SOP for Cleaning, Operation and Calibration of Antibiotic Zone Reader : Pharmaceutical Guidelines

SOP for Cleaning, Operation and Calibration of Antibiotic Zone Reader

Standard operating procedure to clean and calibrate the antibiotic zone reader used in antibiotic assay.


To lay down the procedure for cleaning, operation and calibration of Antibiotic Zone Reader.


This SOP shall be applicable to Quality Control Dept.




Head Quality Control Department.


5.1 Cleaning

5.1.1 Clean with a non-shedding duster dipped in the disinfectant solution, the outer surfaces of the antibiotic zone reader daily.
5.1.2 Record the cleaning of the “Equipment Cleaning Register”.

5.2 Operation

5.2.1 Ensure that the instrument is clean and free from dust.
5.2.2 Connect the main cord to the supply socket and switch it on.
5.2.3 There is a switch on the right side panel of the instrument. Put this switch on.
5.2.4 The indicator lamp will be on and the main light source of the zone reader will be on.
5.2.5 Set the vernier scale to zero-zero coincidence.
5.2.6 Place the microbiological assay plate and measure accurately the zone of inhibition or exhibition.
5.2.7 Keep the plate on the stage. Adjust the plate such that one side of the circumference of the zone touches the marked line of the view glass.
5.2.8 Turn the knob in the clockwise direction so that the plate moves across the marked line of the view glass until the opposite edge of the zone is in tangent to the marked line of the view glass.
5.2.9 The scale reading gives nearest 0.2 mm on the rotating scale and 1/5 mm on the fixed vernier scale.
5.2.10 Switch off the mains and keep the instrument under cover when not in use.
5.2.11 Record the activity in the log book.

5.3 Calibration

5.3.1 The instrument is to be calibrated once a month.
5.3.2 Mark the diameter of the Acrylic disc by drawing the line.
5.3.3 Measure the diameter of Acrylic discs having the diameter of i)18 mm, ii) 20 mm, iii) 25 mm with the calibrated vernier and note the reading.
5.3.4 While measuring the diameter, measure along the line of diameter by vernier and by Antibiotic zone reader.
5.3.5 Switch on the main switch on the zone reader.
5.3.6 Turn the right side knob in such a way that the fixed vernier scale matches with the rotating scale at ‘0’.
5.3.7 Keep the earlier measured disc in the Petri plate. Keep the plate on the stage. Adjust the plate such that, point where diameter line intercepts circumference of the disc, touches the marked line of the view glass.
5.3.8 Rotate the right side knob in the clockwise direction so that the opposite side’s point of interception of the circumference of disc touches marked the line of the view glass.
5.3.9 Note down the readings from the rotating scale.
5.3.10 Likewise measure three discs of each of different diameter, which is previously measured with calibrated vernier calipers.
5.3.11 Find out the difference. The difference should not be more than ± 0.2 mm
5.3.12 Mention date of calibration, the due date of re-calibration & performed by on label and affix on the instrument.

5.4 Maintenance

5.4.1 The instrument should be handled properly.
5.4.2 The light source should not be kept on for a long period of time.
5.4.3 The lens from which light is reflected should be clean and free from dust.


6.1 QC: Quality Control
6.2 SOP: Standard Operating Procedure
6.3 Dept.: Department

Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of Pharmaceutical Guidelines, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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