2: Quantitative Techniques and Calibration

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Learning Objectives

After completing this module, students will be able to:

Use volumetric glassware and pipettes correctly to create solutions of known concentration.
Collect absorbance data using a single wavelength visible spectrometer (Spec 20).
Use absorbance data to build a external calibration curve and determine a compound's molar absoptivity.
Apply error analysis to determine the validity of a calibration curve.
Determine an unknown concentration.

The purpose of this introductory lab module is to practice using some of the basic quantitative techniques that you will use often in this course and in an analytical chemistry laboratory. These techniques include the use of an analytical balance, quantitative use of pipettes and volumetric glassware, quantitative solution preparation and dilution procedures. Although you may have used these basic equipment in previous laboratory courses, analytical chemistry requires a much higher level of precision and accuracy than you may have experienced in general or organic chemistry courses. One of the requirements for success in this course is the development of correct quantitative laboratory technique.

2.1: Pre-lab assignment
2.2: Basic Equipment
The array of equipment available for making analytical measurements and working with analytical samples is impressive, ranging from the simple and inexpensive, to the complex and expensive. With three exceptions— the measurement of mass, the measurement of volume, and the drying of materials—we will postpone the discussion of equipment to later chapters where its application to specific analytical methods is relevant.
2.3: Preparing Solutions
Preparing a solution of known concentration is perhaps the most common activity in any analytical lab. The method for measuring out the solute and the solvent depend on the desired concentration and how exact the solu- tion’s concentration needs to be known.
2.4: Methods of Calibration
2.5: Uncertainty in values determined from a Calibration Curve
How do we find the best estimate for the relationship between the signal and the concentration of analyte in a multiple-point standardization? The process of determining the best equation for the calibration curve is called linear regression, which is the focus of this section.
2.6: Procedure and instructions for data analysis
2.7: Operating Instructions for Spec 20's