Reversed-phase HPLC isocratic column performance

Purify the FMLPK-Fl on a Cjg reverse-phase HPLC column by isocratic elution with a solution of 30% acetonitrile and 0.2 M acetic acid. Monitor the effluent at 254 nm. The peak corresponding to FMLPK-Fl should be clearly resolved from unreacted FITC and its breakdown products. Confirm the identity of FMLPK-Fl by performing an amino acid analysis of an acid-hydrolyzed sample. 

The ch5unobypsin-catalyzed condensation of 37 (10 mM) with 38 (20 mM) was performed in 0.2 M sodium veronal buffer (pH 9) containing 40% DMSO (0.5 mL). The ch5miobypsin concentration was 1.6 X 10 M. The reaction course was monitored by isocratic reverse-phase HPLC using a C-18 column... 

The final product is analyzed by reverse phase HPLC (Biocad Sprint, USA). The HPLC machine was equipped with a Vydac C4 column. Analysis of DSPE-PEG g -folate is performed with isocratic elution using a solvent mixture of 92 8 v/v methanol and 10 mM sodium phosphate (pH 7) at a flow rate of 1 ml/min (18). 

Purification was performed by preparative reversed-phase HPLC on a Kromasil C8 column (100 A, 5. m, 20 x 250 mm, flow rate 11 ml/min) under isocratic conditions (21% CH3CN in H2O + 0.1% TFA) to give 31 (30 mg, 69% peptide content, 45% overall yield). FABMS, amino acid analysis, and NMR data have been reported (25). 

The HPLC-FTIR technique has recently been used to identify six catechins and two methyl-xanthines present in green tea extracts." " A reversed-phase separation of the compounds was performed on a C-18 column equilibrated at 30°C using an isocratic mobile phase of acetonitrile-0.1% formic acid (15 85), prior to introduction to the deposition interface linked to the FTIR detector. The solvent was evaporated at 130°C and spectra were collected every 6 sec during the run. Two distinct designs for HPLC-FTIR interfaces have been developed flow cells and solvent elimination systems. Flow cell systems acquired spectra of the eluent in the solvent matrix through IR transparent, nonhydroscopic windows. The... 

High-performance LC in the reversed-phase mode (RP-8 or RP-18 column) with UV detection (254 nm) and isocratic conditions was evaluated for the analysis of 15 organophosphorus pesticides. Typically the method could be used to analyze azinphosmethyl in water at 0.5 /rg/L. This compares favorably with GC, since this compound is very difficult to analyze by that method. For other pesticides, such as fenitrothion, which is readily analyzed by GC, the HPLC method can be used for confirmation purposes (31). 

Zarghi et al. [76] developed an HPLC method, using a monolithic column, for quantification of omeprazole in plasma. The method is specific and sensitive with a quantification limit of 10 ng/ml. Sample preparation involves simple, one-step extraction procedure, and analytical recovery was complete. The separation was carried out in reversed-phase conditions using a Chromolith Performance (RP-18e, 100 x 4.6 mm) column with an isocratic mobile phase consisting of 0.01 mol/1 disodium hydrogen phosphate buffer-acetonitrile (73 27) adjusted to pH 7.1. The wavelength was set at 302 nm. The calibration curve was linear over the concentration range 20-1500 ng/ml. The coefficients of variation for intra- and interday assay were found to be less than 7%. 

Peroxidase-Catalyzed Polymerization of p-Cresol. Large scale polymerizations were carried out in a volume of 250 mL in a 500 mL round bottom flask at 25°C with stirring at ca. 250 rpm. p-Cresol (688 mg, 25 mM) was dissolved in 213 mL dioxane and 37 mL aqueous buffer, pH 7 (0.01 M phosphate) added to give a solution consisting of 85% (v/v) dioxane. Horseradish peroxidase (25 mg, free powder) was added and the reaction was initiated by the addition of 0.28 mL of 30% H2O2 (10 mM). The suspension (peroxidase is insoluble in 85% dioxane) immediately turned yellow and the reaction was allowed to proceed 15 min. The concentrations of p-cresol and reaction products were determined by high performance liquid chromatography (HPLC) with a Ci8-reverse phase column (Waters Associates, Milford, MA). The isocratic solvent used was acetonitrile water (56 44) with... 

The separation and identification of natural dyes from wool fibers using reverse-phase high-performance liquid chromotog-raphy (HPLC) were performed on a C-18 column. Two isocratic four-solvent systems were developed on the basis of the Snyder solvent-selectivity triangle concept (1) 10% acetonitrile, 4% alcohol, and 2% tetrahydrofuran in 0.01 M acetic acid and (2)7% acetonitrile, 8% alcohol, and 5% tetrahydrofuran in 0.01 M acetic acid. Samples were also eluted in 30% acetonitrile. Spot tests and thin-layer chromatography were performed on all samples to confirm HPLC results. The systems also were found to be potentially useful in the identification of early synthetic dyes. A system of sample preparation that minimizes the reaction of samples was discussed. The application of this HPLC separation technique to samples from 20th century Caucasian rugs and American samples unearthed from the foundation of Mission San Jose was examined. 

The HPLC determinations were performed using an HPLC system operating at 215 nm. Samples were chromatographed on a stainless steel C18 reverse-phase column eluted isocratically at room temperature, at a flow rate of 1 mL/min. The mobile phases were 180 mM ammonium acetate (pH 3.0)/methanol (4 96, v/v) for retinyl acetate [20], methanol/water (70 30, v/v) for progesterone [21], and phosphate buffer (pH 2.3)/methanol (50 50, v/v) for cromoglycate [22], Drug detection was monitored at the characteristic of each compound. 

Hi h Pressure Liquid Chromatography. Size exclusion chromatography was performed isocratically in 0.2 M ammonium acetate (flow-1.5 ml/min) with a Water s Model 840 HPLC with a Toyo-Soda G2000SWXL column (30 cm x 7.8 mm). Eluting components were monitored in the UV at 214 nm and by fluorescence (Ex - 230 nm, Em - 300 nm) and collected in 4 minute fractions for bioassay. Reverse phase chromatography was conducted with a Hewlett-Packard Model 1090 HPLC equipped with a Vydac C-18 column using a linear gradient over one hr from 10% to 50% acetonitrile in 0.1% TFA. Sample was monitored with a diode array detector from 190 to 350 nm in the UV. 

In previous papers/ we reported the effect of column temperature on resolution in reversed-phase high-performance liquid chromatography (RP-HPLC) to separate various (3-lactams (penicillins and cephalosporins) from a single sample. In this work we describe the effect of column temperature and volume fraction of an organic solvent on resolution in the isocratic elution conditions of some (3-lactam antibiotics. 

Fig. 7.2 HPLC separation of hyoscyamine 1 and scopolamine 6. The analysis was performed by using Waters HPLC system, equipped with Waters 1,525 binary pump, a Dual X Waters 2,487 absorbance detector, and Symmetry C18 reversed phase chromatographic column (250 mm x 4.6 mm, 5 pm). The operation temperature was 26 °C. The mobile phase consisted of acetonitrile methanol 0.05 mol ammonium acetate (20.9 27.9 51.2), and elution speed was 0.6 mL min in isocratic regime...

Numerous methods for high-performance Uquid chromatography (HPLC) of tropane alkaloids have been developed. The chromatographic conditions depend on the variability of the analyzed matrices (extracts from different plant tissues, pharmaceutical preparations, clinical, and forensic probes) and analytes (pure compounds or alkaloid mixtures with different composition). Most often, columns packed with reverse-phase Cl 8 stationary phase are used for the separation of tropane alkaloids. Gradient or isocratic elution generally involves buffered mixtures at the acidic pH of water—acetonitrile or acetonitrile—methanol, such as acetonitrile-triethylammonium phosphate buffer (25 75) at pH 6.2 [65] acetonitrile-50 mM phosphate buffer at pH 2.95 (10 90 and 20 80) [66], methanol-0.05 M... 

Perform anti-estrogenic agents acquisition for all samples, calibrators, negative and positive control urines using the reversed phase C8 HPLC column and an isocratic mobile phase of acetonitrile and 5 mM ammonium acetate buffer at a 70 30 ratio, with a flow rate of 0.2 mL/min. Retention times and MRMs for the internal standard and anti-estrogenic agents... 

Procedure Flavonoids are then further purified with 2 ml of methanolic HC1 (2 N), followed by centrifugation (2 min, 15 600 g), hydrolyzation of 150 il of suspension in an autoclave (15 min, 120 C). A reverse osmosis-Millipore UF Plus water purification system is used in high performance liquid chromatography (HPLC) with an autosampler. After injections of 5 pg of samples, the mobile phases flow at a rate of 1 ml/minute with isocratic elution in a column at 30 C. 

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