Colorimeter - Vernier Software & Technology
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1. s law curve as shown on the previous page its concentration is determined on the horizontal axis Alternatively its concentration may be found using the slope of the Beer s law curve Using the Colorimeter The Colorimeter is easy to use and maintain Simply connect it to your data collection interface configure your software and you are ready to make measurements For best results let the system stabilize at the desired wavelength for 5 minutes prior to calibration or data collection Wavelength Selection You can select one of four LED light wavelengths with the Vernier Colorimeter violet 430 nm blue 470 nm green 565 nm and red 635 nm You can select one of these nearly monochromatic colors using the wavelength selection arrows on the top of the Colorimeter shown here There are several ways you can decide which of the four wavelengths to use e Look at the color of the solution Remember that the color of a solution is the color of light that passes through it You want to use a different color of light that will be absorbed rather than transmitted for example with a blue copper II sulfate CuSO z solution 470nm 565nm use the red LED 635 nm asna e Another easy method is to place a cuvette containing the solution in question in the Colorimeter and check to see which of the wavelengths yields the highest absorbance e Directions for most colorimetry experiments express a recommended wavele2. concentration experiments you will be prompted to keep the absorbance value when it stabilizes and enter the concentration of the standard solution Repeat the process for the remaining standards e In absorbance vs time experiments readings will be taken in real time for the amount of time set up in the data collection program d Data collection will end when you choose Stop or when the pre set experiment length has been reached e After data collection is completed you may use some of the tools in our data collection programs to analyze the collected data For example in absorbance vs concentration Beer s law experiments you can perform a linear fit on the data then interpolate along the resulting linear fit to determine the concentration of an unknown Data Collection Software This sensor can be used with an interface and the following data collection software e Logger Pro 3 This computer program is used with LabQuest LabQuest Mini LabPro or Go Link e Logger Pro 2 This computer program is used with ULI or Serial Box Interface e Logger Lite This computer program is used with LabQuest LabQuest Mini LabPro or Go Link e LabQuest App This program is used when LabQuest is used as a standalone device e EasyData App This calculator application for the TI 83 Plus and TI 84 Plus can be used with CBL 2 LabPro Vernier EasyLink We recommend version 2 0 or newer which can be downloaded from the Vernier web site
3. ability of the solute the distance traveled by the light through the solution and the concentration of the solution For a given solution contained in a cuvette with a constant cell width one can assume and b to be constant This leads to the equation A keC Beer s law where k is a proportionality constant This equation shows absorbance to be related directly to concentration and represents a mathematical statement of Beer s law Beer s law is discussed in more detail below In this guide and in some of our computer programs transmittance is expressed as percent transmittance or T Since T T 100 the formula can be rewritten as A log 00O T or A 2 log T Beer s Law L In general absorbance is important 5 Beer s Law because of its direct relationship with concentration according to Sencentiaton 6 23 mall 8 ft 0 44 Absorbance 0 2713 Beer s law Many experiments in chemistry and biology are based on 3 this concept To obtain a Beer s 5 S Uz law curve several standards qt solutions of known concentration 942 are prepared and their absorbance iiaii values are determined using a a l 0 0 0 1 0 2 0 3 0 4 0 5 Colorimeter A graph of Concentration mol L absorbance vs concentration 1s then plotted A solution of unknown concentration is placed in the colorimeter and its absorbance measured When the absorbance of this solution is interpolated on the Beer
4. used to monitor the extent of cellular membrane damage Experiment 9 Biology with Vernier Population Dynamics In this experiment students monitor the growth in yeast populations using a Colorimeter NOTE This product is to be used for educational purposes only It is not appropriate for industrial medical research or commercial applications 10 Warranty Vernier warrants this product to be free from defects in materials and workmanship for a period of five years from the date of shipment to the customer This warranty does not cover damage to the product caused by abuse or improper use 11 AAT E Vernier Measure Analyze Learn Vernier Software amp Technology 13979 S W Millikan Way e Beaverton OR 97005 2886 Toll Free 888 837 6437 e 503 277 2299 e FAX 503 277 2440 info vernier com e www vernier com Rev 2 16 10 Logger Pro Logger Lite Vernier LabQuest Vernier LabQuest Mini Vernier LabPro Go Link Vernier EasyLink and other marks shown are our trademarks or registered trademarks in the United States CBL 2 and CBL TI GRAPH LINK and TI Connect are trademarks of Texas Instruments All other marks not owned by us that appear herein are the property of their respective owners who may or may not be affiliated with connected to or sponsored by us ey Printed on recycled paper ue 12
5. Colorimeter Order Code COL BTA The Vernier Colorimeter is designed to determine the concentration of a solution by analyzing its color intensity The color of a solution may be inherent or derived by adding another reagent to it The Colorimeter measures the amount of light transmitted through a sample at a user selectable wavelength Using the front panel arrow keys you may choose from four wavelengths 430 nm 470 nm 565 nm and 635 nm Features such as automatic sensor identification and one step calibration make this sensor easy to use How the Colorimeter Works Source Detector Light from a LED light source passes through a D gt gt cuvette containing a solution sample as shown in LED Transmitted Figure 1 Some of the incoming light is absorbed light by the solution As a result light of a lower intensity strikes a photodiode Figure 1 Important Software and LabPro CBL 2 OS Updates 1 If you are using Logger Pro computer software you will want to update your Logger Pro Colorimeter experiment files The easiest way to obtain these is to update Logger Pro to Logger Pro 3 2 If you are using a calculator and the firmware version on your LabPro or CBL 2 is older than 6 23 dated 08 22 02 you will need to update the operating system You can do this by going to our web site www vernier com select Downloads and select LabPro and CBL 2 operating system updates Transmittance and Absorbance T
6. e slot Close the Colorimeter lid d Next press the CAL button to begin the calibration process Release the CAL button when the red LED begins to flash The absorbance should now be 0 000 or 0 001 e When the LED stops flashing the calibration 1s complete and your unit is ready to collect data Important Unlike older versions of the Colorimeter with this model you do not need to go to a special calibration menu in our data collection programs Arrow 5 Collecting data a There are two common modes for Colorimeter data collection e Absorbance vs concentration Beer s law If you want to collect data in Events with Entry mode you can open a different Logger Pro Colorimeter file with a computer With calculators or handhelds you will need to change from Time Graph to Events with Entry mode e Absorbance vs time When the Colorimeter is automatically identified by Logger Pro it will already be set up to collect in this mode With calculators or handhelds auto ID will set the mode to Time Graph b Place the cuvette with a sample into the Colorimeter cuvette slot Important Line up one of the clear sides of the cuvette with the arrow at the top of the cuvette slot c Begin collecting data choose Collect or Start in the program If you are using Logger Pro 2 with either a ULI or SBI the sensor will not auto ID Open an experiment file for the Colorimeter in the Probes amp Sensors folder e In absorbance vs
7. e small scratch is eliminated using the 100 calibration As an alternative you may choose to match cuvettes Matched cuvettes are a set of cuvettes that all absorb light when empty at approximately the same level This involves more work on the part of the teacher but saves time in student procedures If students have 5 or 6 cuvettes with similar absorbance levels then each sample can be added to a different cuvette eliminating the drying or rinsing step described in the previous paragraph Caps are supplied for the original 15 cuvettes A cuvette may or may not have a cap on it when placed in the Colorimeter The purpose of the cap is to prevent evaporation of solvent when an experiment is run over a period of several days You may find it convenient to store standard solutions in capped cuvettes If you purchase a replacement set of 100 cuvettes 20 caps will be included We felt teachers would probably not need to have one cap per cuvette The caps can certainly be reused as cuvettes are replaced Replacement cuvettes may be purchased using the order code CUV This package includes 100 cuvettes and 20 caps This sensor is equipped with circuitry that supports auto ID When used with LabQuest LabQuest Mini LabPro Go Link SensorDAQ EasyLink or CBL 2 configure an experiment appropriate to the recognized sensor the data collection software identifies the sensor and uses pre defined parameters to Specifications Color
8. eriments Beer s Law e Crystal Violet Dilute solutions of crystal violet yield a good Beer s law curve using the green LED 565 nm A stock solution of 2 5 x 10 M crystal violet is prepared by adding 0 020 g of solid crystal violet to enough water to yield 2 liters of solution Dilute to obtain standard solutions Copper Sulfate Standard solutions that are 0 1 0 2 0 3 and 0 4 M CuSO will yield a good Beer s law curve at 635 nm red LED Prepare a stock solution by adding 10 g of NH4NO to 10 mL of 0 1 M CuSO and 90 mL of 0 20 M NH forms the Cu NH complex ion and dilute to obtain standard solutions e Food coloring Solutions Red Blue Green A less expensive alternative to using the solutions above is to prepare solutions using food coloring We have obtained very good Beer s law curves using these solutions We added about 6 drops of red blue or green McCormick brand food coloring to 1 liter of water The red solution can be analyzed using the blue LED 470 nm the green solution with the blue LED 470 nm or the red LED 635 nm and the blue solution with the red LED 635 nm Since the actual concentration of the solutions will not be known refer to the original solution as 100 and then dilute to 80 60 40 and 20 Check the original solution to see that its absorbance is not greater than 1 0 You can find detailed instructions for the following experiments in the Vernier lab books listed with each expe
9. ettes have a volume of approximately 4 mL Two opposite sides of the cuvette are ribbed and are not intended to transmit the light from the LED The two smooth surfaces are intended to transmit light It is important to position the cuvette correctly in the Colorimeter with a smooth side facing the arrow at the back of the slot and with the ribbed edges facing left and right The light travels from the LED at the top through the cuvette to the detector below the slot Just like most spectrophotometer sample tubes individual plastic cuvettes vary slightly in the amount of light they absorb You may choose to ignore these differences For most lab exercises this variation will not have a noticeable effect on experimental results For best results variation in light absorbed by individual cuvettes can be controlled either by using the same cuvette for all trials of a particular experiment or by matching a set of cuvettes The easiest and most reliable is the first method If a student plans to use five trials for a Beer s law experiment the five standard solutions can be transferred to the same cuvette for each trial This requires that the cuvette be clean and dry after each trial or rinsed several times with the solution that will be added to it This method takes very little time and successfully controls a potential variable It also eliminates concerns over possible scratches that may eventually develop on a cuvette The effect of the sam
10. he amount of light that passes through a solution is known as transmittance Transmittance can be expressed as the ratio of the intensity of the transmitted light It and the initial intensity of the light beam Io as expressed by the formula T L l The Colorimeter produces an output voltage which varies in a linear way with transmittance allowing a computer calculator or handheld to monitor transmittance data for a solution The reciprocal of transmittance of the sample varies logarithmically base ten with the product of three factors the molar absorptivity of the solution b the cell or cuvette width and C the molar concentration logd T ebC If you are using Logger Pro 2 update to version 2 2 1 You can do this for free on our web site at Www vernier com In addition many experiments designed to use a Colorimeter require a related measurement absorbance At first glance the relationship between transmittance and absorbance would appear to be a simple inverse relationship that is as the amount of light transmitted by a solution increases the amount of light absorbed might be expected to decrease proportionally But the true relationship between these two variables is inverse and logarithmic base 10 It can be expressed as A log T Combining the two previous equations the following expression is obtained A e ebC In effect this formula implies that the light absorbed by a solution depends on the absorbing
11. imeter range 0 to 3 absorbance Useful Range 0 05 to 1 0 absorbance 90 to 10 T Wavelengths 430 nm 470 nm 565 nm 635 nm 13 bit resolution SensorDAQ 0 018 T 12 bit resolution LabQuest 0 035 T LabQuest Mini LabPro ULI II SBI 10 bit resolution CBL 2 0 14 T Supply voltage SVDC 25 mV Supply current typical 40 mA Power up time 700 ms maximum Output voltage range 0 4 V Transfer function Stored Calibration Values Vout 0 035 T 0 Slope 28 571 Intercept O Using Vernier Sensors with Other Interfaces Our sensors may be used with interfaces from manufacturers other than TI or Vernier Software amp Technology Some interfaces may not use the same connectors Please contact the interface manufacturer for an adapter or go to www vernier com probes specs pinout html for pin assignments and other information Interfaces that have power saving features typically battery powered units may cause problems with sensors that require a longer warm up period gt 1 sec If available select a constant power option for these sensors Extending the Length of the Cable The cable length may be increased by using an extension cable order code EXT BTA These cables are 2 m in length and allow you to extend the sensor farther from the interface If longer cabling is needed contact Vernier for assistance Ordering Information Replacement Cuvettes pkg of 100 with 20 lids CUV Suggested Exp
12. ngth Use the wavelength closest in value to the recommended wavelength Even if the LED wavelength is somewhat different a Beer s law curve can usually be obtained at almost any wavelength in the vicinity of the recommended wavelength Collecting Data with the Colorimeter This sensor can be used with the following interfaces to collect data e Vernier LabQuest as a standalone device or with a computer e Vernier LabQuest Mini with a computer e Vernier LabPro with a computer TI graphing calculator or Palm handheld e Vernier Go Link e Vernier EasyLink e Vernier SensorDAQ e CBL2 Here is the general procedure to follow when using the Colorimeter 1 Connect the Colorimeter to the interface 2 Start the data collection software 3 The software will identify the Colorimeter Proceed to Step 4 to calibrate the Colorimeter The Colorimeter needs to be powered about 5 minutes before calibrating in Step 4 One of the four green wavelength indicator lights will be turned on when it is powered 4 Calibrate the Colorimeter a Press the lt or gt button on the Colorimeter to select the correct wavelength setting for your experiment 430 nm 470 nm 565 nm or 635 nm b Open the Colorimeter lid c Insert a cuvette usually filled with distilled water for your blank cuvette 100 transmittance or 0 absorbance Important Line up one of the clear sides of the cuvette with the arrow at the top of the cuvett
13. not second order Tests 7 and 8 Water Quality with Vernier Ortho Phosphates Total Phosphates and Nitrates To determine the concentration of an ion in a colorless solution using a colorimeter an agent must be added to the solution to yield color such as a colored complex ion or turbidity through the formation of a precipitate The assumption is that the intensity of the color and its resulting ability to absorb light from the LED is proportional to the concentration of the ion in solution Hach Company markets pre massed pillows for analysis of such ions as nitrate NO and phosphate PO as well as many other colorimetric tests Water Quality tests for these ions using a Vernier Colorimeter are described in our Water Quality lab books Experiment 7 Biology with Vernier Photosynthesis In this experiment students monitor the progress of photosynthesis using a blue dye 2 6 dichlorophenol indophenol or DPIP As photosynthesis proceeds the dye turns from blue to colorless when reduced Experiment 8 Biology with Vernier The Effect of Alcohol on Biological Membranes Students see the effect of different alcohols on beet cell membranes by examining the amount of red pigment released with the Vernier Colorimeter Experiment 13 Biology with Vernier Biological Membranes In this experiment students determine the stress of various factors osmotic balance detergents or pH on biological membranes The absorbance of light is
14. riment Experiment 11 Chemistry with Vernier Determining the Concentration of a Solution Beer s Law This experiment uses standard and unknown solutions of NiSO or green food coloring using the Vernier Colorimeter Use the red LED 635 nm Data from this experiment is shown here using the Logger Pro program Note that our programs allow you to determine the concentration of an unknown sample by interpolating its absorbance value along the regression curve Beer s Law Concentration 0 23 moll Absorbance 0 2713 Lid Pu BJ a w Absorbance i o 0 1 02 03 o4 Concentration mol L Experiment 20 Chemistry with Vernier Chemical Equilibrium Finding a Constant K Our lab books contain an experiment for determining the equilibrium constant for this well known reaction in chemistry Fe aq SCN aq lt FeSCN aq Experiment 30 Chemistry with Vernier Determination of the Rate Law for Reaction of Crystal Violet The data here were obtained by reacting 10 mL of 2 5 x 10 M crystal violet solution and 10 0 mL of 0 10 M NaOH The first graph is absorbance vs time The next graph shown is the natural log of absorbance vs time showing the reaction to be first order with respect to crystal violet Ah nihamie wa Titia In absorbance vs time reaction is first order Abesthance we Time f TA m ee l absorbance vs time reaction is
15. www vernier com easy easydata html and then transferred to the calculator See the Vernier web site www vernier com calc software index html for more information on the App and Program Transfer Guidebook DataMate program Use DataMate with LabPro or CBL 2 and TI 73 TI 83 TI 84 TI 86 TI 89 and Voyage 200 calculators See the LabPro and CBL 2 Guidebooks for instructions on transferring DataMate to the calculator Data Pro This program is used with LabPro and a Palm handheld LabVIEW National Instruments LabVIEW software is a graphical programming language sold by National Instruments It is used with SensorDAQ and can be used with a number of other Vernier interfaces See www vernier com labview for more information Absorbance and Transmittance Ranges for the Colorimeter For best results our laboratory testing of the colorimeter indicates that absorbance or transmittance values should fall within these ranges percent transmittance 10 90 absorbance 0 05 1 0 5 We have found that Beer s law experiment results begin to lose their linearity at absorbance values above 1 0 percent transmittance values less than 10 If you have a solution that transmits such a low level of light consider diluting the solution so that it falls within this range Using cuvettes with the Colorimeter The Colorimeter is designed to use polystyrene cuvettes Fifteen of these cuvettes and lids are supplied with the Colorimeter The cuv
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