HPLC A Praactical User''''''''S Guide Part 11 pot

... solvent. 8 ADVANTAGES AND DISADVANTAGES OF HPLC 1 ADVANTAGES AND DISADVANTAGES OF HPLC 3 The first things we need to understand are how an HPLC system works, its best applications and advantages over ... remember that HPLC is both an analytical and a preparative tool. Often the preparative capabilities of the HPLC are over- looked. While normal analytical injections contain picogra...

Ngày tải lên: 23/01/2014, 04:20

... remember that HPLC is both an analytical and a preparative tool. Often the preparative capabilities of the HPLC are over- looked. While normal analytical injections contain picogram to nanogram quantities, ... tool.Twenty-five years in HPLC, first as a user, then in field sales and application support for HPLC manufacturers, and finally working as a teacher and consultant has shown m...

Ngày tải lên: 03/07/2014, 12:20

... equilibrated and standardized, we are ready to carry out an HPLC separation on a real sample. We might add an internal standard (if necessary, to correct for injection variations), dilute our sample ... internal stan- dard to both our sample and our known standard mixture, we can calculate peak heights or areas relative to that of the internal standard. Variations in the injection size of...

Ngày tải lên: 03/07/2014, 12:20

... Data Acquisition / 13 2 10 .4 Solvent Conservation / 13 3 III HPLC UTILIZATION 13 5 11 Preparative Chromatography 13 7 11 .1 Analytical Preparative / 13 8 11 .2 Semipreparative / 13 9 11 .3 “True” Preparative ... solvent. 8 ADVANTAGES AND DISADVANTAGES OF HPLC CONTENTS PREFACE xi I HPLC PRIMER 1 1 Advantages and Disadvantages of HPLC 3 1. 1 How It Works / 4 1. 1 .1 A...

Ngày tải lên: 05/08/2014, 11:20

... of a packing material, sample clean-ups, and broad separations of classes of materials. They are available in almost any type of packing available for HPLC separations: partition, ion exchange, ... Service and support have always been the differentiating factors that really separate and define the best companies. 2. 1.4 Brand Names and Clones A single supplier working on an O.E.M. basis...

Ngày tải lên: 05/08/2014, 11:20

... peak height times the half peak width. The areas of each peak are summed to give a total area. Dividing this into the area of each peak gives a relative area percentage for each peak. Like peak ... 1 to 8 for analytical separations and 4 to 12 for preparative. a s range from 1 to 2; at a = 1, peaks completely overlap, much above a = 2 and the separation can be made in a separatory...

Ngày tải lên: 05/08/2014, 11:20

... use a technique called sequential analysis (Fig. 5.6). For example, we can make a size separation, then take a size fraction and do a partition separation. This is commonly used in separating a complex ... Anionic packing materials have an affinity for anions (negatively charged ions) and have positively charged functional groups on their surfaces, usually organic amines. Cationic pa...

Ngày tải lên: 05/08/2014, 11:20

... form as a pair of peaks or a badly tailing peak for each compound. Ion-pairing reactions can also be carried out using quaternary amines as counter-charges for organic acid and organic phosphate ... I’m talking about a change that takes place gradually or all at once and remains high. Be aware that gradient mixtures of some solvents like methanol and water go through a pressure maximu...

Ngày tải lên: 05/08/2014, 11:20

... covalently bonded phases available on zirconium that can simulate silica C 18 separations with a- type peak shifting, but bonded phases are available that provide truly unique sep- arations. Many ... monosaccharides and separate alcohol sugars from each other. 8.1.2 Anionic: Weak and Strong In strong anionic ion exchangers, the quaternary amine is attached to the silica surface by an alkyl c...

Ngày tải lên: 05/08/2014, 11:20

... than the inte- grator to store a single chromatogram, however, it can use this raw data to report tables of peak maxima, areas, and heights versus time and recalculate, redisplay, and compare ... reports each as a percent of the total. The computer handles data differently. It measures the voltage at a preset time interval and stores each displacement as a digital word, usually at a...

Ngày tải lên: 05/08/2014, 11:20

... necessary, we can increase to the next size larger loop without affecting resolution. 1 38 PREPARATIVE CHROMATOGRAPHY Table 11.1 A Guide to Preparative Scale-up Analytical Semipreparative Preparative Size ... least important. Here we are gathering grams of material for biological testing and structural analysis, and as reaction intermediates. HPLC: A Practical User’s Guide, Second Ed...

Ngày tải lên: 05/08/2014, 11:20

... concentrations of the standards are injected, areas are measured, and a calibration curve is platted. Unknown samples are then injected, chromatograms run, and areas are calculated and compared ... response factors are calculated relative to the internal standards, and amounts of each unknown present are calculated from the standards calibration factors. Internal standards are usually used...

Ngày tải lên: 05/08/2014, 11:20

... macro programs. 14.6.3 Databases: .DB2 Format To export data files into a database program, a database file format called .DB2 was developed in an early PC database, dBase II. Databases are made up ... retained as a standard format. .WK files are Lotus-1,2,3 formats and .XLS are Microsoft Excel formats that have become spreadsheet standards, allowing transfer of data, calculations, address...

Ngày tải lên: 05/08/2014, 11:20

... American Laboratory, LC/GC Mag- azine, the Journal of Liquid Chromatography, and Chemical Abstracts— HPLC Selects. Chemical Abstracts are also on-line as part of Dialog’s computer database. I have ... Normal- Phase Chromatography.) Alpha (a) —(Separation or chemistry factor). A measure of separation between two peak maxima. Ratio of their k′ values. Attenuation—Measure of detector sensi...

Ngày tải lên: 05/08/2014, 11:20

... sigma (s) width, 49 Acidic phase silica, 93 Alpha (a) 55 A/ D converter, 124 Affinity column, 59, 101 Amine column oxidation, 75–76 Amino acids, 162 AMU (atomic mass unit), 183 Analytical mode, 8 Analog ... centrifugation. Saturation Column—Sacrificial column placed before the injector to protect the main column from pH degradation. Seal—Wear surface that both lubricates and separates moving...

Ngày tải lên: 05/08/2014, 11:20