Filters, water injection systems flow rate

HPLC was performed using Waters 600S solvent delivery system (Waters, Milford, MA, U.S.A.). 2487 UV dual channel detector of Waters was used and injector (20 fit sample loop) from Rheodyne. The data acquisition system was Millenium (Waters). Water filtered 1 Milipore ultra-pure water system (Milipore, Bedford, MA, USA). The wavelength was fixed at 254 nm and the experiment was performed at room temperature. The size of the analytical colunm packed by C g was lS0X4.6mm (Spm) (Alltech, USA). The mobile phase of 0.75% TFA in water and acetonitrile were used in this experiment. The flow rates of the mobile phase were fixed at I ml/min. The constant volume of 0(d, was injected. This experiment was implemented at room temperature. The gradient mode was employed to isolate peptides. The complete gradient condition was listed in Table I. 

HPLC measurements were performed on a Waters radial-compression system with a CN column (particle size 5 xm, cartridge 8-mm i.d.). The HPLC apparatus consisted of an ERC-3110 degasser (Erma Optical Works), a Waters U6K injection system, a filter and a precolumn (CN), and a Beckman 160 UV detector with a zinc lamp at a wavelength of 214 nm. The liquid phase was a mixture of 50 vol % acetonitrile and 50 vol % water that contained 0.005 M dibutylamine phosphate. The flow rate was 2.0 mL min" ... 

The method of characterization by high-performance liquid chromatography [HPLC] is as follows 25 mg of hemicellulose was put into 50 mL volumetric flask and pure water was added to the mark. The mixture was shaken and then filtered [first few milliliters of filtrate was discarded]. The solution was then filtered through a membrane filter of 0.2 pm cellulose nitrate. Then about 100 mL solution was injected into the HPLC system via a loop injector with a 20 mL, using an isocratic elution system with distilled water with a mobile phase, flow rate 0.8 mL/min. The detection was made using a UV detector at a wavelength of 280 nm [34]. 

A filtered and degassed mixture of buffer solution and acetonitrile (85 15). The buffer solution is composed of 3.4g of monobasic potassium phosphate in sufficient water to make 1 L adjusted with phosphoric acid to a pH of 2.2. Chromatographic system A liquid chromatograph is equipped with a 280 nm detector, a precolumn Cig cartridge and a 4.6 mm X 25 cm analytical Cig column that contains 5 p,m packing. A flow rate of about 1.5 ml/min. The resolution, R, between the zalcitabine and zalcitabine related compound A peaks is not less than 1.1, and the tailing factor for the zalcitabine peak is not more than 1.5. The relative standard deviation for replicate injections is not more than 2%... 

Molecular weight and polydispersity were determined by gel permeation chromatography (GPC) analysis with a Waters GPC system (comprising a SIS HPLC pump, a 717 autosampler, a 2410 RI detector, a column heater and two Styragel HT6E coliunns), with a mobile phase of HFIP with 0.0 IM LiBr at the flow rate of O.S ml/min. The specimens were dissolved in hexafluoroisopropanol (HFIP) at a concentration of 2 mg/ml. The solution was filtered with a S ml polypropylene (PP) syringe equi ped with a 0.4S pm PP filter to remove any insoluble materials prior to GPC injection. Polymethyi methacrylate standards with narrow polydispersity were used for calibration. The data was analyzed by Millennium version 3.0S.01 software. 

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