Measurement of ketoprofen in horse urine using gas chromatography-mass spectrometry.

A gas chromatographic-mass spectrometric (GC-MS) method for the determination of ketoprofen, a non-steroidal anti-inflammatory drug (NSAID), in horse urine by selected ion monitoring (SIM) mode is described. Urine samples (2 mL) were extracted by liquid-liquid extraction with diethyl ether. The residues were then evaporated, derivatized and injected into the GC-MS system. Validation of the GC-MS method in the SIM mode using flurbiprofen as the internal standard (IS) included linearity studies (10-10 000 ng/mL), recovery (95%) and limit of quantitation (LOQ) (10 ng/mL). The response was linear, with a correlation coefficient (0.9998) for ketoprofen. When applied to horse urine samples, the present method allowed detection of ketoprofen up to 16 days in FULL SCAN mode after a topical application of 1.1 g of ketoprofen in a gel formulation.

Evaluation on the adsorption capabilities of new chemically modified polymeric adsorbents with protoporphyrin IX.

A chemically modified polymeric adsorbent was synthesized to evaluate the availability as an adsorbent for solid-phase extraction (SPE) of phenol and chlorophenols. Commercially available Amberlite XAD-2 and XAD-4 resins were modified with macrocyclic protoporphyrin IX (PPIX) through the ketone linkage. Adsorption isotherms were obtained by batch experiments and the data were fitted to the Freundlich equation to calculate the adsorption parameters. Breakthrough volumes were measured by column experiments. Physical properties such as surface area, average pore diameter and micropore volume of resins were measured to correlate with the adsorption characteristics. As a result, adsorption capacity was increased for the chemically modified resins and it can be concluded that the increase of pi-pi interaction due to the introduction of the porphyrin molecule is the major factor for the increase of the adsorption capacity.

A disposable amperometric sensor screen printed on a nitrocellulose strip: a glucose biosensor employing lead oxide as an interference-removing agent.

A new type of disposable amperometric sensor is devised by screen printing thick-film electrodes directly on a porous nitrocellulose (NC) strip. The chromatographic NC strip is then utilized to introduce various sample pretreatment layers. As a preliminary application, a glucose biosensor based on hydrogen peroxide detection is constructed by immobilizing glucose oxidase (GOx) on the NC electrode strip and by formulating a strong oxidation layer (i.e., PbO2) at the sample loading area, placed below the GOx reaction band. The screen-printed PbO2 paste serves as a sample pretreatment layer that removes interference by its strong oxidizing ability. Samples applied are carried chromatographically, via the PbO2 paste, to the GOx layer, and glucose is catalyzed to liberate hydrogen peroxide, which is then detected at the electrode surface. The proposed NC/PbO2 strip sensor is shown to be virtually insusceptible to interfering species such as acetaminophen and ascorbic and uric acids and to exhibit good performance, in terms of the sensor-to-sensor reproducibility (standard deviation, +/-0.026 - +/-0.086 microA), the sensitivity (slope, -0.183 microA/mM), and the linearity (correlation coefficient, 0.994 in the range of 0-10 mM).

Ion chromatography detector based on solid-state ion-selective electrode array.

A variety of neutral carrier type ionophores for monovalent cations were employed to prepare solid-state cation-selective electrodes (SSEs) for use as a detector in single-column ion chromatography (IC). The polyurethane-based pseudoreference electrode made it possible to assemble an array type SSE detector for IC. An SSE-based detector provides not only the overall chromatogram for the separated ion species (monensin methyl ester-nonactin-based membrane), but also the enhanced chromatogram for specified ions of interest (valinomycin as K+ and nonactin for NH4+). This feature makes it possible to perform highly quantitative analysis with low detection limits even if the separation efficiency of the ion-exchange is not sufficient. Since SSE-based IC detectors are easily miniaturized and replaceable at low cost, they are an ideal component of a portable IC system.

Toluene distribution of glue sniffers' biological fluid samples in Korea.

We have studied the distribution of toluene in glue sniffers' biological fluid samples by gas chromatography or gas chromatography/mass spectrometry. The determined toluene concentrations ranged from 0.1 to 40.3 mg/L in urine samples and from 0.1 to 74.7 mg/L in blood samples, respectively. Among the 120 urine samples, 61% of all cases ranged between 0.1 and 1.0 mg/L and 27% was between 1.0 and 5.0 mg/L, respectively. On the other hand, 39% and 46% of all 99 blood samples ranged between 0.1 and 1.0 mg/L, or 1.0 and 5.0 mg/L, respectively. In the fatal cases (36 cases), the distribution of toluene ranged from 0.3 to 40.5 mg/L in the blood samples.