Fabrication of ferrocene functionalised ionic liquid/carbon nanotube nanocomposite modified carbon-ceramic electrode: application to the determination of hydrazine

A novel ionic liquid, 1-(ferrocenyl butyl)-3-methylimidazolium tetrafluoroborate (Fc-IL), was synthesised. The nanocomposite of Fc-IL and multi-walled carbon nanotubes (MWCNTs) was constructed and used for surface modification of carbon-ceramic electrode. The modified electrode was applied to the determination of hydrazine. Operational parameters such as pH of the solution, ionic liquid volume and amount of carbon nanotubes, which affect the analytical performance of the modified electrode, were optimised. The linear range of the modified electrode toward hydrazine concentration was 0.96–106.10 μg L^–1 with a detection limit of 0.64 μg L^–1 (S/N = 3). The modified electrode displayed high repeatability, reproducibility, long-term life time and low response time (<3 s). The applicability of this method was further tested by analysing the hydrazine content in boiler-feed water samples containing different concentrations of hydrazine and the results were in good agreement with the spectrophotometry method.     

Antifungal activity of essential oil from Asteriscus graveolens against postharvest phytopathogenic fungi in apples

The essential oils of the aerial parts of Asteriscus graveolens have been studied using GC and GC-MS. Twenty-eight compounds were identified in the essential oil amounting to 94.9% of the total oil. The aerial part oils showed similar chromatographic profiles and were characterized by having a high content of oxygenated sesquiterpenes with 6-oxocyclonerolidol (66.7% +/- 5.5) and 6-hydroxycyclonerolidol (8.8% +/-1.2) as the major components. The antifungal effect of the essential oil from A. graveolens leaves was evaluated in vitro against three phytopathogenic fungi of apples (Alternaria sp., Penicillium expansum, and Rhizopus stolonifer). The results suggest that this essential oil has fungicidal properties towards Alternaria sp. from direct contact assay at 0.2% (v/v) and to P. expansum from vapor assay tests at 80 microL.     

Stripping voltammetric determination of copper(II) in natural waters and human hairs based on the adsorption of its complex with Kryptofix 22 on the carbon paste electrode

Traces of copper(II) can be determined by adsorptive stripping voltammetry using Kryptofix 22 as complex forming reagent. First, copper(II)-Kryptofix 22 complex was adsorbed on the carbon paste electrode in phosphate buffer pH 5.3 with an accumulation potential of −0.5 V. Following this, the adsorbed complex was oxidized and detected by anodic differential pulse voltammetric scan from −0.2 to 0.1 V. The effective parameters of sensor response were examined. The detection limit of copper(II) was 1.1 μg/L and relative standard deviations for 50 and 150 μg/L of Cu(II) were 1.2 and 0.96%, respectively. The calibration curve was linear for 2–150 μg/L of copper(II). This technique does not use mercury and therefore is environmentally beneficial. The method, which is reasonably sensitive and selective, has been successfully applied to the determination of trace amounts of copper(II) in water and human hair samples.     

Evaluation of the inhibitive effect of essential oil of Lavandula multifida L., on the corrosion behavior of C38 steel in 0.5 M H2SO4 medium

The essential oil of the aerial parts of Lavandula multifida L., collected in Errachidia region (three samples) in southeast Morocco, was extracted by hydrodistillation and analyzed by GC and GC-MS. The oil was predominated by carvacrol (57.9–59.0%). L. multifida oil was tested as corrosion inhibitor of C38 steel in 0.5 M H₂SO₄ using weight loss measurements, electrochemical polarization, and EIS methods. The results obtained by measurements of weight loss showed that inhibition efficiency increases with inhibitor concentration to attain 72.2% at 2 g/l of oil at 298 K. Polarization curves revealed that L. multifida oil acts as mixed type inhibitor. The temperature effect on the corrosion behavior of steel in 0.5 M H₂SO₄ without and with the inhibitor at 2 g/l was studied in the temperature range from 303 and 343 K. The adsorption of inhibitor on the C38 steel surface was found to be a spontaneous process and to obey Langmuir’s adsorption isotherm. The associated activation energy has been determined.     

Determination of silver in real samples using homogeneous liquid-liquid microextraction based on ionic liquid

A new solvent-free mode of homogeneous liquid-liquid microextraction based on ionic liquid (IL) named as modified cold induced aggregation microextraction (M-CIAME), was developed. The method is a fast, solvent free, robust against high medium salt content, and simple for extraction and preconcentration of metal ions from various samples. The extraction of silver was preformed in the presence of 4,4-bis(dimethylamino)thiobenzophenone (TMK) as the complexing agent and sodium hexafluorophosphate (NaPF₆) was added to the sample solution (50°C) containing small amounts of 1-hexyl-3-methylimidazolium tetrafluoroborate [Hmim][BF₄]. Afterwards, the solution was placed in the ice bath and a cloudy solution was formed due to the decrease of IL solubility. After centrifuging, the fine droplets of extraction phase were settled of the bottom of the conical bottom glass centrifuge tube. Under the optimum conditions, the limit of detection (LOD) was 0.4 ng/mL. The relative standard deviation (RSD) was 1.8% for 50 ng/mL of silver (n = 5).     

Solid-phase molecularly imprinted pre-concentration and spectrophotometric determination of isoxicam in pharmaceuticals and human serum

A selective molecularly imprinted polymer (MIP) has been synthesized for isoxicam pre-concentration, followed by its spectrophotometric determination based on hydrogen bonding interactions between examined drug and alizarin yellow GG. This method is able to evaluate isoxicam in range of 1.0 × 10⁻³ to 20.0 μg mL⁻¹, with a limit of determination of 1.0 ng mL⁻¹. The retention capacity and pre-concentration factor of prepared sorbent are 18.5 mg g⁻¹ and 200, respectively; and the prepared MIPs can be reused at least for five times. The MIP capability for isoxicam selection and extraction from the solution is higher than non-imprinted polymer (NIP). Under optimum conditions, this procedure can be successfully applied to assay trace amounts of isoxicam in pharmaceutical and biological samples.     

A fluorescence detection scheme for ultra large molecules after gas phase separation

A system was proposed to remove the upper mass limitation of mass spectrometry. In present study, ultra large molecules were separated in the gas phase by mass analyzer after electrospray ionization. Instead of conventional detection with electron multiplier, a laser-induced-fluorescence detection scheme was applied. The instrument sensitivity is independent of molecular weight, but related to the spectroscopic properties of the fluorophores presented by the large biomolecules.     

Thermal decomposition of ammonium fluoromanganates(III)

The thermal decomposition of ammonium fluoromanganates (III) has been investigated in air and argon by simultaneous thermogravimetry and differential thermal analysis. Chemical analysis, X-ray powder data, and infrared spectra have been employed to characterise the intermediate and final products. The thermal decomposition can be described by the sequence (NH₄₃MnF₆ → (NH₄)₂MnF₅ → NH₄MnF₄ → MnF₂. Although penta- and tetra-fluoromanganates are well-defined compounds, the intermediate states could not be separated. In addition, a high temperature form of ammonium hexafluoromanganate has been observed.     

Practical considerations when using radio frequency-only quadrupole ion guide for atmospheric pressure ionization sources with time-of-flight mass spectrometry

Construction details and performance evaluation of a radio frequency (rf)-only quadrupole ion guide for use with an electrospray ionization time-of-flight mass spectrometer is presented in this paper. Angiotensin III and cytochrome c were used in these experiments to investigate the ion transmission properties of the rf-only quadrupole for different m/z species. In addition, influence of ion kinetic energies along with the characteristic fragmentation due to collision induced dissociation (CID) were studied. These experiments demonstrate that the transmissions of different m/z ions were not only dependent on the frequency and magnitude of the rf waveform, which is similar to a high vacuum rf-only quadrupole ion guide, but also on the pressure inside the quadrupole chamber. For the pressure range tested, low m/z ions are better focused with increasing pressure. As expected, transmission of ions are subject to space charge limitations when significant numbers of ions are focused on the axis of the quadrupole. It is also observed that CID results are related to transverse motion and longitude motion of ions inside the quadrupole region. Consequently, CID is useful for fragmentation of linear peptides and it is not effective (in present configuration) for large bulky proteins. The kinetic energy of ions that enter the repelling region of the TOFMS is ultimately determined by the ensemble effect resulting from the dc bias potential of the quadrupole (the dominant factor), skimmer-2, pressure inside the quadrupole chamber, and jet expansion. While this system is tested with an ESI source, the operational principle and design criteria are directly applicable for improving other atmospheric pressure ionization sources with time-of-flight mass analyzers such as an inductively coupled plasma ion source.     

Effect of pulegone and pulegone oxide on the corrosion of steel in 1?M HCl

The inhibitive action of pulegone and pulegone oxide toward acid corrosion of steel in molar hydrochloric acid was studied by weight loss measurements, potentiodynamic polarization, and impedance spectroscopy (EIS) methods. The pulegone is extracted starting from oil of Pennyroyal Mint (Mentha pulegium). The natural compound was found to delay the corrosion rate. The pulegone oxide is prepared by oxidation of pulegone. The inhibition efficiency was found to increase with the inhibitor content to attain 81 and 75% at 5 g dm⁻³ for pulegone and pulegone oxide. The increase in temperature leads to an increase in the inhibition efficiency of the natural compared.