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Stock Solution and Calibration Standard Preparation

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    Exercise Learning Objectives:

    1. Apply concepts of accuracy, tolerances, and significant figures to a practical laboratory scenario.
    2. Develop scientific “common sense”.
    3. Communicate (oral and written) scientific concepts related to calibration and standardization.

    In Class Exercise:

    • Work in groups of 3-4 students.
    • Develop a consensus for a proposed laboratory procedure.
    • Summarize the laboratory procedure in written form and be prepared to present the procedure to your fellow classmates.

    Introduction: In the Kinney lab we frequently monitor the concentration of trace quantities of pharmaceuticals and personal care products (PPCPs) in environmental matrices. There is growing awareness that PPCPs are common environmental contaminants, especially in environments impacted by wastewater end products. Modern instrumentation such as an LC/MS or LC/MS/MS allows chemists to measure fluoxetine (an antidepressant) and other PPCPs down into the ppb and ppt concentration ranges. When studying a PPCP like fluoxetine we generally prepare a relatively large quantity (25 - 100 mL) of stock (standard) solution of the analyte from which calibration standards and spiked samples can be prepared from.

    1. Stock Solution Preparation: Provide a detailed description of a practical stepwise process to produce 50 mL of a 5 - 20 mg/mL stock fluoxetine (C17H18F3NO; CAS 54910-89-3; 309.33 g·mol-1) solution in methanol. You have a bottle of fluoxetine (99.8%) analytical standard to start with, and you can propose to use any common laboratory tools at CSU-Pueblo such as:
      Analytical balance Transfer Pipet (1, 2, 5, 10, & 25 mL) Pasteur Pipet
      Top Loading Balance Range of Volumetric Flask Funnels
      Range of Erlenmeyer Flasks 50 mL Class A buret Range of Beakers
      Range of graduated cylinders (5, 10, 25, 100 mL) Micropipets  

      If there are other laboratory tools you would like to propose using,

      In addition to the steps to take to prepare such a standard, please provide a specific example with sample calculations and the final concentration of the fluoxetine solution that is produced.


    1. Concentration: Express the concentration of the fluoxetine solution in parts per million (ppm).


    1. Calibration Standards: Describe in detail how to practically prepare 50, 100, and 250 parts per billion (ppb) fluoxetine solutions in methanol to be use to calibrate an instrument. The calibration solutions will need to go in a 2 mL sample vial that can be used in an instrument's auto sampler.


    1. Big Picture: What considerations did you make when developing your stock solution and calibration standards?


    Contributors and Attributions

    This page titled Stock Solution and Calibration Standard Preparation is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Contributor.