We have reported a one-step method for creating one-dimensional metallic nanoarrays on surfaces. This method is based on the processes of solvent vapor-induced buildup and controlled drying front movement, and forms parallelly aligned metallic nanoarrays exceeding several hundred micrometers in length on a poly(dimethylsiloxane) (PDMS) sheet. Strong light scattering originating from highly localized electromagnetic (light) fields was observed on prepared metallic nanoarrays. Furthermore, the enhancement of electromagnetic fields localized on prepared metallic nanoarrays strongly depended on the incident-light polarization.
In this review, a new classification of elements based on behavior in hydrofluoric acid (HF) solution is presented for the precise quantitative analysis of each element by inductively coupled plasma mass spectrometry (ICP-MS). The elements are divided into 7 groups: (1) "fluorophile" elements; (2) insoluble fluoride-forming elements; (3) "bromophile" or "iodophile" elements; (4) "oxophile" elements; (5) "aquaphile" elements; (6) bare cation elements; and (7) other elements. Especially, the importance of fluorophile and insoluble fluoride-forming elements in elemental analysis is described. Due to the elemental characteristics, these two groups of elements cannot be dissolved simultaneously in the same solution, and thus cannot be measured together. In addition, coprecipitation of the fluorophile elements with the insoluble fluorides occurs in some conditions and hinders accurate analysis. The peculiar conditions when the coprecipitation occurs are discussed, and the "Al-addition" and "Mg-addition" methods for overcoming these problems are described. In addition, some state-of-the-art analytical techniques in ICP-MS are shown, and future directions of the element analysis are presented.
Tellurium and antimony are widely used in industry because of their unique chemical and physical properties. Although these metalloids, which belong to period 5 of the periodic table of elements, are known to be non-essential and harmful, or the so-called "exotic" elements, little is known about their toxic effects and metabolism. The present review describes the role of speciation in considering the metabolism of tellurium and antimony from the viewpoint of toxicometallomics. Inorganic tellurium in the form of tellurite is reduced and simply methylated in the body. Rat red blood cells accumulate tellurium in the form of dimethylated tellurium, and tellurium is excreted into urine as trimethyltelluronium. Although selenium, which belongs to the same group as tellurium, is known to be excreted in the form of selenosugar as the major urinary metabolite, tellurosugar was not detected by an inductively coupled plasma-mass spectrometer hyphenated with an HPLC. Speciation studies revealed that the major metabolic pathway of antimony is oxidation in human and rat, and methylation also occurs as a minor metabolic pathway in humans.
A simple, rapid, and sensitive on-line liquid chromatographic electrochemistry/electrospray/tandem mass spectrometry (LC-EC/ESI-MS/MS) method for the determination of zotepine in human serum was developed using a new generated-electrochemically fragment ion, and was validated. A recent novel technique of LC-EC/ESI-MS/MS that combines LC-MS/MS and the on-line EC reaction is potentially applicable to developing a quantification method for drugs in biological samples. Newly formed products generated by the on-line EC cell are expected to provide appropriate precursor and product ions for the MS/MS determination method. This technique was successfully applied to a drug assay in a biological matrix. After adding imipramine (IS) to a 30-μL aliquot of human serum, the resulting sample was simply deproteinated with acetonitrile for a measurement. The analytical run time was 5 min. The calibration curve was linear in the concentration range of 10 − 2000 ng/mL. The intra-assay precision and accuracy were in the range of 1.8 − 8.9 and 98.4 − 113%, respectively.
A selective, sensitive gas chromatography-mass spectrometry (GC-MS) method with negative chemical ionization (NCI) was developed for the detection and quantification of clopidol in chicken muscle. Chicken muscle samples were extracted with acetonitrile and concentrated to dryness; the residue was redissolved in ethyl acetate and applied to an Alumina B cartridge for cleanup. The residue was derivatized with Sylon BFTTM and analyzed by GC-NCI-MS. The selected-ion monitoring mode was performed at m/z values of 156, 158, 191, and 193. The differences in the ratios for the standards and spikes in chicken muscle were within the acceptability criteria. All recoveries of the drug from chicken muscle spiked at 0.5, 5.0 and 50.0 μg/kg were 74.5 − 95.6% intra-day, and 71.6 − 94.8% inter-day, respectively, with relative standard deviations being lower than 15%. The limits of detection and quantitation were 0.1 and 0.5 μg/kg, respectively. The NCI mode had better selectivity and sensitivity than the electron impact (EI) mode for clopidol.
A simple, sensitive and selective liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed and validated for the analysis of venlafaxine (VX) and its major active metabolite O-desmethyl venlafaxine (ODV) in rat plasma using carbamazepine as an internal standard (IS). The analytes from the biological matrix were extracted by liquid-liquid extraction using tert-butyl methyl ether (TBME). The HPLC separation of the analytes was performed on a water symmetry C18 (150 × 4.6 mm i.d., 5 μm) column, using a 10 mM ammonium formate:methanol (20:80 v/v) as mobile phase. The calibration curve concentration range was 10.10 to 8000.00 ng/mL for VX and ODV with coefficient of determination above 0.9970. The lower limit of quantification (LLOQ) of VX and ODV were 3.35 and 3.86 ng/mL, respectively. The intra- and inter-day coefficients of variation were within 15%.
We developed a rapid, simple and sensitive LC/MS/MS method for the simultaneous quantitation of tegafur (FT) and gimeracil (CDHP) in human plasma with a concentration range of 20 − 5000 and 2 − 500 ng/mL, respectively. Methanol was chosen as a precipitation agent for sample preparation. Chromatographic separation was performed on an inertsil ODS-3 C18 column using 1.0% formic acid in water and methanol (80/20, v/v) at a flow rate of 0.3 mL/min. The MS detection was operated with selected reaction monitoring (SRM) in the positive-ion mode. The matrix effect ranged from −8.9 to 7.8% for all analytes. The intra- and inter-day precisions were less than 8.6 and 9.5%, and the accuracy was within ±7.5% for all analytes, respectively. The mean recoveries were 76.5 ± 5.2 and 78.3 ± 5.9% for FT and CDHP, respectively. The analytes were stable under all possible conditions of storing and handling for each compound.
The enantioseparation of four stereoisomers of palonosetron hydrochloride (PALO) by capillary zone electrophoresis using high concentration β-CD as chiral selector was described in this study. For optimization of the method of enantioseparation, several parameters such as β-CD concentration, separation buffer pH and concentration, the types and concentration of organic modifiers, and the applied voltage were evaluated. The optimum conditions were obtained as follows: 30 mmol L−1 NaH2PO4 (pH 3.0) containing 150 mmol L−1β-CD and 10% (v/v) methanol with an applied voltage of 15 kV. Under these conditions, baseline separation of the four PALO stereoisomers was achieved within 35 min, and the reproducibility (expressed as relative standard deviation, RSD) of the migration times and the peak areas were below 0.5, 2.5% (intra-day), and 1.9, 4.4% (inter-day), respectively.
The electrocatalytic oxidation of L-tyrosine was investigated on a gold nanoparticles self-assembled glassy carbon electrode (gold nanoparticles/cysteamine/glassy carbon) using cyclic voltammetry and differential pulse voltammetry. Cyclic voltammetry was carried out to study the electrochemical oxidation mechanism of L-tyrosine, which showed an irreversible oxidation process at a potential of 0.681 V at a modified electrode and 0.807 V at a bare glassy carbon electrode. The anodic peak current linearly increased with the square root of the scan rate, suggesting that the oxidation of L-tyrosine at this kind of modified electrode is a diffusion-controlled process. A good linear relationship between the oxidation peak current and the L-tyrosine concentration in the range of 1.0 × 10−7 to 3.0 × 10−4 mol L−1 was obtained in a phosphate buffer solution at pH 7.0. Good sensitivity, selectivity and stability of the modified electrode make it very suitable for L-tyrosine determination in a commercial amino acid oral solution.
A chemically modified carbon-paste electrode has been described for the sensitive and selective determination of amantadine. β-Cyclodextrin was used as modifier. The electrode shows a sub-Nernstian response of 51.0 ± 1.0 mV decade−1 for amantadine in the concentration range of 6.3 × 10−10 − 7.1 × 10−7 M at 25°C. The optimum pH value was maintained at 4.5 using a 0.02 M acetate buffer. The limit of detection of the electrode was 6.3 × 10−10 M of amantadine. The electrode responded very rapidly (<60 s) to changes in the concentration of amantadine, and its lifetime was more than three months. The relative standard deviation of measurements for a 2.0 × 10−7 M of amantadine was 0.68% (n = 7). The application of a modified carbon-paste electrode to the determination of amantadine in its pharmaceutical preparations showed a relative error of 2%. The recovery of amantadine (2.5 × 10−8 M) from a blood-serum sample was 94%.
A kinetic fluorometric method was proposed for the quantitative determination of epinephrine (EP) in human plasma samples with the aid of second-order calibration methods based on alternating trilinear decomposition (ATLD) and alternating fitting residue (AFR) algorithms. It was based on that EP could be gradually converted to a highly fluorescent intermediate product by an oxidation reaction, and further to a non-fluorescent degradation product (o-quinone). These methodologies fully exploit the second-order advantage of the employed three-way kinetic fluorescence data, allowing the concentrations of EP to be quantified even in the presence of uncalibrated interferences. The average recoveries obtained from ATLD and AFR with a factor number of 2 (N = 2) were 100.7 ± 3.3 and 100.4 ± 2.2%, respectively. In addition, elliptical joint confidence region (EJCR) tests as well as figures of merit (FOM) were employed to evaluate the accuracy of the two algorithms.
The fluorescence intensity of the europium (Eu3+)-thenoyltrifluoroacetone (TTA) complex can be remarkably enhanced by human serum albumin (HSA) in a Britton-Robinson buffer solution. Based on this fact, a simple, rapid, and sensitive method has been developed for the determination of proteins at the nanogram level by fluorescence spectroscopy. Under the optimum conditions, the enhanced fluorescence intensity is proportional to the concentration of HSA. The linear ranges for HSA are 0 − 5.1 and 5.1 − 44.4 μg ml−1 and the limit of detection is 20.7 ng ml−1. Moreover, there is very little interference from common inorganic ions and other coexisting compounds. The binding site number and the binding constant of Eu3+-TTA used as a fluorescence probe to HSA were calculated by using the Rosenthal graphic method. This method has been applied to the determination of total protein in human serum samples. The results are good agreement with data obtained by clinical physicians.
This paper presents a novel spectrophotometric method to measure peroxidase activity using paraphenylenediamine dihydrochloride (PPDD) and Mequinol (MQ). The PPDD traps the free radical, and gets oxidized to electrophilic 1,4-diimine; this couples with MQ to an give intense violet-colored chromogenic species with the maximum absorbance at 560 nm. This assay was adopted for the quantification of hydrogen peroxide between 10 × 10−6 to 80 × 10−6 M. From the kinetic data, a two-substrate ping-pong mechanism of peroxidase was established. Catalytic efficiency and catalytic power of commercial peroxidase were 0.204 × 106 M−1 min−1 and 2.86 × 10−4 min−1, respectively. The catalytic constant (kcat) of the proposed method was 0.2080 × 103 min−1. As a simple, rapid, precise and sensitive technique, PPDD-MQ stands as a potential replacement for the traditional guaiacol method. Applications to the plant extracts increase its relevance in the field of biochemical analysis.
A new spectrophotometric reagent for the determination of trace amounts of fluoride has been introduced. This method is based on the decolorization of a complex of Al(III) with xylenol orange (XO) as an ultra-sensitive colored reagent. Since the Al-XO complex plays an important role in this method, the protonation and complexation of XO with Al(III) at an ionic strength of 0.1 mol L−1 at 25°C has been studied by a spectrophotometric global analysis method. The EQUISPEC program was used to evaluate the protonation constants of XO and the stability constants of the formed complexes with Al(III). The protonation and the stability constants of the major complex species such as ML, MLH and MLH2, were determined. Finally, a spectrophotometric method for the assay of fluoride based on a decrease of the color intensity of the Al-XO complex, in an aqueous solution has been designed. The effects of some important variables on the determination of fluoride based on the proposed method were investigated. The method was applied to the determination of fluoride under the optimum conditions (pH 5.2, ionic strength 0.1 mol L−1, 25°C). The determination of fluoride in the range of 0.08 − 1.4 μg mL−1 (SD = 1.2%) was successfully performed. Interferences of Fe(III) were easily eliminated by using ascorbic acid. The proposed method was applied to the determination of trace amounts of fluoride content of some real water samples.
The effect of ionizing radiation on florfenicol (FF), an antibiotic with wide antibacterial properties was investigated to determine whether it can be sterilized using high-energy radiation. FF was irradiated by E-beam radiation to doses of 25 − 800 kGy, and then changes in the physico-chemical properties were examined using chromatographic methods (TLC and HPLC), spectroscopic methods (NMR and MS) and hyphenated methods (HPLC-MS). It was found that a standard sterilizing dose of 25 kGy led to the formation of two new products of radiolysis as well as lowering the content of FF by 0.95%. With higher doses of radiation, the content of FF further decreased (by 12.27% with a dose of 800 kGy), and new products of radiolysis appeared (up to five with a dose of 800 kGy). However, there were no differences between the NMR and MS spectra of irradiated and non-irradiated samples of FF. A linear dependence was found between the dose of radiation and the FF content (correlation coefficient of 0.9951) as well as between the melting point and the sum of products of radiolysis (correlation coefficient of 0.9975). It was found that a radiodegradation of FF took place by the breaking of an amide bond, leading to the formation of an aliphatic amine, which was subsequently oxidized to 4-methylsulfonylbenzoic acid. The radiolytic yield for the radiodegradation of FF was calculated to be 10.24 molecules/100 eV for a dose of 25 kGy. As a result of our investigation, we can conclude that FF shows a reasonably good radiostability in the range of doses used for sterilization, i.e. 25 kGy and below, and therefore it can be sterilized using high-energy radiation without changing its physicochemical, properties and hence its therapeutic efficacy.
In order to compare and evaluate the atomization process occurring in several types of graphite furnaces for atomic absorption spectrometry, the authors estimated temporal variations in the gas temperature by using a two-line method under the assumption of a Bolzmann distribution. The atomization furnaces employed were a graphite tube, a graphite tube coated with pyrolitic carbon, a graphite tube with a platform and a graphite cup. Differences in the temporal variation in the gas temperature among these graphite furnaces were observed.