SH internal Ellman's Reagent CO₂H disulfide crosslink O₂N- HO₂C solvent- exposed thiol UV Absorbance at 412 nm O₂N- O₂C TNB2- alkaline pH + O₂N- -SH 2-nitro-5-thiobenzoate (TNB) -NO₂ mixed disulfide CO₂H a) Provide a detailed arrow-pushing mechanism for the reaction of a thiol (you can use R-SH) with Ellman's reagent to produce a mixed disulfide and TNB. Ellman's Reagent CO₂H S -NO2 - R-SH + O₂N- S HO₂Cmo CO₂H S + NO2 O₂N- SH R-S HO₂C Mixed disulfide TNB

SH internal Ellman's Reagent CO₂H disulfide crosslink O₂N- HO₂C solvent- exposed thiol UV Absorbance at 412 nm O₂N- O₂C TNB2- alkaline pH + O₂N- -SH 2-nitro-5-thiobenzoate (TNB) -NO₂ mixed disulfide CO₂H a) Provide a detailed arrow-pushing mechanism for the reaction of a thiol (you can use R-SH) with Ellman's reagent to produce a mixed disulfide and TNB. Ellman's Reagent CO₂H S -NO2 - R-SH + O₂N- S HO₂Cmo CO₂H S + NO2 O₂N- SH R-S HO₂C Mixed disulfide TNB

Principles of Instrumental Analysis

7th Edition

ISBN:9781305577213

Author:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Publisher:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Chapter9: Atomic Absorption And Atomic Fluorescence Spectrometry

Section: Chapter Questions

Problem 9.6QAP

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A 5.00-mL sample of blood was treated with trichloroacetic acid to precipitate proteins. After centrifugation, the resulting solution was brought to pH 3 and extracted with two 5-mL portions of methyl isobutyl ketone containing the lead-complexing agent APCD. The extract was aspirated directly into an air/acetylene flame and yielded an absorbance of 0.527 at 283.3 nm. Five-milliliter aliquots of standard solutions containing 0.400 and 0.600 ppm of lead were treated in the same way and yielded absorbances of 0.396 and 0.599. Find the concentration of lead in the sample in ppm assuming that Beer’s law is followed.
A 5.00-mL sample of blood was treated with trichloroacetic acid to precipitate proteins. After centrifugation, the resulting solution was brought to pH 3 and extracted with two 5-mL portions of methyl isobutyl ketone containing the lead-complexing agent APCD. The extract was aspirated directly into an air/acetylene flame and yielded an absorbance of 0.569 at 283.3 nm. Five-milliliter aliquots of standard solutions containing 0.400 and 0.600 ppm of lead were treated in the same way and yielded absorbances of 0.396 and 0.599. Please calculate the concentration of lead in the sample in ppm.
Exactly 6.00 ml of acetic acid (density = 1.05 g/mL), MW =60.05) was added to a 1 –liter volumetric flask, and the flask was filled to the mark with distilled water. A portion of the resulting solution was added to a conductance cell (k = 1.25 cm-1), and the conductance was found to be 416 μS. Calculate the dissociation constant Ka of acetic acid. ΛoH+= 349.8 Scm2/mole and ΛoCH3COO- = 41 Scm2/mole
A solution prepared by dissolving 25.8 mg of benzene (C6H6, FM 78.11) in hexane and diluting to 250.0 mL has an absorption peak at 256 nm, with an absorbance of 0.266 in a 1.000-cm cell. Hexane does not absorb at 256 nm. Find the molar absorptivity of benzene at this wavelength.
Using the absorbance of [FeSCN]+2 at the wavelength of maximum absorption which you obtained in part B, and the diameter of the tube, obtained in part A,calculate the molar extinction coefficient. given info: Concentration of Fe3+ stock solution, C1 = 0.001 M Volume of stock Fe3+ solution pipetted, V1 = 25mL Concentration of diluted stock solution, C2 = 0.0004 M Volume of Fe2+ solution and KSCN (upon mixing) = 10mL Weight of KSCN = 1g The reaction taking place is given as: The reaction taking place is given as: F e 3+ (aq) + SC N − (aq) ⇔Fe [SCN] 2+ (aq) the concentration of [FeSCN]2+ after the mixing of Fe3+ and SCN- is 2.5 x 10-3 M. Moles of [FeSCN]2+ = 2.5 x 10-5 moles Diameter:1.2cm The wavelength at which maximum absorption takes place is = 480 nm
At 21 °C, a solution of 12 mL each of 0.00200 M Fe3+ and 0.001000 M SCN- was mixed and brought to 25.0 mL with 0.1 M HNO3. The absorbance at 450 nm was measured to be 0.350 (A450 = 0.350). This solution was then heated to 45 °C and the absorbance at 450 nm was measured to be 0.142 (A450= 0.142). Is the reaction: Fe3+(aq) + SCN -(aq) → FeSCN2+(aq) exothermic or endothermic? Explain.
analyte concentration(C)(mg/ml) injection volume (ul) elution time (time) peak DAD signal(mAU) caffeine 1 1 4.67 302.85 aspartame 5 1 7.53 15.83 benzoic acid 1 1 8.14 89.98 saccharin 1 1 1.91 84.86 mixture(add everything above with 1:1:1:1 ratio) 1 4.47 69.58 How to get the concentration of the mixture in this case?
1) Calculate the molar extinction coefficient (molar absorptivity) of tartrazine in units of 1/(M·cm). Assume a cuvette path length of 1.00 cm. 2) If Ana determines the absorbance of an unknown tartrazine sample to be 0.662, what is the concentration of the sample in µM?
Calculate the concentration of lycopene in your orange fraction using using Beer's law equation A=ExBxC A is the measured absorbance, E is the molar extinction coefficient (M-1cm-1) at a particular wavelength, B is the path length (in cm) and C is the analyte concentration (M). A= 0.602. Wavelenght is 500.95nm. Molar extinction coefficients is 123,000M-1cm-1
(9.29 × 105/8)-20.81 = with correct sig figs
When 8.0 ml of 0.00200M KSCN is mixed with 2.0 ml of 0.00200M Fe(NO3)3, the measured absorbance (A) at 450 nm is 0.285. The cell’s pathlength (b) is 1.0 cm; the absorptivity (ε) constant is 4700M-1cm-1. Calculate Kf for Fe(SCN) +2.
15.5 mg of Anthracene was dissolved in 200 mL of cyclohexane to prepare thestock solution. 10 mL of the stock solution was transferred to a 1000 mLvolumetric flask and made up to the mark with cyclohexane. The concentrationof the diluted Anthracene solution was measured by Fluorescence spectroscopyand showed to be 740 ppb. Calculate the % error