What is the pipette for? Rules for working with volumetric glassware when carrying out analytical measurements. Concept and types of pipettes

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Pipette

eyedropper in the crossword dictionary

Dictionary of Medical Terms

pipette (French pipette)

device for measuring a certain volume of liquid or gas;

glass tube, tapered at one end, designed to measure liquid drops.

Explanatory dictionary of the Russian language. D.N. Ushakov

pipette

pipettes, f. (French pipett - tube) (special). Narrow glass tube with rubber tip for aspirating, drawing in a small amount of liquid and releasing it in drops. Eyedropper for eye drops. Ink dropper (edges are used to pour ink into the eternal pen).

Explanatory dictionary of the Russian language. S.I.Ozhegov, N.Yu.Shvedova.

pipette

And, well. Glass tube with rubber cap for measuring the liquid drop by drop, dropper (in 3 values). P. for eye drops. Drip with a pipette.

adj. pipette, th, th.

New explanatory and derivational dictionary of the Russian language, T. F. Efremova.

pipette

f. A small glass tube with a rubber tip for drawing in, drawing in liquid and discharging it in drops.

Wikipedia

Pipette

Pipette- a measuring or dosing vessel, which is a tube, or a container with a tube having an end with a small hole to limit the rate of fluid outflow.

A variety of pipettes are widely used for measuring precise volumes of liquids or gases, in medicine, chemistry and biology, and especially widely in analytical chemistry and biochemistry.

Examples of the use of the word pipette in the literature.

Holders, test tubes, conical flasks, allonges, retorts, cylinders, agate mortars, porcelain crucibles from the royal factory in Sevres, crystallizers ordered from Lavoisier's drawings to the Venetian glass factory on the island of Murano , graded pipettes, scales, burettes, cuvettes - all this fantastic glass world, at the behest of the scientist, advancing on avaricious nature, breaking its secrecy, burned and sparkled in the sun of a Parisian evening, shimmering with colored lights, the rainbow play of a sunbeam, so simple and white, decaying with joy for a thousand color overflows in the laboratory of Antoine Lavoisier, as if above, where Madame Poluse reigns, again turn into austere, white and colorless, even as if it has become mean, sunlight.

The first-aid kit should contain: dressing materials - cotton wool, bandages, sterile gauze napkins, mustard plasters, a thermometer, waxed compress paper, a glass for taking medications, an eye pipette, fingertips.

The donuts were rearranged into a continuous arc, from which the soloist, the senior laboratory assistant researcher from the department of organophosphorus compounds: My boss looks at me without nagging, How the test tubes were washed by me, Because he uses on the couch pipette.

When Oscar got up from the table, Meisner told the doctor who was dripping from pipettes medicine in a glass: - Go.

TO pipette, a test tube, a spoon and a stirrer - devices that allow the perfumer to master the complex process of mixing Grenouille has never touched.

Fat man with pipette while Nuri bargained, he stood aside and watched with obvious pleasure.

At the request of the cyber, Jafar dripped from pipettes on the removed cover, and the spider kept dropping the tip of the manipulator into the puddle, transferring a drop of lubricant into the mechanism.

A quarter of an hour later, Jafar returned from pipette and generously poured the spider's manipulators, hoping that the grease would get where it needed to be.

Plastic pipette was kept in my shoe, a safety pin stuck in my belt.

To find out, he, Baldini, would have to experiment for several days in a row - a terrible job, perhaps even worse than simple identification of parts, because he had to measure and weigh and record, and at the same time be devilishly attentive, for the slightest carelessness - trembling pipettes, an error in the count of drops - could ruin everything.

V pipette there remained an iridescent thin film of blood, and the white paper collar was soaked all over with it, like a bandage.

I just want to draw the attention of readers to the fact that the investigating authorities considered it necessary to question in detail precisely the former officers of the detachment about the poison and pipette, about the actions of the offender, his age and signs.

Then, with calm and at the same time quick movements, he took it off the small shelf and brought the utensils necessary for the experiment: a large pot-bellied milk bottle, a glass funnel, pipette, small and large beakers - and in exemplary order placed it all in front of him on an oak lid.

Then, without haste, he took pipette- such a glass tube, with a small rubber cap at the end, which is usually buried in the eyes.

I ran to the closet, grabbed a bottle of drops pipette and began the most important operation of the day.

Traditionally, pipettes have been made of glass; in recent years, a variety of polymeric materials have been increasingly used.

Medical pipettes

The most common pipettes are for infusing drugs in the form of drops (into the eyes, nose, or ears). Such pipettes consist of a piece of glass tube, one of the ends of the tube, strongly melted or drawn, has a small hole, and the other is closed with a flexible rubber (or polymer) container (tube, ball) and is designed to draw liquid into the pipette by suction.

In medical microbiology, there is also a special device - the Pasteur pipette (Pasteur pipette).

Measuring pipettes for chemical and biochemical research

Most often it is a glass vessel used to accurately measure (dispense) the volume of a liquid.

Various types of volumetric pipettes are available for a wide variety of purposes, with different classes of accuracy and for different volumes.

Traditional glass pipettes for analytical chemistry are available in two types:

Mohr's measuring pipette(ungraded), for a given volume(1, 5, 10, 20, 50, 100, 200 ml, etc.) Mohr pipettes have one circular mark in the upper part and are intended for sampling liquids of a certain volume. Such pipettes usually provide a lower measurement error than graduated ones. GOST 29169-91 defines the permissible errors of pipettes. The error depends on the volume being measured, so a 25 ml pipette has a permissible measurement error of 25 ± 0.06 ml.
graduated(usually cylindrical, 1, 2, 10 ml, etc.) For example, 5 ml pipettes are usually graduated through 0.5 ml. Graduated pipettes allow volume measurement, usually with an accuracy of ± 0.1 or 0.2 ml.

Mohr's single-label pipettes are sometimes referred to as aliquot pipettes.

Gas pipettes

Special pipettes

Rules for the use of glass pipettes

The pipettes are calibrated for free flow of liquid. You should not blow out or quickly squeeze out the liquid - in the first case, an excess volume will come out of the pipette, which should remain in its nose due to capillary forces, and in the second case, due to the leakage effect, the volume of the outflowed liquid will be less than the standard one.

Pipette calibration and pipetting accuracy

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An excerpt characterizing the Pipette

In the movement of the Russian army from Tarutin to Krasny, fifty thousand left sick and backward, that is, a number equal to the population of a large provincial city. Half of the people dropped out of the army without a fight.
And about this period of the campaign, when the troops without boots and fur coats, with incomplete provisions, without vodka, spend the night for months in the snow and at fifteen degrees of frost; when the day is only seven and eight o'clock, and the rest is night, during which there can be no influence of discipline; when, not like in a battle, for a few hours only people are brought into the area of death, where there is no longer discipline, and when people live for months, every minute fighting death from hunger and cold; when half of the army perishes in a month - historians tell us about this period of the campaign, how Miloradovich had to make a flank march there, and Tormasov there then and how Chichagov had to move there that (move above the knee in the snow), and how that knocked over and cut off, etc., etc.
The Russians, who were half dying, did everything that could and should have been done to achieve a goal worthy of the people, and it is not their fault that other Russian people, sitting in warm rooms, assumed to do what was impossible.
All this strange, now incomprehensible contradiction of the fact with the description of history occurs only because the historians who wrote about this event wrote the history of the wonderful feelings and words of different generals, and not the history of events.
For them, the words of Miloradovich, the awards that this and this general received, and their assumptions seem very amusing; and the question of those fifty thousand who remained in hospitals and graves does not even interest them, because it is not subject to their study.
Meanwhile, one has only to turn away from studying the reports and master plans, but to delve into the movement of those hundreds of thousands of people who took a direct, direct part in the event, and all the questions that seemed previously insoluble, suddenly, with extraordinary ease and simplicity, are undeniably resolved.
The purpose of cutting off Napoleon with the army never existed, except in the imagination of a dozen people. It could not exist because it was meaningless and it was impossible to achieve it.
The goal of the people was one: to cleanse their land from the invasion. This goal was achieved, firstly, by itself, since the French fled, and therefore it was only necessary not to stop this movement. Secondly, this goal was achieved by the actions of the people's war, which destroyed the French, and, thirdly, by the fact that a large Russian army followed the French, ready to use force if the French movement stopped.
The Russian army was supposed to act like a whip on a running animal. And an experienced driver knew that the most advantageous thing was to keep the whip raised, threatening them, and not to lash a running animal on the head.

When a person sees a dying animal, horror seizes him: what he himself is - his essence, in his eyes is obviously destroyed - ceases to be. But when a dying person is a person, and a beloved person is felt, then, in addition to the horror of the destruction of life, one feels a rupture and a spiritual wound, which, like a physical wound, sometimes kills, sometimes heals, but always hurts and is afraid of an external annoying touch.
After the death of Prince Andrei, Natasha and Princess Marya felt this equally. They, morally bent over and closing their eyes from the formidable cloud of death hanging over them, did not dare to look into the face of life. They carefully guarded their open wounds from offensive, painful touch. Everything: a carriage quickly drove along the street, a reminder of dinner, a girl's question about a dress that needs to be prepared; even worse, the word of insincere, weak sympathy painfully irritated the wound, seemed an insult and broke the necessary silence in which they both tried to listen to the terrible, strict chorus that had not yet been heard in their imagination, and prevented them from peering into those mysterious endless distances that for a moment opened In front of them.
Only the two of them were not offended or hurt. They spoke little to each other. If they talked, it was about the most insignificant subjects. Both the one and the other equally avoided mentioning anything related to the future.
To admit the possibility of the future seemed to them an insult to his memory. Even more carefully they avoided in their conversations everything that could be related to the deceased. It seemed to them that what they experienced and felt could not be expressed in words. It seemed to them that any mention of the details of his life in words violated the greatness and sanctity of the sacrament that had taken place in their eyes.
The incessant abstinence of speech, the constant diligent circumvention of everything that could suggest a word about him: these stops from different sides on the border of what could not be said, even clearer and clearer exposed before their imaginations what they felt.

But pure, complete sorrow is as impossible as pure and complete joy. Princess Marya, by her position as one independent mistress of her fate, guardian and educator of her nephew, was the first to be called by life from that world of sorrow in which she lived for the first two weeks. She received letters from relatives to which she had to answer; the room in which they put Nikolenka was cheese, and he began to cough. Alpatych came to Yaroslavl with business reports and with suggestions and advice to move to Moscow to the Vzdvizhensky house, which remained intact and required only minor repairs. Life did not stop, and it was necessary to live. No matter how hard it was for Princess Marya to leave that world of solitary contemplation in which she had lived until now, no matter how sorry and as if ashamed it was to leave Natasha alone, the worries of life demanded her participation, and she involuntarily gave herself up to them. She checked the scores with Alpatych, consulted with Desal about her nephew and made orders and preparations for her move to Moscow.

When carrying out volumetric analytical measurements in titrimetry, special volumetric vessels are used: volumetric flasks, pipettes, burettes, graduated cylinders and test tubes. Working with it requires certain skills and abilities. To obtain correct results in a volumetric analysis, all operations must be performed very carefully, the utensils used must be clean and appropriate for the purposes and tasks of the measurements being carried out.

Volumetric flasks

Volumetric flasks are thin-walled, flat-bottomed round vessels with a long, narrow neck marked with a thin ring line. They come in different capacities: from 25 ml to 2 liters (Fig. 3).

Rice. 3. Volumetric flasks

Volumetric flasks are designed for the preparation of solutions of precise concentration (i.e. standard solutions), as well as for diluting existing solutions to the specified volumes.

Dry weighed portions (including the contents of the fixed channels) or the existing solution (when diluted) are introduced into a volumetric flask through a funnel, then rinsing off the remainder of the substance from the funnel (and rinsing the ampoule of the fixed channel) with distilled water (Fig. 4).

Rice. 4. Preparation of the working solution from the fixed channel

To dissolve the introduced substance, distilled water is added to the flask (up to about half of its volume). The contents of the flask are thoroughly mixed with rotary movements until a homogeneous solution is formed. After that, add another portion of water through the funnel until the liquid level is 3-5 mm below the circular mark on the neck of the flask. Then the rest of the water is added dropwise and the volume of the solution is brought exactly to the mark. For correct measurement of the volume of liquid in a volumetric flask (and in other volumetric vessels), it is necessary that the observer's eye and the circular mark on its neck are in the same horizontal plane (Fig. 5).

Rice. 5. Readout of the level of liquid in the vessel at different positions of the eye 2 - correct position of the eye, 1, 3 - incorrect

The volume of transparent liquids is measured along the lower edge of their meniscus (which should coincide with the circular mark of the flask), and intensely colored (for example, KMnO 4 solution) - along the upper one.

It is not recommended to store the resulting solution in a volumetric flask. After preparation, it must be transferred to a glass vessel intended for this purpose, equipped with a well-ground glass stopper.

Pipettes

Pipettes are designed to take small, precisely measured volumes of liquid and transfer them from one vessel to another. Distinguish Mohr pipettes, graduated pipettes and automatic pipettes otherwise called pipette dispensers(fig. 6, 10).

Rice. 6. Pipettes: a- simple (Mohr's pipette); b - graduated.

Mohr's pipettes are a glass tube with a drawn-out spout and an extension in the middle part. They are designed to select a strictly defined volume of liquid, which is indicated by a number on one of the expansion walls.

Graduated pipettes are designed for measuring various small volumes of liquid using a scale applied to their wall. They are also glass tubes with a retracted spout.

To select the required volume of liquid with a Mohr pipette and a graduated pipette and transfer it to another vessel, proceed as follows:

1. A rubber bulb is placed on the neck of the pipette, squeezed until the air is properly removed. Then the pipette is placed into the vessel with the sampled solution (as deep as possible, until the tip of the pipette touches the bottom of the vessel), release the pear and wait until the liquid level in the pipette rises 3-4 cm above the upper zero mark.

2. Remove the pear. Quickly close the upper part of the pipette (or its neck) with the index finger and, holding the pipette itself with your thumb and middle fingers, quickly pull it out of the vessel with the solution(fig. 7).

Rice. 7. As follows (a), and should not (b) hold a pipette

Holding the pipette vertically above the surface of the solution, weaken the pressure of the index finger on its neck, so that the liquid slowly falls from the pipette nose into the solution until the lower part of its meniscus (or the upper part, if the solution is intensely colored) is equal to the upper zero mark on the pipette wall. After that, the pressure on the neck of the pipette is rapidly increased until the flow of liquid stops completely (Fig. 8).

Rice. 8. Position of the pipette when setting the meniscus at the line level

To remove a drop of liquid remaining on the outer side of the pipette tip, touch the inner wall of the vessel with the sample to be taken.

3. The pipette is transferred to another vessel (most often in a titration flask) and, releasing the pressure of the index finger, allow the required volume of liquid to flow out of it (Fig. 9).

Rice. 9. Pouring the solution out of the pipette

Recently, more and more widely used pipette dispensers or automatic pipettes. These are special devices that allow you to accurately select the required volume of liquid from the solution by simply pressing the button device located in their upper part (Fig. 10).

Rice. 10. Pipette dispenser

The variable volume of liquid required for sampling is set using a digital display located on the pipette handle. Before working with a pipette dispenser, you must carefully read the instructions for use. These devices are more convenient in comparison with Mohr's and graduated pipettes, they allow faster sampling of a given volume of liquid and by now prevail in the everyday practice of scientific and research laboratories. The only drawback of pipette pipettes is that they are much more expensive than conventional glass pipettes.