Questions and Answers
Sampling is not critical for the accuracy of measurements.
False
What is the act of collecting samples to produce meaningful information called?
What is the purpose of sampling?
To obtain a representative sample of the whole sample that can be taken to the laboratory for chemical analysis.
Which sampling technique involves dividing a material into quarters and taking samples from them?
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Match the terms to their definitions:
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What does homogeneous mean in the context of sampling?
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The _________ sample is a smaller portion obtained from a gross sample for analysis.
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What are the steps involved in sampling bulk material?
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Liquids are __________ to sample compared to solids.
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What is an example of a tool for solid sampling?
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Study Notes
Sampling Overview
- Sampling is a critical step in analysis that affects measurement accuracy.
- Proper collection, transport, and selection of samples are essential for reliable results.
- Sampling involves obtaining a representative and homogeneous sample from a larger population.
Types of Samples
- Population: Entire group from which samples are drawn.
- Sample: Subset of the population for analysis.
- Sampling: Process of collecting samples that accurately reflect the bulk content.
Sample Classification
- Meso: Weight > 100 mg, Volume > 100 μL
- Semimicro: Weight 10-100 mg, Volume 50-100 μL
- Micro: Weight 1-10 mg, Volume < 50 μL
- Ultramicro: Weight < 1 mg
- Minor: Weight 0.1-1 mg
- Trace: Weight < 0.1 mg
- Ultratrace: Parts per million or lower.
Sampling Techniques
- Selection of sampling technique depends on:
- Size of bulk material.
- Physical state of the sample (solid, liquid, gas).
- Chemical properties of the sample.
- Samples should not destroy or alter the identity/quantity of the analyte.
Steps in Sampling Bulk Material
- Identify the target population.
- Collect a gross sample that properly represents the population.
- Reduce the gross sample to a suitable laboratory sample.
Sampling Solids
- Solid samples can be difficult due to material inhomogeneity.
- Grab Sample: A random sample taken, assumed to be representative.
- Recommended to take 1/50 to 1/100 of the total bulk for reliable results.
Coning and Quartering Method
- Divide a bulk sample into quarters.
- Take samples from each quarter and crush to form a conical pile.
- Flatten and cut the conical pile into quarters, randomly selecting two opposite quarters.
- Crush the selected quarters further until a laboratory sample is obtained.
Tools for Solid Sampling
- Tablet Sampler: Designed for sampling tablets and capsules during filling.
- Tubular Sampler: For taking samples from soft and semi-solid materials.
- Scooper: Stainless steel scoop (5 oz capacity) for sampling powders, soil, and gravel.
Sampling Liquids
- Liquid samples are generally homogeneous and easier to sample compared to solids.
- Procedures for sampling liquids ensure consistency and representativeness.
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Description
Explore the essential concepts in Chapter 4 of the analysis course, focusing on the critical aspects of sampling, techniques of sampling for solids, liquids, and gases, and methods for sample storage. This quiz emphasizes the importance of accuracy and reliability in analytical results.
