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1.
ACS Omega ; 4(7): 12938-12947, 2019 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-31460420

RESUMO

Flow-through optical chromatography (FT-OC), an advanced mode of optical chromatography, achieved baseline separation of a mixture of silica microparticles (SiO2, 1.00 and 2.50 µm) and a mixture of polystyrene microparticles (PS, 1.00, 2.00, and 3.00 µm) based on particle size. Comparisons made between experimentally determined velocities for the microparticles and theoretically derived velocities from Mie theory and Stokes' law validated the data collection setup and the data analysis for FT-OC. A population shift in live macrophages (cell line IC-21, ATCC TIB-186) responding to environmental stimuli was sensitively detected by FT-OC. The average velocity of macrophages stressed by nutritional deprivation was decreased considerably together with a small but statistically significant increase in cell size. Mie scattering calculations demonstrated that the small increase in cell size of macrophages stressed by nutritional deprivation was not entirely responsible for this decrease. Confocal fluorescence microscopy and atomic force microscopy (AFM) studies revealed morphological changes of macrophages induced by nutritional deprivation, and these changes were more likely responsible for the decrease in average velocity detected by FT-OC. Confocal Raman microspectroscopy was used to shed light upon biochemical transformations of macrophages suffering from nutritional deprivation.

2.
Methods Mol Biol ; 1906: 87-97, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30488387

RESUMO

Micellar electrokinetic chromatography (MEKC) is a mode of capillary electrophoresis that allows for the separation of neutral molecules in an electric field. Typically, neutral molecules move with electroosmotic flow (EOF) or bulk flow during electrophoretic separations resulting in no temporal resolution between mixtures of neutral analytes. Inclusion of surfactant micelles in the separation buffer allows for the separation of neutral analytes from one another through association with the micelle. Here we outline the implementation of MEKC for the separation of neutral molecules using a mixture of nitroaromatic explosives and their degradation products serving as a test analyte mixture.


Assuntos
Cromatografia Capilar Eletrocinética Micelar/métodos , Substâncias Explosivas/análise , Eletro-Osmose , Substâncias Explosivas/química , Tensoativos/química
3.
Rev Sci Instrum ; 88(3): 034104, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28372430

RESUMO

A novel vapor delivery testbed, referred to as the Trace Explosives Sensor Testbed, or TESTbed, is demonstrated that is amenable to both high- and low-volatility explosives vapors including nitromethane, nitroglycerine, ethylene glycol dinitrate, triacetone triperoxide, 2,4,6-trinitrotoluene, pentaerythritol tetranitrate, and hexahydro-1,3,5-trinitro-1,3,5-triazine. The TESTbed incorporates a six-port dual-line manifold system allowing for rapid actuation between a dedicated clean air source and a trace explosives vapor source. Explosives and explosives-related vapors can be sourced through a number of means including gas cylinders, permeation tube ovens, dynamic headspace chambers, and a Pneumatically Modulated Liquid Delivery System coupled to a perfluoroalkoxy total-consumption microflow nebulizer. Key features of the TESTbed include continuous and pulseless control of trace vapor concentrations with wide dynamic range of concentration generation, six sampling ports with reproducible vapor profile outputs, limited low-volatility explosives adsorption to the manifold surface, temperature and humidity control of the vapor stream, and a graphical user interface for system operation and testing protocol implementation.

4.
J Chromatogr A ; 1451: 83-90, 2016 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-27207576

RESUMO

Hexamethylene triperoxide diamine (HMTD) is an easily synthesized and highly sensitive organic peroxide frequently used as a primary explosive. The vapor pressure of HMTD is very low, impeding vapor detection, especially when compared to other peroxide explosives, such as triacetone triperoxide (TATP) or diacetone diperoxide (DADP). Despite this fact, HMTD has a perceptible odor that could be utilized in the indirect detection of HMTD vapor. Headspace measurements above solid HMTD samples confirm that HMTD readily decomposes under ambient conditions to form highly volatile products that include formic acid, ammonia, trimethylamine and formamides. The presence and quantity of these compounds are affected by storage condition, time, and synthetic method, with synthetic method having the most significant effect on the content of the headspace. A kinetic study of HMTD decomposition in solution indicated a correlation between degradation rate and the presence of decomposition species identified in the headspace, and provided further insight into the mechanism of decomposition. The study provided evidence for a proton assisted decomposition reaction with water, as well as an intramolecular decomposition process facilitated by the presence of water.


Assuntos
Compostos Bicíclicos Heterocíclicos com Pontes/análise , Compostos Bicíclicos Heterocíclicos com Pontes/química , Substâncias Explosivas/análise , Substâncias Explosivas/química , Prótons , Água/química , Amônia/análise , Armazenamento de Medicamentos , Formamidas/análise , Formiatos/análise , Cinética , Metilaminas/análise , Fatores de Tempo , Pressão de Vapor , Volatilização
5.
Anal Chem ; 88(7): 3747-53, 2016 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-26971624

RESUMO

The generation of trace 2,4,6-trinitrotoluene (TNT), cyclotrimethylenetrinitramine (RDX), and pentaerythritol tetranitrate (PETN) vapors using a pneumatically modulated liquid delivery system (PMLDS) coupled to a polytetrafluoroethylene (PTFE) total-consumption micronebulizer is presented. The vapor generator operates in a continuous manner with final vapor concentrations proportional to the explosive concentration in aqueous solution delivered through the nebulizer and the diluent air flow rate. For quantitation of concentrations in the parts per billionvolume (ppbv) to parts per trillionvolume (pptrv) range, Tenax-TA thermal desorption tubes were used for vapor collection with subsequent analysis on a thermal-desorption system programmable-temperature vaporization gas chromatograph (TDS-PTV-GC) with a µ-ECD detector. With 30 min sample times and an average sampling rate of 100 mL min(-1), vapor concentrations of 38 pptrv for TNT, 25 pptrv for RDX, and 26 pptrv for PETN were determined. For parts per quadrillionvolume (ppqv) vapor quantitation of TNT and RDX, an online PTV-GC system with a negative-ion chemical ionization mass spectrometer (methane reagent gas) was used for direct sampling and capture of the vapor on the PTV inlet. Vapor concentrations as low as 160 ppqv and 710 ppqv for TNT and RDX were quantified, respectively, with an instrument duty cycle as low as 4 min.


Assuntos
Substâncias Explosivas/análise , Tetranitrato de Pentaeritritol/análise , Triazinas/análise , Trinitrotolueno/análise , Cromatografia Gasosa-Espectrometria de Massas , Nebulizadores e Vaporizadores , Politetrafluoretileno
6.
Analyst ; 141(7): 2191-8, 2016 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-26953357

RESUMO

Horseradish peroxidase (HRP) was encapsulated in self-assembled lithocholic acid (LCA) based organic nanotubes and its catalytic activity before and after thermal treatment was measured for comparison with free HRP. The apparent kcat (kcat/Km) for nanotube encapsulated HRP remained almost the same before and after thermal treatment, reporting an average value of 3.7 ± 0.4 µM(-1) s(-1). The apparent kcat value for free HRP decreased from 14.8 ± 1.3 µM(-1) s(-1) for samples stored at 4 °C to 2.4 ± 0.1 µM(-1) s(-1) after thermal treatment for 8 h at 55 °C. The Michaelis-Menten constants, Km, determined for encapsulated HRP and free HRP were relatively unperturbed by storage conditions at 4 °C or thermally treated at 55 °C for varying time periods from 2-8 h, with encapsulated HRP having a slightly higher Km than free HRP (13.4 ± 0.9 µM versus 11.7 ± 0.4 µM). The amount of HRP encapsulated in LCA nanotubes increased dramatically when the mixture of HRP and LCA nanotubes was brought to an elevated temperature. Within 4 h of thermal treatment at 55 °C, the amount of HRP encapsulated by the LCA nanotubes was more than 4 times the amount of HRP encapsulated when equilibrated at 4 °C for 7 days. Molecular dynamics (MD) simulations show that the higher degree of exposure of hydrophobic residues in HRP at elevated temperatures enhances the hydrophobic interaction between HRP and the nanotube wall, resulting in the increased amount of HRP surface adsorption and, hence, the overall amount of encapsulation inside the nanotubes.


Assuntos
Biocatálise , Peroxidase do Rábano Silvestre/química , Peroxidase do Rábano Silvestre/metabolismo , Nanotubos/química , Adsorção , Cápsulas , Estabilidade Enzimática , Enzimas Imobilizadas/metabolismo , Cinética , Temperatura
7.
J Chromatogr A ; 1429: 8-12, 2016 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-26718189

RESUMO

A novel analytical method has been developed for the quantitation of trace levels of ammonia in the headspace of ammonium nitrate (AN) using derivatized solid phase microextraction (SPME) fibers with gas chromatography mass spectrometry (GC-MS). Ammonia is difficult to detect via direct injection into a GC-MS because of its low molecular weight and extreme polarity. To circumvent this issue, ammonia was derivatized directly onto a SPME fiber by the reaction of butyl chloroformate coated fibers with the ammonia to form butyl carbamate. A derivatized externally sampled internal standard (dESIS) method based upon the reactivity of diethylamine with unreacted butyl chloroformate on the SPME fiber to form butyl diethylcarbamate was established for the reproducible quantification of ammonia concentration. Both of these compounds are easily detectable and separable via GC-MS. The optimized method was then used to quantitate the vapor concentration of ammonia in the headspace of two commonly used improvised explosive device (IED) materials, ammonium nitrate fuel oil (ANFO) and ammonium nitrate aluminum powder (Ammonal), as well as identify the presence of additional fuel components within the headspace.


Assuntos
Técnicas de Química Analítica/métodos , Cromatografia Gasosa-Espectrometria de Massas , Nitratos/análise , Microextração em Fase Sólida
8.
J Colloid Interface Sci ; 454: 97-104, 2015 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-26004574

RESUMO

Organic nanotubes form in aqueous solution near physiological pH by self-assembly of lithocholic acid (LCA) with inner diameters of 20-40nm. The encapsulation of enhanced green fluorescent protein (eGFP) and resultant confinement effect for eGFP within these nanotubes is studied via confocal microscopy. Timed release rate studies of eGFP encapsulated in LCA nanotubes and fluorescence recovery after photobleaching (FRAP) indicate that the diffusive transport of eGFP out of and/or within the nanotubes is very slow, in contrast to the rapid introduction of eGFP into the nanotubes. By encapsulating two fluorescent proteins in LCA nanotubes, eGFP and mCherry, as a fluorescence resonance energy transfer (FRET) pair, the FRET efficiencies are determined using FRET imaging microscopy at three different protein concentrations with a fixed donor-to-acceptor ratio of 1:1. Förster theory reveals that the proteins are spatially separated by 4.8-7.2nm in distance inside these nanotubes. The biomimetic nanochannels of LCA nanotubes not only afford a confining effect on eGFP that results in enhanced chemical and thermal stability under conditions of high denaturant concentration and temperature, but also function as protein concentrators for enriching protein in the nanochannels from a diluted protein solution by up to two orders of magnitude.


Assuntos
Proteínas de Fluorescência Verde/química , Ácido Litocólico/química , Proteínas Luminescentes/química , Nanotubos/química , Difusão , Composição de Medicamentos , Recuperação de Fluorescência Após Fotodegradação , Transferência Ressonante de Energia de Fluorescência , Cinética , Microscopia de Fluorescência , Simulação de Dinâmica Molecular , Nanotubos/ultraestrutura , Tamanho da Partícula , Estabilidade Proteica , Soluções , Termodinâmica , Água/química
9.
Rev Sci Instrum ; 85(5): 054101, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-24880386

RESUMO

A novel liquid injection vapor generator (LIVG) is demonstrated that is amenable to low vapor pressure explosives, 2,4,6-trinitrotoluene and hexahydro-1,3,5-trinitro-1,3,5-triazine. The LIVG operates in a continuous manner, providing a constant and stable vapor output over a period of days and whose concentration can be extended over as much as three orders of magnitude. In addition, a large test atmosphere chamber attached to the LIVG is described, which enables the generation of a stable test atmosphere with controllable humidity and temperature. The size of the chamber allows for the complete insertion of testing instruments or arrays of materials into a uniform test atmosphere, and various electrical feedthroughs, insertion ports, and sealed doors permit simple and effective access to the sample chamber and its vapor.

10.
J Chromatogr A ; 1331: 38-43, 2014 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-24508355

RESUMO

Two methods for quantitation of triacetone triperoxide (TATP) vapor using a programmable temperature vaporization (PTV) inlet coupled to a gas chromatography/mass spectrometer (GC/MS) have been demonstrated. The dynamic headspace of bulk TATP was mixed with clean humid air to produce a TATP vapor stream. Sampling via a heated transfer line to a PTV inlet with a Tenax-TA™ filled liner allowed for direct injection of the vapor stream to a GC/MS for vapor quantitation. TATP was extracted from the vapor stream and subsequently desorbed from the PTV liner for splitless injection on the GC column. Calibration curves were prepared using solution standards with a standard split/splitless GC inlet for quantitation of the TATP vapor. Alternatively, vapor was sampled onto a Tenax-TA™ sample tube and placed into a thermal desorption system. In this instance, vapor was desorbed from the tube and subsequently trapped on a liquid nitrogen cooled PTV inlet. Calibration curves for this method were prepared from direct liquid injection of standards onto samples tube with the caveat that a vacuum is applied to the tube during deposition to ensure that the volatile TATP penetrates into the tube. Vapor concentration measurements, as determined by either GC/MS analysis or mass gravimetry of the bulk TATP, were statistically indistinguishable. Different approaches to broaden the TATP vapor dynamic range, including diluent air flow, sample chamber temperature, sample vial orifice size, and sample size are discussed. Vapor concentrations between 50 and 5400ngL(-1) are reported, with stable vapor generation observed for as long as 60 consecutive hours.


Assuntos
Ar/análise , Substâncias Explosivas/análise , Compostos Heterocíclicos com 1 Anel/análise , Peróxidos/análise , Cromatografia Gasosa-Espectrometria de Massas/métodos , Temperatura Alta , Volatilização
11.
Anal Chem ; 85(18): 8647-53, 2013 Sep 17.
Artigo em Inglês | MEDLINE | ID: mdl-23964641

RESUMO

Results are reported from a combined optical force and electrokinetic microfluidic device that separates individual particulates from molecular components in a mixed sample stream. A pico-Newton optical force was applied to an orthogonal electroosmotic flow carrying a hydrodynamically pinched, mixed sample, resulting in the separation of the various particles from the sample stream. Different combinations of polystyrene, PMMA, and silica particles with a commercially available dye were utilized to test the different separation modes available, from purely optical force to combined optical and electrophoretic forces. The impact of various particle properties on particle separation and separation efficiency were explored, including size (2, 6, 10 µm), refractive index, and electrophoretic mobility. Particle addressability was achieved by moving particles to different outlets on the basis of particle size, refractive index, and electrophoretic differences. Separations of 6 and 10 µm polystyrene particles led to only 3% particle contamination in the original sample stream and interparticle type enrichment levels >80%. The unique addressability of three different particle materials (polystyrene, PMMA, and silica) of the same size (2 µm) led to each being separated into a unique outlet without measurable contamination of the other particle types using optical force and electrophoretic mobility. In addition to particle separation, the device was able to minimize dye diffusion, leading to >95% dye recovery. This combined platform would have applications for noninvasive sample preparation of mixed molecular/particulate systems for mating with traditional analytics as well as efficient removal of harmful, degrading components from complex mixtures.

12.
Electrophoresis ; 34(8): 1175-81, 2013 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-23404174

RESUMO

Presented here are the results from numerical simulations applying optical forces orthogonally to electroosmotically induced flow containing both molecular species and particles. Simulations were conducted using COMSOL v4.2a Multiphysics® software including the particle tracking module. The study addresses the application of optical forces to selectively remove particulates from a mixed sample stream that also includes molecular species in a pinched flow microfluidic device. This study explores the optimization of microfluidic cell geometry, magnitude of the applied direct current electric field, EOF rate, diffusion, and magnitude of the applied optical forces. The optimized equilibrium of these various contributing factors aids in the development of experimental conditions and geometry for future experimentation as well as directing experimental expectations, such as diffusional losses, separation resolution, and percent yield. The result of this work generated an optimized geometry with flow conditions leading to negligible diffusional losses of the molecular species while also being able to produce particle removal at near 100% levels. An analytical device, such as the one described herein with the capability to separate particulate and molecular species in a continuous, high-throughput fashion would be valuable by minimizing sample preparation and integrating gross sample collection seamlessly into traditional analytical detection methods.


Assuntos
Eletro-Osmose/instrumentação , Técnicas Analíticas Microfluídicas/instrumentação , Simulação por Computador , Microesferas , Tamanho da Partícula , Software
13.
J Chromatogr A ; 1282: 178-82, 2013 Mar 22.
Artigo em Inglês | MEDLINE | ID: mdl-23415141

RESUMO

A simple method for establishing calibration curves with sorbent-filled thermal desorption tubes has been demonstrated for nitroaromatic and nitramine vapor samples using a thermal desorption system with a cooled inlet system (TDS-CIS), which was coupled to a gas chromatograph (GC) with an electron capture detector (ECD). The method relies upon the direct liquid deposition of standard solutions onto the glass frit at the head of sorbent-filled thermal desorption tubes. Linear calibration results and ideal system conditions for the TDS-CIS-GC-ECD were established for mixtures containing both cyclotrimethylenetrinitramine, a.k.a. RDX, and 2,4,6-trinitrotoluene (TNT). Because of the chemical characteristics of RDX, a higher TDS-CIS flow rate relative to the optimized approach for TNT was required for efficient RDX desorption. Simultaneous quantitation of TNT and RDX using the direct liquid deposition method with optimized instrumentation parameters for RDX were compared to results from a standard split/splitless GC inlet and a CIS.


Assuntos
Cromatografia Gasosa/métodos , Triazinas/análise , Calibragem , Modelos Lineares , Trinitrotolueno/análise
14.
Lab Chip ; 12(6): 1128-34, 2012 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-22315144

RESUMO

A unique microfluidic system is developed which enables the interrogation of a single particle by using multiple force balances from a combination of optical force, hydrodynamic drag force, and electrophoretic force. Two types of polystyrene (PS) particles with almost identical size and refractive index (plain polystyrene (PS) particle - mean diameter: 2.06 µm, refractive index: 1.59; carboxylated polystyrene (PS-COOH) particles - mean diameter: 2.07 µm, refractive index: 1.60), which could not be distinguished by optical chromatography, reveal different electrokinetic behaviors resulting from the difference in their surface charge densities. The PS-COOH particles, despite their higher surface charge density when compared to the PS particles, experience a lower electrophoretic force, regardless of ionic strength. This phenomenon can be understood when the more prominent polarization of the counter ion cloud surrounding the PS-COOH particles is considered. The surface roughness of the carboxylated particles also plays an important role in the observed electrokinetic behavior.

15.
J Chromatogr A ; 1217(45): 7153-7, 2010 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-20926092

RESUMO

The packing of submicrometer sized silica beads inside a microchannel was enabled by a novel method which avoids the complication and limitations of generating a frit using conventional approaches and the restriction of flow using a submicrometer sized weir. A micrometer sized weir and two short columns of 5 µm and 800 nm silica beads packed in succession behind the weir together functioned as a high pressure frit to allow the construction of a primary packed bed of 390 nm silica beads. This packed bed microchannel was tested as an EOF pump, wherein it exhibited superior performance with regards to pressure tolerance, i.e., sustaining good flow rate under extremely high back pressure, and maximal pressure generation. Under a modest applied electric field strength of 150 V/cm, the flow rate against a back pressure of 1200 psi (∼8.3 MPa) was 40 nL/min, and the maximal pressure reached 1470 psi (∼10 MPa). This work has demonstrated that it is possible to create a high performance packed bed microchannel EOF pump using nanometer sized silica beads, as long as proper care is taken during the packing process to minimize the undesirable mixing of two different sized particles at the boundaries between particle segments and to maximize the packing density throughout the entire packed bed.


Assuntos
Eletro-Osmose/instrumentação , Eletro-Osmose/métodos , Dispositivos Lab-On-A-Chip , Nanopartículas/ultraestrutura , Algoritmos , Estabilidade de Medicamentos , Desenho de Equipamento , Microscopia Eletrônica de Varredura , Modelos Teóricos , Tamanho da Partícula , Pressão , Dióxido de Silício
16.
J Chromatogr A ; 1217(26): 4487-93, 2010 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-20452605

RESUMO

Practical considerations for the injection and separation of nitroaromatic explosives in seawater sample matrices are discussed. The use of high surfactant concentrations and long electrokinetic injections allows for improved detection limits. Sensitivity was enhanced by two mechanisms, improved stacking at the detector-side of the sample plug and desorption of analyte from the capillary wall by surfactant-containing BGE from the inlet side of the sample plug. Calculated limits of detection (S/N=3) for analytes prepared in pure seawater were 70-800 ppb with injection times varying from 5 to 100 s.


Assuntos
Cromatografia Capilar Eletrocinética Micelar/métodos , Substâncias Explosivas/química , Nitrocompostos/química , Água do Mar/análise , Poluentes Químicos da Água/química
17.
Lab Chip ; 9(7): 954-60, 2009 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-19294307

RESUMO

A fritless, microchip electroosmotic flow (EOF) pump is microfabricated and demonstrated on a planar soda lime glass substrate to be capable of supplying reasonable flow rates under high back pressures, such as that required for micro-high pressure liquid chromatography (micro-HPLC). The microchip EOF pump is composed of a densely packed microchannel containing 800 nm silica particles and was capable of generating a maximum pressure > 1000 psi ( approximately 7 MPa) and a maximum flow rate of 282 nL/min (aqueous cyclohexylamino alkyl sulfonate (CHES) buffer, 10 mM, pH 9.0, 200 V/cm). Other pumping fluids, such as CHES buffer-acetonitrile mixture (50%, v/v), CHES buffer-methanol mixture (50%, v/v), and pure acetonitrile were also used in a characterization of pump performance that included determinations of the maximum flow rate, maximum pressure, and resulting flow rate against an applied, downstream back pressure. The flow rate under a 200 psi ( approximately 1.4 MPa) back pressure at an applied electric field strength of 250 V/cm ranged from 285 nL/min for aqueous CHES buffer to 44 nL/min for CHES buffer-acetonitrile mixture (50%, v/v), indicating that this EOF pump will meet the future requirements of a micro-HPLC system.

18.
Anal Chem ; 80(21): 8287-92, 2008 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-18837518

RESUMO

An electroosmotic flow (EOF)-based pump, integrated with a sol-gel stationary phase located in the electric field-free region of a microchip, enabled the separation of six nitroaromatic and nitramine explosives and their degradation products via liquid chromatography (LC). The integrated pump and LC system were fabricated within a single quartz substrate. The pump region consisted of a straight channel (3.0 cm x 230 microm x 100 microm) packed with 5-microm porous silica beads. The sol-gel stationary phase was derived from a precursor mixture of methyltrimethoxy- and phenethyltrimethoxysilanes and was synthesized in the downstream, field-free region of the microchip, resulting in a stationary-phase monolith with dimensions of 2.6 cm x 230 microm x 100 microm. Fluid dynamic design considerations are discussed, especially as they relate to integrating the EOF pump with the LC system. Pump and separation performance, as characterized by flow rate measurements, injection, elution, separation, and detection, point to a viable analytical chemistry platform that encompasses all of the benefits expected of portable, laboratory-on-chip systems, including reduced sample requirements and small packaging.

19.
J Sep Sci ; 31(21): 3727-31, 2008 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-18925621

RESUMO

Implementation of an uncomplicated SPE process for the rapid extraction and preconcentration of the alkaloids, colchicine, strychnine, aconitine, and nicotine, from water, apple juice, and nonfat milk samples is presented. When coupled to analysis via micellar EKC (MEKC), the total analysis time per sample was less than 15 min for the water and juice samples and less than 20 min for the milk. The SPE process allowed for anywhere from a three to a fourteen-fold improvement in the LOD for each alkaloid when compared to detecting the alkaloids in a nontreated water sample matrix. Following SPE, the LODs for colchicine, strychnine, and nicotine were sufficient to meet levels from 150 to 5000 times more dilute than the LD(50) for a 50 kg individual drinking 12 oz of a contaminated beverage. Aconitine, on the other hand, was detected at approximately the LD(50) level. The percent recoveries for the SPE ranged from 37% to as high as 99%. Nicotine attained the highest recovery efficiencies, followed by colchicine, and finally, aconitine and strychnine, which were nearly identical. The greatest recovery efficiencies were achieved from apple juice and water, whereas nonfat milk yielded the lowest.


Assuntos
Alcaloides/análise , Bebidas/análise , Cromatografia Capilar Eletrocinética Micelar/métodos , Espectrofotometria Ultravioleta/métodos , Aconitina/análise , Aconitina/isolamento & purificação , Alcaloides/isolamento & purificação , Animais , Colchicina/análise , Colchicina/isolamento & purificação , Contaminação de Alimentos , Humanos , Estrutura Molecular , Nicotina/análise , Nicotina/isolamento & purificação , Sensibilidade e Especificidade , Estricnina/análise , Estricnina/isolamento & purificação
20.
Electrophoresis ; 29(4): 803-10, 2008 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-18203247

RESUMO

A microchip device is demonstrated for the electrophoretic separation and UV-absorbance spectral detection of four toxic alkaloids: colchicine, aconitine, strychnine, and nicotine. A fused-silica (quartz) microchip containing a simple cross geometry is utilized to perform the separations, and a miniature, fiber-optic CCD spectrometer is coupled to the microchip for detection. Sensitive UV-absorbance detection is achieved via the application of online preconcentration techniques in combination with the quartz microchip substrate which contains an etched bubble-cell for increased pathlength. The miniature CCD spectrometer is configured to detect light between 190 and 645 nm and LabView programming written in-house enables absorbance spectra as well as separations to be monitored from 210 to 400 nm. Consequently, the configuration of this microchip device facilitates qualitative and quantitative separations via simultaneous spatial and spectral resolution of solutes. UV-absorbance limits of quantification for colchicine, 20 microM (8 mg/L); strychnine, 50 microM (17 mg/L); aconitine, 50 microM (32 mg/L); and nicotine, 100 microM (16 mg/L) are demonstrated on the microchip. With the exception of aconitine, these concentrations are > or =20-times more sensitive than lethal dose monitoring requirements. Finally, this device is demonstrated to successfully detect each toxin in water, skim milk, and apple juice samples spiked at sublethal dose concentrations after a simple, SPE procedure.


Assuntos
Aconitina/análise , Cromatografia Capilar Eletrocinética Micelar/métodos , Colchicina/análise , Eletroforese em Microchip/métodos , Nicotina/análise , Estricnina/análise , Eletroforese em Microchip/instrumentação , Espectrofotometria Ultravioleta/métodos
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