Quantification of the plant-derived hallucinogen Salvinorin A in conventional and non-conventional biological fluids by gas chromatography/mass spectrometry after Salvia divinorum smoking

A gas chromatography method with mass spectrometric detection is described for the determination of Salvinorin A, the main active ingredient of the hallucinogenic mint Salvia divinorum. The method was validated in plasma, urine, saliva and sweat using 17-alpha-methyltestosterone as internal standard. The analytes were extracted from biological matrices with chloroform/isopropanol (9:1, v/v). Chromatography was performed on a 5% phenyl methyl silicone capillary column and analytes were determined in the selected ion monitoring mode. The method was validated over the concentration range 0.015-5 microg/mL plasma, urine and saliva and 0.01-5 microg/patch in the case of sweat. Mean recoveries ranged between 77.1 and 92.7% for Salvinorin A in different biological matrices, with precision and accuracy always better than 15%. The method was applied to the analysis of urine, saliva and sweat from two consumers after smoking 75 mg plant leaves to verify the presence of the active ingredient of S. divinorum in human biological fluids as a biomarker of plant consumption. Salvinorin A was detected in urine (2.4 and 10.9 ng/mL) and saliva (11.1 and 25.0 ng/mL), but not in sweat patches from consumers.     

Consecutive processes in the photolysis of dimethyl-s-tetrazine molecules in the vapor phase

Experimental studies of the variation of the fluorescence yield and photochemical product yield are presented for dimethyl-s-tetrazine (DMT) at 0.6 Torr and 300 K. Results are also reported for the variation of these yields upon adding argon buffer gas. The fluorescence yield decreases with increasing excitation energy (0 to 4200 cm^?1 vibrational energy excess in the first excited singlet state) but the decrease is insufficient to account for the corresponding increase in product yield. Added gas (600 Torr argon) quenches the photochemistry but not the fluorescence. The results imply that the photo-dissociation involves a bottleneck (B) in the non-radiative singlet decay. The molecules in B can be relaxed by collisions, relax to photostable DMT molecules without collisions, or undergo photodissociation.     

Cavitand-based nanoscale coordination cages

This communication reports design, self-assembly, solution, and solid-state characterization of nanoscale coordination cages formed by tetradentate cavitand ligands and appropriate metal precursors. The preorganization of the cavitand ligand in terms of structural rigidity and relative orientation of the pyridyl units leads to the exclusive formation of coordination cages in a wide temperature and concentration range. Desired features of the cage self-assembly process, such as reversibility in the presence of a competitive ligand and self-recognition of the cavitand components, have been assessed.     

Application of a liquid chromatography tandem mass spectrometry method to the analysis of water-soluble vitamins in Italian pasta

A sensitive and selective liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the determination of several water-soluble vitamins, namely vitamins B₁, B₂, B₆ (pyridoxine, pyridoxal, and pyridoxamine), and PP (nicotinamide and nicotinic acid), pantothenic acid, and folic acid was developed and validated. The analytes were characterized by means of their electrospray (ESI) and atmospheric pressure chemical ionization (APCI) mass spectra. In general, the positive ion spectra were 100- to 1000-fold more intense than the corresponding negative ion ones. Chromatography of water-soluble vitamins was obtained by using a reversed-phase C16 Amide (15 cm, 5 μm) column and a mobile phase made of ammonium formate buffer (20 mM, pH 3.75)/methanol under gradient elution conditions. Linearity of the MS response was observed over three to four orders for both ESI and APCI, and limits of detection were in the low μg/l range for both the ionization techniques. In particular, the sensitivity of ESI was about two- to five-fold higher for all vitamins except PP vitamers, for which APCI produced a better response. Precision calculated at two concentration levels (0.05 and 1.0 mg/l) was within 0.2-7.4% for all intra- and inter-day determinations and for all analytes. The LC-ESI-MS/MS method was applied to the quantitative analysis of the natural content of vitamins in typical Italian pasta samples, as well as in fortified pasta samples produced for the US market.     

PHOTODYNAMIC THERAPY OF B16 PIGMENTED MELANOMA WITH LIPOSOME-DELIVERED Si(IV)-NAPHTHALOCYANINE

The possibility of extending photodynamic therapy to the treatment of highly pigmented neoplastic lesions was tested by using Si(IV)-naphthalocyanine (SiNc) as a tumor-localizing agent. Si(IV)-naphthalocyanine displays intense absorbance at 776 nm (ɛ= 5 × 10⁵ M⁻¹ cm⁻¹), where melanin absorption becomes weaker. As an experimental model we selected B16 pigmented melanoma subcutaneously transplanted to C57BL mice. Upon injection of 0.5 or 1 mg kg⁻¹ of liposome-incorporated SiNc, maximal accumulation of the photosensitizer in the tumor was observed at 24 h with recoveries of 0.35 and 0.57 μg g⁻¹, respectively. However, the tumor targeting by SiNc shows essentially no selectivity, since the photosensitizer concentrations in the skin (peritumoral tissue) were very similar to those found in the tumor at all postinjection times examined by us. Irradiation of SiNc-loaded melanoma with 776 nm light from a diode laser at 24 h postinjection induces tumor necrosis and delay of tumor growth. The effect appears to be of purely photochemical nature at dose rates up to 260 mW cm⁻²; at higher dose rates, thermal effects are likely to become important.     

Copolymers of vinyl chloride with the vinyl esters and acrylates of low molecular weight polyesters of hydroxyacids

Vinyl esters and acrylates of polyesters derived from C₁₀?C₁₈ hydroxyacids have been synthesized and copolymerized with vinyl chloride with the hope of achieving an internally plasticized poly(vinyl chloride). Copolymers containing 10–30% polyester are film-forming materials, and the films cast from THF solutions are generally flexible. A number of these vinyl chloride copolymers with polyesters at approximately 15 and 25% level have been tested for various properties. The internal plasticization is not extensive.     

Mesomeric dipole moments. Part 12

The dipole moments of para-substituted azoxybenzenes (1, a-e) and phenylazoxycyanides (2, a-e) were analyzed in terms of bond moments and additional contributions expressing electron delocalization. The results are compatible with a significant participation of the polar mesomeric formula B (25% or 34% for1 and2, respectively), the N-O bond acquiring considerable double-bond character. Comparison of known x-ray structures reveals that this bond is significantly shortened, whereas the N=N bond is extended only very slightly. Hence we can consider the possibility that the N1 atom allocates somewhat more than eight valence electrons, similarly to nitro compounds. In all respects the properties of the azoxy group are between those of the nitro and imino-N-oxide groups.Part 11 appears in Exner, O.J. Phys. Org. Chem. 1990,3, 190.     

Stereoselective iodocyclisation of 3-acylamino-2-methylene alkanoates: a computational insight

In order to explain the high stereocontrol occurring in the iodocyclisation of 3-acylamino-2-methylenealkanoates, either the conformational space of the starting products or the cyclisation reaction potential energy surface (PES) was explored at DFT level of theory, the polarised continuum formalism (PCM) for chloroform being used in order to consider the solvent effect. The observed stereoselection was ascribed to both the near attack conformations (NACs) distribution and the energy differences between the two possible and competitive cyclisation pathways leading to cis- and trans-diastereomers.     

Flexible use of symbolic tools for problem solving, generalization, and explanation

We provide evidence that student representations can serve different purposes in the context of classroom problem solving. A strategy used expressly to solve a problem might be represented in one way, and in another way when the problem is generalized or extended, and yet in another way when the solution strategy is explained to peers or a teacher. We discuss the apparent long-term memory implications this has regarding the preferences that students have for their original versus later developed representations, and how these preferences relate to the use of representational flexibility in classroom settings.