Name: preparing standard solutions in the lab
Uploaded: 2024-12-05T18:31:54.000Z
Duration: 1 min 14 s
Channel: JoVE

Una soluzione standard è una soluzione con una quantità di sostanza nota con precisione. Viene preparato a partire da uno standard primario: una sostanza altamente pura, ad alta massa molare, idrofila e stabile.
La preparazione consiste nel pesare accuratamente la quantità appropriata di uno standard primario in una barca di pesatura e trasferirla in un matraccio tarato utilizzando un imbuto. Il recipiente di pesatura vuoto viene ripesato per verificare la presenza di eventuali residui di sostanze solide.
Aggiungere piccole quantità di acqua distillata per far scendere i solidi nell'imbuto nel pallone. Il matraccio tarato viene fatto roteare per sciogliere completamente il solido. Viene aggiunta altra acqua fino a quando il suo livello non si avvicina al segno di calibrazione. A questo punto, l'acqua viene pipettata per aumentare il livello della soluzione esattamente fino al segno di calibrazione.
Il pallone viene chiuso e capovolto più volte per garantire una miscelazione completa. Etichettare il pallone con la composizione chimica, la concentrazione e la data di preparazione.
Questa soluzione standard primaria viene utilizzata per standardizzare gli standard secondari: sostanze meno pure e meno stabili.

soluzioni standard

Le soluzioni standard si riferiscono a soluzioni con una concentrazione, o composizione, nota con precisione. Uno standard primario è una sostanza stabile, altamente pura, con massa molare elevata e completamente solubile in acqua, si tratta del solvente più comunemente usato nella chimica analitica. La soluzione standard primaria può essere utilizzata per standardizzare gli standard secondari, che sono delle sostanze con concentrazioni note ma meno pure e stabili. Le soluzioni standard sono essenziali per ottenere dei risultati accurati e affidabili nelle procedure analitiche, quindi comprenderle è fondamentale per chiunque lavori in un ambiente di laboratorio.

La preparazione di una soluzione standard utilizzando uno standard primario comporta diversi passaggi:

<ul style="list-style-type: disc; display: flex; flex-direction: column; padding: 0 0 0 30px;">
	<li>Pesare lo standard primario: utilizzare un contenitore per pesate per pesare la quantità appropriata di standard primario. È fondamentale utilizzare una bilancia di pesata in grado di fornire delle misurazioni precise.</li>
	<li>Trasferire lo standard in un matraccio volumetrico: utilizzare un imbuto per trasferire con attenzione lo standard primario pesato in un matraccio volumetrico pulito e asciutto. Assicurarsi che tutto il solido venga trasferito dal contenitore per pesate al matraccio. Dopo il trasferimento, ripesare il contenitore per pesate vuoto, per confermare che non rimangano residui.</li>
	<li>Lavare l'imbuto: usare delle piccole quantità di acqua distillata per lavare via qualsiasi materiale solido dall'imbuto nel matraccio volumetrico. Questo garantisce che tutto lo standard primario sia disciolto nella soluzione.</li>
	<li>Sciogliere il solido: ruotare il matraccio volumetrico fino a quando il solido non è completamente disciolto. Potrebbe essere necessario aggiungere gradualmente dell’acqua fino a quando il solido non è completamente disciolto.</li>
	<li>Avvicinarsi alla linea di calibrazione: aggiungere altra acqua distillata per portare il livello della soluzione vicino al segno di calibrazione sul collo del matraccio volumetrico. Assicurarsi che il solido sia completamente disciolto prima di aggiungere altro solvente, così da evitare di superare la linea di calibrazione.</li>
	<li>Regolare il menisco: utilizzare una pipetta per aggiungere l’acqua goccia a goccia, fino a quando il fondo del menisco (la curva sulla superficie del liquido) si allinea esattamente con il segno di calibrazione. Questo passaggio garantisce che la soluzione abbia il volume e la concentrazione corretti.</li>
	<li>Miscelare la soluzione: chiudere saldamente il matraccio volumetrico e capovolgerlo più volte per garantire una completa miscelazione della soluzione.</li>
	<li>Etichetta: etichettare il pallone volumetrico con la composizione chimica, la concentrazione della soluzione e la data di preparazione. Queste informazioni aiutano a identificare e utilizzare correttamente la soluzione.</li>
</ul>

Soluzioni standard

Le soluzioni standard si riferiscono a soluzioni con una concentrazione o una composizione nota con precisione. Uno standard primario è un elevato grado di purezza, ad alta massa molare, ...

Education

Didattica

JoVE Core

Analytical Chemistry

Chimica Analitica

Unit 1

Unità 1

Method Development and Sampling Techniques

Sviluppo del Metodo e Tecniche di Campionamento

method-development-and-sampling-techniques

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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 less pure and less stable. This makes primary standards especially useful when exact measurements are needed in a laboratory setting.

The preparation starts by weighing the primary standard with a balance that gives precise measurements. The solid is then transferred through a funnel into a clean, dry volumetric flask. It is important to move all of the material from the weighing boat into the flask. The empty weighing boat is reweighed to confirm that no residue remains.

Next, small amounts of distilled water are used to wash any solid from the funnel into the volumetric flask. The flask is then swirled until the solid dissolves completely. More water is added gradually until the liquid is close to the calibration line on the neck of the flask.

The final volume is set by adjusting the meniscus, which is the curved surface of the liquid. A pipette is used to add water drop by drop until the bottom of the meniscus lines up exactly with the calibration mark. The flask is then closed and inverted several times to mix the solution well. At the end, the flask is labeled with the chemical composition, the solution concentration, and the preparation date.

Preparing Standard Solutions in the Lab

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

Quality control charts, proficiency testing, and lab records are key parts of quality control in a laboratory. These steps help keep a system under statistical control. They also help track data, show trends, and spot variations that may affect the accuracy of an analysis. One common tool is a quality control chart. This chart plots one or more analytical characteristics over time. The measured values are taken at different times during the analysis and compared with the known value of...

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 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...

standard solutions

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...

sampling methods: overview

How Sampling Shapes Lab Results

Sampling shapes lab results by determining how a smaller sample represents a larger population. In analytical chemistry, testing an entire population is often impractical or impossible, so samples are collected to make inferences about the whole group. The sampling method is the process used to choose individuals or items for that sample. Common sampling methods include random, judgemental, systematic, stratified, and cluster sampling. Each method can affect the quality of the data in a...

sampling methods: sample types

Sampling Materials in Solid, Liquid, Gas

Sampling materials are grouped as solid, liquid, or gas. The type of sample helps decide the right collection method. Solid samples can include sediments from water bodies, soil, metals, and biological tissues. Sediment sampling from water bodies can be done in two common ways. Grab sampling uses a device to collect a discrete sample from the bottom with minimal disturbance. These samples may not show the full area because conditions can vary from place to place. Piston coring collects a...

sampling plans

Choosing Samples for Reliable Results

Sampling is a key step in analytical chemistry. It helps researchers collect data that represents a larger population. The main sampling methods in this topic are random, judgmental, systematic, stratified, and cluster sampling. Random sampling gives each member of the population an equal chance of being chosen. Researchers often use a random number generator or a lottery-style method. For example, a polymer sheet can be divided into 1 cm x 1 cm sections, and 10 sections can be selected at...

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 standard solutions are prepared from a primary standard using a volumetric flask, accurate weighing, meniscus adjustment, and proper labeling.

Preparing Standard Solutions in the Lab | 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.

Preparing Standard Solutions in the Lab

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