Profiling of impurities in illicit methamphetamine by high-performance liquid chromatography and capillary electrochromatography

High performance liquid chromatography (HPLC) with photodiode array (PDA) UV and fluorescence (FL) detection, and capillary electrochromatography (CEC) with laser-induced fluorescence (LIF) detection were investigated for the analysis of acidic extracts derived from illicit methamphetamine. These compounds include major impurities from the hydriodic acid/red phosphorous reduction method, i.e., 1,3-dimethyl-2-phenylnaphthalene and 1-benzyl-3-methylnaphthalene, and other trace-level, structurally related impurities. For certain of these solutes, HPLC with conventional FL detection gave at least a 60× increase in sensitivity over UV detection. In addition, other highly fluorescent impurities were detected in methamphetamine produced via four other synthetic routes. The use of a rapid scanning FL detector (with acquisition of “on the fly” excitation or emission) provided structural information and gave “optimum” excitation and emission detection wavelengths. CEC with LIF detection using UV laser excitation provided greatly improved chromatography over HPLC, with good detection limits in the low ng/ml range. Both methodologies provide good run-to-run repeatability, and have the capability to distinguish between samples.     

Effect of Pr-Ca substitution on the transport and magnetic behavior of LaMnO3 perovskite

The effect of simultaneous substitution of a fluctuating cation and a divalent cation in LaMnO₃ perovskite modifies the properties of the material to exhibit large valence colossal magnetoresistance (CMR) effect. A good example of these properties is (La_1−2x Pr _x Ca _x )MnO₃ (LPCMO) type CMR material. In this communication it is reported that, with the increase in x (for x=0.1, 0.15, 0.2), the T _c varies between 100 and 120 K with improvisation in metal-insulator transition. Interestingly, resistance increases with x from few hundred ohms to few kilo ohms with corresponding decrease in the unit cell volume. The results of the studies using X-ray diffraction (XRD), electrical resistivity, magnetoresistance and ac susceptibility measurements on LPCMO samples for understanding the structural, transport and magnetic properties are discussed in detail.     

Pilot-Scale Fermentation of Aqueous-Ammonia-Soaked Switchgrass

Aqueous-ammonia-steeped switchgrass was subject to simultaneous saccharification and fermentation (SSF) in two pilot-scale bioreactors (50- and 350-L working volume). Switchgrass was pretreated by soaking in ammonium hydroxide (30%) with solid to liquid ratio of 5 L ammonium hydroxide per kilogram dry switchgrass for 5 days in 75-L steeping vessels without agitation at ambient temperatures (15 to 33 °C). SSF of the pretreated biomass was carried out using Saccharomyces cerevisiae (D₅A) at approximately 2% glucan and 77 filter paper units per gram cellulose enzyme loading (Spezyme CP). The 50-L fermentation was carried out aseptically, whereas the 350-L fermentation was semiaseptic. The percentage of maximum theoretical ethanol yields achieved was 73% in the 50-L reactor and 52–74% in the 350-L reactor due to the difference in asepsis. The 350-L fermentation was contaminated by acid-producing bacteria (lactic and acetic acid concentrations approaching 10 g/L), and this resulted in lower ethanol production. Despite this problem, the pilot-scale SSF of aqueous-ammonia-pretreated switchgrass has shown promising results similar to laboratory-scale experiments. This work demonstrates challenges in pilot-scale fermentations with material handling, aseptic conditions, and bacterial contamination for cellulosic fermentations to biofuels.     

Light‐Controlled Interconversion between a Self‐Assembled Triangle and a Rhombicuboctahedral Sphere

Stimuli‐responsive structural reorganizations play an important role in biological processes, often in combination with kinetic control scenarios. In supramolecular mimics of such systems, light has been established as the perfect external trigger. Here, we report on the light‐driven structural rearrangement of a small, self‐assembled Pd₃L₆ ring based on photochromic dithienylethene (DTE) ligands into a rhombicuboctahedral Pd₂₄L₄₈ sphere measuring about 6.4 nm across. When the wavelength is changed, this interconversion can be fully reversed, as confirmed by NMR and UV/Vis spectroscopy as well as mass spectrometry. The sphere was visualized by AFM, TEM, and GISAXS measurements. Due to dissimilarities in the photoswitch conformations, the interconversion rates between the two assemblies are drastically different in the two directions.     

Aqueous Ammonia Soaking of Switchgrass Followed by Simultaneous Saccharification and Fermentation

Simultaneous saccharification and fermentation (SSF) of switchgrass was performed following aqueous ammonia pretreatment. Switchgrass was soaked in aqueous ammonium hydroxide (30%) with different liquid–solid ratios (5 and 10 ml/g) for either 5 or 10 days. The pretreatment was carried out at atmospheric conditions without agitation. A 40–50% delignification (Klason lignin basis) was achieved, whereas cellulose content remained unchanged and hemicellulose content decreased by approximately 50%. The Sacccharomyces cerevisiae (D₅A)-mediated SSF of ammonia-treated switchgrass was investigated at two glucan loadings (3 and 6%) and three enzyme loadings (26, 38.5, and 77 FPU/g cellulose), using Spezyme CP. The percentage of maximum theoretical ethanol yield achieved was 72. Liquid–solid ratio and steeping time affected lignin removal slightly, but did not cause a significant change in overall ethanol conversion yields at sufficiently high enzyme loadings. These results suggest that ammonia steeping may be an effective method of pretreatment for lignocellulosic feedstocks.     

Reversed-phase electrochromatography of amino acids and peptides using porous polymer monoliths

Efficient harvest and recovery of high-purity monoclonal antibodies was achieved using hydrophobic charge induction chromatography (HCIC). Both simple and complex feedstocks were studied, including protein-free cell culture supernatant and the clarified/concentrated milk of transgenic goats. Viral clearance studies demonstrated a 4-log reduction of MVM virus (minute virus of mice), along with substantial reduction of DNA content. Sorbent characterization studies confirmed that HCIC is based on the pH-dependent behavior of a dual-mode, ionizable ligand. Binding, based on hydrophobic interaction, was achieved under near-physiological conditions, and in the absence of lyotropic salt. Desorption was accomplished under mild conditions--pH 4.0. At this pH, both ligand and antibody carry a net positive charge, and desorption occurs on the basis of electrostatic charge repulsion. pH-based control of chromatographic function was demonstrated. Chromatography on this antibody-selective HCIC sorbent was evaluated as a cost-effective, process-compatible alternative to affinity chromatography protein A sorbents.     

Fabrication,chemical modification,and topographical patterning of reactive gels assembled from azlactone‐functionalized polymers and a diamine

The work reported here demonstrates an approach to the fabrication of chemically reactive and topographically patterned hydrogels using the azlactone‐functionalized polymer poly(2‐vinyl‐4,4'‐dimethylazlactone) (PVDMA) and the hydrophilic diamine Jeffamine®. Gels were initially assembled in DMSO but can be subsequently transferred into aqueous media to form hydrogels. Spectroscopic characterization of assembled gels demonstrated that variation in the stoichiometric ratio of azlactones to amines during gel synthesis permits control over the extent of crosslinking in the gels. Residual azlactones not consumed during crosslinking can be exploited to further functionalize these gels with hydrophobic, hydrophilic, and macromolecular amines that influence the physicochemical properties of these materials in aqueous solvents. The surface and bulk of these gels can be differentially functionalized (i.e., different functional groups on the gel surface relative to the bulk) by taking advantage of different rates of diffusion of macromolecular amines versus small molecule amines into assembled gels. Finally, these azlactone‐functionalized gels can be topographically patterned with microwell arrays using a replica molding technique and chemically modified postfabrication with amine nucleophiles. This reactive approach to the fabrication of topographically patterned and chemically functionalized hydrogels offers a straightforward method for the rapid synthesis of micropatterned scaffolds of interest in a broad range of applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3185–3194     

Cr(VI) Oxidation of Cholesterol—A Kinetic Study Using N-Cetylpicolinium Dichromates,A Class of Novel Phase Transfer Oxidants

Kinetics and Catalysis - Kinetic study of cholesterol oxidation has been studied using a series of N-cetylpicolinium dichromates (CPDC), a class of phase transfer oxidants, in acetic acid medium...