Name: calibrating lab glassware for accurate volume
Uploaded: 2024-12-05T18:31:54.000Z
Duration: 1 min 11 s
Channel: JoVE

Genaue Volumenmessungen sind entscheidend für lösungsbasierte Analysen. Zur volumetrischen Standardausrüstung gehören Kolben, Pipetten und Büretten.
Messkolben werden verwendet, um Lösungen für ein bestimmtes Volumen vorzubereiten und zu verdünnen. Sie sind mit TC gekennzeichnet, was für "to contain" steht.
Sie sind so kalibriert, dass sie bei bestimmten Temperaturen ein genaues Volumen enthalten, wobei der minimale Glasausdehnungskoeffizient trotz geringfügiger Änderungen ein nahezu konstantes Volumen ermöglicht.
Pipetten mit der Bezeichnung TD geben ein bestimmtes Volumen bei einer bestimmten Temperatur ab. Sie sind so kalibriert, dass sie die Foliendrainage an Glaswänden berücksichtigen, die mit der Lieferzeit variiert.
Volumetrische Pipetten mit korrekter Kalibrierung liefern ein einzelnes Volumen mit einer Genauigkeit von bis zu vier oder fünf signifikanten Zahlen. Messpipetten liefern unterschiedliche Volumina mit einer geringeren Genauigkeit von bis zu drei signifikanten Ziffern.
Eine Bürette ist ein kalibriertes Röhrchen zum Halten des Titriermittels, das über das manuelle Ventilsystem genau dosiert werden kann, um den Titriermittelfluss zu steuern.

kalibrierung von glaswaren

Eine genaue Kalibrierung von Glaswaren wie Messkolben, Pipetten und Büretten ist unerlässlich, um genaue Messungen im Analyselabor sicherzustellen. Die Kalibrierung hilft dabei, die Konsistenz über Messungen hinweg aufrechtzuerhalten und Fehler durch ungenaue Volumina zu vermeiden. Messkolben

Messkolben sind so konzipiert, dass sie wässrige Lösungen mit genauen Volumina genau herstellen können und über eine Kalibrierungslinie am Hals verfügen. Um einen Messkolben zu kalibrieren, ist es wichtig, ihn mit destilliertem Wasser zu füllen, bis der Meniskus (die gewölbte Oberfläche der Flüssigkeit) mit der Kalibrierungsmarkierung übereinstimmt. Das Betrachten des Meniskus auf Augenhöhe gewährleistet genaue Messwerte. Die Kalibrierung wird normalerweise bei einer bestimmten Temperatur (~20 °C) durchgeführt, um die Auswirkungen der Temperatur auf das Volumen zu berücksichtigen. Wenn der Wasserstand über der Linie liegt, lassen Sie ihn vorsichtig ab, bis er die Markierung erreicht. Wenn die Wasserlinie darunter liegt, fügen Sie tropfenweise mehr Wasser hinzu, bis die Markierung erreicht ist. Nach der Kalibrierung kann die Kapazität des Kolbens bestätigt werden, indem das Wasser gewogen und mit dem theoretischen Wert basierend auf seiner Dichte verglichen wird.

Pipetten

Pipetten werden verwendet, um bestimmte Flüssigkeitsvolumina zu übertragen.

Vollpipetten: Diese sind so konzipiert, dass sie ein einzelnes, hochgenaues Volumen liefern, normalerweise auf vier oder fünf signifikante Stellen. Zur Kalibrierung wird die Pipette zunächst gereinigt und mit der zu messenden Lösung gespült, bis zur Kalibrierungsmarkierung gefüllt und vollständig in einen Behälter abgelassen. Die Genauigkeit wird dann überprüft, indem das gelieferte Wasser gewogen und mit dem theoretischen Volumen basierend auf der Wasserdichte verglichen wird.

Messpipetten: Im Gegensatz zu Vollpipetten sind Messpipetten mit einer Reihe von Linien markiert und können mehrere Volumina liefern, jedoch mit etwas geringerer Genauigkeit – im Allgemeinen bis zu drei signifikante Stellen. Der Meniskus muss während der Kalibrierung und Messung ebenfalls sorgfältig beobachtet werden.

Bürette

Eine Bürette ist ein langes, skaliertes Glasrohr mit einem Hahn an einem Ende, das variable Mengen einer Lösung genau abgibt, insbesondere bei Titrationen. Stellen Sie beim Kalibrieren einer Bürette sicher, dass der Meniskus vor und nach der Titration richtig mit den Markierungen ausgerichtet ist, und überprüfen Sie, ob das abgegebene Volumen den Erwartungen entspricht, indem Sie das Gewicht des abgegebenen Wassers mit seinem theoretischen Wert vergleichen. Der Behälter der Bürette enthält Markierungen, die das Flüssigkeitsvolumen angeben. Der Absperrhahn oder Hahn an der Unterseite dient als manuelles Ventil, mit dem Benutzer den Flüssigkeitsfluss aus dem Behälter steuern und die abgegebene Menge präzise messen können.

Andere Glaswaren

Andere Arten von Laborglaswaren, wie z. B. Messzylinder, werden ebenfalls häufig für Volumenmessungen verwendet, bieten jedoch eine geringere Genauigkeit als volumetrische Geräte. Sie liefern normalerweise Volumina bis zu drei signifikanten Stellen und sind für weniger präzise Arbeiten geeignet. Die Kalibrierung dieser Gegenstände ist jedoch weiterhin wichtig, um die Messzuverlässigkeit aufrechtzuerhalten.

Die Kalibrierung von Laborglaswaren gewährleistet genaue und zuverlässige Messungen, was für die Aufrechterhaltung der Integrität der Analyseergebnisse von entscheidender Bedeutung ist. Unabhängig davon, ob Sie Messkolben, Pipetten, Büretten oder andere Glaswaren verwenden, helfen richtige Kalibrierungstechniken, Fehler zu vermeiden und die Präzision der Laborarbeit zu verbessern.

Kalibrierung von Glaswaren

Die genaue Kalibrierung von Glaswaren wie Messkolben, Pipetten und Büretten ist unerlässlich, um genaue Messungen in der ...

Education

Lehre

JoVE Core

Analytical Chemistry

Analytische Chemie

Unit 1

Einheit 1

Method Development and Sampling Techniques

Methodenentwicklung und Probenahmetechniken

method-development-and-sampling-techniques

KEY TERMS AND CONCEPTS

WICHTIGE BEGRIFFE UND KONZEPTE

Glassware Calibration

calibrating lab glassware for accurate volume

Calibrating lab glassware helps students measure liquids accurately in the analytical laboratory. It reduces volume errors and supports consistent results across measurements. This matters when using volumetric flasks, pipettes, burettes, and other tools that depend on precise volume readings.

Volumetric flasks are used to prepare aqueous solutions with a precise final volume. They have a calibration line on the neck. To calibrate one, fill it with distilled water until the meniscus, the curved surface of the liquid, lines up with the mark at eye level. This is usually done at about 20°C because temperature can affect volume. If the water rises above the line, drain it carefully. If it is below the line, add water drop by drop until it reaches the mark. The flask’s capacity can then be checked by weighing the water and comparing it with the theoretical value from its density.

Pipettes are used to transfer set amounts of liquid. Volumetric pipettes are made to deliver one highly accurate volume, often to four or five significant figures. To calibrate one, clean it and rinse it with the solution to be measured, fill it to the calibration mark, and let it drain completely into a container. The volume delivered is checked by weighing the water and comparing it with the theoretical volume based on water density. Graduated pipettes have a series of marks and can deliver different volumes, but they are slightly less accurate. They are generally used to about three significant figures, so the meniscus must still be read carefully.

Burettes are long, graduated glass tubes with a tap at one end. They are used to dispense variable amounts of solution, especially during titrations. When a burette is calibrated, the meniscus must be aligned with the markings before and after use. The volume dispensed is then compared with the expected value by weighing the water delivered. The reservoir shows the liquid level, and the stopcock, or tap, acts as a manual valve that controls flow for precise measurement.

Other glassware, such as graduated cylinders, is also used for measuring volume. These tools are less accurate than volumetric equipment, but they are still useful for work that does not need the highest precision. They usually measure up to three significant figures. Even so, calibration remains important for reliable measurements in the lab. Careful calibration of lab glassware helps protect the accuracy and integrity of analytical results.

Calibrating Lab Glassware for Accurate Volume

calibrating-lab-glassware-for-accurate-volume

development of analytical methods

Analytical Methods: Technique to Protocol

Analytical methods follow a clear path from technique to protocol. In analytical chemistry, a technique is the scientific principle used to explain a chemical measurement. A method applies that technique to a sample of interest. The next steps are procedure and protocol. A procedure gives the directions for carrying out the analysis with an analytical method. A protocol is the detailed set of guidelines for that procedure, and it should be followed closely to get the desired results. <br...

quality control

Quality Control Charts and Lab Records

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quality assurance

Quality Checks in Analytical Testing

Quality assurance in analytical testing brings together the checks that help a system perform properly. It includes quality control, quality assessment, and internal corrective measures. These parts work in a cycle to support reliable results. Quality control happens before and during the analysis. Quality assessment takes place during and after the investigation. Internal corrective measures are then based on the results of post-analysis quality assessment, or they may be applied before a new...

data validation

How Analytical Methods Are Checked

Method validation checks whether an analytical chemistry method gives reliable results. It is especially important when the same method is used with different sample matrices or when the procedure is changed. Validation helps show that the method still meets acceptable standards in each case. Several key checks are used in method validation. Specificity means the method can measure the target analyte without interference from other substances. Linearity means the result changes in direct...

qualitative analysis

Classical and Instrumental Sample ID

Qualitative analysis identifies the elements, ions, or compounds in an unknown sample. It is the first step in the hierarchy of analytical goals. That makes it the starting point for scientific study before quantitative analysis or other forms of analysis. Two main approaches are used in qualitative analysis: classical methods and instrumental methods. Classical methods depend on the visible or sensory result of a chemical reaction, such as a color change, a precipitate, or even a smell. These...

quantitative analysis

Measuring Analyte Concentration

Quantitative analysis measures the amount of a specific substance, called the analyte, in a sample. If the sample composition is unknown, qualitative analysis comes first. That step identifies the components so the correct substances can be measured during the quantitative phase. This method depends on two key measurements. Scientists measure the sample quantity and also a property that is proportional to the amount of analyte. Together, these measurements help determine the analyte...

instrument calibration

Calibrating Lab Instruments for Accurate Results

Calibration helps lab instruments produce accurate and consistent results. It is important in manufacturing, healthcare, testing laboratories, and scientific research. Each instrument needs a calibration process that matches its design and function. This process improves data accuracy and helps results stay reliable. An analytical balance measures mass and needs regular calibration to stay precise. It is calibrated by comparing its readings with known standard weights. These weights act as...

glassware calibration

Calibrating lab glassware helps students measure liquids accurately in the analytical laboratory. It reduces volume errors and supports consistent results across measurements. This matters when using volumetric flasks, pipettes, burettes, and other tools that depend on precise volume readings. Volumetric flasks are used to prepare aqueous solutions with a precise final volume. They have a calibration line on the neck. To calibrate one, fill it with distilled water until the meniscus, the...

standard solutions

Preparing Standard Solutions in the Lab

Standard solutions are prepared to have a precisely known concentration or composition. In analytical chemistry, this accuracy is important because it supports reliable results. A primary standard is a highly pure, stable substance with a high molar mass. It is fully soluble in water, which is the most commonly used solvent in analytical chemistry. A primary standard solution can be used to standardize a secondary standard. Secondary standards have known concentrations, but they are usually...

blank solutions

Blank Solutions in Analytical Testing

Blank solutions are used in analytical testing to show the background signal before a sample is measured. A blank solution does not contain the analyte, which is the substance of interest being tested or measured. It is usually made with the same reagents and procedure as the sample solution, but without the analyte. The main purpose of a blank solution is to control for background interference and contamination. Reagents, solvents, or lab equipment can sometimes create a detectable signal on...

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sampling methods: sample types

Sampling Materials in Solid, Liquid, Gas

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sampling plans

Choosing Samples for Reliable Results

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sample preparation for analysis: overview

Preparing Samples by State and Form

Sample preparation depends on the state and form of the sample before analysis. It helps make the sample ready for accurate measurement. The main goal is to extract the analyte, which is the substance being measured, and remove parts that could interfere with the analysis. Solid samples often need the most handling. Large solids are usually ground, crushed, or milled to make them smaller and increase surface area. The sample is then sieved and mixed so it has a uniform composition. After that,...

sample preparation for analysis: advanced techniques

sample-preparation-for-analysis-advanced-techniques

Preparing Complex Samples for Analysis

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sample handling

Sample Transport and Storage Basics

Sample transport and storage help keep specimens intact before testing. Moving a sample from the collection point to the laboratory requires careful handling. The sample should be sealed well and clearly labeled. These steps help prevent cross-contamination and support reliable results. Temperature control is also important during transport. Some samples travel in insulated containers, cool packs, or refrigerated vehicles so they stay within the needed temperature range. After the samples...

contaminants and errors

Sampling Errors in Sample Preparation

Sampling errors in sample preparation can affect the accuracy of laboratory results. Two common problems are concentration bias from poor sample splitting and contamination from reducing particle size by grinding or homogenization. Recognizing these errors helps make analysis more reliable. The number of samples also matters when a target population follows a normal distribution. In that case, the sample size ns can be found with a formula that uses the t-value for the chosen confidence level,...

key terms and concepts

Learn how volumetric flasks, pipettes, burettes, and graduated cylinders are calibrated to improve volume accuracy, consistency, and lab reliability.

Calibrating Lab Glassware for Accurate Volume | JoVE K12

analytical chemistry

JoVE Core Analytical Chemistry simplifies complex chemical principles by breaking them down into clear, engaging animations, making topics from SI Units to NMR spectroscopy more accessible and straightforward. Additionally, the scientist-in-action videos highlight the application of these concepts in real-world research conducted in laboratories globally.

Calibrating Lab Glassware for Accurate Volume

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