CHEM 312 Lab Manual_2023-7

.pdf

School

Concordia University *

*We aren’t endorsed by this school

Course

312

Subject

Chemistry

Date

Oct 30, 2023

Type

pdf

Pages

Uploaded by AgentMoon9736

Intermediate Analytical Chemistry CHEM 312 Laboratory Manual Brigitte Desharnais, Cameron D. Skinner Summer 2023 revision Adapted from the 2008 revised version of the laboratory manual. Revised Summer 2023.

2 Table of Contents Prelabs ............................................................................................................................................ 3 Lab Report Instructions ................................................................................................................... 4 Statistics and Data Processing ...................................................................................................... 11 Determination of Trace Amounts of Copper and Zinc in an Aqueous Solution by Atomic Absorption Spectroscopy .............................................................................................................. 14 Determination of Riboflavin by Fluorescence Spectrophotometry ................................................ 21 Determination of Aspartame, Caffeine and Benzoic Acid by High Performance Liquid Chromatography (HPLC) ............................................................................................................... 26 Gas Chromatographic Determination of Isopropanol in a Mixture ................................................ 32 Determination of Ascorbic Acid by Differential Pulse Voltammetry .............................................. 38 Coulometric Determination of Arsenate ........................................................................................ 47 Quantitative Analysis of Citrus Essential Oils by Gas Chromatography – Mass Spectrometry .... 52

3 Prelabs: You must be prepared to enter the lab. To that end, you will prepare a prelab document for each experiment to be carried-out. It will have the following sections: • Your name & ID • Name of the experiment • Objectives One paragraph explaining the experimental objectives and general procedure. Underline 5 keywords/ideas relevant to carrying-out the lab. • Keywords Prepare one sentence explanations for each of the keywords/ideas • Procedures Prepare a step-by-step overview of the procedure(s). e.g. Step 1: obtain sample (record #, dry, weigh 3.0g, record weight) Step 2: prepare stock standard (weigh/record 1.0 g of Zinc, dissolve in 500 mls 10% HNO3, dilute to 1000 ml in volumetric) Step 3: etc… • Hazards List known/expected hazards both chemical and physical Prelabs ( as Word documents ) need to be emailed to Chem312@concordia.ca before 9 PM the night before the lab. Put “PRELAB: Experiment #” in the subject, replace the “#” with your experiment #. Only one prelab per email. Failure to do this will bar you from entering the lab.

4 Lab Report Instructions Late submissions will be penalized 10% per day late. For your all your lab reports, you must use the Word template available on Moodle. All lab reports ( as Word documents ) need to be emailed to Chem312@concordia.ca . Name your electronic files/documents as: Last name_ID number_experiment number (e.g. Skinner_12345678_1) . Notice the following: • In the title, each “major” word is capitalized but not the minor words (e.g. “Gas Chromatographic Determination of Isopropanol in a Mixture”). Follow the capitalization found in the table of contents of this lab manual if you have any hesitation; • Pages should be numbered; • Section titles should be capitalized and bolded. Abstract This should be a concise 1 paragraph summary of your report, approximately 100 words. It should describe the goal(s) of the experiment, the techniques used in the analysis (instrumental and calibration) and the significant findings (LOD, LOQ, number of the unknown and its calculated concentration with confidence interval). Example: In this experiment, a gas chromatograph coupled with a flame ionization detector was used to determine the concentration of ethanol in an unknown aqueous sample. An internal standard calibration was performed using four samples of known concentration. The LOD and LOQ of the method, set at 3 and 10 σ blank respectively, were found to be 0.001 and 0.003 mg/mL. The method was calibrated using a linear regression analysis and the concentration of unknown #1045 was determined to be (0.700 ± 0.005) mg/mL at the 95% confidence level.

5 Introduction The introduction should explain the theory behind the experiment. 1-2 pages should be sufficient (2 pages max) . This includes a description of the theoretical principles behind the instrumentation used and how the instrument itself works. This should show clearly how quantification of the analyte was accomplished. You should also include details on the calibration method used (external standard, internal standard, standard addition) and the appropriateness of choosing this method (its advantage(s)). The introduction should contain no specifics on the experiment itself (e.g. column used, solvent used, analyte treated or results obtained). NEW FOR 2023 There will be no Introduction section to any of the lab reports EXCEPT the “oral” lab report and the electrochemistry lab report (presentation) . For the Introduction section just write “Introduction: Not required” Experimental Procedure This section is intended to briefly describe the experimental procedure that was used to obtain the data. However, since you usually make no changes to the procedure laid out in the lab manual, you can simply cite it and note any changes from the established procedure. Example: As per lab manual (1). Changes to the established procedure: The standards concentrations were changed to 0, 0.2, 0.4, 0.6, 0.8 and 1.0 ppm. Note that the number in parenthesis in the example above refers to the reference number. The full reference of the lab manual must appear in the "Reference" section of your report, under (1). Results This section must include the following: 1) Original data, in a table 2) Treated data, in a table (data after calculations/transformations, if applicable) 3) Calibration graph (including error bars, if possible) 4) Calibration data, in a table (slope and intercept value, with their associated error) 5) Unknown concentration and its associated error (confidence interval) 6) LOD and LOQ

6 Everywhere a calculation is done (e.g. for the treated data, the unknown concentration, its error, the LOD and the LOQ), a sample calculation is required . Building equations in Word documents is quite easy now (Insert/Equation) also, many of the basic equations can be copy/pasted from the formula sheet (Word version available on Moodle is likely to work best, reference…) So ALL sample calculations must be typewritten (no hand-written equations/calculations, yes, you can skip over basic steps in a multi-step calculation. The purpose here is to make sure you’re using the correct equation and variables/values) Tables and graphs should be titled and numbered. Notice, the convention is to put the caption above tables and below for figures. Example: Table 1: Calibration Data for Isopropanol Concentration ( %) Peak Area (mV*min) Ratio Methanol Isopropanol 20 490248 387957 0.791348 25 411197 411094 0.999750 30 411651 480145 1.16639 35 382722 650770 1.70037 Figure 1: Calibration Curve for Isopropanol

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version