Selectivity liquid chromatography

High performance liquid chromatography-mass spectrometric methods Nitin et al. [75] developed and validated a sensitive and selective liquid chromatography-tandem mass spectrometric method (LC MS MS) for the simultaneous estimation of bulaquine and its metabolites primaquine in monkey plasma. The mobile phase consisted of acetonitrile ammonium acetate buffer (20 mM, pH 6) (50 50, v/v) at a flow rate of 1 mL/min. The chromatographic separations were achieved on two Spheri cyano columns (5 pm, 30 cm x 4.6 mm), connected in... 

A sensitive and selective liquid chromatography-tandem mass spectrometry (LC-MS-MS) assay for the simultaneous determination of donepezil (D) and its pharmacologically active metabolite, 6-O-desmethyl donepezil (6-ODD) in human plasma is developed using galantamine as IS [30]. The analytes and IS were extracted from 500 /A aliquots of human plasma via solid-phase extraction (SPE) on Waters Oasis HLB cartridges. Chromatographic separation was achieved in a rim time of 6.0 min on a Waters Novapak Ci8 (150 mm x 3.9 mm, 4 /an) column under isocratic conditions. Detection of analytes and IS was done by tandem mass... 

Patel BN, Sharma N, Sanyal M et al (2009) Analysis of second-generation antidepressant drug, sertraline and its active metabolite, N-desmethyl sertraline in human plasma by a sensitive and selective liquid chromatography-tandem mass spectrometry method. J Chromatogr B Anal Technol Biomed Life Sci 877 221-229... 

A selective liquid chromatography analysis of emu I si liable concentrates and aerosol formulations of pyrethroids, utilizing an IR spectrophotometer as a detector, was described by Papadopoulou-Mourkidou et al. (1981). The mobile phase consisted of various combinations of solvents, depending on the pyrethroids under study. 

Stationary phase optimized selectivity liquid chromatography basic possibilities of serially connected columns using the PRISMA principle. /. Chromatogr. A, 1157 (1-2), 122-130. 

Due to its high sensitivity and selectivity, liquid chromatography-mass spectrometry (LC-MS) is a powerful technique. It is used for various applications, often involving the detection and identification of chemicals in a complex mixture. Ultra Performance Liquid Chromatography Mass Spectrometry Evaluation and Applications in Food Analysis presents a unique collection of up-to-date UPLC-MS/MS methods for the separation and quantitative determination of components, contaminants, vitamins, and aroma and flavor compounds in a wide variety of foods and food products. 

S Toirado, EJ Caballero, R Cadorniga, J Torrado. A selective liquid chromatography assay for the determination of dl-a-tocopherol acetate in plasma samples. J Liq Chromatogr 18 1251-1264, 1995. 

Ballesteros-Gomez A, Rubio S, van Leeuwen S. Tetrahydrofuran-water extraction, inline clean-up and selective liquid chromatography/tandem mass spectrometry for the... 

Liquid chromatography is a separation technique based on the selective adsorption on a solid, siiica or alumina for example, or a mixture of the two, of the different components of a liquid mixture. 

Schematic diagram of an orthogonal Q/TOF instrument. In this example, an ion beam is produced by electrospray ionization. The solution can be an effluent from a liquid chromatography column or simply a solution of an analyte. The sampling cone and the skimmer help to separate analyte ions from solvent, The RF hexapoles cannot separate ions according to m/z values and are instead used to help confine the ions into a narrow beam. The quadrupole can be made to operate in two modes. In one (wide band-pass mode), all of the ion beam passes through. In the other (narrow band-pass mode), only ions selected according to m/z value are allowed through. In narrow band-pass mode, the gas pressure in the middle hexapole is increased so that ions selected in the quadrupole are caused to fragment following collisions with gas molecules. In both modes, the TOF analyzer is used to produce the final mass spectrum.

For selective estimation of phenols pollution of environment such chromatographic methods as gas chromatography with flame-ionization detector (ISO method 8165) and high performance liquid chromatography with UV-detector (EPA method 625) is recommended. For determination of phenol, cresols, chlorophenols in environmental samples application of HPLC with amperometric detector is perspective. Phenols and chlorophenols can be easy oxidized and determined with high sensitivity on carbon-glass electrode. 

Selectivity of chromatographic separation is known to be varied by changing both the nonstationary phase composition and adsorbent nature. It is shown that the less are the values of the reached selectivity coefficient the higher are the requirements to column effectiveness. In this connection the choice of stationai y phase with high and predicted selectivity coefficient for the compounds being separated is still remains a topical problem of high-performance liquid chromatography. 

It was shown that selectivity of adsorbents in liquid chromatography might be considered as sum of nonspecific and specific pai ts. The angulai factor of dependence E = f(Q,) determines nonspecific chai ge-controlled selectivity of adsorbents ... 

The value of for calcium hydroxyapatite can be defined by charge of Ca + and PO ions. From this point of view calcium hydroxyapatite can be used as high-selective adsorbents for high performance liquid chromatography because with increasing of will be rise a selectivity coefficient a. 

The liquid chromatography - tandem mass spectrometry (LC/MS/MS) technique was proposed for the determination of corticosteroids in plasma and cerebrospinal fluid (CSF, liquor) of children with leucosis. Preliminai y sample prepai ation included the sedimentation of proteins, spinning and solid-phase extraction. MS detection was performed by scanning selected ions, with three chai acteristic ions for every corticosteroids. The limit of detection was found 80 pg/ml of plasma. 

R. E. Boehm and D. E. Martiie, A unified theory of retention and selectivity in liquid chromatography. 1. Eiquid-solid (adsorption) clrromatography , J. Phys. Chem. 84 3620-3630(1980). 

S. Palmarsdottir and L. E. Edholm, Enhancement of selectivity and concentration sensitivity in capillary zone electrophoresis by on-line coupling with column liquid chromatography and utilizing a double stacking procedure allowing for microliter injections , 7. Chromatogr. 693 131-143 (1995). 

High performance liquid chromatography (HPLC) is an excellent technique for sample preseparation prior to GC injection since the separation efficiency is high, analysis time is short, and method development is easy. An LC-GC system could be fully automated and the selectivity characteristics of both the mobile and stationary... 

Figure 13.7 Selectivity effected by employing different step gradients in the coupled-column RPLC analysis of a surface water containing 0.40 p-g 1 bentazone, by using direct sample injection (2.00 ml). Clean-up volumes, (a), (c) and (d) 4.65 ml of M-1, and (b) 3.75 ml of M-1 transfer volumes, (a), (c) and (d), 0.50 ml of M-1, and (b), 0.40 ml of M-1. The displayed cliromatograms start after clean-up on the first column. Reprinted from Journal of Chromatography, A 644, E. A. Hogendoom et al, Coupled-column reversed-phase liquid chromatography-UV analyser for the determination of polar pesticides in water , pp. 307-314, copyright 1993, with permission from Elsevier Science.

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