Silver CD-R based substrate as a SERS active material

A silver Compact Disc Recortable (CD-R) based substrate has been proposed as an alternative to silver colloids as active material successfully used in surface-enhanced Raman spectroscopy (SERS). Scanning Electron Microscope (SEM) and Energy-Dispersive X-ray Spectroscopy (EDXS) measurements revealed that silver nanoparticles are present over the entire surface of the uncovered reflective layer of commonly used CD-R. The process of preparation of the CD-R based surface is simple, fast and repeatable. Recorded Raman spectra of 10 µM Rhodamine 6G applied to the substrate corroborate strong enhancement of Raman signal. The maximum value of EF was calculated to be about 5.76 × 10⁶. Raman maps are consistent with SEM micrographs and confirmed the presence of a numerous SERS hot spots occurring on the trucks of CD-R based substrate.     

1H and 13C NMR spectral data of new saponins from Cordia piauhiensis

Two new bidesmoside triterpenoid saponins were isolated from stems of Cordia piauhiensis. Their structures, characterized as 3-O-alpha-L-rhamnopyranosyl-(1 --> 2)-beta-D-glucopyranosyl pomolic acid 28-O-beta-D-glucopyranosyl ester (1) and 3-O-alpha-L-rhamnopyranosyl-(1 --> 2)-beta-D-glucopyranosyl oleanolic acid 28-O-beta-D-glucopyranosyl-(1 --> 6)-beta-D-glucopyranosyl ester (2), were unequivocally established after extensive NMR (1H, 13C, DEPT 135 degrees, COSY, HSQC, HMBC, TOCSY, and NOESY) studies.     

Analysis of some stilbenes in Italian wines by liquid chromatography/tandem mass spectrometry

Stilbenes from grapes and wines play a central role in the human diet because of their antioxidant, antimutagenic and anticarcinogenic properties. We describe a method for the direct determination of some stilbenes (cis- and trans-resveratrol, cis- and trans-resveratrol glucoside, cis- and trans-piceatannol, and cis- and trans-piceatannol glucoside) in wine by high-performance liquid chromatography/mass spectrometry using a triple quadrupole (QqQ) mass spectrometer, in multiple reaction monitoring (MRM) mode, acquiring two diagnostic product ions from the chosen precursor. All the target analytes were separated on a C-18 column using gradient elution, in a single run. Electrospray ionization (ESI) in negative ion mode gives higher sensitivity for all the target compounds than atmospheric pressure chemical ionization (APCI). For the identification of piceatannol glucoside (astringin), because of the lack of a suitable standard, an HPLC/TOFMS method was used. The method permits direct injection of samples and it is time-saving, removing the need for sample pre-treatment. The detection limits were 48.0 ng mL(-1) for cis- and trans-resveratrol and for cis- and trans-resveratrol glucoside, and 50.0 ng mL(-1) for cis- and trans-piceatannol. The procedure proved to be simple and suitable for routine and confirmatory purposes. A total of 19 red and 3 white Italian wines were analyzed and differences in the stilbene composition were found among these samples. Copyright (c) 2007 John Wiley & Sons, Ltd.     

Development and validation of an MEKC method for determination of nitrogen-containing drugs in pharmaceutical preparations

A fast and accurate micellar electrokinetic capillary chromatography method was developed for quality control of pharmaceutical preparations containing cold remedies as acetaminophen, salicylamide, caffeine, phenylephrine, pseudoephedrine, norephedrine and chlorpheniramine. The method optimization was realized on a Beckman P/ACE System MDQ instrument. The baseline separation of seven analytes was performed in an uncoated fused silica capillary internal diameter (ID)=50 microm using tris-borate (20 mM, pH=8.5) containing sodium dodecyl sulphate 30 mM BGE. On line-UV detection at 214 nm was performed and the applied voltage was 10 kV. The operating temperature was 25 degrees C. After experimental conditions optimization, the proposed method was validated. The evaluated parameters were: precision of migration time and of corrected peak area ratio, linearity range, limit of detection, limit of quantification, accuracy (recovery), ruggedness and applicability. The method was then successfully applied for the analysis of three pharmaceutical preparations containing some of the analytes listed before.     

Isolation, purification and determination of 4-n-nonylphenol and 4-tert-octylphenol in aqueous and biological samples

The aim of the present study was to attempt to describe the procedure of isolation, purification, enrichment and determination of 4-n-nonylphenol (4-n-NP) and 4-tert-octylphenol (4-t-OP) in water and biological samples (fish tissue). There were five procedures of solid phase extraction (SPE) tested using different sorbents for the isolation of analytes from water samples. Moreover, we isolated these chemicals from biological matrices with the aid of various extraction methods. The purpose of it was to perform an optimisation of ultrasonic bath, accelerated solvent extraction (ASE) and solid phase extraction process of alkylphenols from biological samples, through the choice of selective sorbents (octadecyl, octadecyl end-capped and amine) and search solvents (methylene chloride, methanol, hexane). Reversed-phase HPLC with diode array detection was used for the determination of 4-n-NP and 4-t-OP in water and fish tissue samples. Sensitivity was evaluated by determining the limit of detection (LOD=0.06 and 0.04ng microL(-1)) and limit of quantification (LOQ=0.18 and 0.16ng microL(-1)) of 4-NP and 4-t-OP, respectively. A series of standard solutions for 4-n-NP and 4-t-OP provided the basis for plotting an analytical curve and obtaining a linear dependence in the range of approximately 1-25ng microL(-1). The best efficiencies obtained for 4-n-NP and 4-t-OP in water samples were 76.65% (+/-1.49) and 83.08% (+/-3.73), respectively. In the case of fish tissue, different situation was observed because the obtained values were considerably lower, being 68.32% for 4-t-OP using hexane (program 1) as solvent and 72.35% (program 2) for 4-n-NP using acetonitrile.     

Advantages of pentafluorophenylpropyl stationary phase over conventional C18 stationary phase--application to analysis of triamcinolone acetonide

A pentafluorophenylpropyl (PFPP) stationary phase was for the first time tested for the simultaneous determination of triamcinolone acetonide, its degradation product triamcinolone and two preservatives, methylparaben, and propylparaben. A new simple isocratic reversed phase HPLC method with UV detection, using estradiol hemihydrate as an internal standard, has been developed and validated. Chromatography was performed on a Discovery HS F5 column (150 mm x 4.6 mm, 5 microm) using a binary mobile phase composed of acetonitrile and water 45:55 (v:v). The flow-rate was 0.6 mL/min, the column temperature 25 degrees C and the UV detection was accomplished at 240 nm. The chromatography results using PFPP stationary phase were compared with those obtained using conventional C18 columns.     

Diterpenoic Acids Analysis Using a Coupled TLC-Surface-Enhanced Raman Spectroscopy System

Hyphenation of thin layer chromatography (TLC) with surface-based spectral methods requires a homogeneous surface for direct and quantitative analysis on the chromatographic plate after separation. Since most chromatographic materials do not produce strong background signals in Raman spectroscopy (RS) or surface-enhanced RS (SERS), we tested the suitability of two different chromatographic substrates and one interface for coupling SERS with TLC. This was carried out by using a chromatographic thin layer, specially produced for RS measurements, and a monolithic silica thin layer. A typical TLC plate with a modified aluminium backplate foil on one side was used as an interface. Three biologically active diterpenes, namely gibberellic acid (GA), abietic acid (AA) and kaurenoic acid (KA), were used as test analytes. Stock solutions were applied directly onto the surface, followed by the addition of silver colloid and measurements were taken by SERS. The strongest signal (excitation at 514.5 nm) was obtained for GA using a Raman treated thin layer where the enhancement factor value was determined to be 10². Several fundamental Raman bands for GA were found at 1622, 1593, 1570, 1542, 1366 and 1236 cm⁻¹. When the monolithic silica layer was used, no useful SERS signals were observed. The SERS spectra on modified aluminium backplate for AA and GA were quite similar and no SERS spectrum was obtained for KA. Future research will be concerned towards the use of nanostructured surfaces for SERS analysis. An erratum to this article can be found at     

ESI-MS studies of mixed-ligand Fe(II) complexes containing 1,10-phenanthroline and 1,10-phenanthroline-5,6-dione as ligands

In order to monitor the progression of the synthesis and the separation of novel mixed-ligand iron complexes containing 1,10-phenanthroline, 1,10-phenanthroline-5,6-dione, and NCS- as ligands all products were mass analyzed by electrospray ionization ion trap MS/MS. The spectra of methanol (MeOH), acetonitrile (ACN), water, and ethanol (EtOH) solutions were collected and the results were compared. It was detected under applied electrospray ionization mass spectrometry (ESI-MS) conditions that MeOH, water, and EtOH formed solvent clusters around the free or complexed 1,10-phenanthroline-5,6-dione. Owing to the solvent-ligand hydrogen-bond formation, the solvent-ligand clusters were formed in the polar protic solvents. The number of protic solvent molecules per complex ion in cluster depended on the number of 1,10-phenanthroline-5,6-dione ligands in the complex ion. Unlike MeOH, EtOH, or water, ACN was not involved in the formation of the solvent clusters with the iron complexes containing 1,10-phenanthroline-5,6-dione as ligand. We also showed that the NCS- group under certain solvent conditions served as a bidentate ligand.     

A Ruthenium Bridge in Fullerene–Ferrocene Arrays: Synthesis of [Ru(C60Me5)R(CO)2] (R=C6H4Fc,C≡CFc) and Their Charge‐Transfer Properties

New fullerene–ferrocene arrays, [Ru(C₆₀Me₅)(C₄H₆Fc)(CO)₂] (Fc=ferrocenyl) and [Ru(C₆₀Me₅)(CCFc)(CO)₂], in which the ruthenium complex functions as a conjugative bridge, were synthesized by the reaction of [Ru(C₆₀Me₅)Cl(CO)₂] with FcC₆H₄MgBr and FcCCLi, respectively. These compounds were investigated by electrochemical measurement, single‐crystal X‐ray structural analysis, and photophysical measurement. Upon photoirradiation, the former compound was converted rapidly into the corresponding triplet state in toluene (τ_singlet=21 ps), whereas the charge‐separated state was predominant in THF (τ_singlet=10.5 ps; τ_CS=355 ps). The latter compound, on the other hand, formed the charge‐separated state in both toluene and THF (τ_singlet=3.0 ps; τ_CS=152 ps). Thus, the structural difference between the phenylene and acetylene bridges in 1 and 2 , respectively, was found to change the outcome of the photophysical processes.     

Otoacoustic emission sensitivity to low levels of noise-induced hearing loss

With the aim of investigating the capability of otoacoustic emission (OAE) in the detection of low levels of noise-induced hearing loss, audiometric and otoacoustic data of young workers (age: 18-35) exposed to different levels of industrial noise have been recorded. These subjects are participating in a long-term longitudinal study, in which audiometric, exposure (both professional and extra-professional), and OAE data (transient evoked and distortion product) will be collected for a period of several years. All measurements have been performed, during routine occupational health surveillance, with a standard clinical apparatus and acquisition procedure, which can be easily used in the occupational safety practice. The first study was focused on the correlation between transient evoked OAE signal-to-noise ratio and distortion product (DPOAE) OAE level and the audiometric threshold, investigating the causes of the rather large intersubject variability of the OAE levels. The data analysis has shown that, if both OAE data and audiometric data are averaged over a sufficiently large bandwidth, the correlation between DPOAE levels and audiometric hearing threshold is sufficient to design OAE-based diagnostic tests with good sensitivity and specificity also in a very mild hearing loss range, between 10 and 20 dB.