Benzophenone Lab Report
wavelength Percentage concentration (methanol: water) Peak H value (height equivalent to a theoretical plate) (mm)
230nm 80:20 Phenol 0.0373 Benzophenone 0.0196 Naphthalene 0.0164
235nm 80:20 Phenol 0.0327 Benzophenone 0.0203 Naphthalene 0.0147
260nm 80:20 Phenol 0.0318 Benzophenone 0.0202 Naphthalene 0.0146
Figure 11: table for the height equivalent of the theoretical plates.
It can be observed that the H values or height equivalent to a theoretical plate for phenol at the three wavelengths (230, 235, and 260nm) are all fairly similar, they are all around the 0.03mm mark (use of one significant figure), with all three H value being above 0.03mm. It can be seen in the results that the theoretical plate height decreases as the wavelength …show more content…
increases, starting at 0.0373mm at 230nm, it then decreases to 0.0327mm at 235nm, and decreases again to 0.0318mm at 260nm. This decrease is expected and shows that as the theoretical plate number increases the height equivalent to a theoretical plate decreases. This is because the best separations occur in columns that have a greater theoretical plate number and a lower height equivalent to a theoretical plate. This is followed at all three wavelengths, with the most efficient wavelength being 260nm, as this shows the lowest number for the height equivalent to a theoretical plate. This can be improved by the use of a more optimum solvent mixture/consistency, for example the use of 90/10 methanol/water or 70/30 methanol/water, could be used to determine if the results follow the same pattern at a stronger or weaker solvent mixtures. The optimum wavelength could also be used as a constant throughout the whole experiment, this would minimise the possible errors that could occur, and will give for better results.
It can be observed that the H values or height equivalent to a theoretical plate for benzophenone at the three wavelengths (230, 235, and 260nm) are all fairly similar, they are all around the 0.02mm mark (use of one significant figure), with two above it and one below 0.02mm. In these results it can be seen that the height equivalent to a theoretical plate is best at a wavelength of 230nm where its 0.0196mm, this is because benzophenone has the greatest theoretical plate number at 230nm in these results. At 235nm the height equivalent to a theoretical plate is 0.0203mm and at 260nm the height equivalent to a theoretical plate is 0.0202mm which are fairly similar to one another. This could be because of an internal error in the instrumentation, however this is unlikely because there would be indication of this through the rest of the results. But it can still be seen that as the theoretical plate number increases the height equivalent to a theoretical plate decreases. This is again because the best separations occur in columns that have a greater theoretical plate number and a lower height equivalent to a theoretical plate.
The benzophenone follow this concept at the three wavelengths, but the most efficient wavelength shown for benzophenone is 230nm as this shows the lowest number for the height equivalent to a theoretical plate. This could be improved by the use of a more optimum solvent mixture, for example, as described for phenol. The use of 90/10 methanol/water or 70/30 methanol/water, could be used to determine if the results follow the same pattern at a stronger or weaker solvent mixtures, and the use of the optimum wavelength, or most optimum wavelength could also be used as a constant throughout the whole experiment, this would minimise the possible errors that could occur.
It can be observed that the H values or height equivalent to a theoretical plate for naphthalene at the three wavelengths (230, 235, and 260nm) are all fairly similar, they are all around the 0.015mm mark (use of two significant figures), with one H value above and two H values below 0.015mm. It can be observed in the results for the naphthalene that as the wavelength increases the height equivalent to a theoretical plate decreases, starting at 230nm the height equivalent to a theoretical plate is 0.0164mm, this then decreases to 0.0147mm at 235nm and decrease again to 0.0146mm at 260nm. This decrease for naphthalene is expected and shows that as the theoretical plate number for the naphthalene increases the height equivalent to a theoretical plate decreases. This is again as mention for phenol, and benzophenone, because the best separations occur in columns that have a greater theoretical plate number and a lower height equivalent to a theoretical plate. This is followed at all three wavelengths for naphthalene, with the most efficient wavelength being 260nm, as this shows the lowest number for the height equivalent to a theoretical plates. This separation could be improved by the use of a more optimum solvent mixture, for example, as described for phenol, and benzophenone. The use of 90/10 methanol/water or 70/30 methanol/water mixture, which could be used to determine if the results follow the same pattern at a stronger or weaker solvent mixtures. The use of the optimum wavelength for naphthalene could also be used throughout the whole experiment, this would hopefully help to minimise the possible errors that could occur.
H Value Calculation – H = L/N
• Length given in this calculation is in mm, not cm (mm were used as the measurement of column length).
H values:
230nm
Phenol:
H = 150 mm/ 4017.237345 = 0.03733909329 mm
Benzophenone:
H = 150 mm/ 7669.87742 = 0.01955702703 mm
Naphthalene:
H = 150 mm/ 9142.356629 = 0.01640714819 mm
235nm
Phenol:
H = 150 mm/ 4580.171901 = 0.0327498625 mm
Benzophenone:
H = 150 mm/ 7397.438085 = 0.02027729036 mm
Naphthalene:
H = 150 mm/ 10180.53041 = 0.01473400638 mm
260nm
Phenol:
H = 150 mm/ 4714.114215 = 0.03181933936 mm
Benzophenone:
H = 150 mm/ 7423.662336 = 0.02020566039 mm
Naphthalene:
H = 150 mm/ 10251.59699 = 0.01463186664 mm
Plate height, H, is another measure of column efficiency also known as the height equivalent to a theoretical plate, which gets the notation of H.
plate height is calculated using the equation:
H = L/N
Plate height is normally reported in millimetres. The ability of a column to separate components of a mixture is improved by decreasing the plate height, so therefore an efficient column will have more theoretical plates with smaller plate heights than an inefficient column with less theoretical plates and larger plate heights. The smaller the plate height in the column, the narrower the bandwidths will be (17, Harris, 2010).
The height equivalent to a theoretical plate, as discussed above, is defined as the proportionality constant relating the length of the column and the number of theoretical plates. Thus, the defining equation of the height equivalent to a theoretical plate is as displayed above. In which N is the number of theoretical plates and L the length of the column (18, 2015). eluent phenol benzophenone naphthalene
Values for the peak area at 260nm, and concentration mixture of 90% methanol 10% water. 2520.496 2595.128 1751.678 2521.154 2595.098 …show more content…
1752.204 2523.293 2595.796 1753.371 2525.385 2600.794 1754.142 2526.798 2597.263 1755.376 2526.918 2597.851 1756.332
Mean 2524.007 2596.988 1753.851
Standard deviation 2.797934 2.179777 1.801717
Relative standard deviation <2% 0.110853 0.083935 0.102729
Figure 12: table for the retention times of phenol, benzophenone and naphthalene at 260nm, testing for repeatability.
The composition of the mobile phase effects the retention times of the components and the resolution between the components, because the more polar that the mobile phase is the longer the components will take to elute from the column, this then effects the resolution. The more polar the mobile phase the larger or greater the resolution will be, and the larger the resolution is the clearer the separation between the components is.
The best detection wavelength was 260nm, this is because at 260nm the wavelength contains the least amount, if any background noise, which give extra peaks. The signal varies with wavelength because of its ability to detect the peak of interest at its maxima, and higher wavelengths this is quantitatively better because of the peak heights, at higher wavelengths the peaks heights are
larger.
It can be observed from figure 12 (Table for the retention times of phenol, benzophenone and naphthalene at 260nm, testing for repeatability) that the reproducibility of the peak areas for phenol is rather good the mean peak area is 2524.007, it has a standard deviation of 2.797934 and a relative standard deviation of 0.110853. This is a good indicator that the reproducibility is rather high for the results. This can also be seen for the benzophenone which has a mean peak area of 2596.988, and a standard deviation of 2.179777, the relative standard deviation for the benzophenone is really good because it is less than 0.1%, the relative standard deviation for benzophenone is 0.083935.
230nm 80:20 Phenol 0.0373 Benzophenone 0.0196 Naphthalene 0.0164
235nm 80:20 Phenol 0.0327 Benzophenone 0.0203 Naphthalene 0.0147
260nm 80:20 Phenol 0.0318 Benzophenone 0.0202 Naphthalene 0.0146
Figure 11: table for the height equivalent of the theoretical plates.
It can be observed that the H values or height equivalent to a theoretical plate for phenol at the three wavelengths (230, 235, and 260nm) are all fairly similar, they are all around the 0.03mm mark (use of one significant figure), with all three H value being above 0.03mm. It can be seen in the results that the theoretical plate height decreases as the wavelength …show more content…
increases, starting at 0.0373mm at 230nm, it then decreases to 0.0327mm at 235nm, and decreases again to 0.0318mm at 260nm. This decrease is expected and shows that as the theoretical plate number increases the height equivalent to a theoretical plate decreases. This is because the best separations occur in columns that have a greater theoretical plate number and a lower height equivalent to a theoretical plate. This is followed at all three wavelengths, with the most efficient wavelength being 260nm, as this shows the lowest number for the height equivalent to a theoretical plate. This can be improved by the use of a more optimum solvent mixture/consistency, for example the use of 90/10 methanol/water or 70/30 methanol/water, could be used to determine if the results follow the same pattern at a stronger or weaker solvent mixtures. The optimum wavelength could also be used as a constant throughout the whole experiment, this would minimise the possible errors that could occur, and will give for better results.
It can be observed that the H values or height equivalent to a theoretical plate for benzophenone at the three wavelengths (230, 235, and 260nm) are all fairly similar, they are all around the 0.02mm mark (use of one significant figure), with two above it and one below 0.02mm. In these results it can be seen that the height equivalent to a theoretical plate is best at a wavelength of 230nm where its 0.0196mm, this is because benzophenone has the greatest theoretical plate number at 230nm in these results. At 235nm the height equivalent to a theoretical plate is 0.0203mm and at 260nm the height equivalent to a theoretical plate is 0.0202mm which are fairly similar to one another. This could be because of an internal error in the instrumentation, however this is unlikely because there would be indication of this through the rest of the results. But it can still be seen that as the theoretical plate number increases the height equivalent to a theoretical plate decreases. This is again because the best separations occur in columns that have a greater theoretical plate number and a lower height equivalent to a theoretical plate.
The benzophenone follow this concept at the three wavelengths, but the most efficient wavelength shown for benzophenone is 230nm as this shows the lowest number for the height equivalent to a theoretical plate. This could be improved by the use of a more optimum solvent mixture, for example, as described for phenol. The use of 90/10 methanol/water or 70/30 methanol/water, could be used to determine if the results follow the same pattern at a stronger or weaker solvent mixtures, and the use of the optimum wavelength, or most optimum wavelength could also be used as a constant throughout the whole experiment, this would minimise the possible errors that could occur.
It can be observed that the H values or height equivalent to a theoretical plate for naphthalene at the three wavelengths (230, 235, and 260nm) are all fairly similar, they are all around the 0.015mm mark (use of two significant figures), with one H value above and two H values below 0.015mm. It can be observed in the results for the naphthalene that as the wavelength increases the height equivalent to a theoretical plate decreases, starting at 230nm the height equivalent to a theoretical plate is 0.0164mm, this then decreases to 0.0147mm at 235nm and decrease again to 0.0146mm at 260nm. This decrease for naphthalene is expected and shows that as the theoretical plate number for the naphthalene increases the height equivalent to a theoretical plate decreases. This is again as mention for phenol, and benzophenone, because the best separations occur in columns that have a greater theoretical plate number and a lower height equivalent to a theoretical plate. This is followed at all three wavelengths for naphthalene, with the most efficient wavelength being 260nm, as this shows the lowest number for the height equivalent to a theoretical plates. This separation could be improved by the use of a more optimum solvent mixture, for example, as described for phenol, and benzophenone. The use of 90/10 methanol/water or 70/30 methanol/water mixture, which could be used to determine if the results follow the same pattern at a stronger or weaker solvent mixtures. The use of the optimum wavelength for naphthalene could also be used throughout the whole experiment, this would hopefully help to minimise the possible errors that could occur.
H Value Calculation – H = L/N
• Length given in this calculation is in mm, not cm (mm were used as the measurement of column length).
H values:
230nm
Phenol:
H = 150 mm/ 4017.237345 = 0.03733909329 mm
Benzophenone:
H = 150 mm/ 7669.87742 = 0.01955702703 mm
Naphthalene:
H = 150 mm/ 9142.356629 = 0.01640714819 mm
235nm
Phenol:
H = 150 mm/ 4580.171901 = 0.0327498625 mm
Benzophenone:
H = 150 mm/ 7397.438085 = 0.02027729036 mm
Naphthalene:
H = 150 mm/ 10180.53041 = 0.01473400638 mm
260nm
Phenol:
H = 150 mm/ 4714.114215 = 0.03181933936 mm
Benzophenone:
H = 150 mm/ 7423.662336 = 0.02020566039 mm
Naphthalene:
H = 150 mm/ 10251.59699 = 0.01463186664 mm
Plate height, H, is another measure of column efficiency also known as the height equivalent to a theoretical plate, which gets the notation of H.
plate height is calculated using the equation:
H = L/N
Plate height is normally reported in millimetres. The ability of a column to separate components of a mixture is improved by decreasing the plate height, so therefore an efficient column will have more theoretical plates with smaller plate heights than an inefficient column with less theoretical plates and larger plate heights. The smaller the plate height in the column, the narrower the bandwidths will be (17, Harris, 2010).
The height equivalent to a theoretical plate, as discussed above, is defined as the proportionality constant relating the length of the column and the number of theoretical plates. Thus, the defining equation of the height equivalent to a theoretical plate is as displayed above. In which N is the number of theoretical plates and L the length of the column (18, 2015). eluent phenol benzophenone naphthalene
Values for the peak area at 260nm, and concentration mixture of 90% methanol 10% water. 2520.496 2595.128 1751.678 2521.154 2595.098 …show more content…
1752.204 2523.293 2595.796 1753.371 2525.385 2600.794 1754.142 2526.798 2597.263 1755.376 2526.918 2597.851 1756.332
Mean 2524.007 2596.988 1753.851
Standard deviation 2.797934 2.179777 1.801717
Relative standard deviation <2% 0.110853 0.083935 0.102729
Figure 12: table for the retention times of phenol, benzophenone and naphthalene at 260nm, testing for repeatability.
The composition of the mobile phase effects the retention times of the components and the resolution between the components, because the more polar that the mobile phase is the longer the components will take to elute from the column, this then effects the resolution. The more polar the mobile phase the larger or greater the resolution will be, and the larger the resolution is the clearer the separation between the components is.
The best detection wavelength was 260nm, this is because at 260nm the wavelength contains the least amount, if any background noise, which give extra peaks. The signal varies with wavelength because of its ability to detect the peak of interest at its maxima, and higher wavelengths this is quantitatively better because of the peak heights, at higher wavelengths the peaks heights are
larger.
It can be observed from figure 12 (Table for the retention times of phenol, benzophenone and naphthalene at 260nm, testing for repeatability) that the reproducibility of the peak areas for phenol is rather good the mean peak area is 2524.007, it has a standard deviation of 2.797934 and a relative standard deviation of 0.110853. This is a good indicator that the reproducibility is rather high for the results. This can also be seen for the benzophenone which has a mean peak area of 2596.988, and a standard deviation of 2.179777, the relative standard deviation for the benzophenone is really good because it is less than 0.1%, the relative standard deviation for benzophenone is 0.083935.