for this article is available at and is accessible for authorized users.This paper is dedicated to Professor Michael T. Pope in honor of his substantial and sustained contributions to polyoxometalate chemistry and his inspiration to scientists working in the field.