Voltammetric analysis of the acaricide amitraz and its degradant, 2,4-dimethylaniline

Amitraz is a formamide acaracide used in the control of ticks and mites in livestock. An electrochemical method for the determination of total amitraz residues and its final breakdown product, 2,4-dimethylaniline, is presented. Cyclic voltammetry at a glassy carbon electrode showed the irreversible oxidation of amitraz and of 2,4-dimethylaniline. A linear current response was obtained with an extrapolated limit of detection of 2 × 10⁻⁸ M for amitraz and 1 × 10⁻⁸ M for 2,4-dimethylaniline. The biological degradation of amitraz and subsequent formation of 2,4-dimethylaniline was readily monitored in spent cattle dip. Amitraz and 2,4-dimethylaniline was also monitored in milk and honey samples.     

Disposition Kinetics of Amitraz in Lactating Does

Amitraz, a member of the formamidine pesticide family, commonly used for ectoparasite control, is applied as a dip or low-pressure hand spray to cattle and swine, and the neck collar on dogs. Data on amitraz were generated mainly on laboratory animals, hens, dogs, and baboons. The data on the toxicity and disposition of amitraz in animals and its residues in the milk are inadequate. Therefore, the present study was intended to analyze the disposition kinetics of amitraz and its pattern of elimination in the milk of lactating does after a single dermal application at a concentration of 0.25%. Blood at predetermined time intervals and milk twice daily were collected for eight days post application. The drug concentration was assayed by high-performance liquid chromatography (HPLC). Amitraz was detected in whole blood as early as 0.5 h, which attained a peak concentration at 12 ± 5 h, followed by a steady decline; however, detection persisted until 168 h. Amitraz was present in the blood at its 50% C_max even after 48 h, and was still detectable after 7 days. The disposition after a single dermal application was best described non-compartmentally. The mean terminal half-life (t_1/2), mean residence time (MRT), and area under the curve (AUC_0–t) were 111 ± 31 h, 168 ± 39 h, and 539 ± 211 µg/mL/h, respectively. The apparent volume of distribution (Vd_area) was 92 ± 36 mL/g with an observed clearance (Cl) of 0.57 ± 0.33 mL/kg/h. Thus, the drug was well absorbed, widely distributed and slowly eliminated from the animal body. Amitraz achieved milk concentration approximating 0.2 per cent of the total dose after a single exposure and the steady-state elimination of amitraz in milk above the recommended maximum residue limit (MRL) of 0.01 mg/kg can act as a source of public health concern when applied on lactating animals.     

Synthesis,crystal structure,and luminescence properties of [TbGd(NAA)6(phen)2] and [Tb2(NNA)6(phen)2] · 2C3H7NO

Lanthanide(III) heteronuclear and binuclear complexes [TbGd(NAA)₆(phen)₂] (1) and [Tb₂(NAA)₆(phen)₂] · 2C₃H₇NO (2) (NAA = 1-naphthylacetic acid, phen = 1,10-phenanthroline) were prepared and their crystal structures were determined. In 1 and 2, each lanthanide is nine-coordinate by two bidentate-bridging and two tridentate chelating-bridging carboxylate groups, one bidentate chelating carboxylate and one phen molecule in a distorted monocapped square antiprism. The solid-state luminescence behavior and the antibacterial activities were studied. Complexes 1 and 2 exhibited characteristic emission of Tb(III) ion ⁵D₄ → ⁷F_J (J = 6–0) under UV radiation at room temperature. A main excitation peak (359 nm) of 2 appears under red emission of 615 nm. By contrast, all emission peak intensities of 1 were enhanced by addition of gadolinium(III), and the 545 nm band is much stronger than the 615 nm band, attributed to, under perturbation of the ligand field, the probability of ⁵D₄ → ⁷F₃ transition of Tb(III) was greatly enhanced in 2. Because of perturbation of the ligand field by addition of gadolinium(III), the probability of ⁵D₄ → ⁷F₅ transition of Tb(III) was greatly enhanced in 1 and green fluorescence was observed. The antibacterial activity showed that the two complexes were active against Escherichia coli, Staphylococcus aureus and Bacillus subtilis.     

Eliminating false positive C4 sugar tests on New Zealand Manuka honey

Carbon isotope analyses (δ¹³C) of some New Zealand Manuka honeys show that they often fail the internationally recognised Association of Official Analytical Chemists sugar test (AOAC method 998.12) which detects added C₄ sugar, although these honeys are from unadulterated sources. Failure of these high value products is detrimental to the New Zealand honey industry, not only in lost export revenue, but also in brand and market reputation damage. The standard AOAC test compares the carbon isotope value of the whole honey and corresponding protein isolated from the same honey. Differences between whole honey and protein δ¹³C values should not be greater than +1.0‰, as it indicates the possibility of adulteration with syrups or sugars from C₄ plants such as high fructose corn syrup or cane sugar. We have determined that during the standard AOAC method, pollen and other insoluble components are isolated with the flocculated protein. These non‐protein components have isotope values which are considerably different from those of the pure protein, and can shift the apparent δ¹³C value of protein further away from the δ¹³C value of the whole honey, giving a false positive result for added C₄ sugar. To eliminate a false positive C₄ sugar test for Manuka honey, prior removal of pollen and other insoluble material from the honey is necessary to ensure that only the pure protein is isolated. This will enable a true comparison between whole honey and protein δ¹³C isotopes. Furthermore, we strongly suggest this modification to the AOAC method be universally adopted for all honey C₄ sugar tests. Copyright © 2010 John Wiley & Sons, Ltd.     

Characterization and monitoring of amitraz degradation products in honey

Capillary gas chromatography in combination with atomic emission and electron impact-chemical ionizaion mass spectrometry detectors have been used to detect amitraz degradation products in honey storage, characterize their structure, and evaluate their occurrence over a 100 day peroid. To this end, honey samples were extracted with an 8:2 v/v n-hexane/acetone mixture. Amitraz was found to be rapidly decomposed into five related compounds, of which N-(2,4-dimethylphenyl)formamide was the most abundant and persistent.     

Aggregation of Alkyl Substituted Salchxn Complexes Studied by 1H-N.M.R

Abstract

A difference in the ¹H-n.m.r. peak shift due to aggregation was observed between chloroform-d₁ solutions of optically active and racemic forms of chiral (4′,4′'-dihexyl-N, N'-disalicylidene)-1,2-diaminocyclohexanenickel(II) (1). The difference is caused by the formation of racemic dimer in the racemic form of 1, which is not formed in the optically active form. The equilibrium constants of dimer formations and the aggregation structures were estimated from the concentration dependence of ¹H-n.m.r.     

The interactions of (=O→Si)-(benzoyloxymethyl)trifluoro-and -(benzoyloxymethyl) methyldifluorosilanes with a solvent

The IR spectra of solutions of (=OSi)-(benzoyloxymethyl)trifluorosilane (1),-(benzoyloxymethyl)methyldifluorosilane (2), and butyl benzoate (3) are examined in the region of thev(C=O) stretching vibrations in 24 solvents. The ability of compounds1—3 to undergo specific intermolecular interactions is evaluated from the dependence ofv(C=O) on the Kamlet-Taft (^*,, ) parameters, which was obtained for the carbonyl groups involved in the intramolecular coordinate (=OSi) bond and for free carbonyl groups. The corresponding values of the coefficients in the Kamlet-Taft equations are indicative of a weak ability of pentacoordinate silicon compounds1 and2 to undergo acid-base interactions.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 689–692, April, 1995.     

Highly Effective Detection of Amitraz in Honey by Using Surface-Enhanced Raman Scattering Spectroscopy Coupled with Chemometric Methods

As an effective and universal acaricide, amitraz is widely used on beehives against varroasis caused by the mite Varroa jacobsoni. Its residues in honey pose a great danger to human health. In this study, a sensitive, rapid, and environmentally friendly surface-enhanced Raman spectroscopy method (SERS) was developed for the determination of trace amount of amitraz in honey with the use of silver nanorod (AgNR) array substrate. The AgNR array substrate fabricated by an oblique angle deposition technique exhibited an excellent SERS activity with an enhancement factor of ∽10⁷. Density function theory was employed to assign the characteristic peak of amitraz. The detection of amitraz was further explored and amitraz in honey at concentrations as low as 0.08 mg/kg can be identified. Specifically, partial least square regression analysis was employed to correlate the SERS spectra in full-wavelength with C_amitraz to afford a multiple-quantitative amitraz predicting model. Preliminary results show that the predicted concentrations of amitraz in honey samples are in good agreement with their real concentrations. Compared with the conventional univariate quantitative model based on single peak’s intensity, the proposed multiple-quantitative predicting model integrates all the characteristic peaks of amitraz, thus offering an improved detecting accuracy and anti-interference ability.     

Rationalizing chain microstructure in the polyα-olefins synthesized by cationic AlCl3/H2O catalytic system

In this study, three middle range α-olefin monomers including 1-hexene, 1-octene, and 1-decene were oligomerized using conventional AlCl₃/H₂O catalytic system. Molecular weight and microstructure of the oligomers were analyzed by GPC and ¹HNMR, respectively. By ¹HNMR spectra, both internal (CHR=CHR′ and CHR=CR′R′′) and external (CH₂=CR′R′′) olefins containing di and tri-substituted C=C bonds were detected. After successful oligomerization, synthesized polyα-olefins underwent hydrogenation process using Pd(0)-Hal catalyst to yield synthetic oils of PHex, POct, and PDec, respectively and then completion of the hydrogenation was confirmed by ¹HNMR spectroscopy. The microstructure of the synthesized oligomers was rationalized using the ratio under the peak of CH?+?CH₂/CH₃ hydrogens (S1/S2) in ¹HNMR spectra and the degree of oligomerization obtained from M_n. According to the results, the best match between theoretical and real S1/S2 is obtained when considering double bond isomerization in the synthesized PAOs. By knowing PAO molecular weight, a relationship between monomer type and S1/S2 in the PAO homopolymers was detected. Our suggested methodology can be generalized to the unknown PAO homopolymers to unravel their monomer type by simple ¹HNMR and GPC analyses.     

Preparation,characterization and electrochemistry of an iron-only hydrogenase active site model covalently linked to a ruthenium tris(bipyridine) photosensitizer

An NH₂-functionlized [Fe₂S₂] model complex of the iron-only hydrogenase active site was covalently linked to the tris(bipyridine)ruthenium photosensitizer. The [RuFeFe] trinuclear complex 1 was characterized by MS, IR, UV-vis, ¹H & ¹³C NMR spectra. A quasi-reversible reduction peak at ?1.41 V versus Ag/Ag⁺ for the Fe^IFe^I/Fe^IFe⁰ process is observed in the cyclic voltammogram of 1.     

An Electrochemical Sensor Based on Electropolymerization of ß‐Cyclodextrin and Reduced Graphene Oxide on a Glassy Carbon Electrode for Determination of Neonicotinoids

An electrochemical sensor of glassy carbon electrode modified with reduced graphene oxide and β‐cyclodextrin (GCE/rGO/β‐CD) was developed as an effective alternative in the determination of neonicotinoid insecticides, imidacloprid, clothianidin and thiamethoxam, in honey samples. The peak current variation obtained with the proposed sensor was higher compared to the bare GCE in all the analytes. In the determination of imidacloprid the response increased by 1300 %, clothianidin by 670 % and thiametoxam by 630 %. In addition, the optimization of the experimental conditions provided the construction of a sensor with greater sensitivity. The study of interferers showed that inorganic ions (Ca²⁺, Mg²⁺, Fe²⁺, K⁺, Na⁺, e NH₄⁺) and other insecticides (acetamiprid and dinotefuran) did not influence the reduction of imidacloprid, clothianidin and thiamethoxam. The determination of imidacloprid, clothianidin and thiamethoxam in honey samples exhibited recovery values within the EPA range (between 107.75 and 116 %). In conclusion, the developed sensor GCE/rGO/β‐CD proved to be an effective alternative in the determination of neonicotinoid insecticides in honey samples.     

Amino acid analysis by using comprehensive two-dimensional gas chromatography

The separation characteristics of alkylchloroformate-derivatised amino acids (AAs) by using comprehensive two-dimensional gas chromatography (GC×GC) is reported. The use of a low-polarity/polar column set did not provide as good a separation performance as that achieved with a polar/non-polar column set, where the latter appeared to provide less correlation over the separation space. The degree of component correlation in each column set was estimated by using the correlation coefficient (r²; for ¹t_R and ²t_R data) with the low-polarity/polar and polar/low-polarity sets returning correlation coefficients of 0.86, and 0.00 respectively, under the respective conditions employed for the experiments. The 1.5-m non-polar ²D column (0.1-mm ID; 0.1-m film thickness) gave peak halfwidths of the order of 50–80 ms. Linearity of detection was good, over a three order of magnitude concentration range, with typical lower detection limit of ca. 0.01 mg L^–1, compared with 0.5 mg L^–1 for normal GC operation with splitless injection. The method was demonstrated for analysis of AAs in a range of food and beverage products, including wine, beer and honey. The major AA in these samples was proline. The Heineken beer sample had a relatively more complex and more abundant AA content compared with the other beer sample. The wine and honey samples also gave a range of AA compounds. Repetition of the sample preparation/analysis procedure for the honey sample gave acceptable reproducibility for individual AAs.     

A 2-D Ag(I) complex with μ 4-bte containing infinite tubes (bte = 1,2- bis (1,2,4-triazole-1-yl)ethane)

Using the flexible ligand 1,2-bis(1,2,4-triazole-1-yl)ethane (bte) and corresponding Ag(I) salts, a new two-dimensional (2-D) silver(I) complex {[Ag₄(μ ₄-bte)(μ ₂-H₂O)₂](SiF₆)₂} _n (1) has been isolated. 1 crystallizes in the orthorhombic Pcca space group. The bte adopts an unusual μ ₄-tetradentate coordination mode to link neighboring Ag^I atoms forming infinite 1D Ag-bte tubular structures. Further neighboring Ag-bte tubes are inter-connected by relatively long Ag-(μ ₂-H₂O) bonds forming a 2-D layered structure. Solid-state fluorescence spectrum of 1 shows that the excitation peak is at 320 nm while the maximum emission peak is at 425 nm.     

Synthesis,structure, and luminescence of rhenium(I) complexes with substituted bipyridines

Two new rhenium(I) complexes chelated by a substituted 2,2′-bipyridine with general formula Re(CO)₃LCl, where L?=?6?-(2″-methoxyphenyl)-2,2′-bipyridine (L₁ ) and 6?-(4″-diphenylaminophenyl)-2,2′-bipyridine (L₂ ), are synthesized and characterized by IR, NMR, and elemental analysis. Structure of 1 was determined by single-crystal X-ray crystallography, revealing that rhenium is six-coordinate octahedral. The electrochemical, photophysical, and thermal properties of the two rhenium(I) complexes were investigated. Electroluminescent devices were fabricated by doping 1 in polymer blend host of poly(vinylcarbazole) and 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole using simple solution spin-coating technique. The device exhibits a maximum current efficiency of 2.97?cd?A^?1 and peak brightness in excess of 2390?cd?m^?2.     

Fast quantitation of 5-hydroxymethylfurfural in honey using planar chromatography

An approach for rapid quantitation of 5-hydroxymethylfurfural (HMF) in honey using planar chromatography is suggested for the first time. In high-performance thin-layer chromatography (HPTLC) the migration time is approximately 5 min. Detection is performed by absorbance measurement at 290 nm. Polynomial calibration in the matrix over a range of 1:80 showed correlation coefficients, r, of ≥ 0.9997 for peak areas and ≥ 0.9996 for peak heights. Repeatability in the matrix confirmed the suitability of HPTLC–UV for quantitation of HMF in honey. The relative standard deviation (RSD, %, n = 6) of HMF at 10 ng/band was 2.9% (peak height) and 5.2% (peak area); it was 0.6% and 1.0%, respectively, at 100 ng/band. Other possible detection modes, for example fluorescence measurement after post-chromatographic derivatization and mass spectrometric detection, were also evaluated and can coupling can be used as an additional tool when it is necessary to confirm the results of prior quantitation by HPTLC–UV. The confirmation is provided by monitoring the HMF sodium adduct [M + Na]⁺ at m/z 149 followed by quantitation in TIC or SIM mode. Detection limits for HPTLC–UV, HPTLC–MS (TIC), and HPTLC–MS (SIM) were 0.8 ng/band, 4 ng/band, and 0.9 ng/band, respectively. If 12 μL honey solution was applied to an HPTLC plate, the respective detection limits for HMF in honey corresponded to 0.6 mg kg⁻¹. Thus, the developed method was highly suitable for quantitation of HMF in honey at the strictest regulated level of 15 mg kg⁻¹. Comparison of HPTLC–UV detection with HPTLC–MS showed findings were comparable, with a mean deviation of 5.1 mg kg⁻¹ for quantitation in SIM mode and 6.1 mg kg⁻¹ for quantitation in TIC mode. The mean deviation of the HPTLC method compared with the HPLC method was 0.9 mg kg^-1 HMF in honey. Re-evaluation of the same HPTLC plate after one month showed a deviation of 0.5 mg kg⁻¹ HMF in honey. It was demonstrated that the proposed HPTLC method is an effective method for HMF quantitation in honey.      

Determination of Imidacloprid Based on the Development of a Glassy Carbon Electrode Modified with Reduced Graphene Oxide and Manganese (II) Phthalocyanine

An electrochemical sensor of glassy carbon electrode modified with reduced graphene oxide and manganese (II) phthalocyanine (GCE/rGO/MnPc) was developed as an effective alternative in the determination of imidacloprid in honey samples. The peak current variation obtained with the proposed sensor, in the presence of imidacloprid, was higher compared to the bare GCE. The followed experimental conditions were optimized: reduced graphene oxide concentration (2.0 mg mL^?1), manganese (II) phthalocyanine concentration (1.5 mg mL^?1), electrolyte pH (6.5) and electrolyte concentration (1,50 mol L^?1). The study also showed that the process of reduction of imidacloprid is irreversible and diffusion‐controlled, with a single reduction peak of approximately ?0.9 V corresponding to the reduction of the nitro group (?NO2) present in the structure, generating a derived from hydroxylamine, in a process involving about four electrons. The determination of imidacloprid in honey samples exhibited recovery values within the EPA range (between 90.5 and 101.9 %). The proposed sensor GCE/rGO/MnPc can be used as an effective alternative in the determination of imidacloprid in honey samples.     

Synthesis and spectral studies of some new dimeric [(μ-Cl)2M2(L)2 · xTHF] [M = Zn(II) and Hg(II)] complexes containing Schiff-base ligands

A series of binuclear Schiff-base complexes of zinc(II) and mercury(II) containing bidentate ligands (HL) [HL?=?salicylidene-2-methyl-1-aminobenzene (HL¹), salicylidene-2-aminopyridine (HL²), and salicylidene-3-nitro-1-aminobenzene (HL³)] with “N” and “O” donors have been synthesized by simple metathetic reactions of anhydrous metal chlorides with sodium salts of Schiff bases (in tetrahydrofuran (THF)/MeOH) in equimolar ratio to produce [(µ-Cl)₂M₂(L)₂?·?xTHF] [where M?=?Zn(II) and Hg(II); L?=?HL¹, HL², and HL³; x?=?0 for (1), (4), (6) and x?=?2 for (2), (3), (5)]. The main emphasis on the complexes [(µ-Cl)₂M₂(L)₂?·?2THF] (2), (3), and (5) is given due to their five-coordinate environment around metal ions. The complexes have been characterized by elemental analyses (M, Cl, C, H, N), melting point, and spectral (FT-IR, ¹H-NMR, and ¹³C-NMR) studies. The structural composition of the complexes has been determined by FAB-MS spectral studies. FAB-MS showed the isotopic molecular ion peak [M⁺] and fragments supporting the formulation. Powder X-ray diffraction study of 6 is also reported showing the crystallite size (404.5?Å) of the complex.     

Synthesis and characterization of an anion triazole framework containing μ 3-Cl and μ 2-Cl bridges

Using 3,5-dimethyl-4-amino-1,2,4-triazole (L) and corresponding Ag(I), K(I) salts under ammonia solution and hydrothermal conditions, a triazole–silver(I)–potassium(I) complex {K[Ag₂L₂(μ ₃-Cl)(μ ₂-Cl)₂]} _n (1) has been isolated. In 1, μ ₃-Cl, μ ₂-Cl and L bridge Ag^I ions forming a rare 1-D [Ag₂L₂(μ ₃-Cl)(μ ₂-Cl)₂]^? anion while K⁺ cations are located between neighboring anion chains. Strong solid-state fluorescence spectrum of 1 was also investigated showing that the excited peak is located at 320 nm while the maximum emission peak is located at 440 nm.     

Étude par spectrométrie raman laser de l'extraction liquide-liquide du FeCl3 par le chlorhydrate de trilaurylamine

Raman spectra of aqueous 1 M chloroferrate(III) solutions indicate the presence of FeCl₃ and FeCl₄^- in proportion to the hydrochloric acid concentration, but FeCl₄^- is only present in solutions of acidity higher than 5 M HCl. The liquid-liquid extraction of the aqueous chloroferrate phases ( 1 M HCl) by trilaurylamine hydrochloride in cyclohexane, shows that iron(III) is extracted only in its FeCl₄^- form, even though this species does not appear in the aqueous solutions. A quantitative spectroscopic study of the organic phases by means of the v₁ line of FeCl₄^- at 332 cm^-1 leads to the following conclusions: (a) the plot of the scattering coefficient of the 332 cm^-1 line versus iron(III) concentration shows the presence of two complex species in the organic phase; (b) the distribution curves of the complex species could be calculated. On the basis of the Raman results, an ion-pair type compound is proposed for the two complexes.     

以苯四甲酸和双(咪唑基甲基)苯为配体的三维Cd-MOF材料的合成、结构及荧光性质

选择刚性的1,2,4,5-均苯四甲酸（H₄L）为主配体,以1,3-双（1H-咪唑-1-基甲基）苯（1,3-bib）为辅助配体,在水热条件下,与过渡金属离子Cd²⁺配位合成了配合物[Cd（L）_0.5（1,3-bib）（H₂O）]·H₂O（1）。利用元素分析、红外光谱、X射线单晶衍射、热重和X射线粉末衍射对其结构进行了表征,并研究了化合物的荧光性质。结果表明：配合物1属正交晶系,空间群Pbca,a=0.857 08（4）nm,b=1.912 23（10）nm,c=2.451 60（12）nm。配合物1中Cd²⁺与L^4-配体的羧基通过双齿螯合配位,通过1,3-bib连接形成三维网状结构。配合物1具有较强的荧光,其对丙酮溶剂、MnO₄^-、Hg²⁺离子有一定的荧光猝灭。