Simple and rapid extraction, separation, and detection of alkaloids in beverages.

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.

Microchip micellar electrokinetic chromatography separation of alkaloids with UV-absorbance spectral detection.

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.

Micellar electrokinetic chromatography and capillary electrochromatography of nitroaromatic explosives in seawater.

The ability to separate nitroaromatic and nitramine explosives in seawater sample matrices is demonstrated using both MEKC and CEC. While several capillary-based separations exist for explosives, none address direct sampling from seawater, a sample matrix of particular interest in the detection of undersea mines. Direct comparisons are made between MEKC and CEC in terms of sensitivity and separation efficiency for the analysis of 14 explosives and explosive degradation products in seawater and diluted seawater. The use of high-salt stacking with MEKC results, on average, in a three-fold increase in the number of theoretical plates, and nearly double resolution for samples prepared in 25% seawater. By taking advantage of long injection times in conjunction with stacking, detection limits down to sub mg/L levels are attainable; however, resolution is sacrificed. CEC of explosive mixtures using sol-gels prepared from methyltrimethoxysilane does not perform as well as MEKC in terms of resolving power, but does permit extended injection times for concentrating analyte onto the head of the separation column with little or no subsequent loss in resolution. Electrokinetic injections of 8 min at high voltage allow for detection limits of explosives below 100 microg/L.

Ultraviolet absorbance detection of colchicine and related alkaloids on a capillary electrophoresis microchip.

The separation and UV absorbance detection of four toxic alkaloids, colchicine, thiocolchicine, colchicoside, and thiocolchicoside, on a microchip-based capillary electrophoresis device are reported. To increase the sensitivity of UV absorbance detection, optical cells with extended path lengths were integrated into the separation channel during the microfabrication process. The absorbance values realized on the microchip using these optical cells were proportional to the increase in average depths according to the Beer-Lambert Law, resulting in sensitivity enhancements by as much as five times. Linearity of response was observed from 5.0 to 500 mg L(-1) of colchicine, with detection limits ranging from 2 to 6 mg L(-1) depending upon the specific alkaloid and the dimension of the optical cell. The extraction of colchicine from spiked milk samples was performed and an average recovery rate of 83% with a relative standard deviation of 3.8% was determined using the optimized conditions on the microchip.

Colorimetric detection of uranium(VI) on building surfaces after enrichment by solid phase extraction.

A method for detecting and quantifying uranium(VI) levels on building materials that include concrete, Plexiglas, glass and steel surfaces is presented. Uranium(VI) was extracted from building material surfaces using a pH 2.2 buffer rinse and, subsequently complexed by an organic chelating agent, arsenazo III. The application of a uranium-chelating molecule, arsenazo III, allows for concentration enhancement using C(18) solid phase extraction and colorimetric detection of the uranium complex using ultraviolet-visible spectroscopy at 654nm. The method has a detection limit (based on 3sigma) of 40ng/L (5ng/cm(2)) and an overall extraction efficiency greater than 80% for each surface type (concrete, Plexiglas, glass, steel). Methods to prevent interference by metal ions commonly found on building materials are discussed.

Separation of thiol and cyanide hydrolysis products of chemical warfare agents by capillary electrophoresis.

The fluorescence derivatizing agent, o-phthalaldehyde (OPA), has been applied to the separation and detection of cyanide and several structurally similar thiols by capillary electrophoresis (CE)-laser induced fluorescence (LIF). Of particular interest to this investigation was the separation of 2-dimethylaminoethanethiol, 2-diethylaminoethanethiol, and cyanide, each of which are hydrolysis products or hydrolysis product simulants of the chemical warfare (CW) agents O-ethyl S-2-diisopropylaminoethyl methylphosphonothiolate (VX), O-isobutyl S-2-diethylaminoethyl methylphosphonothiolate (R-VX), and tabun (GA). Other structurally similar thiols simultaneously resolved by this method include 1-pentanethiol and 2-mercaptoethanol. Instrumental parameters were probed and optimum values for capillary length (50 cm) and inner diameter (75 microm), injection time (30 s) and field strength (15 kV) were determined. Sample stacking methods enabled detection limits of 9.3 microg/L for cyanide, 1.8 microg/L for 2-diethylaminoethanethiol, 35 microg/L for 2-dimethylaminoethanethiol, 15 microg/L for 2-mercaptoethanol, and 89 microg/L for 1-pentanethiol. The linearity of the method was verified over an order of magnitude and the reproducibility was found to be 3.0%.

Capillary electrophoresis as a method for ozone determination in atmospheres.

Capillary electrophoresis (CE) is used to quantify nitrate and nitrite extracted from nitrite-impregnated glass fiber filters (IGFF) that are used to monitor ozone in atmospheres. The amount of nitrate produced from conversion of nitrite in the filters is directly related to the amount of ozone passed over the filter. The limit of detection for ozone using the CE method is 1.17 ppml and the method is linear over two orders of magnitude. The effect of the excess nitrite in the IGFF on the limits of detection is discussed. Results from CE analyses of both active and passive filters are presented. The active filter results are compared to ion chromatographic analyses.