Capillary electrochromatographic separation of illicit drugs employing a cyano stationary phase

In this study, we present a capillary electrochromatographic method for separation of basic compounds of interest in forensic science (amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine, 3,4-methylenedioxymethamphetamine, 3,4-methylenedioxyethylamphetamine, cocaine, codeine, heroin, morphine, and 6-monoacethylmorphine). Several analytical conditions were taken into account to completely separate in the same run the 10 drugs of abuse analyzed. Chromatographic retention, selectivity and efficiency were evaluated in dependence of the type of stationary phase (CN and RP-C₁₈ derivatized silica particles), mobile phase composition, buffer type and pH, sample injection. The optimum separation parameters were set up using a mixture of aqueous sodium phosphate buffer (pH 2.5)/acetonitrile (80/20, v/v) as the mobile phase, 10 kV and 20 °C as applied voltage and capillary temperature, respectively. Under these conditions all the studied analytes were baseline resolved within 20 min. The method performance was investigated in terms of precision, linearity, sensitivity and accuracy to demonstrate the applicability of the developed capillary electrochromatographic system to forensic analysis. Calibration curves provided a good linearity over a working range of 100–1200 ng/mL for all analytes. Limits of detection and quantification were in the range 5–12 ng/mL and 10–30 ng/mL, respectively. Then the method was applied to the analysis of a human urine sample spiked with a basic compounds’ mixture. Urine samples’ pre-treatment was carried out through a solid phase extraction (SPE) procedure on strong cation exchange (SCX) cartridges.     

Towards Controlling the Threading Direction of a Calix[6]arene Wheel by Using Nonsymmetric Axles

Traffic control : By exploiting the interplay of kinetic and thermodynamic effects, the direction of threading/dethreading in a nonsymmetric calixarene wheel can be selected by an appropriate choice of the head group incorporated in the molecular axle (see figure).

     

Equations Defining Symmetric Varieties and Affine Grassmannians

Suppose be a simpleinvolution of a semisimple algebraic group and suppose H is the subgroup of G of pointsfixed by . If the restrictedroot system is of type or and G is simplyconnected, or if the restricted root system is of type and G is of adjoint type, then we describe astandard monomial theory and the equations for the coordinatering using the standardmonomial theory and the Plücker relations of an appropriate(maybe infinite-dimensional) Grassmann variety.     

New isoperimetric estimates for solutions to Monge–Ampère equations

We prove some sharp estimates for solutions to Dirichlet problems relative to Monge–Ampère equations. Among them we show that the eigenvalue of the Dirichlet problem, when computed on convex domains with fixed measure, is maximal on ellipsoids. This result falls in the class of affine isoperimetric inequalities and shows that the eigenvalue of the Monge–Ampère operator behaves just the contrary of the first eigenvalue of the Laplace operator.     

A case study of dispersion in the lee of an obstacle

Summary The influence of hills, valleys and other obstacles on the atmospheric boundary layer is such that in their lee the mean wind velocity is reduced. Intermittent or fully separated flow conditions can arise, including regions of negligible mean wind. In these conditions dispersion is driven mainly by turbulent fluctuations, which prevail over the mean motion. In this work we review the general features of mean flow and turbulence intensity in the lee of a 2D obstacle. Using published wind tunnel data, we examine a case study of dispersion from a source placed in the lee and compare the measured concentrations with those of a random walk model simulation. Paper presented at the GNFAO/EURASAP Meeting, Turin, September 1989. To speed up publication, proofs were not sent to the authors and were supervised by the Scientific Committee.     

Soluzioni periodiche di equazioni ellittiche totalmente non lineari

Sunto In questo lavoro dimostriamo due teoremi di esistenza di soluzioni periodiche per due classi di equazioni ellittiche totalmente non lineari.

---

Summary Existence theorems for periodic solutions of totaly non linear elliptic equations are given.

---

---

Lavoro eseguito nell'ambito del G.N.A.F.A. del C.N.R.     

A diagnostic study of turbulence features in wind tunnel flow over simple topographic shapes

Summary The turbulence features observed in wind tunnel experiments of flow over isolated simple-shaped two-dimensional hills and valleys are analysed in the light of transport equations of Reynolds stresses in the streamline coordinate system. The analysis has shown that near the surface the streamwise pressure gradient is the driving parameter for all the stresses. At higher levels, the effects of streamline curvature and streamwise pressure gradient act differently on the source terms of stresses, showing that the shear stress is the most sensitive to streamline curvature, whereas the streamwise stress is the most sensitive to streamwise pressure gradient. Although two of the considered topographies are specular images, the turbulence response is not so, since it depends on the sequence of curvatures to which it is subjected. The information and analysis presented will constitute a valuable resource to those seeking an understanding of atmospheric boundary layer development over complex terrain. It will also provide a support for the development and validation of more rigorous turbulence models.     

A diode-laser-based spectrometer for in-situ measurements of volcanic gases

We report the first results of the field operation of a novel, portable diode-laser spectrometer for gas-concentration measurements in volcanic areas. Remote detection of direct absorption line shapes was possible thanks to a telecom single-mode optical fiber that delivered radiation from a room-temperature distributed-feedback diode laser, emitting at 1.997 m, to an open-path multiple-reflection cell, placed on gas effluxes. The system was deployed on two different active volcanoes in Italy, where simultaneous and continuous monitoring of CO₂ and H₂O concentrations has been demonstrated. PACS 42.62.Fi; 07.60.Vg; 93.85.+q     

Use of nano-liquid chromatography for the analysis of glycyrrhizin and glycyrrhetic acid in licorice roots and candies

Glycyrrhizin (G) and glycyrrhetic acid (GA) were separated by using nano-liquid chromatography (nano-LC) in a fused silica capillary packed with RP18 stationary phase (75 microm ID, effective length 33 cm, packed 23 cm) eluting at 300 nL/min in a gradient mode. The mobile phase was a mixture of water-MeOH-MeCN-acetic acid (29:35:35:1, v/v/v/v) that was delivered for one minute and after this was modified by reducing the water content (14:42.5:42.5:1, v/v/v/v). The intra-day and inter-day relative standard deviations (of retention time and peak area) were satisfactory (lower than 2.9 and 4%, respectively). The linearity of the nano-LC method was assessed in the range 0.62-5.00 microg/mL and 80-200 microg/mL for GA and G, with R2 = 0.996 and 0.995, respectively. The licorice was extracted with a mixture of ethanol-water, diluted with the mobile phase, and injected for the analysis.     

Quality control in combinatorial chemistry: determinations of amounts and comparison of the "purity" of LC-MS-purified samples by NMR, LC-UV and CLND

The absolute purities of 20 purified samples from a combinatorial library have been determined by a new method that uses the DMSO sidebands [1J[13C-1H]] as an internal standard for quantification. The obtained absolute amounts are compared with the amounts of sample obtained by weighing, with the calculated weights obtained by chemiluminescent nitrogen detection (CLND) chromatography and with the relative purities obtained by LC-UV chromatography.