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Organosilica materials containing [lambda]-carrageenan on their surface are synthesized. The conditions for the immobilization of the polysaccharide, such as phase contact time and pH and concentration of solutions, are optimized. It is shown that the chemisorption of the polysaccharide passes through ion exchange multipoint immobilization, which provides a high hydrolytic stability of the prepared organosilica. The rate of washing of [lambda]-carrageenan to the solution does not exceed 0.5%. The physical and chemical characteristics of the new material are studied. In particular, it is shown that the material is completely stable up to 200[degrees]C and reversibly desorbs water at 120[degrees]C; it well adsorbs 1,4-dioxane from the gas phase and desorbs it under heating to 70[degrees]C. This ensures the use of the prepared carrageenan-containing material as an adsorbent for a solid-phase cartridge designed for the adsorption preconcentration of 1,4-dioxane in its headspace gas chromatographic determination in samples of nonionic surfactants. The developed procedure ensures the determination of 1,4-dioxane by gas chromatography with a flame ionization detector in the concentration range 0.012-3.750 mg/L with a limit of detection of 0.0014 mg/L. Preconcentration lowers the limit of detection in the determination of 1,4-dioxane by 50 times. Keywords: 1,4-dioxane, GC-FID, silica, [lambda]-carrageenan, adsorption preconcentration, nonionic surfactants, 1,4-Dioxane is widely used in the chemical industry as an aprotic polar solvent, extractant, stabilizer of organochlorine substances, etc. [1]. This compound is toxic (the maximum permissible concentration in air, [...]

A polyaniline-multiwalled carbon nanotubes composite fiber was electrodeposited onto a platinum wire using cyclic voltammetry. This fiber was used for headspace solid-phase microextraction combined with gas chromatography and flame ionization detector of trace levels of benzaldehyde in some injectable pharmaceutical formulations. Three solid-phase microextraction parameters including temperature, time and stirring rate were investigated simultaneously using a three-level-three-factor Box-Behnken as experimental design on the extraction capability. The as-made fiber has a lifetime of over 300 extractions without any obvious decline in extraction efficiency. At the optimum conditions (extraction temperature 60[degrees]C, extraction time 15 min, stirring rate 700 rpm), the method displays excellent linearity over the concentration range of 25-1000 ng/mL of benzaldehyde with RSD values ranging from 1.0 to 6.8%. The limits of quantitation and detection were 25 and 10 ng/mL, respectively. Keywords: benzaldehyde, experimental design, solid-phase microextraction, GC-FID, polyaniline-multi-walled carbon nanotubes, The determination of impurities in pharmaceutical excipients is essential for the improvement of pharmaceuticals due to the toxicity of some types of them. Benzyl alcohol is an antimicrobial preservative or [...]

A method is proposed for determining formaldehyde by headspace gas chromatography using an o-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) derivatizing agent. Formaldehyde in urine was derivatized to o-(pentafluorobenzyl)oxime and extracted by heating an urine sample with PFBHA in a sealed vial. Gas-chromatographic analysis of the headspace was performed in the temperature-programmed mode using an HP-5 capillary column with a flame ionization detector. The limit of detection is 3.5 [micro]g/L. The accuracy of the procedure, equivalent to an extended relative uncertainty, does not exceed 21%. The examination of the procedure using urine samples of the population of the Irkutsk region has shown that the regional reference levels of formaldehyde concentration are in the range 44-83 [micro]g/L. Keywords: formaldehyde in urine, o-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine, headspace gas-chromatographic analysis, Determination of formaldehyde in biological media as a component of the biological monitoring of individual exposure is more relevant and appropriate than its determination in ambient air and indoor air. [...]

A simple and efficient approach as directly suspended droplet microextraction (DSDME) was applied to the determination of organochlorine pesticides in rice prior to analysis by gas chromatography--mass spectrometry (GC-MS). The extraction parameters such as organic solvent type and volume, extraction time, and ion strength were systemically optimized. Furthermore, method linearity, recovery, limits of detections (LODs), and precision were also investigated. The proposed method provided good linearity ([R.sup.2] = 0.9900-0.9996). LODs determined by GC-MS in selected-ion monitoring (SIM) mode were between 0.0005-0.033 mg/kg. The relative standard deviations (RSDs) varied from 2.0-14.0%, while the enrichment factors were between 221-550. The experimental results suggest that DSDME followed by GC-MS is a simple, sensitive, low-cost and little solvent consumption for the determination of organochlorine pesticides in rice, and has high enrichment factors suitable to trace analysis. Keywords: directly suspended droplet microextraction, GC--MS--SIM, organochlorine pesticides, residue, rice DOI:10.1134/S1061934814030095, Because of their carcinogenicity, teratogenicity and mutagenicity, the use of organochlorine pesticides is forbidden in most countries. This kind of pesticides is one of the main sources of environmental pollution. [...]

Using a bonded polymeric zwitterionic stationary phase, in HILIC mode, polar quaternary herbicides like Diquat can easily be retained, with good peak symmetry. The impact of ionic strength and organic [...]

Ibuprofen is widely known as a nonsteroidal anti-inflammatory drug. In nature it can be found in two enantiomeric forms: (S) and (R) ibuprofens. Useful as a drug agent is the [...]