Alpha-1000 User Manual
Contents
1. 1 1000 SPECTROPHOTOMETER USER S MANUAL V 1 0 Revision Laxco Inc http www laxcoinc com Table of Contents MISC 4 Working Principle 4 5 Unpacking 00 6 re 6 Operation IP AINE 6 Changing Sample 6 222 8 IT MC PC 9 Absorbance and Transmittance Measurement 9 Making Measurements at Different Wavelengths 10 1 ERN 11 1 6 ET Dt 12 Absorbance Accuracy and Stray Light Checking 13 Sample EXperiments oia tci 13 Experiment 1 A Brief Introduction to Beer s 13 Experiment 2 Measurement of an Absorption 15 Experiments Study of rne ti EIN CIN M RE 15 Experiment 4 Deter2. 10 11 Transfer the solution from the beaker to the 100 ml volumetric flask Dilute the de ionized water and mix thoroughly This is your diluted extraction solution Filter 20 ml of the diluted extraction mixture through filter paper in a gravity funnel into a flask or beaker Wash the volumetric flask thoroughly with de ionized water Pipette 10 ml of the diluted extraction solution into the flask dilute to the mark and mix thoroughly This second diluted extraction solution is the unknown solution Transfer the solution to an Erlenmeyer flask and label it Place the second order filter lever in the white position and set the wavelength to 508 nm Fill a cuvette with de ionized water and insert it into the sample compartment Blank the instrument according to the procedure in Basic Operation Fill another cuvette with the first standard Insert the cuvette into the sample compartment and record the absorbance Repeat step 10 for the other three standards and the unknown Note The range of iron levels in the vitamin tablets can be quite broad As a result the prepared unknown solution may not yield an absorbance value that can be properly interpreted from the standard curve Therefore you may have to make adjustments in the concentration of iron in the unknown solution by trial and error If the absorbance of the unknown turns out to be higher than that of standard 4 go back to Step 8 and use smaller amount e g 5 ml of the
3. a A LUE 1 Power COD EE 1 GCUVEtte LOUNG eem Boxof12 1 Square Cuvette Adapter eee Uter 1 DN EOD S 1 Allen drei ER 1 User 1 Installation 1 Place the instrument in a suitable location away from direct sunlight In order to have the best performance from your instrument keep it as far as possible from any strong magnetic or electrical fields or any electrical device that may generate high frequency fields Set the unit up in an area that is free of dust corrosive gases and strong vibrations 2 Remove any obstructions or materials that could hinder the flow of air under and around the instrument 3 Turn on the instrument and allow it to warm up for 15 minutes before taking any readings Operation Panel The key operating components of the Alpha 1000 spectrophotometers are shown in Figure 2 amp Figure 3 The power switch is located on the back of the instrument Power Switch Turns the instrument on and off 0A 100 T Knob Adjust Digital Display reading to 10096 T and 0 000A when blank reference solution is in Sample Compartment Sample Compartment Accept 10 mm test tube or 10 mm square cuvette the sq
4. blanking solution is placed into the sample compartment If not repeat the blanking process again Lamp Changing 1 Remove any cuvettes from the sample compartment 2 Unplug your spectrophotometer and turn it upside down Locate the screw that holds the lamp housing in place refer to the diagram shown below 3 Remove the screw and retain BE CAREFUL THE BULB MAY BE HOT 4 Remove the old bulb and place the leads of the new bulb into the holes in the lamp socket Secure the bulb with the metal bracket Use replacement bulbs with an Item Number of A 110 505 5 Replace the lamp housing panel Secure the screw Bottom View Spill release stopper Figure 6 Bottom View of the Alpha 1000 11 Caution Bulb can be VERY HOT Figure 7 Bulb View of the Alpha 1000 Lamp Adjustment The position of your lamp has been factory adjusted to its optimal setting Follow these steps below for adjusting the lamp position These steps should NOT be needed Unfortunately one should COMPLETELY close the light chamber between adjustment settings attempts The bulb is driven by high voltage Plus the light output is blinding and will cause eye damage if directly viewed with the unprotected eye 1 Loosen the screw on the lamp panel to reveal the light bulb within the lamp housing 2 Make certain that the light bulb is fully inserted into its holder The bulb socket has been permanently mounted in the optimal position
5. 12 ml alkaline copper titrate solution 12 ml phosphomolybdic acid PMA solution 10 ml unknown soft drink sample two 600 ml beakers a 50 ml burette six Erlenmeyer 16 flasks a 2 ml pipette a 10 ml pipette six 25 ml test tubes six round or square cuvettes and a hot plate Procedure 1 Fill the burette to the top calibration line 50 ml with the glucose stock solution Deliver 5 ml of the glucose solution from the burette into the volumetric flask Dilute the flask to the mark with de ionized water cape the flask and mix the diluted solution thoroughly Transfer this first standard to an Erlenmeyer flask calculate its concentration and label the flask Rinse the volumetric flask with de ionized water and repeat step 2 for standards 2 3 and 4 using 10 ml 15 ml and 20 ml of the stock solution 4 Pour 10 ml of the soft drink into the 100 ml volumetric flask swirl it until bubbling stops and dilute to the mark Transfer this solution to an Erlenmeyer flask Rinse the volumetric flask pipette 10 ml of the diluted soft drink solution into it dilute and mix Transfer this solution to another Erlenmeyer flask Rinse the pipette and volumetric flask Pipette 10 ml of the second dilution into the volumetric flask dilute and mix This final unknown solution is the 1 1000 dilution of the original soft drink 5 Label six test tubes Fill them with 25 ml of water using a pipette mark the solution level and empty them
6. Pipette 2 ml of water the unknown and the four standards into the tubes respectively Rinse the pipette after each use 6 Using a graduated cylinder add 2 ml of the alkaline copper titrate solution to each test tube and stir by swirling the tubes Rinse the graduated cylinder well 7 Fill half of a 600 ml beaker with water and place it on a hot plate to boil Prepare an ice water bath in a second 600 ml beaker 8 Immerse the six tubes into the boiling water for exactly six minutes to oxidize the glucose Remove the tubes from the boiling water and immerse them in the ice water bath for exactly 3 minutes to allow them to cool 9 Using a graduated cylinder add 2 ml to the phosphomolybdic acid solution to each tube and stir by swirling them Allow the solution two minutes to react and then dilute them to the 25 ml mark with de ionized water 10 Place rubber stopper in each tube and mix by inverting the tubes several times 11 Set the wavelength to 780 nm and put the second order filter lever in the red position Fill a cuvette with a blank solution and insert it into the sample compartment Blank the instrument according to the procedure in Basic Operation 12 Fill another cuvette with the first standard and measure its absorbance on the spectrophotometer Repeat Step 12 for the other three standards and the unknown solution Calculation 1 Ona piece of regular graph paper label the horizontal axis concentration and mark it in eq
7. diluted extraction solution in making the unknown If the absorbance of the unknown is lower than that of standard 1 use a larger amount e g 20 ml instead Keep doing the above until the desired unknown is obtained Calculations 1 On a regular piece of graph paper label the horizontal axis concentration and mark it in equal intervals from O to the value of standard 4 Label the vertical axis absorbance and mark it in equal intervals from zero to a convenient round value above your highest data point Plot absorbance versus concentration for the four standard solutions Draw the best straight line through the four points and the origin of the graph Use the working graph to determine the concentration of Iron II ion in the unknown solution Using the dilution data from the experiment calculate the concentration of the diluted extraction solution and the mass of iron in mg present in the vitamin tablet 19 Parts List Table 3 Alpha 1 Series Parts List Item Number Description A 1000 Model Alpha 1000 Spectrophotometer 15 nm Band pass Wavelength range 400 1000 nm Complete with 10 mm Test Tube Cuvettes 12 pcs 10 mm Cuvette Adapter Dust Cover User Manual Accessories A 100 101 Experiment manual includes safety in the lab 10 experiments instructor guide A 110 102 Test Tube Sample Holder for 10 mm diameter Test Tubes A 110 103 Squa
8. grating The grating disperses the light beam to produce the spectrum a portion of which is focused on the exit slit of the Monochromator by a collimating mirror From here the beam is passed to a Sample Compartment through one of the filters which helps to eliminate unwanted second order radiation from the diffraction grating Upon leaving the Sample Compartment the beam is passed to the silicon photodiode Detector and causes the Detector to produce an electrical signal that is shown on the Digital Display window Specifications Table 1 lists the specification for the Alpha 1000 Table 1 Wavelength Range 400 1000 nm Spectral Slit Width 15 nm Wavelength Accuracy 3 Wavelength Readability 1 nm Stray Radiant Energy lt 2 T at 400 nm Photometric Range 0 to 125 T 0 3A to 2 0A Photometric Accuracy Better than 2 0 T Data Output USB amp RS232 Power Requirements 85 240 VAC 50 60 Hz Dimensions 455 L x 340 W x 165 H mm Net Weights 7 kg The USB port can be used for connecting to a Windows based computer which is running the Application Software The RS232 port can be used for upgrading the firmware Unpacking Instructions Carefully unpack the contents and check the materials against the following packing list to ensure that you have received everything in good condition Packing List Description Quantity SpectrapDotemieler
9. amp not adjusted properly moved during transit Refer to Lamp Replacement instructions in this manual Lamp old or defective Replace with a new lamp Sample Holder Misaligned Refer to Lamp Replacement instructions in this manual Unstable power supply Call an authorized service Defective or dirty detector or engineer defective electronic component Incorrect Insufficient sample volume Fill cuvette with more sample readings Wrong wavelength setting Check analytical procedure obtained Failed to blank 0A 10096T and wavelength setting Failed to set 0 Check wavelength accuracy according to procedure in this manual Stray sample preparation vapors Prepare sample away from instrument Use proper ventilation Bubbles or particles in solution Check sample preparation and analytical procedure Instrument out of electronic calibration Call an authorized service engineer 22
10. ance varies from 0 to 100 A transmittance of 0 T represents complete absorption by the sample whereas 100 T represents no absorption by the sample The absorbance A is defined as A log 1 T When the transmittance is 100 T 1 A log 1 0 and increases as the transmittance decreases The maximum value of the absorbance read by the Alpha 1000 is 2 0 This represents a Transmittance of T 1 107 or about 1 This is a very small transmittance and is essentially zero It is found that absorbance is directly proportional to concentration so that A EBC Where A The absorbance C The concentration in moles liter and B The width of the sample cell or cuvette in cm E A proportionality constant called the molar absorptivity measured in liters mole cm The linear relationship between absorbance and concentration and sample cell width is called Beer s Law If we have a standard sample with a known absorbance and concentration and a measured absorbance it is easy to determine an unknown concentration of the sample substance via linear interpolation See Figure 8 Absorbance Concentration Figure 8 Absorbance vs Concentration 14 Experiment 2 Measurement of an Absorption Spectrum The absorption spectrum of a substance helps identify it In this experiment you will measure the absorbencies of chromium III ions at a series of wavelengths in the visible light region and draw its absorption spectr
11. by the factory So the rest of steps should not be needed The lamp socket is mounted on an L shaped bracket This bracket is held in place by 2 screws Slightly loosen the 2 screws such that you may move the bracket a little You should then re tighten the screws completely Close the lamp chamber and then power up Set your spectrophotometer to T Continue to adjust the bracket position so that you reach the optimum transmittance reading Tip Don t loosen the screws too much as you adjust the bracket Very small movements are desired Small movements are required to help lessen the chance of missing the optimum positioning 12 4 Once the optimum position has been obtained verify that the lamp chamber door is secure and all items are returned to their original state except the lamp bracket position Absorbance Accuracy and Stray Light Checking Specification 2 at 1 100DPlus 196 at and 2A The absorbance accuracy and Stray Light should be checked against a set of neutral density filters accurately calibrated to the NIST standards Contact Customer Service for more information Sample Experiments Experiment 1 A Brief Introduction to Beer s Law A spectrophotometer is primarily used to identify unknown substances and to determine their concentrations The following principles outline how this is accomplished Matter absorbs energy when it interacts with an energy source such as sound or ligh
12. e holder shutter Light beam blocked Check sample holder e Holder misaligned e Shutter Lamp is old or defective Replace Lamp Lamp is off alignment Refer to Lamp Replacement instructions in this manual Defective electronic component Call an authorized service engineer T cannot be Sample holder Remove Cuvette Adapter or set to 00 0 T test tube Sample holder shutter May be stuck open Close shutter Defective electronic component Call an authorized service engineer Incorrect Bubbles or particles in solution Check sample preparation Transmittance to Absorbance correlation and analytical procedure Defective electronic component Call an authorized service engineer Digital Display does not change regardless of sample concentration Wrong wavelength setting Check sample procedure and wavelength setting Insufficient sample volume Fill cuvette with more sample Stray sample preparation vapors Prepare the sample away from the instrument Use proper ventilation Bubbles or particles in solution Check sample preparation and analytical procedure Defective electronic component or loose wiring Call an authorized service engineer 21 Possible Cause Solution PROBLEM Instrument drift No sufficient warm up time Check lamp has been and noise Significant temperature change properly installed or has L
13. ed water and insert it into the sample compartment Blank the instrument according to the procedure in Basic Operation 5 Fill another cuvette with the first standard and insert it into the sample compartment Measure the absorbance of the first standard at this wavelength 6 Repeat step 5 for the other three standards Calculations 1 On a sheet of graph paper label the horizontal axis concentration and mark it in equal intervals from 0 to 0 02 M Label the vertical axis absorbance and mark it in equal intervals from 0 to a convenient round value above your highest data point 2 Plot absorbency versus concentration for the four standard solutions 3 Using a transparent ruler draw a straight line from the origin such that there are equal numbers of points above and below the line This is the Beer s law plot Experiment 4 Determination of the Concentration of a Solution You will prepare a Beer s Law plot from a series of molybdenum blue standards and determine the amount of glucose in a soft drink The glucose is able to reduce Cu to under the reaction conditions The is then used to reduce phosphomolybdic acid dodeca molybdophosphoric acid PMA to molybdenum blue which absorbs light at a wavelength of 780 nm The amount of molybdenum blue formed is directly proportional to the amount of glucose originally present in the solution The materials required for this experiment are 50 ml 2 g l glucose stock solution
14. ing a measurement of absorbance and transmittance is a two step process In the first step a test tube filled with a transparent solution is placed into the sample compartment This solution will typically be distilled water but can be the aqueous in water medium that you are using for your experiment The transmittance of this solution is made to read 100 T This process is called blanking Blanking must be done each time a new wavelength is selected Note When using square cuvettes use the cuvette adapter provided to cradle the cuvette for insertion into the spectrophotometer The second step is to remove your blanking solution and replace it with the sample solution The absorbance and transmittance can be read from the digital display The step by step procedure for making an absorption transmittance measurement is as follows 9 10 Turn on the spectrophotometer by pressing the power switch the power switch is located on the right side of the back of the instrument In order to stabilize the lamp and detector allow the instrument to warm up for at least 15 minutes Turn the wavelength control knob to the desired wavelength Fill a test tube full with blanking solution and with a tissue wipe off any residue and fingerprints on the outside of the test tube If the test tube has no guide mark some may wish to use a permanent marker to draw an approximate 14 inch vertical line at the lip of the test tube or c
15. mination of the Concentration of a Solution 16 Experiment 5 Determination of a Species in a Solid 18 PANTS LST c 0 5 YX 20 iX 21 Introduction The Alpha 1000 is a single beam spectrophotometer which is designed to meet the needs of both students and instructors Its digital display easy operation and wavelength range of 400 nm to 1000 nm makes this unit ideal for spectrophotometric experiments in the visible wavelength region of the electromagnetic spectrum Working Principle The spectrophotometer consists of five parts 1 Light Source Halogen lamp to supply the light 2 A Monochromator to isolate the wavelength of interest and eliminate the unwanted second order radiation 3 A Sample Compartment to accommodate the sample solution 4 A Detector to receive and convert the transmitted light to an electrical signal 5 A Digital Display to show absorbency and transmittance Figure 1 illustrates the relationship between these parts v g 100 T lt C gt gt gt gt 0A ais EN mm Light Source Monochromator Sample Compartment Detector Digital Display Figure 1 Block Diagram for the Spectrophotometer In the spectrophotometer light from the Halogen Lamp is focused on the entrance slit of the Monochromator where the collimating mirror directs the beam onto the
16. re Cuvette Adapter for 10 mm Cuvettes A 110 113 Test Tube Sample Holder for 34 inch Test Tubes A 110 114 Test Tube Sample Holder for 1 inch Test Tubes A 110 115 COD Vial Sample Holder A 110 220 Power Cord European plug A 150 115 Holmium Oxide Filter 10 mm x 10 mm x 45 mm requires A 110 103 A 150 116 Didymium Filter 10 mm x 10 mm x 45 mm requires A 110 103 Glassware A 301 Test Tube Cuvette 10 mm diameter 12 pcs A 302P 100 Disposable Cuvette Polystyrene 10 mm path length 100 pcs A 302P 500 Disposable Cuvette Polystyrene 10 mm path length 500 pcs A 304G Square Cuvettes Optical Glass Set of 4 A 305P Disposable semi micro Cuvette Polystyrene 10 mm path length 500 pcs Misc and Replacement Items A 110 505 Tungsten Halogen Lamps Package of 2 6V 10W G4 type A 110 508 Printer Paper Package of 3 A 110 509 Printer A 110 511 User Manual A 110 512 Dust Cover A 110 513 Fuse 3A quantity 1 size 5 x 20 A 110 521 Allen Wrench A 120 111 Black block 20 Troubleshooting PROBLEM Possible Cause Solution Instrument Power cord not connected to outlet Plug instrument in Inoperative Internal fuse blown or defective Call an authorized service Power indicator electronic component engineer has no light Instrument No Cuvette Adapter in the Sample Cuvette Adapter must be in cannot be set to Compartment Sample Compartment to 100 0 000A open sampl
17. t Due to its distinctive atomic structure each substance only absorbs energy at specific frequencies Since energy is proportional to frequency E hc A where h 6 6262 x 107 Joules Plank s constant c 2 998 x 10 m s the speed of light in a vacuum often rounded to 3 00 x 10 m s and A wavelength of light Every substance has a characteristic absorbance of the light spectrum which means that there are wavelengths where the atoms of a substance become highly excited For example hydrogen H absorbs light at the following wavelengths in the visible region 410 7 nm 433 8 nm 485 7 nm and 657 9 nm We can verify the existence of hydrogen in an unknown sample by comparing the wavelengths absorbed by the unknown sample to the wavelengths at which hydrogen absorption is known A spectrophotometer is required to measure absorption spectrums in order to identify an unknown substance The spectrophotometer is used to measure the amount of light absorbed at distinct wavelengths This can be plotted and the graph can be used to identify the presence of a particular substance A spectrophotometer can also be used to determine the concentration of an unknown sample When a light beam is incident to a sample part is absorbed and part is transmitted The transmittance T is defined as the ratio of the transmitted intensity of the light beam X to the initial intensity of the light beam Y or T2X Y 13 The transmitt
18. the concentration of an unknown solution It states that there is a linear relationship between the absorbance and the concentration of the absorbing substance In order to verify Beer s law we can measure the absorbance for different concentrations of a substance at the same wavelength plot them on a piece of graph paper and see if the data points lie along a straight line Actually the points probably will not form an ideal straight line due to the uncertainty in the measurements 15 The materials required for this experiment are 500 ml 0 04 g l thymol blue solution 40 ml 1 M HCL aqueous a 50 ml burette a 10 ml graduated cylinder a 100 ml volumetric flask five round cuvettes and four Erlenmeyer flasks Procedure 1 Fill the burette to the top calibration line 50 ml with the thymol blue stock solution 2 Deliver 5 ml of the thymol blue solution from the burette into the volumetric flask Measure 10 ml HCL aq in a graduated cylinder and add to the flask Dilute the flask to the mark with de ionized water cap the flask and mix the diluted solution thoroughly Transfer this first standard to an Erlenmeyer flask calculate its concentration and label the flask 3 Rinse the volumetric flask with de ionized water and repeat step 2 for 15 ml 20 ml and 30 ml of HCL These are standards 2 3 and 4 4 Place the wavelength at 545 nm and the second order filter in the white position Fill a cuvette with de ioniz
19. tion 10 ml 196 w v 1 10 phenanthroline ortho solution a 100 ml beaker a 50 ml burette five Erlenmeyer flasks a 50 ml graduated cylinder a 10 ml pipette six round cuvettes a hot plate a stirring rod a gravity funnel and some filter paper Procedure 1 Fill the burette to the top calibration line 50 ml with the Fe stock solution 2 Deliver 5 ml of the stock solution form the burette into a clean 100 ml volumetric flask Measure 10 ml of the acetate solution and 10 ml of the phenanthroline solution into the graduated cylinder respectively and add to the flask Allow the mixture to stand for five minutes dilute the flask to the mark with de ionized water cap the flask and mix the diluted solution thoroughly Transfer this first standard to the Erlenmeyer flask calculate the concentration of the standard and label the flask 3 Rinse the volumetric flask with de ionized water and repeat Step 2 for 10 ml 15 ml and 20 ml of the stock solution from the burette These are standards 2 3 and 4 4 Place the vitamin tablet into a 100 ml beaker Measure 50 ml of the 0 1 M HCL aq into the graduated cylinder and add it to the beaker 5 Place the beaker on a hot plate and heat the extraction solution to boiling Gently boil the acid extraction solution for 15 minutes Break apart the tablet with a clean stirring rod while boiling Remove the beaker from the hot plate and allow the solution to cool to room temperature 18
20. ual intervals from 0 to the value of standard 4 Label the vertical 17 axis absorbance and mark it in equal intervals from 0 to a convenient round value above your highest data point 2 Plot absorbance versus concentration for the four standards Draw the best straight line through the origin and the four points 3 Using the working graph determine the concentration of the unknown solution 4 Multiply the concentration of the unknown by 1000 to get the concentration of glucose in the original soft drink Experiment 5 Determination of a Species in a Solid Sample In order to determine the amount of a species in a solid sample it is necessary to make an extraction solution containing that species with a proper solvent and then measure the concentration of the species in the solution using the same method described in the last experiment As an example you will determine the amount of iron in a vitamin tablet lron Il forms a colored complex with 1 10 phenanthroline which absorbs light energy at 508 nm A working curve will be prepared for standard solutions of Iron Il phenanthroline complex and the concentration of an unknown sample will be determined from the working curve data The materials required for this experiment are a vitamin tablet 50 ml 0 1M HCL aq solution 50 ml 0 19 1 Fe aq solution 10 ml 1 w v HONHs CL aq hydroxylamine hydrochloride solution 10 ml 1M aq sodium acetate solu
21. uare cuvette adapter is required Wavelength Control Knob Select desired wavelength in nanometers nm Wavelength Readout Window Displays desired wavelength USB port It is used for connecting to Computer with Application Software RS232 It is used for Firmware upgrading Digital Display Sample Compartment P P Operation Instructions Wavelength Control Knob 0 100 Knob Wavelength Readout Window Figure 2 Alpha 1000 Spectrophotometer Power Switch Air Vent Power Socket Han USB Port RS 232 Figure 3 Back view of Alpha 1000 Changing Sample Holders Your Alpha 1000 comes standard with the A 110 102 Sample Holder We offer three additional holders as optional accessories Please refer to Table 3 Alpha 1 Series Parts List in Alpha 1 Series Parts List of this manual for details Follow the steps below to change the Cuvette Sample Holder e Open the lid of the Sample Holder and locate the Sample Holder Locking Screw as shown in Figure 4 e Use Allen Wrench A 110 521 Figure 5 to loosen the Screw counterclockwise e Remove the Sample Holder you want to change insert the one you want to install align it properly and fasten the Screw Lock Screw Figure 4 Changing Sample Holders Figure 5 Allen Wrench Basic Operation Simple OPERATION INSTRUCTIONS are printed on the front panel of your Alpha 1000 Absorbance and Transmittance Measurement Mak
22. um The materials required for this experiment 20 ml 0 5M Cr aq solution and two round cuvettes Procedure 1 Place the wavelength dial at a position of 400 nm and adjust the second order filter lever position 2 Fill one cuvette with de ionized water and insert it into the sample compartment Blank the instrument according to the procedure in Basic Operation Then remove the cuvette 3 Fill another cuvette or the same cuvette rinsed thoroughly with the stock solution with the Cr 3 stock solution and inset it into the sample compartment Record the absorbance of the solution at this wavelength and then remove the cuvette Repeat Step 1 through Step 3 for wavelengths from 400 to 650 nm at 20 nm intervals Make sure that the meter display 0 and 100 T readings are adjusted at each new wavelength Calculations 1 Study the data and identify the points where the peaks are likely to be found Make measurements at smaller intervals e g 5 nm around these points to locate the peaks more accurately 2 On regular graph paper label the horizontal axis wavelength and mark it from 400 to 650 nm in 20 nm intervals Label the vertical axis absorbance and mark it in equal intervals from zero to a convenient round value above your highest absorbance 3 Plot the absorbance for wavelength measured Draw a smooth curve through the data points Experiment 3 Study of Beer s Law Beer s Law is the basis for the determination of
23. uvette this ensures that you minimize the bearing of any differences in reflection due to small changes in the thickness in the wall of the test tube Place a test tube into the sample compartment with the test tube guide mark aligned with the mark at the top of the compartment this mark is located at the front of the sample compartment Be sure that the test tube has been firmly pressed into the sample compartment and the lid of the sample compartment has been closed Adjust the display to 100 T and 0 00A by turning the 100 T knob Remove the test tube from the sample compartment and empty the blank solution Rinse the test tube twice with small volumes of the sample solution to be measured then fill the test tube 2 3 full with the sample solution and wipe it clean Place the test tube in the sample compartment aligning the guide marks if any Close the lid of the sample compartment Sample site can also be covered Read the T and absorbance from the digital display Remove the test tube from the sample compartment empty it and repeat Step 7 to 10 for any additional samples Making Measurements at Different Wavelengths Repeat Step 2 to Step 10 above and remember to blank your spectrophotometer whenever a measurement is being made at different wavelengths In addition when operating at a fixed wavelength for an extended period of time check to make sure that the transmittance reads 100 T when the 10
Download Pdf Manuals
Related Search