science

Isotachophoresis

Isotachophoresis is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Isotachophoresis rather than just read about it. In short: Isotachophoresis (ITP) is a technique in analytical chemistry used for selective separation and concentration of ionic analytes. It is a form of electrophoresis; charged analytes are separated based on ionic mobility, a quantity which tells how fast an ion migrates through an electric field.

Key takeaways

Isotachophoresis belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Isotachophoresis to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Isotachophoresis from memory before moving on to harder problems.

Reference excerpt

Isotachophoresis (ITP) is a technique in analytical chemistry used for selective separation and concentration of ionic analytes. It is a form of electrophoresis; charged analytes are separated based on ionic mobility, a quantity which tells how fast an ion migrates through an electric field.

Overview In conventional ITP separations, a discontinuous buffer system is used. The sample is introduced between a zone of fast leading electrolyte (LE) and a zone of slow terminating (or: trailing) electrolyte (TE). Usually, the LE and the TE have a common counterion, but the co-ions (having charges with the same sign as the analytes of interest) are different: the LE is defined by co-ions with high ionic mobility, while the TE is defined by co-ions with low ionic mobility. The analytes of interest have intermediate ionic mobility. Application of an electric potential results in a low electrical field in the leading electrolyte and a high electrical field in the terminating electrolyte. Analyte ions situated in the TE zone will migrate faster than the surrounding TE co-ions, while analyte ions situated in the LE will migrate slower; the result is that analytes are focused at the LE/TE interface. ITP is a displacement method: focusing ions of a certain kind displace other ions. If present in sufficient amounts, focusing analyte ions can displace all electrolyte co-ions, reaching a plateau concentration. Multiple analytes with sufficiently different ionic mobilities will form multiple plateau zones. Indeed, plateau mode ITP separations are readily recognized by stairlike profiles, each plateau of the stair representing an electrolyte or analyte zone having (from LE to TE) increasing electric fields and decreasing conductivities. In peak mode ITP, analytes amounts are insufficient to reach plateau concentrations, such analytes will focus in sharp Gaussian-like peaks. In peak mode ITP, analyte peaks will strongly overlap, unless so-called spacer compounds are added with intermediate ionic mobilities between those of the analytes; such spacer compounds are able to segregate adjacent analyte zones. A completed ITP separation is characterized by a dynamic equilibrium in which all coionic zones migrate with equal velocities. From this phenomenon ITP has obtained its name: iso = equal, tachos = speed, phoresis = migration. Isotachophoresis is exactly equal to the steady-state-stacking step in discontinuous electrophoresis.

Transient ITP A popular form of ITP is transient ITP (tITP). It alleviates the limitation of conventional ITP that it has limited separation capacity because of analyte zone overlap. In transient ITP, analytes are first concentrated by ITP, and then can be baseline separated by zone electrophoresis. Transient ITP is usually accomplished by dissolving the sample in the TE and sandwiching the sample/TE plug between LE zones - or vice versa: a sample/LE plug can also be sandwiched between TE zones. In the first case, analytes are focused at the front TE/LE interface. Meanwhile, the back of the TE plug becomes dissolved in the LE because the faster LE ions overcome the TE ions. When all of the TE ions are dissolved, the focusing process ceases and the analytes are separated according to the principles of zone electrophoresis. tITP is nowadays more widespread than conventional ITP because it is easily implemented in capillary electrophoresis (CE) separations as a preconcentration step, making CE more sensitive while profiting from its powerful separation capacities.

References

Adam, Albert; Schots, Carlo (1980). Biochemical and biological applications of isotachophoresis. Elsevier Scientific Pub. Co. ISBN 0-444-41891-1.

Illustrations

Worked examples

Example 1 — a first encounter with Isotachophoresis

Start with the simplest possible case. Write down what Isotachophoresis claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Isotachophoresis before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Isotachophoresis ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Isotachophoresis

In research: Isotachophoresis appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Isotachophoresis in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Isotachophoresis is common in secondary-school and first-year university syllabi. It links to neighbouring topics Electrophoresis, so understanding it makes those chapters shorter.
In everyday life: Look for Isotachophoresis outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Isotachophoresis in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Isotachophoresis means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Isotachophoresis out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Isotachophoresis in simple terms?

Why does Isotachophoresis matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Isotachophoresis?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Isotachophoresis.