Analytical balance

Detailed about Analytical Balance used in the Pharmaceutical and Medical Laboratoty

1. Analytical Weighing Balance Md. Abdul Karim Mia Analyst National Control Laboratory (NCL), DGDA, Dhaka, Bangladesh

2. Balance Balance: A weighing device, especially one consisting of a rigid beam horizontally suspended by a low-friction support at its center, with identical weighing pans hung at either end, one of which holds an unknown weight while the effective weight in the other is increased by known amounts until the beam is level and motionless . Analytical balance is a class of balance designed to measure small mass in the sub-milligram range. The measuring pan of an analytical balance (0.1 mg or better) is inside a transparent enclosure with doors so that dust does not collect and so any air currents in the room do not affect the balance's operation. This enclosure is often called a draft shield . National Control Laboratory (NCL), DGDA, Dhaka, Bangladesh

3. History of Balance National Control Laboratory (NCL), DGDA, Dhaka, Bangladesh Simple Balance was used as early as 2400- 1800 B.C near Indus river valley ( Now Pakistan) Balance comes from the Latin word “ Lilanx ” means `Two pans` The lightweight technique is developed Joseph Black. The modern analytical balance originated during the mid-18th century

4. Types Of Balance National Control Laboratory (NCL), DGDA, Dhaka, Bangladesh Type- I Type- II Type- III Light weighing capacity and Highly Sensitivity Built-in weights for analytical balances and Laboratory weights for routine analytical weights Precision Balances and all other weighing equipments Semi Micro balance: 5 µg to 500mg Micro balance: 2mg to 20 gm Analytical balance 100 mg to 100 gm Top Load balance 1.0 kg to 2.0 kg

5. Sartorius Analytical balance National Control Laboratory (NCL), DGDA, Dhaka, Bangladesh Weighing pan Tare/Zero switch Gram/g Display Level Indicator CAL button On/off switch Adjustable feet Windbreak door Function Key Calibration Tag

6. Where to locate analytical Balance Install the balance on a solid bench that is (AVT) anti vibration table. Doesn't locate AVT corner of the room-room access through a sliding door. The balance should not be installed near sources of electromagnetic radiation such as radio frequency generators, electric motors, hand held communication devices (including card less telephones and cell phones) humidity range 45 - 60% Operate. H umidity range <20 – 80<% Never operate Never disconnect the balance from the power supply and leave it always switched on / STAND BY mode. If “OFF” mode: warm-up for 1 hour after switching ‘ON’ the power supply. Note : Stable anti vibration table-has affect on balance for measurement 0.01g or less . National Control Laboratory (NCL), DGDA, Dhaka, Bangladesh

7. Weighing Procedure of analytical Balance Ensure the instrument is clean and free from dust. If presence clean with soft brush Check the adjustment bubble within the center and calibration tag within expiry date. Ensure that daily calibration is done and check the log book. Place the weighing paper on the weighing pan, close the windbreak door and press tare button to zero. Place the sample of standard or sample on the weighing pan using spatula and close the windbreak door. Take the reading from display shows as gram after stabilized. Record the weighing results on log book. Carefully remove the weight and left clean for another analyst National Control Laboratory (NCL), DGDA, Dhaka, Bangladesh

8. Calibration Parameters National Control Laboratory (NCL), DGDA, Dhaka, Bangladesh Minimum Weight/Repeatability: Repeatability is a measure of the ability of a balance to supply the same result in repetitive weighing's with one and the some load under the same measurement conditions. Measurements must be carried out by the same operator, using the same weighing method, in the same location on the same pan support, in the same installation location, under constant ambient conditions, and without interruption. Procedure: Take measurement of 50 % or more load of the balance for 10 times. Record the value and calculate as follow Minimum weight: IF SD>0.41d Desired minimum weight = 2*SD*1000 IF SD<0.41d Desired minimum weight = 2*0.41d*1000=820d Repeatability: 2*SD / Desired minimum sample weight Lt: ≤0.1%

9. Calibration Parameters National Control Laboratory (NCL), DGDA, Dhaka, Bangladesh Accuracy : Accuracy is defined as the proximity of measured results to the reference value. Accuracy is the systematic error . Procedure: Determine the range of test weights that will be used to make sure their mass is between 5-100 % of the balance capacity. Measure the test weight placing in center position on weighing pan. Repeat the measurement for all weight previously determined in that range. Record the value and compare within range or not. Lt: Measured value does not deviate by more than 0.1% of the test weight value.

10. Calibration Parameters National Control Laboratory (NCL), DGDA, Dhaka, Bangladesh Accuracy and Precision ( i ) Accuracy : refers to how close an answer is to the “true” value Generally, don’t know “true” value Accuracy is related to systematic error ( ii) Precision : refers to how the results of a single measurement compares from one trial to the next Reproducibility Precision is related to random error Low accuracy, low precision Low accuracy, high precision High accuracy, low precision High accuracy, high precision

11. Calibration Parameters National Control Laboratory (NCL), DGDA, Dhaka, Bangladesh Linearity : Linearity describes how well a balance can follows the linear relation between the load and the displayed value. A characteristic weighing curve should be a straight line from zero to the maximum load. Non-linearity defines the limits within which a measured value can deviate (positively or negatively) from the ideal linear curve. Eccentricity (Corner Test): Deviation of the measurement value through off-center (eccentric) loading. The corner load increases with the weight of the load and its distance from the center of the pan support.

12. Trouble shooting National Control Laboratory (NCL), DGDA, Dhaka, Bangladesh Display Cause Solution No segments appears in display No AC power is available The power supply is not plugged in Check the AC power supply Plug in the power supply H The load exceeds the balance capacity Unload the balance L or Err 54 Something is touching the weighing pan CPA2P-F model: calibration/ adjustment nor possible without cover Move the object touching the weighing pan To calibrate/adjust position either the standard pan (8g) or the filter pan (5g) along with the cover(3g) Err 01 Display overrun Change the configuration in operating menu Err 02 Calibration parameter not meet. Eg -Balance not zeroed - Load on weighing pan Calibrate balance when zero is displayed. Err 10 Tare memory not allowed Press (tare)

13. Trouble shooting National Control Laboratory (NCL), DGDA, Dhaka, Bangladesh Display Cause Solution Err 10 The tare key is blocked when there is data in the second memory, only one tare function can be used at a time Press (CF) to clear the memory and release the tare keys Err 22 Weight id too light or when using the application program, there is no sample on the balance Increase the weight on the balance Err 30 Interface port for the printer output is blocked Reset the menu factory settings Err 235 Connecting cable do not correctly plugged in Plug in the cable correctly

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