1. CHEM 213 Instrumental Analysis Lab Lecture – Glucose and GC

2. 2 Determination of Sucrose and Glucose Sucrose glucose Glucose Autoanalyzer Glucose enzyme H2O2H2O2 Detect H 2 O 2 electrochemically Does not detect sucrose

3. 3 Outline of Procedure 1.Solution prep and hydrolysis of sucrose to glucose 1.5-2 hours Done 1-2 weeks in advance slow 2. Run samples and standards on autoanalyzer Book 35 min time slot

4. 4 2. Principle Controlled rate of diffusion of glucose to electrode  -D-Glucose + O 2 (g) Glucose oxidase Product + H 2 O 2 Allows only H 2 O 2 to electrode 2H + + O 2 + 2e - H 2 O 2 E applied = 0.7 V Other species can be oxidized Current  [H 2 O 2 ]  [glucose]

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6. 6 Reactions In the electrode, have two reactions –At enzyme layer –At electrode surface β-D-glucose + O 2 ⇌ Glucono-δ-lactone + H 2 O 2 H 2 O 2 ⇌ 2 H + + O 2 + 2e −

7. 7 (PL Current) baseline current Current due to solution

8. 8 Blood Glucose Monitor (Sec. 17-4, p357-359) Where is this used (A LOT) ?

9. 9 Determination of Sucrose and Glucose Sucrose Fructose  -D-glucose Step F glucose

10. 10 Reactions During the week before analysis –Hydrolysis of sucrose –Establish equilibrium between α - and β -glucose

11. 11 Step E Pg 39 Glucose Standards PL current for flasks 1, 3, 5, 7

12. 12 Step E  (Glucose + Sucrose) Standards Pg 39 For sucrose alone PL sucrose = PL 2 – PL 1

13. 13 Polar particles volatility & surface interactions Benzene by Gas Chromatography helium

14. 14 3. Quantitative Analysis (pg 1 HotTips) Internal standard Standard Prep Table (pg 55) Measure weight Sample ampoule

15. 15 Chromatogram of Sample Label the chromatograms!!! Sample, Run #1 You are using internal standard calibration Response used for plotting is: I analyte I Benzene I Int. Std I Toluene

16. 16 4. Notes on Procedure F (pg 2 HotTips) Chromatogram of Sample Chart speed = 50

17. 17 5. Notes on Calculations (pg 2 HotTips) 1. N = number of theoretical plates = 16(t R /W) 2 N = 18 6 (unitless)

18. 18 5. Notes on Calculations (pg 2 HotTips) 2. R s = resolution = t R,2 – t R,1. ½(W 1 + W 2 ) R s = 0.95 (unitless)

19. 19 5. Notes on Calculations (pg 2 HotTips) 3. k′ = capacity factor = (t R -t M )/t M k’ = 8. 1 (unitless) air peak