Basic Analytical Techniques, Calorimeter, and Conductivity Meter Santosh Vijapur ABC s of Electrochemistry 01/12/2012
Outline Calorimeter Conductivity meter ph meter Analytical balance Glassware cleaning Micro-pipette 2
Calorimeter Definition Calorimetry is the science of measuring quantities of heat and instruments used for such measurements are known as calorimeters. http://itl.chem.ufl.edu/2045/lectures/lec_9.html http://www.dartmouth.edu/~chemlab/techniques/calorimeter.html http://www.physicsclassroom.com/class/thermalp/u18l2c.cfm 3
Calorimeter History French scientist and statesman, Berthelot (1827-1907), was the first to develop principles of modern calorimetric methods using oxygen under pressure to affect combustion. Calorimeter bomb he developed was lined with platinum to withstand the gases produced during combustion. It was modified in 1892 by Mahler by depositing porcelain enamel on the steel, to replace the expensive platinum lining. Further modifications were made by Fischer, Hempel and others between 1844-1907. http://www.parrinst.com/wp-content/uploads/downloads/2011/07/tn104_parr_calorimeter-applications- Tech-Note.pdf 4
Calorimeter Types of calorimeters Adiabatic calorimeters: Used to investigate runaway reactions. Reaction calorimeters: Measures amount of energy released or absorbed in a chemical reaction. Constant pressure calorimeters: Measures changes in enthalpy occurring in solution at constant atmospheric pressure. Differential scanning calorimeters: Measures the difference in the amount of heat required to increase the temperature of a sample and reference as a function of temperature. Bomb calorimeters: Measures the heat of combustion of a particular reaction. 5
Calorimeter: Basic operating principle Coffee Cup Calorimeter constant pressure Q m C T p http://itl.chem.ufl.edu/2045/lectures/lec_9.html Constant volume calorimetry measures the change in Internal energy, whereas constant pressure calorimetry directly measures enthalpy change during the reaction. 6
Bomb calorimeters Standard instruments for measuring calorific values of solid and liquid combustible samples The calorific values denotes the overall heat liberated by combustion of carbon and hydrogen along with oxidation of elements like sulfur present in the sample. http://itl.chem.ufl.edu/2045/lectures/lec_9.html 7
Bomb calorimeter Bomb Calorimeter constant volume http://itl.chem.ufl.edu/2045/lectures/lec_9.html Both instruments work on a similar principle. Heat evolved during a chemical reaction changes the temperature of a substance (water bath) with a known heat capacity. This measurement of difference in temperature facilitates the determination of the heat crossing the system boundary. 8
Bomb calorimeter Applications of Bomb calorimeters Solid and Liquid Fuel Testing Waste and Refuse Disposal Food and Metabolic Studies Propellant and Explosive Testing Fundamental Thermodynamic Studies http://www.parrinst.com/wp-content/uploads/downloads/2011/07/tn104_parr_calorimeter-applications- Tech-Note.pdf 9
Conductivity meter Description Two electrodes with an applied AC voltage are placed in the solution. A current is generated depending upon the conductive nature of the solution. The meter reads this current and displays in terms of conductivity. http://www-ec.njit.edu/~grow/sensors/conprob.htm http://www.hannainst.com/usa/knowledge.cfm#whatisec 10
Conductivity meter Standardization Select calibration mode. One point calibration Freeze reading Repeat using conductivity standard. Rinse the sensor. http://us.mt.com/global/en/home/supportive_content/product_documentation/operating_instructions/operating_instruction_mc2 26.rxHgAwXLlLnPBMDSzq--.MediaFileComponent.html/Operating_Instruction_mc226.pdf 11
Conductivity meter How to Select measurement mode. Measure sample Freeze reading Rinse sensor http://us.mt.com/global/en/home/supportive_content/product_documentation/operating_instructions/operating_instruction_mc2 26.rxHgAwXLlLnPBMDSzq--.MediaFileComponent.html/Operating_Instruction_mc226.pdf 12
Conductivity meter Operating tips The solution to be measured should be above the cell chamber slot. The cell chamber should be free of bubbles. Immerse the sensor at an angle and then raise to the vertical position in order to reduce air bubbles. Rinse sensor with distilled water between measurements, and after use. For greatest accuracy, standards and samples should be at the same temperature and should be close in value. http://us.mt.com/global/en/home/supportive_content/product_documentation/operating_instructions/operating_instruction_mc2 26.rxHgAwXLlLnPBMDSzq--.MediaFileComponent.html/Operating_Instruction_mc226.pdf 13
Conductivity meter Prevention & Care Rinse with DI water. Wipe the meter with a damp cloth. Clean any spillages. http://us.mt.com/global/en/home/supportive_content/product_documentation/operating_instructions/operating_instruction_mc2 26.rxHgAwXLlLnPBMDSzq--.MediaFileComponent.html/Operating_Instruction_mc226.pdf 14
http://www.denverinstrument.com/denverusa/media /pdf/opmanublongreva.pdf ph meter Description ph-sensing glass bulb is sensitive to hydrogen ions. A potential is developed at the glass membrane and is related to the ph of the solution. A reference electrode is paired to complete the circuit and provides a stable reference point. These two electrodes are joined to create a combination electrode. The combination glass electrode is connected to the ph meter 15
ph meter Standardize daily, or more often, for accurate results. Clear existing buffers when doing a new standardization, by pressing setup and enter buttons. Immerse the electrode in three different buffers to standardize the meter. Immerse the electrode in a buffer, stir gently and then press standardize. When reading is stable or when you press enter, the buffer is entered. Repeat for other buffers. Standardization http://www.denverinstrument.com/denverusa/media/pdf/opmanublongreva.pdf http://www.dartmouth.edu/~chemlab/techniques/phd.html 16
ph meter Prevention & Care Before using your ph electrode, or whenever the electrode is dry, soak over-night in an Electrode Storage or KCI solution. Rinse electrodes with DI water or the solution to be measured and blot-dry (do not wipe) between each measurement. Store ph electrodes in an Electrode Storage or KCI solution. http://www.denverinstrument.com/denverusa/media/pdf/opmanublongreva.pdf 17
Weighing balance Place weighing dish on the balance pan. Close the doors. Wait for the stability indicator to appear on the display, indicating that the weight is stable. Press the tare button to cancel out the weight of the weighing dish. Add the desired substance into the dish carefully up to the desired mass. Close the doors and wait for the stability indicator to appear. Weigh the dish 3 times to get an average weight of the substance. http://www.dartmouth.edu/~chemlab/techniques/a_balance.html How to 18
Weighing balance Prevention & Care Do not lift the weighing dish by bare hands as the finger prints could add to the mass. Do not lean on the bench while weighing. It is advisable to record the mass of the weighing dish just in case you need it. Also, it is necessary to check the screw levels of the weighing balance. Use brush to clean any spills in chamber and around the balance. Discard unnecessary dish, kimwipes, etc. into the waste can. http://www.dartmouth.edu/~chemlab/techniques/a_balance.html 19
Calibration necessary: before the first use. at regular intervals. After location change. Weighing balance Calibration Fully automatic calibration in some balances (time interval, temperature deviation, after turning on the balance). http://us.mt.com/global/en/home/supportive_content/product_documentation/operating_instructions/operating_instructions_ms-s_ms- L_EN.rxHgAwXLlLnPBMDSzq--.ExternalFileComponent.html/Operating_Instructions_MS-S_MS-L_%28OP-EN%29.pdf 20
Weighing balance External Calibration http://us.mt.com/global/en/home/supportive_content/product_documentation/operating_instructions/operating_instructions_ms-s_ms- L_EN.rxHgAwXLlLnPBMDSzq--.ExternalFileComponent.html/Operating_Instructions_MS-S_MS-L_%28OP-EN%29.pdf 21
Glassware cleaning Clean glassware is an important criteria in a Good Laboratory Practice. PPE must be used when cleaning glassware's. Clean glasswares immediately after use. Soap/detergent can be used to clean glasswares and should be scrubbed with a brush. Precipitates or organic matter that make the glasswares unduly cloudy can be cleaned using concentrated acids or bases. Special precaution should be taken and proper procedure should be followed in such case. http://catalog2.corning.com/lifesciences/media/pdf/cls_an_112_cleaningglassware.pdf 22
Glassware cleaning Glasswares should be properly rinsed with running tap water. Acetone or similar solvents can be used to remove grease. Soaking can also be implemented in some cases. The glassware s should be air dried by placing them on the wooden pegs with their mouth downward. http://catalog2.corning.com/lifesciences/media/pdf/cls_an_112_cleaningglassware.pdf 23
Micro-pipette Description Most of the micro-pipettes have color coded volume display http://www.denvillescientific.com/products.php?cat=109 24
Micro-pipette How to Insert the shaft into the tip and press down firmly. Do not touch the tip with bare hands to avoid contamination. The tip box should be closed when not in use to prevent contamination. Micro-pipette should be immersed to the minimum necessary depth into the liquid. Hold the micro-pipette in vertical position. Pre-rinse the tip with the liquid to be pipetted. Change the tip while using different liquid, or when volume setting is changed. http://faculty.buffalostate.edu/wadswogj/courses/bio211%20page/resources/micropipetting%20lab.pdf http://www.denvillescientific.com/products.php?cat=109 25
Use smooth motion. Micro-pipette The liquid should never enter the shaft of the micro-pipette (Do not turn the pipette upside down or place it sideward's when liquid inside the tip). Do not overshoot the limits. Prevention & Care Do not pipette liquids with temperature beyond recommended point. After pipetting acids or corrosive substances, disassemble the shaft, then clean the piston and seal with DI water. http://faculty.buffalostate.edu/wadswogj/courses/bio211%20page/resources/micropipetting%20lab.pdf http://www.denvillescientific.com/products.php?cat=109 26
Calibration necessary: When a part is replaced. Micro-pipette Calibration At periodic intervals, depending on the usage. Types: Gravimetric method, Photometric method, Titrimetric method, and Isotopic method. Gravimetric and Photometric method are common methods. http://www.biotekcalibrations.com/images/pipette-standards-handbook.pdf 27
Micro-pipette Calibration: Gravimetric method Gravimetric method requires a controlled environment, a high precision balance, a skilled technician, distilled water, and understanding of statistics. It works on the principle that, given a certain mass of water with a known specific gravity; its volume can then be predicted. The accuracy and precision of the pipette can then be assessed by statistical approach. http://www.biotekcalibrations.com/images/pipette-standards-handbook.pdf 28
Micro-pipette Calibration: Photometric method Photometric method involves the analysis of volumes of diluted dye in a cell of known path length. It works on the principle of Beer-Lambert Law If a beam of monochromatic radiation passes through homogeneous solutions of equal path length, the absorbance measured is proportional to the dye concentration. An unknown dye volume can be pipetted into a known diluent volume. The concentration of dye can be measured photometrically, and the volume can be calculated. http://www.biotekcalibrations.com/images/pipette-standards-handbook.pdf 29
Micro-pipette The adjustment is performed at the lower volume. The pipette service tool is placed into the openings of the calibration nut. Turn the tool clockwise to increase the volume or counter clockwise to decrease the volume. Recheck the calibration. Adjustment http://www.pipette.com/support/guidetopipetting.pdf 30
For more information, please contact: ceer@ohio.edu www.ohio.edu/ceer