Chromatographic performance phase ratio

Throughout the optimization procedure, the role played by the capacity ratio has not been examined, and (k ) has been treated as a constant in the equations. As a consequence, the effect of the magnitude of (k1) on chromatographic performance has not been considered, This is because, in choosing the phase system to provide the maximum separation ratio for the critical pair, the value for (k ) is automatically defined by the phase system... 

Gagliardi et al. [72] developed a simple high performance liquid chromatographic method for the determination of miconazole and other antimycotics in cosmetic antidandruff formulations. This high performance liquid chromatographic method was carried out on a Discovery RP Amide Ci6 column and spectrophotometric detection was performed at 220 nm. The initial mobile phase was a mixture of acetonitrile and aqueous 0.001 M sodium perchlorate (pH 3) in the ratio of 15 85 (v/ v) then a linear gradient less than 46% acetonitrile in 70 min, and less than 50% in 80 min. The extraction procedure was validated by analyzing samples of shampoo... 

The delicate structure of proteins makes it difficult to achieve all goals of a separation procedure simultaneously. At the moment, the best approach is to find the main goal of a separation and to set the chromatographic conditions according to it. Protein mapping for identification and analytical information, or the isolation of proteins for subsequent chemical analysis of the ratio and sequence of the amino acids can be conducted under conditions that violate the tertiary structure. Separations for this purpose can be performed in reversed-phase mode using organic solvents. 

A paired-ion, reversed-phase high-performance liquid chromatographic method was developed for the simultaneous determination of sweeteners (dulcin, saccharin-Na, and acesulfame-K), preservatives (sodium dehydroacetate, SA, salicyclic acid, BA, succinic acid, methyl-para-hydroxybenzoic acid, ethyl-para-hydroxybenzoic acid, n-propyl-para-hydroxybenzoic acid, n-butyl-para-hydroxybenzoic acid, and isobutyl-para-hydroxybenzoic acid), and antioxidants (3-tertiary-butyl-4-hydroxyanisole and tertiary-butyl-hydroquinone). A mobile phase of acetonitrile-50 ml aqueous tr-hydroxyisobutyric acid solution (pH 4.5) (2.2 3.4 or 2.4 3.6, v/v) containing 2.5 mM hexadecyltrimethylammonium bromide and a Clg column with a flow rate of 1.0 ml/min and detection at 233 nm were used. This method was found to be very reproducible detection limits ranged from 0.15 to 3.00 p,g. The retention factor (k) of each additive could be affected by the concentrations of hexadecyltrimethylammonium bromide and a-hydroxyisobu-tyric acid and the pH and ratio of mobile phase. The presence of additives in dried roast beef and sugared fruit was determined. The method is suitable for routine analysis of additives in food samples (81). 

A sensitive, simple, and specific liquid chromatographic method coupled with electrospray ionization-mass spectrometry for the determination of donepezil in plasma was developed, and its pharmacokinetics in healthy, male, Chinese was studied [34]. Using loratadine as the IS, after extraction of the alkalized plasma by isopropyl alcohol-n-hexane (3 97, v/v), solutes are separated on a Cig column with a mobile phase of methanol-acetate buffer (pH 4.0) (80 20, v/v). Detection is performed with a TOF mass spectrometer equipped with an electrospray ionization source operated in the positive-ionization mode. Quantitation of donepezil is accomplished by computing the peak area ratio (donepezil [M + H](+) m/z 380-loratadine [M + H](+) mlz 383) and comparing them with the calibration curve (r = 0.9998). The linear calibration curve is obtained in the concentration range 0.1-15 ng/ml. The limit of quantitation is 0.1 ng/ml. The mean recovery of donepezil from human plasma is 99.4 6.3% (range 93.4-102.6%). The inter- and intra-day RSD is less than 15%. After an oral administration of 5 mg donepezil to 20 healthy Chinese volunteers, the main pharmacokinetic parameters of donepezil are as follow T(max), 3.10 0.55 h tV2j 65.7 12.8 h C(max), 10.1 2.02 ng/ml MRT,... 

Menet et al. [6] have compared performances of CCC and preparative HPLC owing to a separation of two antibiotics X and Y. The CCC apparatus used was a centrifugal partition chromatograph (CPC, Sanki LLN) of 250 mL internal volume. For this purpose, classical parameters of preparative-scale chromatography were calculated experimental duration, including the sample preparation and the separation time, solvent consumption, including the volume of the mobile phase, the stationary phase and the injection solvent, and purity of the purest fraction in Y. The parameter purity in Y was chosen because Y is the solute most difficult to purify because of its physical properties (particularly hydrophobicity) which are close to those of the main impurities. The hourly yield (g/h) is defined as the ratio of the recovered quantity to the experimental duration. The volumic yield (g/L) is defined as the ratio of the recovered quantity to the solvent consumption. Table 1 summarizes the results of... 

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