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Fundamentals of HPLC

Posted: Tue May 19, 2015 12:08 am
by tom jupille
I'm going to invoke "administrator's privilege" here to tell everyone about the upcoming "Fundamentals of HPLC" course that I'll be presenting "Live on the Web" on June 1, 3, & 5.

You can get course details and registration information from our web site at http://www.lcresources.com/training/trfund.html. The same course is available in an "On-Demand" video format through our partners Analytical Training Solutions (http://www analyticaltrainingsolutions.com).

This one-day course is intended for managers, auditors, or reviewers who work with HPLC data or results but do not necessarily operate the systems themselves. It is also an ideal introductory course for bench chemists with limited or no chromatography background. A basic background or experience in physical or life sciences is assumed (equivalent to one year of college chemistry).

At the end of the course, participants will have a basic understanding of how HPLC works , what it can do, and (most important) what it cannot do. They will be familiar with commonly used terms, definitions procedures.

The course is taught in three 2.5-hour sessions (June 1, 3, & 5, 2015) starting at 8:00 am (Pacific Time). Sessions are recorded, so you can review (or catch a missed session). Slides are presented via the internet, with two-way audio via telephone. This is not a "canned" webinar, but a fully interactive, live course -- participants can ask questions of the instructor in real-time.

Here's what we'll cover:

Section 1. Overview

What is HPLC?
"High Performance" Liquid Chromatography, "High Pressure" Liquid Chromatography, even "High Priced" Liquid Chromatography (and now, "Ultra-High Performance" Liquid Chromatography!); all of these interpretations have some validity. In this introduction, we'll take a look at some of the reasons it has become the most widely used analytical technique in the world.

A brief history of HPLC & UHPLC
From the origins of chromatography at the beginning of the 20the century to the conceptual breakthroughs at mid-century and the revolution in technology of the 1970s, we'll trace the evolution of today's HPLC technology -- any look at the possible future

From Apparatus to Instrument
In the final part of our overview, we'll look at the underlying reasons why HPLC technology evolved the way it did.

Section 2. Instrumentation

Pumps & Degassing
Starting at beginning of the flow patch, we'll look at the different types of solvent delivery systems used in HPLC, and pay particular attention to effective removal of dissolved gas from the solvent.

Injectors & Autosamplers
Because the interior of an HPLC system is well above ambient pressure, some provision must be made for sample introduction. We'll look at the typical design of injector valves and compare the three different types of autosamplers that are used to load those valves.

Connecting Tubing, Fittings, & Column Hardware
Continuing through the system, we'll take a look at how the characteristics of connecting tubing (inertness, pressure resistance, internal volume) fit the requirements in different parts of the HPLC system.

Detectors
Separating compounds by HPLC is only part of the story -- they must also be detected. We'll compare the most common detector technologies used: UV-VIS absorbance, fluorescence, refractive index, electrochemical, evaporative, and mass spectrometry.

Section 3. Measurements & Parameters

Retention
In many respects, retention (k')is the most important characterization parameter in HPLC. We'll look why it's defined the way it is and on the reason it has an optimum range of values.

Selectivity & Efficiency
While retention is important, it's only part of the story. We'll look at measures for selectivity (alpha) and efficiency (N) and how they affect chromatographic results.

Resolution & Asymmetry
Ultimately, the quality of a separation is measured by resolution. We'll look at how it's defined and measured, and why the measurement can be misleading. We'll end by looking at measurements that characterize non-ideal peak shape.

Section 4. It's all about chemistry

Reversed-phase
"Reversed-phase" is unquestionably the most widely used mode of HPLC. We'll look at the definition, how it got that awkward name, and the parameters that control the way it works.

pH & Ion-pair
By implication, reversed-phase chromatography deals with neutral molecules. We'll look at the impact of pH on ionizable analytes in reversed-phase, and explore the use of a ion-pair chromatography(in effect, a variant of reversed-phase) for ionized compounds.

Normal-phase & HILIC
Today, the original "liquid chromatography" would be classed as "normal-phase" chromatography. We'll look at the mechanism of normal-phase and the types of samples to which it is applicable, as well as covering it's variant, HILIC (Hydrophilic Interaction Chromatography).

Ion Exchange & Size Exclusion
The last two modes of chromatography we will cover are ion-exchange and size exclusion, including both GFC (Gel Filtration Chromatography) and GPC (Gel Permeation Chromatography).

What Can Go Wrong?
While troubleshooting is outside the purview of this course (see our more extensive HPLC Basics, Equipment, & Troubleshooting course) there are some common problem areas that are of concern to auditors, managers, and supervisors, particularly in the area of ambiguous documentation.

Gradients
Up to here, we have focused entirely on isocratic separations (a big word meaning "the solvent doesn't change during the run"). In many cases, solvent gradients (changing composition) are used. We'll discuss the situations where gradients are applicable and explore similarities and differences between gradient and isocratic HPLC.

Section 5. Quantitation

Integration
In most cases, the area under a peak is proportional to the mass of that compound injected. We'll cover the algorithms used to measure area and look at some of the pitfalls that can occur.

Calibration
The response factor (the proportionality between area and amount injected) must be determined by calibration. We'll compare the pros and cons of external standard calibration and internal standard calibration.