Molecular Recognition of Aflatoxin M1 in Water and Milk Samples

Two stochastic microsensors based on diamond paste modified with 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) were proposed for the molecular recognition of aflatoxin M1 in water and milk samples. Two types of diamond were used: a monocrystalline diamond powder (1 μm) (DP) and a nanopowder of monocrystalline diamond (10 nm) (nDP) for the design of the stochastic microsensors. The microsensors were incorporated as combined stochastic microsensors (a microcell containing the stochastic microsensor and the Pt wire, and a Ag/AgCl sensor) in a platform used for monitoring of waste waters and milk samples. The platforms were used for the fast screening of water and milk samples for the qualitative and quantitative analysis of aflatoxin M1 at very low concentration levels (up to 0.001 fg/L). The linear concentration ranges were wide, being able to cover concentrations between 0.001 fg/L to 20 μg/L. The highest sensitive microsensor (sensitivity of 4.74×10¹⁰ s mg^?1 L) was the one based on nDP. The results provided by the platforms were in agreement with those obtained by utilization of standard method (ISO certified methods (HPLC/fluorescence method)), recoveries being higher than 99.00 % and RSD lower than 1.00 % proving that the method can be reliable used for molecular recognition of aflatoxin M1 in water and milk samples.     

Solid‐phase microextraction based on an agarose‐chitosan‐multiwalled carbon nanotube composite film combined with HPLC–UV for the determination of nonsteroidal anti‐inflammatory drugs in aqueous samples

We describe the preparation, characterization, and application of a composite film adsorbent based on blended agarose‐chitosan‐multiwalled carbon nanotubes for the preconcentration of selected nonsteroidal anti‐inflammatory drugs in aqueous samples before determination by high performance liquid chromatography with ultraviolet detection. The composite film showed a high surface area (4.0258 m²/g) and strong hydrogen bonding between the multiwalled carbon nanotubes and agarose/chitosan matrix, which prevent adsorbent deactivation and ensure long‐term stability. Several parameters, such as sample pH, addition of salt, extraction time, desorption solvent, and concentration of multiwalled carbon nanotubes in the composite film were optimized using a one‐factor‐at‐time approach. The optimum extraction conditions obtained were as follows: isopropanol as conditioning solvent, 10 mL of sample solution at pH 2, extraction time of 30 min, stirring speed of 600 rpm, 100 μL of isopropanol as desorption solvent, desorption time of 5 min under ultrasonication, and 0.4% w/v of composite film. Under the optimized conditions, the calibration curve showed good linearity in the range of 1–500 ng/mL (r² = 0.997–0.999), and good limits of detection (0.89–8.05 ng/mL) were obtained with good relative standard deviations of < 4.59% (n = 3) for the determination of naproxen, diclofenac sodium salt, and mefenamic acid drugs.     

Determination of Total Chromium in Biological Samples by Automated Reagent Injection Chemiluminescence Analysis

A sensitive method for the determination of total chromium in real samples by flow injection–chemiluminescence (FI–CL) analysis was proposed. It was found that the CL intensity from luminol–lysozyme reaction could be markedly quenched, and the decrease of CL intensity was linear with the logarithm of Cr(III) concentrations over the range of 5.0 to 4000 pg mL^?1 with a detection limit of 2.0 pg mL^?1 (3σ) and relative standard deviations (RSDs) of 3.0, 2.6, and 2.0% for 10, 100, and 1000 pg mL^?1 Cr(III) (n = 7), respectively. At a flow rate of 2.0 mL min^?1, the whole process including sampling and washing could be accomplished within 36 s. The proposed CL method was successfully applied to the determination of total chromium in pharmaceutical capsules, a dietary supplement, and spiked human serum samples, with recoveries from 92.2 to 108.4% and RSDs of less than 4.0%. Using the homemade FI–CL model, the binding constant (K = 4.38 × 10⁶ L mol^?1) and the binding sites (n ≈ 1) of Cr(III) to lysozyme were given.     

Electroanalysis of Bisphenols A,F, and Z Using Graphene Based Stochastic Microsensors

Two stochastic microsensors based on immobilization of the complex between protoporphyrin IX and cobalt on nanographene paste and on the reduced graphene oxide paste were proposed for the simultaneous identification and quantification of bisphenols A (BPA), F (BPF) and Z (BPZ) from water samples. The signatures obtained for the BPA, BPF, and BFZ when both stochastic microsensors were used shown that the microsensors can be used for the discrimination between the three bisphenols in water samples. Very low limits of determination were obtained for the three bisphenols: 1fmol/L for BPA and BPF when the microsensor based on the immobilization of the complex between protoporphyrin IX and cobalt on nanographene paste was used, and 10fmol/L for BPZ when the microsensor based on the immobilization of the complex between protoporphyrin IX and cobalt on reduced graphene oxide paste was used. The linear concentration ranges covered by the proposed stochastic microsensors were: between 10^?15 and 10^?5 mol/L for BPA, between 10^?15 and 10^?7 mol/L for BPF, and between 10^?13 and 10^?10 mol/L for BPZ. The recoveries of the bisphenols in water samples were higher than 99.50 %, with RSD values lower than 1.00 %.     

Detection of PCB77 by Antibody-Coated Competitive Fluorescent Quantitative Immuno-PCR Using Molecular Beacon

Abstract

A rapid and quantitative technique is urgently needed in detecting toxicological and carcinogenic polychlorinated biphenyls (PCBs) in the environment. In this study, a high sensitive real time fluorescent quantitative immuno-PCR (FQ-IPCR) approach using molecular beacon (MB) was developed to detect PCB77, which was classified as a human carcinogen. MB-based FQ-IPCR was then performed on serial dilutions of known PCB77 concentrations equivalent to 10-fold dilutions of 10–10⁵ fg/mL. A correlation coefficient of 0.997 was identified, and a linear relationship between 10 fg/mL and 100 pg/mL, with y = 0.543x + 21.779, was obtained. Three soil samples were determined by MB-based FQ-IPCR to proof the validity of the method, and the results of which were further confirmed by conventional enzyme-linked immuno sorbent assay (ELISA). Based on sensitivity and reproduction, the MB-based real time FQ-IPCR technique will become a promising monitoring tool for environmental endocrine disruptors.     

Polymethylenebis(octylarsinic acids), [C8H17As(O)OH]2 (CH2)n,as reagents for the liquid-liquid extraction of cerium(III) and Europium(III)

Summary Cerium(III) and europium(III) are extracted at 50° C by [C₈H₁₇ As(O)OH]₂(CH₂) _n (n=6, 8, 12) inn-octanol from aqueous solutions containing NaCl and acetic acid/sodium acetate in the pH range 6.7–8.0. The extraction coefficient, , reached a maximum of: 10.0, 13.2 forn=6; 10.7, 20.0 forn=8; 4.68, 6.03 forn=12; at an aqueous equilibrium pH of: 7.65, 7.80 forn=6; 7.89, 7.95 forn=8; 7.81, 7.82 forn=12; corresponding to the extraction efficiency of: 91%, 93% forn=6; 92%, 95% forn=8; 80%, 83% forn=12; for cerium and europium, respectively.The log was found to be second power dependent for cerium and one and one-half power dependent for europium on the negative log of the aqueous equilibrium [H⁺] forn=6, 8, 12. The extractions were done at 50°C using organic reagent solutions (1.09×10^–3 M forn=12, 1.08 × 10^–3 M forn=8, 1.32×10^–3 M forn=6) and aqueous solutions of 1.0×10^–5 M for CeCl₃ and EuCl₃, having their Cl^– ionic strengths adjusted to 0.100 molar with NaCl. It was found that the slopes increase in the pH dependence studies in the seriesn=6, 8, and 12 for both cerium and europium metal ions. The reagent dependence studies were done at 50°C and pH: 7.00, 6.80 forn=6; 7.30, 7.20 forn=8; 7.45, 7.35 forn=12; for cerium and europium, respectively. The log was found to be first power dependent on the log of the uncomplexed reagent concentration at equilibrium. It is assumed that the complexes are hexacoordinated.

---

Polymethylenebis-Oktylarsinsäuren als Reagenzien für die Flüssig-flüssig-Extraktion von Cer(III) und Europium(III)

Zusammenfassung Cer(III) und Europium(III) werden aus wäßrigen, Kochsalz und Essigsäure/Acetat enthaltenden Lösungen bei 50°C mit C₈H₁₇As(O)OH₂(CH₂)_n (_n=6, 8, 12) im pH-Gebiet 6,7–8,0 extrahiert. Der Extraktionskoeffizient erreicht ein Maximum von: 10,0, 13,2 für_n=6; 10,7, 20,0 fürn=8; 4,68, 6,03 fürn=12; bei einem wäßrigen Gleichgewicht-pH von: 7,65, 7,80 fürn=6; 7,89, 7,95 fürn=8; 7,81, 7,82 fürn=12, entsprechend dem Aus maß der Extraktion von: 91%, 93% fürn=6; 92%, 95% fürn=8; 80%, 83% fürn=12; für Ce bzw. Eu.Für Cer ist der log in zweiter Potenz, für Europium in erster und 1/2 Potenz abhängig vom negativen log des wäßrigen [H⁺]-Gleichgewichtes fürn=6, 8, 12. Die Extraktionen wurden bei 50°C mit organischen Reagens-lösungen (1,09×10^–3 M fürn=12, 1,08×10^–3 M fürn=8, 1,32×10^–3 M fürn=6) und mit wäßrigen Lösungen von 1,0×10^–5 M für CeCl₃ und EuCl₃ durchgeführt, deren lonenstärke für Cl^– mit NaCl auf 0,100M eingestellt wurde. Bei der Untersuchung der pH-Abhängigkeit bei den Reihenn=6, 8 und 12 ergab sich ein Anstieg sowohl für Ce wie für Eu. Die Reagens-Abhängigkeit wurde bei 50°C und bei pH 7,00, 6,80 fürn=6; 7,30, 7,20 fürn=8; 7,45, 7,35 fürn=12 für Cer bzw. Europium geprüft. Der log war einfach abhängig vom log der Konzentration des unkomplexierten Reagens beim Gleichgewicht. Es wird angenommen, daß die Komplexe hexakoordiniert sind.

     

Analysis of isoquinoline alkaloids using chitosan‐assisted liquid–solid extraction followed by microemulsion liquid chromatography employing a sub‐2‐micron particle stationary phase

A simple, efficient, and green chitosan‐assisted liquid–solid extraction method was developed for the sample preparation of isoquinoline derivative alkaloids followed by microemulsion LC. The optimized mobile phase consisted of 0.8% w/v of ethyl acetate, 1.0% w/v of SDS, 8.0% w/v of n‐butanol, 0.1% v/v acetic acid, and 10% v/v ACN. Compared to pharmacopoeia method and organic solvent extraction, this new approach avoided the use of volatile organic solvents, replacing them with relatively small amounts of chitosan. Under the optimum conditions, good linearity (r² > 0.9980) for all calibration curves and low detection limits between 0.05 and 0.10 μg/mL were achieved. The presented procedure was successfully applied to determine alkaloids in Rhizoma coptidis with satisfactory recoveries (81.3–106.4%).     

Hydrogels of starch-g-(<Emphasis Type="Italic">tert</Emphasis>-butylacrylate) and starch-g-(<Emphasis Type="Italic">n</Emphasis>-butylacrylate) copolymers

The synthesis, characterization, and hydrogel properties of starch-g-(tert-butylacrylate) and starch-g-(n-butylacrylate) copolymers were studied. The optimum conditions for the grafting process of tert-butylacrylate into 1.0 g of starch were as follows: [tert-butylacrylate] = 0.04 mol/L, [CAN] = 9.0 × 10⁻⁴ mol/L, temperature = 20 °C in 100 mL solution, whereas the results using n-butylacrylate monomer were as follows: [n-butylacrylate] = 0.04 mol/L, [CAN] = 4.0 × 10⁻³ mol/L, temperature = 30 °C in 100 mL solution. The grafting evidences of monomers into starch were done through TG and its derivative DTG for thermal changes and mass losses, scanning electron microscope (SEM) for morphological changes, powder X-ray for crystallinity measurements and FTIR for functional group changes. Acid hydrolysis method was used efficiently to allow the calculations of the viscosity average molecular weight (M _v) of the grafted chains on starch and consequently the real percent of grafting efficiency (i.e. %GY). The capability of starch-g-(n-BAC) hydrogel to absorb water were found 10 times more than starch-g-(tert-BAC) hydrogel, which were clarified through the X-ray and SEM results.     

Synthesis,characterisation, mesomorphic investigation and temperature-dependent Raman study of a novel calamitic liquid crystal: methyl 4-(4′-n-alkoxybenzylideneamino)benzoate

A new series of Schiff base calamitic liquid crystal; methyl 4-(4′-n-alkoxybenzylideneamino)benzoate (MABAB), H_2n+1C _n OC₆H₄C(H)=NC₆H₄COOCH₃ (n = 6, 8, 10, 12, 14, 16) has been synthesised and characterised by elemental analyses, Fourier transform infrared spectroscopy (FT-IR), ¹H and ¹³C Nuclear Magnetic Resonance (NMR) spectroscopy. The mesomorphic properties of these compounds were studied by differential scanning calorimetry (DSC) and polarising optical microscopy (POM). All members of the series exhibit enantiotropic smectic A (SmA) mesophase. Temperature-dependent micro-Raman study of one of the members, MABAB-10 has been employed to identify phase transitions and the molecular rearrangement therein. Analysis of Raman marker bands; C–H in-plane bending, C–C stretching of phenyl rings and –C(H)=N– linking group of core confirms the transitions clearly as observed through DSC and POM. An in situ Raman measurement of C–H in-plane bending mode has also been performed to visualise the molecular changes more clearly. The Raman study gives an evidence of induced co-planarity of rings at Cr→SmA phase transition. The density functional theoretical (DFT) optimisation of monomer, dimer and rotational conformer of MABAB-10 also support the induced co-planarity at Cr→SmA phase transition.     

Electrochemical detection of ursolic acid from spruce (Picea abies) essential oils using modified amperometric microsensors

Ursolic acid (UA) is a natural pentacyclic triterpenoid carboxylic acid found in some medicinal plant species. In this paper, amperometric microsensors based on a powder which contained graphite (G) and carbon nanoparticles (CN) (G-CN) unmodified and modified with chitosan (CHIT) and tetraphenyl-porphine cobalt(II) (Co(II)TPP) are proposed for the analysis of UA plant source essential oils obtained from spruce (Picea Abies). Differential pulse voltammetry (DPV) was used to optimize the method and for the determination of ursolic acid from different types of botanical samples. The optimum working pH was 5.00 for the G-CN and (Co(II)TPP)/G-CN microsensors and pH 3.00 for CHIT/G-CN in the presence of a 0.1?mol L^?1 KCl supporting electrolyte. The linear concentration ranges for ursolic acid (UA) were between 0.1 and 100 µmol L^?1 for the unmodified microsensor (G-CN), 0.01, 1 µmol L^?1 for the microsensor modified with chitosan (CHIT/G-CN), and 0.01 and 10 µmol L^?1 for the microsensor modified with (Co(II)TPP)/G-CN). It is the first time these amperometric microsensors have been used for the reliable analysis of ursolic acid (UA) in three original botanical samples obtained from different parts of spruce (Picea abies): resin essential oil, cons essential oil, cons and sprouts essential oil, with recovery rate values up to 99.29%.     

Carbofuran: analytical methods and its determination in natural water samples by flow injection DPA(III)–H2SO4 chemiluminescence

This study proposes, a simple, rapid and sensitive chemiluminescent (CL) method for determination of carbofuran based on diperiodatoargentate(III) (DPA)-sulfuric acid (H₂SO₄) reaction coupled with flow injection (FI) methodology. Under optimum conditions, a linear standard curve is achieved in the range of 0.001–8.0 mg L^–1 (R²= 0.9994 (n = 11) with relative standard deviation (RSD) of 1.4–3.7% (n = 4)), a limit of detection (LOD) 5.0 × 10^–4 mg L^–1 (S/N = 3) and injection throughput 180 h^–1. The proposed method was applied satisfactorily for the analysis of carbofuran in freshwater samples using solid phase extraction (SPE) technique with the recoveries of 94–110% (% RSD = 1.7–3.8, n = 4). A possible CL reaction mechanism has also been discussed briefly.     

Kinetics and mechanism of chelating reaction between chitosan derivatives with Ca(II)

Chitosan derivatives, such as chitosan alpha-ketoglutaric acid (KCTS) and hydroxamated chitosan alpha-ketoglutaric acid (HKCTS), are prepared and their coordination behavior toward Ca(II) was studied. The adsorption isotherms were correlated by dc/dt?=??kcⁿ at 20°C, 30°C, 40°C, 50°C, and 60°C. By linear correlation, the shapes of the isotherm curves were similar to the kinetic function of 1/c?=?kt and the rate equation was dc/dt?=??kc ²; the activation energies were 13.31 and 14.76?kJ?mol^?1 for KCTS and HKCTS, respectively. The overall rate of Ca(II) adsorption is likely to be controlled by the chemical process. The coordination mechanism of chitosan derivatives with Ca(II) was studied by infrared and X-ray photoelectron spectroscopy. The results indicated that –NH– of KCTS was coordinated. Nitrogen of amino, oxygens of hydroxamic acid, and carbonyl in HKCTS coordinated with Ca(II).     

Selective preconcentration of Lanthanum(III) by Coriolus versicolor immobilised on Amberlite XAD-4 and its determination by ICP-OES

Coriolus versicolor, a wood fungus, was immobilised on Amberlite XAD-4 and used as solid-phase biosorbent for preconcentrations of rare earth elements. La(III), Th(IV), U(IV) and Ce(III) were subjected to solid-phase extraction procedure. We observed that La(III) was selectively preconcentrated, while other ions remained in solution at pH 6.0. 5.0 mL of 1.0 mol L^?1 HCl was used to elaute La(III) from column. 250 mg of C. versicolor loaded on 1000 mg of XAD-4 was optimised as solid-phase matrix. Concentrations of ions in solutions were determined by inductively coupled plasma– optical emission spectrometry (ICP-OES). The calibration plot after preconcentration was linear in the range from 1.0 to 50.0 ng mL^?1 for La(III). Limit of detection was found as 0.27 ng mL^?1 for La(III) by SPE method. Relative standard deviation was found lower than 6.7% for 1.0 ng mL^?1 of La(III) solution (n = 10). The sensitivity of ICP-OES was improved by a factor of 46.8. The applicability of the method was validated through the analysis of certified reference samples of tea (NCS ZC-73014) and spinach (NCS ZC-73013).     

Determination of Epinephrine in Carp Brain Cells by Square-Wave Anodic Stripping Voltammetry with Carbon Nanotubes

Real-time assay of the neurotransmitter epinephrine (EP) was investigated using square-wave anodic stripping voltammetry (SWASV) with modified carbon nanotubes (CNE) electrode. The developed results indicated a sensitive oxidation peak current for EP. A linear working range was obtained within of 5–40 and 40–240 ug/L, with a 45-sec accumulation time in an acetic acid electrolyte. Under optimum conditions, the relative standard deviation of 30.0 ug/l EP was 0.1016% (n = 12) via SW. Here analytical detection limit (S/N) was 0.30 ug/L (1.63 × 10^?9 M). The results can be applied to the brain cells and core of a carp. These findings can have applications in biological neurodiagnostics and in other fields of EP analysis.     

Label-free sandwich type of immunosensor for hepatitis C virus core antigen based on the use of gold nanoparticles on a nanostructured metal oxide surface

We report on the construction of a label-free electrochemical immunosensor for detecting the core antigen of the hepatitis C virus (HCV core antigen). A glassy carbon electrode (GCE) was modified with a nanocomposite made from gold nanoparticles, zirconia nanoparticles and chitosan, and prepared by in situ reduction. The zirconia nanoparticles were first dispersed in chitosan solution, and then AuNPs were prepared in situ on the ZrO₂-chitosan composite. In parallel, a nanocomposite was synthesized from AuNPs, silica nanoparticles and chitosan, and conjugated to a secondary antibody. The properties of the resulting nanocomposites were investigated by UV-visible photometry and transmission electron microscopy, and the stepwise assembly process was characterized by means of cyclic voltammetry and electrochemical impedance spectroscopy. An sandwich type of immunosensor was developed which displays high sensitivity to the HCV core antigen in the concentration range between 2 and 512?ng?mL^?1, with a detection limit of 0.17?ng?mL^?1 (at S/N?=?3). This immunosensor provides an alternative approach towards the diagnosis of HCV.

SECM visualization of the spatial variability of enzyme-polymer spots. 3. Enzymatic feedback mode

The responses of a PQQ-GDH entrapped in a polymer structure to mixtures of glucose and maltose were evaluated. Each compound was considered in the concentration range of 0–0.2 mM. Imaging was performed at constant height in the enzymatic feedback mode of scanning electrochemical microscopy (SECM). The enzyme-polymer spot was discretized into 15 × 15 μm² substructures which were treated as independent individual microsensors. The response surfaces of the individual microsensors were approximated with a linear regression model. The coefficients in the derived equations represent contributions from topography, glucose concentration, maltose concentration, and the competition of glucose and maltose for the same active site of PQQ-GDH to the measured signal. The ratio of glucose and maltose contributions to the current at the SECM tip was constant for all microsensors and it was predominantly determined by the ratio of the turnover rates of both analytes in the PQQ-GDH catalyzed reaction. Using the difference between these coefficients, it was possible to select the microsensors within the overall enzyme-polymer spot that provided the best data for quantifying glucose and maltose by the artificial neural network used. The quantification of glucose and maltose was successful, except when the contributions from the components of the mixture were n _g =k n units of glucose and simultaneously n _m = 1.86(1−k)n units of maltose, for each constant n > 0 and k∈<0,1>.     

Fabrication of Tyrosinase Biosensor Based on Multiwalled Carbon Nanotubes‐Chitosan Composite and Its Application to Rapid Determination of Coliforms

A tyrosinase (Tyr) biosensor was fabricated by immobilizing Tyr on the surface of multiwalled carbon nanotubes (MWNTs)‐chitosan (Chit) composite modified glassy carbon electrode (GCE). The MWNTs‐Chit composite film provided a biocompatible platform for the Tyr to retain the bioactivity and the MWNTs possessed excellent inherent conductivity to enhance the electron transfer rate. The Tyr/MWNTs‐Chit/GCE biosensor showed high sensitivity (412 mA/M), broad linear response (1.0×10^?8–2.8×10^?5 M), low detection limit (5.0 nM) and good stability (remained 93% after 10 days) for determination of phenol. The biosensor was further applied to rapid detection of the coliforms, represented by Escherichia coli (E. coli) in this work. The current responses were proportional to the quantity of coliforms in the range of 10⁴–10⁶ cfu/mL. After 5.0 h of incubation, E. coli could be detected as low as 10 cfu/mL.     

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.

     

Nanocarbon Materials Modified with the Zinc Complex of Protoporphyrin IX,Recognized Antibiotics in Water Samples

The complex between protoporphyrin IX and zinc was immobilized on nanocarbon paste and on nanodiamond paste to design two stochastic microsensors. The microsensors were used for the recognition and analysis of antibiotics: amoxicillin, ampicillin, and biotin in water samples. Stochastic sensors provided different signatures for the three antibiotics making possible their simultaneous recognition and assay in water samples. Low limits of determination 0.3 pg/mL for amoxicillin and ampicillin, and 0.21 pg/mL for biotin were obtained when nanocarbon paste was used, and 0.03 pg/mL for amoxicillin, 0.30 pg/mL for ampicillin, and 2.14 fg/mL for biotin were obtained when nanodiamond paste was used. Recoveries higher than 99.32 % with RSD lower than 1.00 % were obtained for the assay of the antibiotics in water samples.     

Reduced Arene Complexes of Scandium

Alkali metal naphthalenide or anthracenide reacted with scandium(III) anilides [Sc(X){N(tBu)Xy}₂(thf)] (X=N(tBu)Xy ( 1 ); X=Cl ( 2 ); Xy=C₆H₃-3,5-Me₂) to give scandium complexes [M(thf)_n][Sc{N(tBu)Xy}₂(RA)] (M=Li–K; n=1–6; RA=C₁₀H₈²⁻ ( 3-Naph-K ) and C₁₄H₁₀²⁻ ( 3-Anth-M )) containing a reduced arene ligand. Single-crystal X-ray diffraction revealed the scandium(III) center bonded to the naphthalene dianion in a σ²:π-coordination mode, whereas the anthracene dianion is symmetrically attached to the scandium(III) center in a σ²-fashion. All compounds have been characterized by multinuclear, including ⁴⁵Sc NMR spectroscopy. Quantum chemical calculations of these intensely colored arene complexes confirm scandium to be in the oxidation state +3. The intense absorptions observed in the UV/Vis spectra are due to ligand-to-metal charge transfers. Whereas nitriles underwent C−C coupling reaction with the reduced arene ligand, the reaction with one equivalent of [NEt₃H][BPh₄] led to the mono-protonation of the reduced arene ligand.