Gas Chromatography and HPLC Techniques for Analytical Chemistry

Gas Chromatography Temperature Programs and HPLC Gradient Elutions

Using text and diagrams as appropriate, answer the following questions. This should probably take about 3-4 pages. Text has to be typed but figures can be hand drawn if necessary. Acknowledge all your sources.Submission must be as a single Word or PDF file to the MyLS Dropbox.(a) Explain what temperature programs are in gas chromatography, AND what gradient elutions are in HPLC.Why are these techniques used?(b) In a preliminary experiment, a solution containing 0.0837 M X and 0.0666 M S gave peak areas ofAX=423andAS=347. To analyze the unknown, 10.0 mL of 0.146 M S were added to 10.0 mL of unknown andthe mixture diluted to 25.0 mL in a volumetric flask. This mixture gaveAX=553 andAS=582. Find theconcentration of X in the original unknown.(c) Solute A has a partition coefficient of 3 between toluene and water, with three times as much in the toluenephase. Suppose that 100 mL of a 0.010 M aqueous solution of A are extracted with toluene. What fractionof A remains in the aqueous phase (i) after one extraction with 500 mL is performed or (ii) if five extractionsof 100 mL are performed?(d) You are tasked with developing an analytical method for a mixture of non-volatile molecules of variablepolarity. How would you proceed? Provide as many details as possible in order to explain how you woulddevelop an analytical protocol. Assume you can have any instrumentation/equipment that you need.(e) Coprostanol is an indicator of sewage input to sediments and can be determined, after solvent extraction,by GC. For this determination 5α-cholestane can be used as an internal standard. Determine the con-centration of coprostanol (in mM/g of sediment) in a sediment sample if the analysis and measurementsproceeded as follows ...•A octanol solution containing 3.12 mM of coprostanol and 1.10 mM of internal standard (5α-cholestane)was prepared.•Upon chromatographic separation of the peak area for coprostanol and internal standard were 3923and 10387, respectively.•5.034 g of sediment was weighed out.•This sediment was extracted with solvents. The final extract was quantitatively dissolved in 10.00 mLof octanol.•1.00 mL of 8.97 mM 5α-cholestane was added to 5 mL of the sediment extract and the mixture wasdiluted to 10.0 mL.•After chromatographic separation this solution gave a peak area of 5723 and 4655 for analyte andinternal standard, respectively.(f) With reference to the figure, explain the basis for quantitative and qualitative analysis by gas chromatogra-phy.CH262 Individual Assignment #31Winter 2021