chm410h-d2009 - Name Student Number UNIVERSITY OF TORONTO...

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Unformatted text preview: Name Student Number UNIVERSITY OF TORONTO Faculty of Arts and Science December 2009 Examination CHM 410H1F / ENV 1410H Analytical Environmental Chemistry Duration — 3 hours Calculators are permitted. Total mark = 97 points over 9 questions with 5 bonus marks possible Total 13 pages Tables 1 and 2 on page 2 for reference Marks for the test are allocated on a ‘mark-a-minute’ basis, so please judge the amount of detail required based on the number of marks allocated for each question. Table 1. Isotopic abundance and mass for select elements. Element Symbol Abundance (°/o) Isotopic mass 9. . 2 Hydrogen H 9 985 1 0078 5 0.015 2.014102 98.90 12.000000 Carbon C 1.10 13.003355 , 99.63 14.003074 Nitrogen N 0.37 15.000109 99.76 15.994915 Oxygen O 0.04 16.999131 _ M _ _ _ I _ _ _ 0.20 17.888160 Fluorine F 100 18.998403 Phosphorus P 100 30.973762 95.03 31.972072 Sulfur S 0.75 32.971459 4.22 33.967868 75.77 34.968853 Chlorine C] 24.33 36.965903 50.69 78.918336 Bromine Br 49.31 80.916289 1.4 203.973029 24.1 205.974449 Lead Pb 22.1 206.975881 52.4 207.976636 Table 2. Performance characteristics of select mass spectrometers. ______________________—_______—_—..—_———-—————— Magnet” Time of Flight FT—ICR Characteristic Quadrupole Ion trap Sector __________________________ Mass Range < 4000 < 4000 15,000 Unlimited >1 O4 ..... WLIPIQWMWW....m.-WW.W..........WW-.-W..WWWW-WWW m... Resolvmg 4000 103_104 102-105 15,000 >106 WWWPJBXYEE ............................................ MWW WWWWWWWWWW W...an ..... W Mass Accuracy 100 50_100 1_5 5_50 1-5 (ppm) ____.__..——————————— 20f13 Question 1. Match the terms in Column 2 with the most appropriate terms from Column 1. (4 marks) Column 1 Column 2 1. Metal analysis __ a. Chromophore 2. Electron impact ionization __ b. Beta particles 3. Electrospray ionization __ C. 13C labelled 4. UV detection __ d. Extraction blanks 5. MALDI __ e. Positive ions 6. Electron capture detector __ f. Desorption 7. Internal calibration __ g. Plasma 8. Quality control h. Taylor cone Question 2. For the following compounds and matrix propose an appropriate extraction technique and method of detection. (10 marks) Cl CI Cl Cl r “O i “D AO7P\0 / A°7P\o / /\O HO Ci Cl napthylene ' I air Chlorpyrlfos Chlorpyrlfos soil degradation product water NH )NkH NH N N N NJKN)K H H H H Acetaminophen water H )k H HN NH U'kfl/ . 0 Ci Cl Chlorhexidine water 3of13 Question 3. You are an analytical chemist interested in quantifying amino acid levels in a specific matrix using HPLC with a suitable light detector (your HPLC is unfortunately not equipped with a mass spectrometer!) In order to analyze for the amino acids, you react your prepared extract with dansyl chloride (structure shown below). The structure of glycine, the simplest amino acid, is also given. ° \N O Rh / 0 OH H —c Q g ' Glycine Dansyl chloride (a) Please draw the reaction product of glycine with dansyl chloride and explain what type of detector would be best suited to quantify this derivative? (3 marks) (b) What are the major advantages and disadvantages of this type of detector (in general, not this specific example)? (5 marks) Question 4. Anion and cation exchange SPE cartridges (WAX and WCX) were only developed for polymeric SPE resin and not for silica based SPE cartridges (ie. C18 SPE). Why? (3 marks) 40f13 Question 5. In a recent paper in Environmental Science and Technology Guerard et al. investigated the photochemical degradation of sulfadimethoxine, a common anti—bacterial agent. . Photochemical Fate of Sulfadimethnxine in Aquaculture Waters IENNIFER I, GUERARD,‘ YUvPI N (3 (3H I.N."" H BATH MASH." AN D CHRiSTOPI—IER M, HADAD§ School qfflmm Sciences and Erwir‘onmenriii Sciences Cmdume Frog/tun, 'e. Ohio Stare Uninsrsftjv, .l25 S. (Mai Mn”, Colmnims Ohio 43210. (1.5. Elwimmzrenm.’ szecn‘ori 5. my, NRMRi/l-‘VSWRD’TTEB. 26 W. .\ [11.17311 Luther King 19!: C mm Ohio 45268. and Dawning!“ of C’lc‘fliiSH)’, 'Ii‘ue Oin‘cv Stare Urnwrsity. MC! Wits}, .LS‘fii zu’P’luff. Colmm‘ms Ohio 433}. In this study they identified Product 1 as a photochemical degradation product of sulfadimethoxine. H3CO H3CO Sulfadimethoxine Product1 (a) For the analysis of sulfadimethoxine please describe an appropriate interface for a time of flight mass spectrometer (i.e. chromatography (GC or LC) and appropriate ionization interface). (3 marks) (b) Could you analyze for Product 1 using your analytical instrument described in part (a)? Why or Why not? (3 marks) 50fl3 Guerard et a1. identified another photodegradation product where a hydroxyl group was added to one of the phenyl rings. However, using their time of flight mass spectrometer they could not determine which phenyl ring had been oxidized (i.e. they could not distinguish between Product 2 and Product 3 shown below). OH l ‘u’ S? H2N / \ fi—NH HZN fi—NH — o N o N / >706...3 HO / \>—OCH3 H300 ch0 Product 2 Product 3 (c) A time of flight mass Spectrometer cannot distinguish between Product 2 and Product 3. Why? (3 marks) (d) Of the mass spectrometers discussed in class could any distinguish between Product 1 and Product 2? Why or why not? (3 marks) (e) Would sulfadimethoxine be an appropriate analyte to use an ELISA assay for the analysis of environmental samples? Why or why not? (3 marks) 6of13 (f) Would ELISA be an appropriate technique to follow the photodegradation experiments of sulfadimethoxine described above? Why or Why not? (3 marks) Question 6. You are interested in analyzing for the antihistamine Dexbromopheniramine from wastewater treatment plant effluent samples. The LC—ESI—MS/MS (electrospray ionization triple quadrupole mass Spectrometer) in your lab has an instrumental detection limit for Dexbromopheniramine of 5 ug/L. You expect the effluent samples to be contaminated with Dexbromopheniramine at concentrations of 100 ng/L. (a) Design a sampling and extraction scheme for the analysis of Dexbromopheniramine from the wastewater treatment plant samples. (5 marks) Br Dexbrompheniramine (b) What is the concentration of Dexbromophem’ramine you expect in your final extract? (1 mark) (c) What is the mass of Dexbromopheniramine that will be present in the instrument after a 10 uL injection of your extract diluted 1:1 with water? (1 mark) 70f13 (d) Explain how gas phase ions of Dexbromopheniramine are delivered to the mass spectrometer by electrospray ionization (ESI). (5 marks) (e) Explain how Dexbromopheniramine ions are analyzed in the triple quadrupole mass spectrometer. (5 marks) (f) Explain how a signal is produced in the mass spectrometer from Dexbromopheniramine ions. (3 marks) 80f13 Question 7. Tetra—ethyl lead was added to gasoline as an anti—knock agent, until concerns over toxicity resulted in its phase out in North America starting in the late 1970s. In a recent paper in Analytical Chemistry Borges et al. used the setup shown below to test the ability of the Direct Analysis in Real Time (DART) ionization source to analyze tetra—ethyl lead by mass spectrometry. Ambient Mass Spectrometric Detection of Organometallic Compounds Using Direct Analysis in Real Time Daniel L. G. Barge-s,M Ralph E. Slur/990m")? Bernhard Weiz,‘ Aditson Jr (Juniors,t and Zoitz’m Mester’ institute for Mamba" flzfeaswemems Starm‘ani’sz National Research Council Canada, Ottawa. Ontario, Canada MA 093, and Deparranmmo de Carmina, Um'versidade Federal de Santa Catarina, 88849989, anlandpoe’is, SC, Brazil In this experimental setup tetra—ethyl lead (structure below) was added to a closed Vial, and the headspace was directed to the DART ion source and the mass spectrometer. N2 + headspace vapor to DART I Ms . out “_____~__> N2 In —-——> ——'+ Mass Spectrometer t Plasma MS inlet Headspace HZCHa vapor fi; flincsz3 H H c gamma 3C 2 CHZCH3 (organometalhc pure or dissolved in toluene) tetra—ethyl lead (a) To validate the results using the DART ion source, describe a different setup to determine the gas phase concentrations of tetra-ethyl lead in the headspace of the Vial. (5 marks) 9of13 The DART source is an atmospheric pressure ionization source that is meant to be used for field analysis. If we were able to take a mass spectrometer with a DART ion source with us to Crawford Lake we could potentially do the analysis directly from the sediment core simply by pointing the DART source at the sediment. DART ionization is a soft ionization source, and so if organic lead species (such as tetra—ethyl lead) are present there is the possibility they could be distinguished and separately quantified from the inorganic lead present in the same sample. (b) Describe the sediment extraction method used for the Crawford Lake sediment samples, and comment on whether this technique allows us to distinguish between the organic and inorganic lead species present in the sediment sample? (4 marks) (c) How does the inductively coupled plasma atomic emission spectroscopy (lCP— AES) instrument detect metals in the sediment extract? (5 marks) 10 0f13 (d) Can the ICP-AES distinguish between organic and inorganic lead species? Explain your answer. (3 marks) (e) Could organic and inorganic lead species be distinguished using an ICP interfaced to a mass spectrometer (ICP—MS)? Explain your answer. (3 marks) The mass spectrum shown below resulted from the gas phase ionization of tetra—ethyl lead by the DART ionization source using helium ions. Although DART is a soft ionization technique, excess energy from the ionization process can result in fragmentation. (Note: the ions in this mass spectrum are positive ions) (f) Which ion is the base peak, and what is the molecular formula of this ion? (2 marks) 200 225 250 275 300 325 350 375 mlz (g) What ion(s) would you select for single ion monitoring? Why? (2 marks) 11 ofl3 (h) Can you predict any problems that may arise by using the ions from part (g) for the analysis of tetra—ethyl lead in environmental samples? (4 marks) Question 8. Triple quadrupole and ion trap mass spectrometers can provide similar information. Triple quadrupoles are commonly hyphenated to a GC or LC, what is the limitation to hyphenating an ion trap mass spectrometer in the same way? (3 marks) Question 9. Why does electron capture negative ionization (ECNI) produce lower limits of detection for hexachlorobenzene as compared to El ionization? (3 marks) 12 ofl3 Bonus Question. You are interested in calibrating a PTR—MS for the analysis of the hydroxyl radicals (OH). Calibration for the analysis of this species is complicated since OH has a lifetime of only about 1 second. Therefore OH must be generated by photolyzing water with a Hg lamp. From the idealized signal below calculate the concentration of OH for the signal observed. (5 marks) (Hint: Convert H20 into number density (molecules cm'3)) Reagent ion = mass63 OH Ion = mass97 Given Temp = 273K Pressure = 1 atm The absorption cross section of water at l84.9 nm (03,20) = 7.2xlO'20 cm2 photon‘1 The lamp output ( ¢184W") = 3.0x1010 photons cm'2 H20 pressure at 273 K = 6.0x10'3 atm Avogadro’s Constant = 6.02xlO'23 molecules mol'1 Ideal Gas Constant (R) = 0.08206 L atm moi‘1 K" Equations Eq 1. pV = nRT Eq 2- [OH] : $184.9an-HZOI:H20] E 3 [OH] :[i mass99] q I [mp T kt mass63 [amp 300,000H ....................................................................................................................................................................... mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm w 1 KM". Reagent Ion 1112:5583 Lamp On 5800Hz ~ . . . . . . . ~ . . . . . . . . _ - . / massSB Signal Background \ 100Hz 20H Time 13 of13 ...
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This note was uploaded on 01/05/2012 for the course CHM 410 taught by Professor - during the Fall '11 term at University of Toronto.

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chm410h-d2009 - Name Student Number UNIVERSITY OF TORONTO...

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