DTC Determination of Sodium Fluoride Content in Mouthwash Lab Report

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I have tried to complete this lab report but I think I could be going about it all wrong, could you please check the answers I have and if they need to be adjusted than please do so.

Also please answer any parts I have left blank and answer all the questions at the end of the lab report. I need this done by Saturday please.

I have also included a blank copy of the lab report template and the lab manual.

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Lab report Practical 2 – Determination of Sodium Fluoride Content in Mouthwash Student Name: Group Number: C Demonstrator: Date: 22/02/21 1. Briefly describe function and use of an Ion-Selective Electrode (approx. half a page) 2. Results & Data Analysis How did you prepare the stock solution and the standard solutions? Show your calculations. For the stock solution, I weighed 0.11 g of NaF powder in a weigh boat and transferred this powder to a 100 mL volumetric flask. I then filled the volumetric flask up to the mark using deionised water. For the standard solutions, I first calculated how much of the stock solution I would need for each one: (2) 0.11g in 100 mL (3) 0.11g in 100 mL (4) 0.11g in 100 mL (5) 0.11g in 100 mL 0.011 in x mL 0.0055 in x mL 0.0022 in x mL 0.0011 in x mL (100 mL) (0.011) = 0.11x (0.0055) (100) = 0.11x (0.0022)(100) = 0.11x (0.0011)(100) = 0.11x X = 10 mL x = 5 mL x= 2 mL x = 1 mL Then, using a pipette, I took 10 mL of the stock solution and transferred this to a 100 mL volumetric flask. I then filled this up to the mark using deionised water. All materials used were plastic. I then repeated the same dilution process for the 5 mL , 2 mL and 1 mL solutions. Insert the potential reading in mV of the four fluoride standards into the table below and calculate the logarithm of the concentration in g/ml (based on the exact weight of NaF used to make up your stock solution): Standard Prep Concentration of NaF Standard (2) (3) (4) (5) 0.0110% 0.0055% 0.0022% 0.0011% Conc. of NaF Standard in g/ml 110 55 22 11 Log10 of conc. Potential (mV) 2.0414 1.7404 1.3424 1.0414 0.6 17.3 39.4 57.2 Equation of the trendline: y = -56.453x + 115.64 r2: 0.9998 Calculate the concentration of NaF (in %) in each of the three mouthwashs taken from the label claim in ppm Fluoride (or vice versa if the label claim is in % NaF): CB12: 50.05 ppm = 50.05 mg/1000 mL We want x g/100 mL Therefore, cross multiply (0.0505 g)(100 mL) = (x)(1000 mL) X = 0.00505 % NaF Dentitex: 50 ppm = 50 mg in 1000 mL We want xg in 100ml Cross multiply, (0.05g)(100 mL) = 1000x X = 0.005 g/100 mL Dentyl: 49 ppm = 59 mg in 1000 mL We want xg in 100ml Cross multiply, (0.059g)(100 mL) = 1000x X = 0.0059 g/100 mL The mouthwash was diluted prior to the labs, by taking a volume of mouthwash equivalent to 50 mg NaF and diluting it to 1000 ml in a volumetric flask. Show how the volume required for this was calculated from the label claim of Fluoride or NaF: ?????? Insert data from the three mouthwash samples you tested in the table below: Mouthwash sample (brand) Label Claim (ppm Fluoride) Label Claim (% NaF) CB12 Dentitex Dentyl 50.05 50 49 0.00505 0.005 0.0059 Volume (ml) of mouthwash used [containing 50 mg of NaF] ?? ?? ?? Potential (mV) 20.1 22.5 31.2 From the measured potential of the Standard preparations and the equation of the trendline, determine the concentration, C, in %, of NaF in the three diluted sample preparations (remember to de-log to obtain the concentration in μg/ml and then convert to % NaF). Equation of the trendline: y = -56.453x + 115.64 Standard prep 2: mV = 0.6 0.6 = -56.453x + 115.64 X = 2.0378 % w/v Dilution factor = 10, 100 (2.0378)(10) = 20.378 % w/v Standard prep 3: mV= 17.3 17.3 = -56.453x + 115.64 X = 1.74198 % w/v Dilution factor = 20 (1.74198)(20) = 34.8396 % w/v Standard prep 4: mV = 39.4 39.4 = -56.453x + 115.64 X = 1.3505 % w/v Dilution factor = 50 (1.3505)(50) = 67.525 % w/v Standard prep 5: mV = 57.2 57.2 = -56.453x + 115.64 X = 1.0352 % w/v Dilution factor= 100 (1.0352)(100) = 103.52 % w/v Calculate the concentration of fluoride ions (in ppm) in each of the three mouthwashs taken, taking into account the volume of mouthwash that was used to make up the 50 mg/L solution: Compare your results to the label claim (complies/does not comply) and evaluate your results. Questions: 1. Why should only plastic lab ware be used for the determination of the fluoride content? 2. What could possibly mask fluoride ions in the assay preparation (i.e., fluoride is present but will not be detected/determined). 3. What is the total ionic strength adjustment buffer (TISAB) made of? Why is this buffer added to the solution? 4. Which other ions are interfering with the selectivity of the electrode? 5. Which reference electrodes can be used with an ISE as specified in BP, Vol. V, Appendix VIII E ‘Potentiometric Determination of Ionic Concentration Using Ion-selective Electrodes’? 6. The expected slope of your graph is approx. -59 mV (25°C). Where does this value come from? How close to this value is the slope of your graph? 7. How reliable do you think your standard curve is? Comment. 8. If the samples did not comply, what would you determine as the most likely reason for this? 9. Write a critical comment on water fluoridation as a method of improving dental health, taking into account health benefits, potential side-effects and ethical considerations. Lab report Practical 2 – Determination of Sodium Fluoride Content in Mouthwash Student Name: Group Number: C Demonstrator: Date: 22/02/21 1. Briefly describe function and use of an Ion-Selective Electrode (approx. half a page) 2. Results & Data Analysis How did you prepare the stock solution and the standard solutions? Show your calculations. For the stock solution, I weighed 0.11 g of NaF powder in a weigh boat and transferred this powder to a 100 mL volumetric flask. I then filled the volumetric flask up to the mark using deionised water. For the standard solutions, I first calculated how much of the stock solution I would need for each one: (2) 0.11g in 100 mL (3) 0.11g in 100 mL (4) 0.11g in 100 mL (5) 0.11g in 100 mL 0.011 in x mL 0.0055 in x mL 0.0022 in x mL 0.0011 in x mL (100 mL) (0.011) = 0.11x (0.0055) (100) = 0.11x (0.0022)(100) = 0.11x (0.0011)(100) = 0.11x X = 10 mL x = 5 mL x= 2 mL x = 1 mL Then, using a pipette, I took 10 mL of the stock solution and transferred this to a 100 mL volumetric flask. I then filled this up to the mark using deionised water. All materials used were plastic. I then repeated the same dilution process for the 5 mL , 2 mL and 1 mL solutions. Insert the potential reading in mV of the four fluoride standards into the table below and calculate the logarithm of the concentration in g/ml (based on the exact weight of NaF used to make up your stock solution): Standard Prep Concentration of NaF Standard (2) (3) (4) (5) 0.0110% 0.0055% 0.0022% 0.0011% Conc. of NaF Standard in g/ml 110 55 22 11 Log10 of conc. Potential (mV) 2.0414 1.7404 1.3424 1.0414 0.6 17.3 39.4 57.2 Equation of the trendline: y = -56.453x + 115.64 r2: 0.9998 Calculate the concentration of NaF (in %) in each of the three mouthwashs taken from the label claim in ppm Fluoride (or vice versa if the label claim is in % NaF): CB12: 50.05 ppm = 50.05 mg/1000 mL We want x g/100 mL Therefore, cross multiply (0.0505 g)(100 mL) = (x)(1000 mL) X = 0.00505 % NaF Dentitex: 50 ppm = 50 mg in 1000 mL We want xg in 100ml Cross multiply, (0.05g)(100 mL) = 1000x X = 0.005 g/100 mL Dentyl: 49 ppm = 59 mg in 1000 mL We want xg in 100ml Cross multiply, (0.059g)(100 mL) = 1000x X = 0.0059 g/100 mL The mouthwash was diluted prior to the labs, by taking a volume of mouthwash equivalent to 50 mg NaF and diluting it to 1000 ml in a volumetric flask. Show how the volume required for this was calculated from the label claim of Fluoride or NaF: ?????? Insert data from the three mouthwash samples you tested in the table below: Mouthwash sample (brand) Label Claim (ppm Fluoride) Label Claim (% NaF) CB12 Dentitex Dentyl 50.05 50 49 0.00505 0.005 0.0059 Volume (ml) of mouthwash used [containing 50 mg of NaF] ?? ?? ?? Potential (mV) 20.1 22.5 31.2 From the measured potential of the Standard preparations and the equation of the trendline, determine the concentration, C, in %, of NaF in the three diluted sample preparations (remember to de-log to obtain the concentration in μg/ml and then convert to % NaF). Equation of the trendline: y = -56.453x + 115.64 Standard prep 2: mV = 0.6 0.6 = -56.453x + 115.64 X = 2.0378 % w/v Dilution factor = 10, 100 (2.0378)(10) = 20.378 % w/v Standard prep 3: mV= 17.3 17.3 = -56.453x + 115.64 X = 1.74198 % w/v Dilution factor = 20 (1.74198)(20) = 34.8396 % w/v Standard prep 4: mV = 39.4 39.4 = -56.453x + 115.64 X = 1.3505 % w/v Dilution factor = 50 (1.3505)(50) = 67.525 % w/v Standard prep 5: mV = 57.2 57.2 = -56.453x + 115.64 X = 1.0352 % w/v Dilution factor= 100 (1.0352)(100) = 103.52 % w/v Calculate the concentration of fluoride ions (in ppm) in each of the three mouthwashs taken, taking into account the volume of mouthwash that was used to make up the 50 mg/L solution: Compare your results to the label claim (complies/does not comply) and evaluate your results. Questions: 1. Why should only plastic lab ware be used for the determination of the fluoride content? 2. What could possibly mask fluoride ions in the assay preparation (i.e., fluoride is present but will not be detected/determined). 3. What is the total ionic strength adjustment buffer (TISAB) made of? Why is this buffer added to the solution? 4. Which other ions are interfering with the selectivity of the electrode? 5. Which reference electrodes can be used with an ISE as specified in BP, Vol. V, Appendix VIII E ‘Potentiometric Determination of Ionic Concentration Using Ion-selective Electrodes’? 6. The expected slope of your graph is approx. -59 mV (25°C). Where does this value come from? How close to this value is the slope of your graph? 7. How reliable do you think your standard curve is? Comment. 8. If the samples did not comply, what would you determine as the most likely reason for this? 9. Write a critical comment on water fluoridation as a method of improving dental health, taking into account health benefits, potential side-effects and ethical considerations. Determination of Sodium Fluoride Content in Mouthwash Reference: BP Vol III – Sodium Fluoride Mouthwash BP Vol V – Appendix VIII E. Potentiometric Determination of Ionic Concentration using Ion-selective Electrodes Textbook: Harris, Quantitative Chemical Analysis, Chapter 15, page 303-305 and 313-314, 7th Ed., Freeman (2007). Additional reading material can be found on Blackboard. Scope: The fluoride ion is a necessary evil, good at low but detrimental at higher concentrations, causing staining, cracking, mottling, and pitting of teeth. At higher concentrations, there have been concerns about musculoskeletal effects, effects on IQ and neurological manifestations, involvement in cancer, cardiovascular disease and other potential negative health effects. A solid-state ion selective electrode (ISE) is used to measure the amount of fluoride in solution. In this experiment, the fluoride concentration is determined by comparing the potential of the sample solutions with a calibration curve constructed from a series of standard fluoride solutions. The fluoride ISE determines fluoride concentration by measuring the potential difference across an interface that responds to fluoride. This active interface is a crystal of lanthanum fluoride (LaF3) that has been doped with a small amount of europium fluoride. Europium lowers the electrical resistance across the crystal and allows ionic charge transfer from the analyte solution and the filling solution of the electrode. The filling solution has a fixed concentration of fluoride and provides a constant potential on the inner surface of the electrode. When immersed in a solution containing fluoride ions, a potential develops across the membrane which depends on the concentration of free fluoride ions in solution and is measured against a constant reference potential with a standard pH/mV meter. The Nernst Equation describes the measured potential as a function of the activity of fluoride ions in solution. 𝑅𝑇 𝐸 = 𝐸 𝑜 + 2.303 log [𝐴] 𝑛𝐹 E: measured electrode potential E°: reference potential R: universal gas constant: R = 8.31 J/Kmol T: temperature in Kelvins (room temp. is approx. 295 K) F: Faraday constant, the number of coulombs per mole of electrons = 9.65*104 C/mol n: charge of the ion 2.303*RT/nF: 54-60 mV at room temperature = slope log[A]: logarithm of the fluoride ion activity level = ‘effective concentration’ of free fluoride ion in solution The fluoride ion activity is related to free fluoride ion concentration, C f, by the activity coefficient, yi. [A] = yi * Cf The equation is only valid for very dilute solutions or for solutions where the ionic strength is constant. Ionic strength is defined by where Zi is the charge on an ion and Ci is its concentration. If background ionic strength is high and constant relative to the sensed ion concentration, the activity coefficient is constant and activity is directly proportional to concentration. The observed potential is a function of activity rather than concentration, but if the ionic strength is kept constant, then the activity will be proportional to the concentration. For fluoride ISE one must be careful to avoid measuring a false response to hydroxide ions by buffering the solution to be slightly acidic, this becomes increasingly important as fluoride concentrations decrease. If pH is too acidic, hydrolysis to HF reduces fluoride activity. The best compromise is pH 5.5. The addition of a high concentration of non-interfering ions in the buffer helps to maintain a constant total ionic strength and pH (Total Ionic Strength Adjustment Buffer, TISAB). The electrode responds only to free ions, it is important to avoid the formation of complexes. British Pharmacopoeia: Sodium Fluoride Mouthwash Content of sodium fluoride, NaF: 95.0 to 105.0% of the stated amount. Labelling — The label states the concentration of sodium fluoride and of fluoride ion in a suitable volume. ASSAY Carry out Method I for potentiometric determination of ionic concentration using ion-selective electrodes, Appendix VIII E, using a fluoride selective electrode. Prepare and store all solutions in plastic containers. For solution (1) dilute a volume of the mouthwash containing 50 mg of Sodium Fluoride to 1000 mL. Solutions (2), (3), (4) and (5) contain 0.0110% w/v, 0.00550% w/v, 0.00220% w/v and 0.00110% w/v of sodium fluoride respectively. To 20 mL of each solution add 20 mL of a buffer solution prepared by mixing 57 mL of glacial acetic acid, 58 g of sodium chloride and 4 g of cyclohexylenedinitrilotetra-acetic acid in 500 mL of water, adjusting the pH to 5.2 with a 50% w/v solution of sodium hydroxide and diluting to 1000 mL with water. In turn, stir each solution, immerse the electrodes and allow to stand for 5 minutes with constant stirring. Determine the potential difference between the electrodes for each of solutions (2), (3), (4) and (5) and plot on semi-logarithmic graph paper the potential difference obtained as a function of concentration of sodium fluoride. Using exactly the same conditions, determine the potential difference obtained with solution (1) and hence calculate the content of sodium fluoride in the mouthwash. Please read the following notes carefully before you start the practical: You will be following the above BP Assay with some small variations ➢ Ensure that all solutions are always labelled very clearly to avoid confusion!! ➢ Solution (1) is the mouthwash, which has already been diluted for you: ➢ A volume of the mouthwash containing 50 mg of NaF was transferred into a 1000 mL volumetric flask and brought up to volume. ➢ You will be analyzing three mouthwash samples, please record the label claim for each mouthwash that you are analyzing, (1a), (1b), (1c) ➢ The standard solutions containing known amounts of NaF you will be preparing yourself: ➢ Prepare 100 mL of a stock solution which contains 0.110% of NaF ➢ Note the exact weight of NaF powder taken in your report sheet ➢ By diluting the stock solution, prepare the following four standard solutions (100 mL each): (2) 0.0110% (3) 0.0055% (4) 0.0022% (5) 0.0011% Calculate how many milliliters of the stock solution are needed to prepare each of the diluted standard solutions (2) - (5). Show your calculations to the demonstrator before proceeding! ➢ The buffer solution (TISAB) has already been prepared and is ready to use. For the assay, measure carefully 20 ml of each solution (1a), (1b), (1c), (2), (3), (4) and (5) with a plastic pipette into separate plastic beakers and add 20 ml of the TISAB buffer solution to each. ➢ When taking measurements, add a magnetic stirring bar, immerse the electrodes in the solution, stir on the magnetic stirrer for 1 to 2 minutes, and record the potential difference in mV. Take care to not bounce the stirring bar against the electrode. ➢ Rinse and dry the electrode between measurements, taking care to avoid damaging the crystal of the ion-selective electrode. Lab Report ➢ Note the concentration of NaF or Fluoride (= label claim) of each of the original mouthwashes. You will need this for your calculations to check if the NaF content complies with the label claim. ➢ Plot the logarithms of the sodium fluoride concentrations, in µg per ml, of the standard preparations (2), (3), (4) and (5) versus the measured potential in mV. Include in the graph the trendline, equation and r2. ➢ From the equation of the standard response trendline, determine the concentration, C, in µg per ml, of NaF in the diluted mouthwashs (de-log). ➢ Calculate the concentration of NaF and ppm of Fluoride in the original mouthwash. ➢ Compare your results to the label claim and evaluate your results. Questions for your lab report: 1. Why should only plastic lab ware be used for the determination of the fluoride content? 2. What could possibly mask fluoride ions in the assay preparation (i.e., fluoride is present but will not be detected/determined). 3. What is the total ionic strength adjustment buffer (TISAB) made of? Why is this buffer added to the solution? 4. Which factors are affecting/interfering with the selectivity of the electrode? 5. Which reference electrodes can be used with an ISE as specified in BP, Vol. V, Appendix VIII E ‘Potentiometric Determination of Ionic Concentration Using Ion-selective Electrodes’? 6. The expected slope of your graph is approx. -59 mV (25°C). Where does this value come from? How close to this value is the slope of your graph? 7. How reliable do you think your standard curve is? Comment. 8. If the samples did not comply, what would you determine as the most likely reason for this? 9. Write a critical comment on water fluoridation as a method of improving dental health, taking into account health benefits, potential side-effects and ethical considerations. What do you think you have learnt in this lab/when writing up this lab report? Evaluation of the practical procedure – did anything not go according to plan? Do you have any suggestions to improve this practical? Determination of Sodium Fluoride Content in Mouthwash STANDARDS Weight of NaF: NaF concentration Exact mL of stock concentration solution used to in μg/ml* make up 100 mL Potential in mV 0.0110% 0.00550% 0.00220% 0.00110% *based on exact amount weighed out. SAMPLES Mouthwash (Brand) Please note any deviations to procedure Label Claim (ppm Fluoride or % NaF) Potential (mV) Lab report Practical 2 – Determination of Sodium Fluoride Content in Mouthwash Student Name: Group Number: Demonstrator: Date: 1. Briefly describe function and use of an Ion-Selective Electrode (approx. half a page) 2. Results & Data Analysis How did you prepare the stock solution and the standard solutions? Show your calculations. Insert the potential reading in mV of the four fluoride standards into the table below and calculate the logarithm of the concentration in g/ml (based on the exact weight of NaF used to make up your stock solution): Standard Prep Concentration of NaF Standard (2) (3) (4) (5) Conc. of NaF Standard in g/ml Log10 of conc. Potential (mV) 0.0110% 0.0055% 0.0022% 0.0011% Plot a graph with logarithms of the fluoride ion concentrations of the Standard preparations versus potential, in mV (this would correspond to using semi-logarithmic graph paper). You can use Excel to plot the data (scatter with smooth lines, trendline, r2 and equation). Equation of the trendline: r2: Calculate the concentration of NaF (in %) in each of the three mouthwashs taken from the label claim in ppm Fluoride (or vice versa if the label claim is in % NaF): The mouthwash was diluted prior to the labs, by taking a volume of mouthwash equivalent to 50 mg NaF and diluting it to 1000 ml in a volumetric flask. Show how the volume required for this was calculated from the label claim of Fluoride or NaF: Insert data from the three mouthwash samples you tested in the table below: Mouthwash sample (brand) Label Claim (ppm Fluoride) Label Claim (% NaF) Volume (ml) of mouthwash used [containing 50 mg of NaF] Potential (mV) From the measured potential of the Standard preparations and the equation of the trendline, determine the concentration, C, in %, of NaF in the three diluted sample preparations (remember to de-log to obtain the concentration in μg/ml and then convert to % NaF). Calculate the concentration of fluoride ions (in ppm) in each of the three mouthwashs taken, taking into account the volume of mouthwash that was used to make up the 50 mg/L solution: Compare your results to the label claim (complies/does not comply) and evaluate your results. Questions: 1. Why should only plastic lab ware be used for the determination of the fluoride content? 2. What could possibly mask fluoride ions in the assay preparation (i.e., fluoride is present but will not be detected/determined). 3. What is the total ionic strength adjustment buffer (TISAB) made of? Why is this buffer added to the solution? 4. Which other ions are interfering with the selectivity of the electrode? 5. Which reference electrodes can be used with an ISE as specified in BP, Vol. V, Appendix VIII E ‘Potentiometric Determination of Ionic Concentration Using Ion-selective Electrodes’? 6. The expected slope of your graph is approx. -59 mV (25°C). Where does this value come from? How close to this value is the slope of your graph? 7. How reliable do you think your standard curve is? Comment. 8. If the samples did not comply, what would you determine as the most likely reason for this? 9. Write a critical comment on water fluoridation as a method of improving dental health, taking into account health benefits, potential side-effects and ethical considerations. What do you think you have learnt in this lab/when writing up this lab report? Evaluation of the practical procedure – did anything not go according to plan? Do you have any suggestions to improve this practical? Plagiarism statement:
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Explanation & Answer

Hi dude,I am sending you the final version of your Laboratory report.Text me if you have additional questions.I am not sure about questions number 4 and 5. Namely, in order to check the answers I need the references cited in the Laboratory manual you provide me : BP Vol III – Sodium Fluoride MouthwashBP Vol V – Appendix VIII E. Potentiometric Determination of Ionic Concentration using Ion-selective Electrodes

Lab report
Practical 2 – Determination of Sodium Fluoride Content in Mouthwash
Student Name:
Group Number: C
Demonstrator:
Date: 22/02/21
1. Briefly describe function and use of an Ion-Selective Electrode (approx. half a page)
Ion-Selective Electrode (ISE) is an instrument that can be used for measurements of the
concentration of different ions in a liquid solution. The determination of ion concentration is based
on the preparation of the calibration curve in the selected range. The measurements are based on
the differences in potential among the ion concentrations in calibration standards (or unknown
solution) and the interface of ISE. For the measurements of fluoride concentrations solutions, the
crystal of LaF3 (lanthanum fluoride) was used. The mentioned crystal gives a measurable response to
the change in fluoride concentration. In order to lower electrical resistance across the crystal,
europium fluoride was used. Also, europium fluoride enables efficient ionic charge transfer between
ISE and solution. The concentration of fluoride ions in ISE is constant. This enables constant potential
across the ISE when the electrode is not immersed in a solution that contains fluoride ions. When ISE
is immersed into a solution containing fluoride ions the change in measured electrical potential
happens. This change can be measured by pH or mV meter. The entire above mentioned can be
presented by Nernst equation (1):
𝑅𝑇
𝐸 = 𝐸 0 + 2.303
log[𝐴]
𝑛𝐹
Where E represents the measured electrode potential, E0 represents the reference potential, R –
universal gas constant, T-temperature (K), F represents Faraday constant, n- charge of the ion, A
represents the effective co...


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