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1
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Ultratrace-level determination of N-Nitrosodimethylamine, N-Nitrosodiethylamine, and N-Nitrosomorpholine in waters by solid-phase extraction followed by liquid chromatography-tandem mass spectrometry

100%
Kadmi Y., Favier L., Soutrel I., Lemasle M., Wolbert D.
Open Chemistry
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2014
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vol. 12
|
issue 9
928-936
EN
N-nitrosamines are a new class of emerging nitrogenous drinking water disinfection by-products. These compounds are probably carcinogenic which could seriously affect the safety of drinking water consumers. The aim of this study is to develop a simple, fast, and specific analytical method for the routine determination of low part per trillion levels of N-nitrosamines in waters. An ultra high pressure liquid chromatography coupled with tandem mass spectrometry (UHPLC/MS/MS) method was developed for the qualitative and quantitative analysis of N-nitrosamines in waters. N-nitrosamines were extracted, purified and concentrated from water samples in one step using a solid-phase extraction (SPE). The compounds were detected in multiple reaction monitoring via electrospray ionisation source with positive ionisation mode. To achieve symmetrical peak shapes and a short chromatographic analysis time, the mobile phase consisting of acetonitrile, water and formic acid (60:40:0.1, v/v/v) was used in the experiment. Chromatographic separation of N-nitrosamines was done in less than two minutes. All calibration curves had good linearity (r2≥ 0.9989). The intra- and inter-day precision of the assay ranged from 0.59% to 3.11% and accuracy ranged from 99.66% to 104.1%. The mean recoveries of N-nitrosamines in spiked water were 98%-101%. The reproducability was acceptable with relative standard deviations of less than 3.53%. The proposed method yielded detection limits very low which ranges from 0.04 to 0.16 ng L−1. Finally, the developed analytical method was successfully applied to the analysis of N-nitrosamines in natural water sample
2
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Use of multivariate statistical techniques to optimize the separation of isoflavones by liquid chromatography

100%
Baranowska I., Magiera S., Baranowski J.
Open Chemistry
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2011
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vol. 9
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issue 6
972-981
EN
The aim of this paper is to optimize and validate a high performance liquid chromatography (HPLC) method for separation and quantification of five isoflavones. A statistical central composite design was used to separate all peaks. These multivariate procedures were efficient in determining the optimal separation condition using resolution, capacity factor, asymmetry and number of theoretical plates. [...] The effective separation of the examined compounds was applied on a Develosil RP Aqueous AR 5 RP-30 column with a gradient mobile phase system and a DAD detector. The isolation and preconcentration of the isoflavones from urine and plasma samples were conducted by means of the solid-phase extraction (SPE). For optimize SPE conditions various sorbents were tested. Furthermore, high recoveries and good relative standard deviations were obtained when the samples were passed through the Oasis HLB column. The developed method was validated and successfully applied for determination of isoflavones in urine and plasma.
3
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The bifunctionality of silica gel modified with Congo red

100%
Kurczewska J., Schroeder G.
Open Chemistry
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2011
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vol. 9
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issue 1
41-46
EN
Silica gel was chemically modified with Congo red and characterized by Fourier transform infrared spectroscopy, elemental and thermogravimetric analysis. The pH-sensitive immobilized Congo red retains the same properties as its solution counterpart and could be applied as solid indicator. The functionalized silica gel was also employed to extract different cations from water solutions. The concentration of cations extracted was determined by inductively coupled plasma optical emission spectrometry. The solid support is able to selectively extract silver and copper from water solutions and retains its properties after treatment with different organic and inorganic solvents. [...]
4
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Targeted extraction of active compounds from natural products by molecularly imprinted polymers

100%
Pardo A., Mespouille L., Dubois P., Duez P., Blankert B.
Open Chemistry
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2012
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vol. 10
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issue 3
751-765
EN
One of the most promising separation techniques that have emerged during the last decade is based on the use of molecularly imprinted polymers (MIPs). MIPs are stable polymers that possess specific cavities designed for a template molecule, endowed with excellent selectivity compared to regular solid phase extraction techniques. Molecularly imprinted solid-phase extraction (MISPE) has already shown a high efficiency for the sample preparation from complex matrices. Natural products received huge attention in recent years. Indeed, the application of MISPE for the screening of natural products appears extremely interesting not only for the selective extraction of a target compound but also for the concomitant discovery of new drug candidates, promising sources of therapeutic benefits. In the present review, examples of recognition and separation of active components from natural extracts are emphasized. MIPs are very promising materials to mimic the recognition characteristics exhibited by enzymes or receptors although further developments are necessary to fully exploit their wide potential.
5
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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. [...]
6
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Application of poly (N-phenylethanolamine) modified MWCNTs as a new sorbent for solid-phase extraction of trace palladium ions in soil and water samples

75%
Behbahani M., Bagheri A., Gorji T., Nabid M. R., Sedghi R., Oskooie H. A., Heravi M. M.
Sample Preparation
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2013
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vol. 1
10-17
EN
This paper describes, a new, sensitive, and low cost solid-phase extraction (SPE) method using a poly(N-phenylethanolamine) /multi-walled carbon nanotubes (MWCNTs) nanocomposite for extraction, pre-concentration, and flame atomic absorption spectrometric (FAAS) determination of trace level palladium in distilled water, tap water, Caspian sea water, Persian Gulf water, spring water, lake water and soil samples, as well as real samples. The poly(N-phenylethanolamine)/MWCNTs nanocomposite were characterized using Fourier Transform-infrared (FT-IR) spectroscopy, thermo-gravimetric analysis (TGA) and scanning electron microscopy (SEM). Factors affecting the pre-concentration of palladium, including sample pH, flow rate, and type and volume of eluent, were investigated. The effect of interfering ions and break through volume on the separation and determination of palladium ions was also determined. The maximum sorbent capacity of the poly (N-phenylethanolamine)/MWCNTs nanocomposite was calculated to be 101.5 mg g−1. The pre-concentration factor, relative standard deviation, and limit of detection of the method were found to be 150, 2.8% (n=10), and 0.09 ng mL−1, respectively. The presented method was compared to certified reference materials, and finally, the presented technique was applied to different matrices spiked with 5 ng mL−1 of analyte.
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