Lab 5: Quantitative Analysis- Phosphates in Water By: A Generous Student. LBS 171L Section 9 TA: Dana October 27, 2005

Transcription

1 How uch Phosphate is the Body Being Exposed to During a Lifetime by Showering? Lab 5: Quantitative Analysis- Phosphates in Water By: A Generous Student LBS 171L Section 9 TA: Dana October 7, 005 [Note: Some small formatting changes have been made by Prof. Sweeder] [Comments have been added.]

2 Abstract The amounts of phosphate the body is being exposed to from water and shampoo during the course of an average (15 minute shower over an average (85 year lifetime were determined to be moles and moles respectively. Therefore, the total amount of phosphate exposure would be moles. The molarity of water and shampoo were found to be 1.09 x -4 and 1.8 respectively. The value of ε for the heteropoly acid was determined to be through graphing, and approximately 1397 through beers law calculations (see questions. This data is supported through experimentation of the two solutions with ocean optics, water and shampoo, and calculations relating the concentration, amount, and time of both solutions within the given restrictions. Since all of this phosphate is not actually being absorbed into the body, this amount is not harmful to be exposed to during the course of a lifetime. Introduction Since ancient roman times, soaps have been used as a primary cleaning agent in many homes. The ability of soap to dissolve grease, or its detergency, is greatly reduced by the amount of mineral ions in the water which the object is being washed. Especially in hard waters where there is a higher presence of these mineral ions, the organic greasesoluble part of the soap molecule is bound up by the minerals. This, in turn, creates a residue or scum on clothing, dishes, or your skin after being washed. To solve this problem, phosphate is added into the soaps to remove calcium, iron, and magnesium ions from the water, therefore softening it, by tying up the minerals, forming a complex

3 soluble phosphate. Phosphate is therefore known as a builder in soaps and detergents because it enhances the washing performance. These builders help to reduce the amount of detergent or soap needed to clean something. Although phosphate is helpful in increasing the cleaning powers in soaps, too much exposure can be harmful to the body. Procedure From the stock solution of phosphate, dilutions in 0 ml volumetric flasks were created for concentrations of 1.00 x -3, 5.00 x -4,.50 x -4, 1.00 x -4, 5.00 x -5,.50 x -5. To make the six different dilutions, 5 ml of stock solution was put into each of six 00 ml beakers. In the first beaker, a 0% solution was made by adding 5 ml of phosphate and no water. The second beaker contained a 50% solution, which was made by adding 5 ml of phosphate with 5 ml of distilled water. The third beaker contained a 5% solution, made by mixing 5 ml of phosphate with 15 ml of distilled water. In the fourth beaker, a % solution was made by adding 5 ml of phosphate with 45 ml of distilled water. The fifth beaker contained 5 ml of phosphate and 95 ml of distilled water, making a 5% solution. The sixth and final beaker contained a.5% solution made by adding 5 ml of phosphate with 195 ml of distilled water..0 ml of each phosphate standard from the six beakers was added to 5.0 ml of ammonium vanadomolybdate reagent in order to measure the absorbance of the known concentration solutions. Each cuvette containing the various concentration solutions was inserted into ocean optics and the maximum wavelength and absorption values were

4 recorded. This data was used to create a calibration curve to determine the concentrations of the unknown samples of phosphates. The first unknown sample of phosphate tested was Garnier Fructis Fortifying Shampoo. A 1/000 concentration of shampoo was created by adding 1 ml of shampoo to L of distilled water. The dilution made to the shampoo was done to obtain a correct reading off of the spectrometer. Any solution with an absorption reading higher than 1.5 must be diluted to get an accurately measurable value. The absorption value from ocean optics for this diluted solution was The sample of shower water was left at full concentration and the absorption value of was obtained from ocean optics. The amount of shampoo used per shower was an estimation. The amount of water used during a 15 minute shower was obtained by measuring the amount used during 1 minute and multiplying by 15. Data Table 1: absorption values of varying concentrations for stock solution phosphate (0.001 Wavelength ax (nm Concentration (% Concentration ( x x x x x x Table : absorbance values and concentrations of water and shampoo Absorption (arbitration units Substance Wavelength ax Concentration Absorption (nm ( (arbitration units Water x

5 Shampoo (1/000 strength Shampoo (full strength x Table 3: amounts of substances with correlating amounts of phosphate * Estimated amount used during the course of an average 15 minute shower * Amount used during the course of an average lifetime, estimated to be 85 years, assuming one shower per day Substance Amount Used Per Shower (L Amount Phosphate Per Shower (mol Amount Used per Lifetime (L Amount Phosphate Per Lifetime (mol Water x Shampoo Total Amount Phosphate Per Lifetime Calculations From the stock solution of 1.00 x -3 phosphate, percent concentrations were found for the various concentrations given. ( 0 = 0% 5.00 ( 0 = 50%.50 ( 0 = 5% ( 0 = % 5.00 ( 0 = 5%.50 ( 0 =.5% To calculate concentrations of unknown phosphate solution, the following formula was used; absorption concentration = ε (slope The slope of the calibration curve was , and the absorptions values were recorded from ocean optics concentration = = 1.09 Sample Water (

6 concentration = = 1.8 Shampoo (1/0000 dilution ( 1.8 L Lshampoo ( Lsolution = = 1.8 Shampoo (full strength The amount of water used during the course of a normal shower (15 minutes was determined by measuring the amount used during 1 minute and multiplying by the time. 7300mL ( 15min = 9500mL min This amount in ml was converted into L for easier use in further calculations. 1L 9500 ml = 9. 5L 00mL To find the amount of water used during an average lifetime (85 years, the following calculations were done; 9.5L shower 365days 85years = L / lifetime shower day year lifetime The same calculations were done for the amount of shampoo used in a lifetime, and results recorded in table 3. To find the moles of phosphate the body is being exposed to during the course of an average shower, the concentration is multiplied by volume of water or shampoo used..09 L 1 ( 9.5L = 1.19 Sample Water 1.8 L (.06L =.9 Shampoo =. 111 Sample Water and Shampoo To find the moles of phosphate the body is being exposed to during the course of an average lifetime, the concentration is multiplied by volume of water or shampoo used.

7 1.09 L ( L = Sample Water 1.8 L ( L = Shampoo = Sample Water and Shampoo Least Squares Analysis Concentration Average ( = 3.1 (3.1 (Concentration Average- Individual Concentration = 4.61 ( = 3.0 ( = ( = ( = ( = Graph 1: calibration curve of absorption vs concentration Absorption (arbitrating units Calibration Curve y = x R = Concentration (

8 Results and Discussion The purpose of this lab was to determine the amount of phosphate that the body is exposed to during the course of an average shower throughout an average lifetime. An average shower was defined as 15 minutes, which would produce 9.5 L of water, and 60 ml of shampoo per shower. It was also assumed that one would take one shower per day for an average lifetime, which was defined as 85 years. The concentration of phosphates in water and shampoo were found by using spectroscopy, the use of light absorption to measure concentration (p. 40 lab 5 introduction. Absorbance is found by the equation A = εbc, where ε is the slope of the Beers Law plot, or calibration curve, b is the length of the cuvet (1 cm, and c is the concentration of the solution. Beer's law expresses the direct correlation between the concentration of a solution and its absorbance at a given wavelength. By finding the value of ε through a Beers Law plot of a known phosphate concentration, the phosphate concentration of unknown substance, such as shampoo, can be found by plugging the absorbance values into the Beers Law equation with the calculated value of ε and the length of the sample cell. The concentrations, in moles per liter, of phosphate in water -4 and shampoo were determined to be 1.09 x and 1.8 respectively. The amount of shampoo used during a shower was an estimate, while the amount of water used during a shower was measured in the following way; a plastic bag was tied to the shower head and the water was allowed to run at full pressure for one minute. The amount of water in the bag was measured out and determined to be approximately 7300 ml. This value was then multiplied by 15 minutes, so that the final amount of water per shower was determined to be 9.5 L.

9 Once the concentrations of phosphate in water and shampoo were found, the moles per liter of phosphate was multiplied by the amount of water and/or shampoo used, and then by the times used per shower and per lifetime to find the amount of exposure to phosphate in a lifetime. The amount of phosphate the body is being exposed to in a lifetime was determined to be moles. The largest possible sources of error in this experiment were inaccurate readings from ocean optics and imprecise measurement of the volume of shampoo. Since ocean optics is somewhat variable, the data given from the unknown phosphate readings, especially the shampoo, seem higher than expected. The other source of error in this experiment came from difficulty in measuring out exactly 1 ml of shampoo. As best could be done, approximately 1 ml of shampoo was extracted with a pipette and added with L of water into a beaker. Excess shampoo may have been left on the inside of the pipette, resulting in an inaccurate measurement. Conclusion The amount of phosphate that the body is being exposed to, over an 85 year lifetime, through normal showering was successfully determined to be moles. This data was determined by multiplying the volumes needed to fit the requirements of an average shower by the concentrations of phosphate per L of substance. The volumes of water and shampoo needed were determined to be 9.5 L of water and 60 ml of shampoo per shower. Therefore, the amount of phosphate per shower from water and shampoo were determined to be 1.19 x - mol and.9 mol respectively. By adding

10 these values together and multiplying by the number of showers, it was determined that the body would be exposed to moles of phosphate in a lifetime. Although moles is a large amount of phosphate to be exposed to, there are no danger or health risks to the human body because hardly any of that amount is actually being absorbed though the skin; most of that phosphate is being rinsed down the drain during a shower. Furthermore, the amount that is actually being absorbed through the skin is being done so over a very long period of time, therefore the build up of phosphate would be very gradual and nontoxic. Questions 1. Since ε b is the slope of the calibration curve, and b is 1 cm, then the value of ε is simply for heteropoly acid. If finding this value through beers law, the following calculations would take place; A = εbc = ε (1cm( ε = = ε (1cm(5.00 ε = = ε (1cm(.50 ε = = ε (1cm( ε = = ε (1cm(5.00 ε = = ε (1cm(.50 ε = 00 The calibration curve had a y-intercept that was close to, but not, zero. This value, 0.01, shows that the beer law is not exactly correct in this case. Therefore, the values used from the curve are slightly off.. Question: How much phosphate is the body being exposed to from shampoo and water by showering once a day for 15 minutes in an average lifetime (85 years?

11 Anwser: The body is being exposed to of phosphate though showering once a day for an average lifetime. Works Cited Bubbles and Soap Composed by J. B. Calvert Created 0 arch Historical Perspective of the Phosphate Detergent Conflict Composed by Chris Knud-Hansen Created February Soap SN Encarta The Disposal of Soaps and Detergents Enviromental Protection Agency (EPA Created April 004