Researcher

David Bulger

Objective

Verification of the SAMS using varying concentrations of benzoic acid in DMF.

Procedure

Benzoic acid was chosen as the solute since it is readily available (inexpensive) and dissolves easily in a variety of solvents. Evaporation has the potential for increasing the concentration measured. Therefore, a solvent with a low vapor pressure should be chosen. For this experiment, DMF was chosen as the solvent. The purity of the solvent will first be confirmed using NMR.
The following concentrations will be tested: 0.01 M, 0.10 M, 0.50 M, 1.00 M. 2.00 M, and 3.00 M. Using 1-mL and 2-mL volumetric flasks, solutions of known concentration will be made up. Then the solution concentrations will be measured using the semi-automated solubility measurement (SAMS) using proton NMR. In ONSC Exp103, Khalid Mirza found the relaxation delay to play an important role in making the signals relatively equivalent across the spectrum. To verify these results, the accuracy of the SAMS method will also be measured with a variable relaxation delay.[note that Khalid used a 50s delay, which is more than 10 times longer than you are using here JCB]
  1. Confirm Purity of Solvent using NMR
  2. Calibrate Pipets
  3. Make 1-mL of 0.01 M solution in 2-mL volumetric flask and mix thoroughly
  4. Run NMR with relaxation delay of 4.00 sec with 1000-uL of solution
  5. Run NMR with relaxation delay of 1.00 sec
  6. Run NMR with relaxation delay of 0.50 sec
  7. Run NMR with relaxation delay of 0.25 sec
  8. Run NMR with relaxation delay of 0.10 sec
  9. Run NMR with relaxation delay of 0.05 sec
  10. Clean volumetric flask and NMR tube with DMSO
  11. Repeat steps 3-10 with 0.10 M, 0.50 M, 1.00 M. 2.00 M, and 3.00 M solutions

Results

Pictures
Exp115_0
Exp115_1
Exp115_2
Exp115_3
Exp115_4
Exp115_5
NMR Spectra
Spectrum 432 - DMSO1
Spectrum 433 - DMSO2
Spectrum 434 - DMSO3
Spectrum 435 - DMF1
Spectrum 436 - DMF2
Spectrum 437 - DMSO4
exp115_440
exp115_445
exp115_448
exp115_451
exp115_454
exp115_457
exp115_460
exp115_463
exp115_466
exp115_469
exp115_472
exp115_475
exp115_478
exp115_481
exp115_484
exp115_487
exp115_490
exp115_493
exp115_496
exp115_499
exp115_502
exp115_505
exp115_508
exp115_511
exp115_514
exp115_517
exp115_520
exp115_523
exp115_526
exp115_529
exp115_532
exp115_535
exp115_538
exp115_541
exp115_544
exp115_547
Raw Data for Spectrum 432 - DMSO1
Raw Data for Spectrum 433 - DMSO2
Raw Data for Spectrum 434 - DMSO3
Raw Data for Spectrum 435 - DMF1
Raw Data for Spectrum 436 - DMF2
Raw Data for Spectrum 437 - DMSO4
Raw Data for exp115_440
Raw Data for exp115_445
Raw Data for exp115_448
Raw Data for exp115_451
Raw Data for exp115_454
Raw Data for exp115_457
Raw Data for exp115_460
Raw Data for exp115_463
Raw Data for exp115_466
Raw Data for exp115_469
Raw Data for exp115_472
Raw Data for exp115_475
Raw Data for exp115_478
Raw Data for exp115_481
Raw Data for exp115_484
Raw Data for exp115_487
Raw Data for exp115_490
Raw Data for exp115_493
Raw Data for exp115_496
Raw Data for exp115_499
Raw Data for exp115_502
Raw Data for exp115_505
Raw Data for exp115_508
Raw Data for exp115_511
Raw Data for exp115_514
Raw Data for exp115_517
Raw Data for exp115_520
Raw Data for exp115_523
Raw Data for exp115_526
Raw Data for exp115_529
Raw Data for exp115_532
Raw Data for exp115_535
Raw Data for exp115_538
Raw Data for exp115_541
Raw Data for exp115_544
Raw Data for exp115_547
IdentificationSpectrum.pdf
Spreadsheets
ONSC115-1[you have to provide ranges and the links to the spectra to get the calculation results JCB]

Discussion

[One point to keep in mind is that to just look at the effect of relaxation time a molecule with a rapidly relaxing methyl group - like 2-phenylbutanoic acid - gives you a way of internally comparing integrations without the additional error of sample preparation JCB] Good point.
[Despite all my caveats I am still very interested in what you have found from your experiment :) JCB]
[Can you put your spectra in the SAMS spreadsheet so we can compare? JCB]
The SAMS spreadsheet doesn't seem to be calculating the integrations correctly as it keeps measuring zero for peaks that clearly exist.

Spectrum
Relaxation Delay (sec)
Known Concentration (M)
Measured Concentration (M)
Percent Error (%)
440-475
NA
0.01-0.1
Undetectable Signal
NA
exp115_481
1
0.5
0.5080
1.60
exp115_484
0.5
0.5
0.4938
1.24
exp115_487
0.25
0.5
0.5123
2.46
exp115_490
0.1
0.5
0.5123
2.46
exp115_493
0.05
0.5
0.5134
2.68
exp115_496
4
1
0.9797
2.03
exp115_499
1
1
1.0090
0.90
exp115_502
0.5
1
0.9689
3.11
exp115_505
0.25
1
0.9413
5.87
exp115_508
0.1
1
1.0090
0.90
exp115_511
0.05
1
0.9758
2.42
exp115_514
4
2
1.9772
1.14
exp115_517
1
2
2.0010
0.05
exp115_520
0.5
2
1.9903
0.49
exp115_523
0.25
2
1.9408
2.96
exp115_526
0.1
2
1.9934
0.33
exp115_529
0.05
2
1.9268
3.66
exp115_532
4
3
3.0136
0.45
exp115_535
1
3
3.0020
0.07
exp115_538
0.5
3
2.9850
0.50
exp115_541
0.25
3
2.9727
0.91
exp115_544
0.1
3
3.0413
1.38
exp115_547
0.05
3
3.0037
0.12
Table 115.1: Percentage Error Comparisons

ONSCEXP115Graphs.docx

The percentage error for several solutions of known concentrations of benzoic acid in DMF were analyzed in relation to concentration and relaxation delay (Table 1,
ONSCEXP115Graphs.docx). A linear line was fitted to the plot of Percentage Error vs Concentration to yield the line y = 0.3464x + 0.732 with R² = 0.824. A linear line was also fitted to the plot of Percentage Error vs Relaxation Delay to yield the line y = -0.2093x + 1.8275 with R² = 0.1357.

The overall percent error was 1.64%, which attests to the accuracy of the SAMS method.

Conclusion

There seemed to be positive correlation between percent error and concentration and no strong correlation between percentage error and relaxation delay. The SAMS method was further supported by the overal percent error of 1.64%.

Log

29.06.09 - Confirm Purity of Solvent

16.10 Gradient Shim and Lock on DMSO sample - failed [You need deuterated solvent to lock - generally we take about 0.1 ml of the sat solution and dilute it with 0.7 ml of CDCl3 JCB]
16.12 Autolock - failed
16.13 Manual Shim
16.14 Gradient Shim and Lock (Z1:1506, Z2:-3058, Z3:-4015, Z4:15671)
16.18 Single Pulse NMR run (Autogain: 1) with relaxation delay of 4 sec: Spectrum 432 - DMSO1
16.26 Cleaned NMR tube
16.44 DMSO (from bottle 5040) Single Pulse (Autogain: 1) with relaxation delay of 4 sec: Spectrum 433 - DMSO2
16.57 Cleaned NMR tube
17:02 DMSO (from other bottle) Single Pulse (Autogain: 1) with relaxation delay of 4 sec: Spectrum 434 - DMSO3
17:06 Clean NMR tube
17.22 Gradient Shim and Lock on DMF sample - not enabled for solvent
17.24 DMF Single Pulse (Autogain: 2) with relaxation delay of 4 sec: Spectrum 435 - DMF1
Note: All spectra so far have unusual tails probably due to troublesome gradient shims from the DMSO
17.25 Gradient Shim on CDCl3 (Z1:-1235, Z2:-1037, Z3:-143, Z4:847)
17.36 DMF Single Pulse (Autogain: 1) with relaxation delay of 4 sec: Spectrum 436 - DMF2
Note: CDCl3 Shimming seems to have solved the problem
17.50 Cleaned NMR tube
17.54 DMSO (from bottle 5040) Single Pulse (Autogain: 1) with relaxation delay of 4 sec: Spectrum 437 - DMSO4

30.06.09
10.50 Calibrate pipets
Pipet - Solvent
Volume (uL)
Predicted Mass (g)
Observed Mass (g)
% Error
100 - 1 000 uL DMF
1 000
0.944 0
0.958 9
1.6
100 - 1 000 uL DMF
1 000
0.944 0
0.956 7
1.3
100 - 1 000 uL DMF
1 000
0.944 0
0.958 9
1.6
100 - 1 000 uL DMF
1 000
0.944 0
0.960 7
1.8
Average % Error: 1.6%
Note: In light of the absence of an internal standard, the volume of concentrated solution does not matter in the overall analysis.
Added 0.002 4 g of benzoic acid to 2-mL volumetric flask
15.01 Added DMF up to 2-mL mark and mixed by hand since no vortexor or sonicator available (benzoic acid readily dissolves - so it should not be a problem at these concentrations) (Exp115_0)
15.06 Trickerated and transfered to 1 dram vial (Exp115_1)
15.08 Cleaned NMR tube
15.15 Transferred 1-mL of 0.01 M solution to NMR tube
15.20 Gradient Shimmed and Locked using CDCl3 (Z1:-1222, Z2:-1005, Z3:-192, Z4:874)
15.25 Single Pulse on 0.01 M sample (autogain: 1) with a relaxation delay of 4 sec: exp115_440
15.35 Single Pulse on 0.01 M sample (autogain: 1) with a relaxation delay of 1 sec: exp115_445
15.39 Single Pulse on 0.01 M sample (autogain: 1) with a relaxation delay of 0.5 sec: exp115_448
15.42 Single Pulse on 0.01 M sample (autogain: 1) with a relaxation delay of 0.25 sec: exp115_451
15.45 Single Pulse on 0.01 M sample (autogain: 1) with a relaxation delay of 0.1 sec: exp115_454
15.47 Single Pulse on 0.01 M sample (autogain: 1) with a relaxation delay of 0.05 sec: exp115_457
15.50 Cleaned NMR tube and volumetric flask with DMF
Added 0.024 4 g benzoic acid
16.00 Added DMF up to 2-mL mark and mixed (Exp115_2)
16.04 Trickerated and transfered to 1 dram vial (Exp115_3)
16.08 Transferred 1-mL of 0.1 M solution to NMR tube
16.13 Single Pulse on 0.1 M sample (autogain: 1) with a relaxation delay of 4 sec: exp115_460
16.17 Single Pulse on 0.1 M sample (autogain: 1) with a relaxation delay of 1 sec: exp115_463
16.20 Single Pulse on 0.1 M sample (autogain: 1) with a relaxation delay of 0.5 sec: exp115_466
16.22 Single Pulse on 0.1 M sample (autogain: 1) with a relaxation delay of 0.25 sec: exp115_469
16.25 Single Pulse on 0.1 M sample (autogain: 1) with a relaxation delay of 0.1 sec: exp115_472
16.32 Single Pulse on 0.1 M sample (autogain: 1) with a relaxation delay of 0.05 sec: exp115_475
16.36 Cleaned NMR tube and volumetric flask with DMF
Added 0.122 1 g benzoic acid
16.52 Added DMF up to 2-mL mark and mixed (Exp115_4)
16.58 Transferred 0.5 M solution to 1 dram vial
17.00 Trickerated and transferred 1-mL to NMR tube
17.03 Single Pulse on 0.5 M sample (autogain: 1) with a relaxation delay of 4 sec: exp115_478
17.07 Single Pulse on 0.5 M sample (autogain: 1) with a relaxation delay of 1 sec: exp115_481
17.11 Single Pulse on 0.5 M sample (autogain: 1) with a relaxation delay of 0.5 sec: exp115_484
17.13 Single Pulse on 0.5 M sample (autogain: 1) with a relaxation delay of 0.25 sec: exp115_487
17.16 Single Pulse on 0.5 M sample (autogain: 1) with a relaxation delay of 0.1 sec: exp115_490
17.18 Single Pulse on 0.5 M sample (autogain: 1) with a relaxation delay of 0.05 sec: exp115_493
17.21 Cleaned NMR tube and volumetric flask with DMF
Added 0.244 2 g benzoic acid
17.35 Added DMF up to 2-mL mark and mixed (Exp115_5)
17.37 Transferred 1 M solution to 1 dram vial
17.41 Trickerated and transferred 1-mL to NMR tube
17.44 Single Pulse on 1 M sample (autogain: 1) with a relaxation delay of 4 sec: exp115_496
17.47 Single Pulse on 1 M sample (autogain: 1) with a relaxation delay of 1 sec: exp115_499
17.51 Single Pulse on 1 M sample (autogain: 1) with a relaxation delay of 0.5 sec: exp115_502
17.54 Single Pulse on 1 M sample (autogain: 2) with a relaxation delay of 0.25 sec: exp115_505
17.57 Single Pulse on 1 M sample (autogain: 1) with a relaxation delay of 0.1 sec: exp115_508
17.59 Single Pulse on 1 M sample (autogain: 1) with a relaxation delay of 0.05 sec: exp115_511
18.03 Cleaned NMR tube and volumetric flask with DMF
01.07.09
10.46 Gradient Shim and Lock on CDCl3 (Z1:-1196, Z2:-1029, Z3:-54, Z4:731)
10.52 Added 0.488 5 g benzoic acid to volumetric flask
11.06 Added DMF up to 2-mL mark and mixed
11.10 Cleaned NMR tube with DMF
11.15 Trickerated and transferred 2 M solution to 1 dram vial
11.17 Transferred 1-mL to NMR tube
11.20 Single Pulse on 2 M sample (autogain: 2) with a relaxation delay of 4 sec: exp115_514
11.24 Single Pulse on 2 M sample (autogain: 2) with a relaxation delay of 1 sec: exp115_517
11.27 Single Pulse on 2 M sample (autogain: 2) with a relaxation delay of 0.5 sec: exp115_520
11.29 Single Pulse on 2 M sample (autogain: 1) with a relaxation delay of 0.25 sec: exp115_523
11.31 Single Pulse on 2 M sample (autogain: 2) with a relaxation delay of 0.1 sec: exp115_526
11.34 Single Pulse on 2 M sample (autogain: 1) with a relaxation delay of 0.05 sec: exp115_529
14.03 Cleaned NMR tube and volumetric flask with DMF
14.17 Added 0.732 7 g benzoic acid to volumetric flask
15.30 Added DMF up to 2-mL mark and mixed
15.37 Trickerated and transferred 3 M solution to 1 dram vial
15.42 Transferred 1-mL to NMR tube
15.45 Single Pulse on 3 M sample (autogain: 2) with a relaxation delay of 4 sec: exp115_532
15.48 Single Pulse on 3 M sample (autogain: 2) with a relaxation delay of 1 sec: exp115_535
15.51 Single Pulse on 3 M sample (autogain: 2) with a relaxation delay of 0.5 sec: exp115_538
15.53 Single Pulse on 3 M sample (autogain: 2) with a relaxation delay of 0.25 sec: exp115_541
15.55 Single Pulse on 3 M sample (autogain: 2) with a relaxation delay of 0.1 sec: exp115_544
15.58 Single Pulse on 3 M sample (autogain: 2) with a relaxation delay of 0.05 sec: exp115_547
16.00 Cleaned NMR tube and volumetric flask with DMF

References

1. Mirza, Khalid. Exp103