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Carbon nanotube assisted sol-gel based hollow fiber solidphase microextraction combined with pre-heating injectionhigh performance liquid chromatography as a novel sample preparation method for determination of nitroaromatics

100%
Golsefidi M. A., Es’haghi Z., Sarafraz-Yazdi A.
Sample Preparation
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2013
|
vol. 1
1-9
EN
A solid-phase microextraction sorbent composite was developed using the sol-gel technique. The multi-walled carbon nanotubes (MWCNTs) were added to a nanocomposite and the homogeneous, doped composite was injected into a polypropylene hollow fiber. This device has been applied for the determination of three nitro aromatic compounds, including m-nitroaniline (NA), nitrobenzene (NB) and p-nitrotoluene (NT), in environmental waters via direct immersion hollow fiber solid-phase microextraction (HF-SPME) and high performance liquid chromatography-photodiode array detector (HPLC-PDA). The results illustrated that this new technique is a simple and reliable method for SPME device preparation: the prepared sorbent did not swell in organic solvents and possessed high mechanical strength; the SPME device employed was not fragile because of the polypropylene protector fiber; and, the fiber was disposable such that no carry-over effects were present. A homemade, pre-heating electrical device was designed for the back-extraction and pre-concentration of the analytes and was utilized before the HPLC injection step. Using this trap significantly increased the efficiency and analyte pre-concentration factors. In optimal conditions, the detection limits of the analytes varied between 0.1 and 3.0 ng mL-1 (n=8), precision was in the range of 0.41–4.19% (n = 3) and linear ranges were within 1.0 - 1000 ng mL-1 for m-nitroaniline; 0.5 - 1000 ng mL-1 for nitrobenzene and 5.0 - 1000 ng mL-1 for p-nitrotoluene. The method was successfully applied to the analysis of environmental water samples with recoveries from 87.9 to 96.1%.
2
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Determination of some frequently used antibiotics in waste waters using solid phase extraction followed by high performance liquid chromatography with diode array and mass spectrometry detection

88%
Opriş O., Soran M.-L., Coman V., Copaciu F., Ristoiu D.
Open Chemistry
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2013
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vol. 11
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issue 8
1343-1351
EN
This study is focused on the determination of some important antibiotics from different classes in waste water samples using solid phase extraction followed by high performance liquid chromatography with two detectors, diode array and mass spectrometer in positive ionisation mode. The investigated antibiotics include three penicillins (amoxicillin, ampicillin, penicillin G), two cephalosporins (ceftazidime, ceftriaxone), and two tetracyclines (tetracycline, doxycycline). The studied antibiotics were extracted from waste water samples using hydrophilic-lipophilic balanced cartridges. The extraction of antibiotics from water matrices was tested at several pH values. The best recoveries were obtained at pH 3 and 7 respectively. Depending on the nature of antibiotic, the limits of detection and quantification were obtained in the range of 0.07–0.92 µg mL−1 and 0.21–2.77 µg mL−1 respectively. Influent and effluent waste water samples were collected from a Waste Water Treatment Plant from Romania in order to detect the studied antibiotics. The antibiotics detected in the influent waste water samples were ceftriaxone (334 µg L−1), tetracycline (146 µg L−1) and doxycycline (110 µg L−1). In effluent waste water samples no target antibiotics were detected. [...]
3
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Analysis of alkaloids from different chemical groups by different liquid chromatography methods

88%
Petruczynik A.
Open Chemistry
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2012
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vol. 10
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issue 3
802-835
EN
Alkaloids are biologically active compounds widely used as pharmaceuticals and synthesised as secondary methabolites in plants. Many of these compounds are strongly toxic. Therefore, they are often subject of scientific interests and analysis. Since alkaloids - basic compounds appear in aqueous solutions as ionized and unionized forms, they are difficult for chromatographic separation for peak tailing, poor systems efficiency, poor separation and poor column-to-column reproducibility. For this reason it is necessity searching of more suitable chromatographic systems for analysis of the compounds. In this article we present an overview on the separation of selected alkaloids from different chemical groups by liquid chromatography thus indicating the range of useful methods now available for alkaloid analysis. Different selectivity, system efficiency and peaks shape may be achieved in different LC methods separations by use of alternative stationary phases: silica, alumina, chemically bonded stationary phases, cation exchange phases, or by varying nonaqueous or aqueous mobile phase (containing different modifier, different buffers at different pH, ion-pairing or silanol blocker reagents). Developments in TLC (NP and RP systems), HPLC (NP, RP, HILIC, ion-exchange) are presented and the advantages of each method for alkaloids analysis are discussed. [...]
4
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Recentchiral selectors for separation in HPLC and CE

88%
Kalíková K., Riesová M., Tesařová E.
Open Chemistry
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2012
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vol. 10
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issue 3
450-471
EN
Enantiomers (stereoisomers) can exhibit substantially different properties if present in chiral environments. Since chirality is a basic property of nature, the different behaviors of the individual enantiomers must be carefully studied and properly treated. Therefore, enantioselective separations are a very important part of separation science. To achieve the separation of enantiomers, an enantioselective environment must be created by the addition of a chiral selector to the separation system. Many chiral selectors have been designed and used in various fields, such as the analyses of drugs, food constituents and agrochemicals. The most popular have become the chiral selectors and/or chiral stationary phases that are of general use, i.e., are applicable in various separation systems and allow for chiral separation of structurally different compounds. This review covers the most important chiral selectors / chiral stationary phases described and applied in high performance liquid chromatography and capillary electrophoresis during the period of the last three years (2008–2011). [...]
5
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Dispersive liquid-liquid microextraction and liquid chromatographic determination of pentachlorophenol in water

88%
Farhadi K., Farajzadeh M., Matin A., Hashemi P.
Open Chemistry
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2009
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vol. 7
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issue 3
369-374
EN
A simple and sensitive dispersive liquid-liquid microextraction method for extraction and preconcentration of pentachlorophenol (PCP) in water samples is presented. After adjusting the sample pH to 3, extraction was performed in the presence of 1% W/V sodium chloride by injecting 1 mL acetone as disperser solvent containing 15 μL tetrachloroethylene as extraction solvent. The proposed DLLME method was followed by HPLC-DAD for determination of PCP. It has good linearity (0.994) with wide linear dynamic range (0.1–1000 μg L−1) and low detection limit (0.03 μg L−1), which makes it suitable for determination of PCP in water samples. [...]
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