LAB 2 : INSTRUMENTATION

Lab 2 : INSTRUMENTATION

Objective

i )  To learn how to use the electrode to determine the Ph meter.

ii)  To use the micropipette with proper way.

iii) To learn how to handle the microscope.

iv) To look the shape from the slide under magnifications  4x, 10x, 40x and 100x .

Introduction

  Most instrumental methods of analysis are relative. Instruments register a signal due to some physical or chemical property of the solution. For example, pH meters measure the electrode potential which must be related to the [H+] or [OH-] of the solution by comparison against known [H+] or [OH-] standard buffers. In other words, the pH meter must be calibrated in order to obtain accurate results. A standard procedure for calibrating pH meters is to prepare a linear working curve known as a calibration curve by plotting the measured potential as a function of pH or pOH. Many calibration descriptions in the literature are rather confusion and misleading. This paper will discuss some basic concepts of pH, pOH, pH glass electrodes, reference electrodes, standard buffers, and pH meters. A micropipette is used to measure and dispense a specific volume of liquid.

      There are two different categories of micropipettes: air displacement and positive displacement (4). Air displacement is most commonly used for aqueous solutions, which was what was being measured in this lab exercise. Both of these pipettes contain a piston which moves inside of the chamber. The only difference is with air displacement, there was still air separating the piston from the liquid and in positive displacement, there was not (4). In this exercise, all of the pipettes measured in the form of microliters.

    Microscopes are an amazing invention; able to observe specimens to the tiniest degree. No matter how small, we are able to view an endless amount of life forms, all because of microscopic technology. Scientists are opened to a  whole new world, things undiscovered, things never seenbefore. Now it is open to everyone, In our very Biologi  class, we are privileged to witness and it can only make us learn through observation.

Materials and apparatus

pH meter,distilled water, beaker, solution x, y, z and tissue paper micropipette tip, microscope, slide of specimen and oil.

Calibration of pH meter

Procedure

1.     The protective and cover was removed from the electrode.

2.     The electrode was cleaned by distilled water and then the excess water was wiped with tissue.

3.     The Setup botton on pH meter was pressed for a few times until the screen display the set of pH buffer that want to be calibrated.( pH 4, 7, 10).

4.     Standardize was pressed was waited for a signal on the screen to place electrode into the first buffer (pH 4). The calibration was started from lower to higher pH buffer.

5.     The meter was recognised the buffer and the first value was displayed. Then, the displayed indicates either good electrode “OK” or electrode error “Error”.

6.     Affter ok is displayed, the electrod was taked out and rinsed with distilled water. The excess water was wiped with tissue. Always make sure the electrode was rinsed with distilled water between each measurement.

7.     Standardize was pressed. The signal on the screen was  waited to place electrode into the second buffer(pH 7). Same procedure was repeated until all buffer have been standardize.

8.     Once, the calibration is done, pH for solution with label x, y, z was measured.

RESULT

What have you learnt?	What error(if any)during handling did you observed?
x = 5.00	·       Make sure the electrode must be soak with distilled water to make sure that the microbe always in wet condition. ·       Clean and wipe the electrode carefully before using it to get an accurate pH value. ·       Before testing the pH of a solution we have to standardize the pH meter .
y = 7.01
Z= 8.07

Questions:

1.In your opinion, why it is necessary for all buffer solution to be at the same temperature during calibration?

 Buffer solution to be at the same temperature during calibration because  it is not consider the phosphate to be involved in any redox reaction with the glss electrode.

2. MICROPIPETTE

METHODS:

1. Desire volume was set by turning  the centrally located rings clockwise to increase or counter clockwise to decrease volume.

2. Sterile tip was loaded. Use the proper size tip for each pipette. The tip box to maintain sterility was closed. Do not allowedthe pipette tip to touch any object.
3. The sample was loaded. At two different plunger positions when it depressed, the plunger will stop. The plunger was pushed down slowly to the point of first resistance : this is the load volume.

4. Holding the plunger at the load volume set point, the tip was putted into solution so that is is immersed just enough to cover the end( 3 - 4 mm).

5. The punger was released slowly to draw up the liquid and keep the tip immersed.

6. The sample was delivered. The second stopping point was found when the plunger depressed beyond the initial resistance. It contact with the body of the pipette. The second stopping point was used for the complete discharging o solutions from plastic tip. Not reach the second stop when drawing liquid into the pipette, when expelling the last drop.

7. The tip was placed into the receiving vessel. The Pluger was depressed all the way to the bottom to expel all the liquid.

8. Discharge slider was pressed on the back of the grip to discharge the tip.

RESULT

What have you learnt ?	What error(if any) during handling did you observed?
Micropipettes are used to measure and deliver accurate volumes of liquid.	o   Not Accounting for the Viscosity of a Sample. o   Cleaning Irregularly.

Questions :

1.     Why it is encourage to always select the smallest size micropipette that will handle the volume you wish to move?

o   To achieve the greatest accuracy. Accuracy decreases as use unnecessarily large pipets for small volumes.

2.     Why the liquids from the micropipette need to be release slowly, especially with large volume pipettes?

o   This prevent liquid from rushing into the end of the  micropipette and clogging it out.

3.     Why the micropipette cannot be point up?

                      o           This may caused liquid to run down into the micropipett destroying it.

3. MICROSCOPE

METHODS :

1.     A prepared slide was picked and was observed under the microscope using different magnification.

2.     Low power (4x) was used on the microscope to locate the specimen on the prepared slide. The shapes were drawn.

3.     The high power carefully switched after you have centered the specimen you are viewed in the center of the field.

4.     The procedure was repeated using higher magnficaations up to 100x magnification.

5.     The shapes under microscope sing 4x, 10x, 40x and 100x magnifications.

RESULT

What have you learnt?	What error(if any? During handling did you observed?
To see the slide deeper with different magnifications.                         4x                            10x                             40x                         100x	Adjust both the focus knob until get the clearer image.

Discussion

Based from this experiment, it basically teaches us how to use lab instruments properly. Example of the lab intrument are pH meter, micropipette and microscope. Before conducting an experiment, we have to know how to use these instrument so that we can get a better result. Most importantly, we have to get the idea of handling it with care to make it last longer and avoid it to be broken, as the instruments are very expensive.

     The first experiment that we have learn is the pH meter. It is necessary to understand the mechanism correctly as it helps to point out remedy errors and teaches us to calibrate the pH meter. From this, we learnt that the microbe below the electrode is so sensitive that it needs to be wet everytime before or after using. We used distilled water to soak the electrode. We also need to clean and wipe the electrode carefully before testing the pH meter. For some reason, if we do not manage to follow this steps, it will effect our reading.

     Next is micropipette. We know that it tip has vary in size, so make sure you pick the right size for each micropipette. To dispense the solution, we have to release it slowly as this will help to prevent the liquid to clogging it up. Bare in mind to always use new tip for each different solution.

     Lastly, a microscope. This instrument help us to see a specimen deeper with different magnification which are 4x, 10x, 40x and 100x. Each magnification give a different view as the higher magnification gives clearer and details image. Make sure to use lower magnification which is 4x to locate the specimen on the right position. In addition, to use 100x, a drop of oil is needed to put on the specimen. Carefull to not let the 40x magnification to touch this oil, as this will make the microscope disfunction properly.

Conclusion

To conclude, basically this experiment teaches us how to use and handle the instrument properly. if we obey the steps of using the instrument properly, we will get a better result. This will also lead to long term of instruments to be used, and also will save cost by avoiding it to be broken.

REFERENCES

i)  Ying, L. R. (2016, August 31). Lab Report: Calibration and Determination pH Value Using pH Meter. Retrieved from https://ying2notebook.wordpress.com/2016/08/31/calibration-and-determination-ph-value-using-ph-meter/

ii) Impact of Pipetting Technique. (n.d.). Retrieved from https://www.artel-usa.com/resource-library/impact-of-pipetting-technique/

Ying, L. R. (2016, August 31). Lab Report: Calibration and Determination pH Value Using pH Meter. Retrieved from https://ying2notebook.wordpress.com/2016/08/31/calibration-and-determination-ph-value-using-ph-meter/

iii) Retrieved from  https://www.coursehero.com/file/21240341/Experiment-1-Microscope/