Refractometer – Operation, Calibration & Maintenance SOP

Refractometer
Operation, Calibration & Maintenance

PURPOSE:

To provide the procedure for operation,
calibration and maintenance of
Refractometer Mettler
Refracto 30 PX
. This instrument operating procedure also provides precautions to be
taken and preliminary checks to be performed during operation.

SCOPE:

Applicable to Refractometer
Mettler Refracto 30 PX
 of Quality Control department.

DEFINITIONS:

°C        Degree
Centigrade
                                                                            

min     Minutes

RESPONSIBILITY :

Quality Control Chemists is responsible for
the
implementation of this Instrument Operating Procedures.

ACCOUNTABILITY:

Manager Quality control is accountable for implementation and
compliance of this Instrument Operating procedure.

PROCEDURE:

1.0 PRELIMINARY CHECK :

1.1 Check
and ensure that :

1.1.1 The instrument is clean and
free from dust.

1.1.2  There should not be any
deposition of the surface of the prism of the instrument if it is there clean
with the soft cloth provided along with the instrument.

1.1.3 Before analysis, perform the
adjustment of the measuring cell with purified water, it should come
<0.0005. 

2.0 BASIC
OPERATION
:

2.1 Measurement
(Measure
)

2.1.1 Procedure
for proper measurement – 
Ensure
that the prism and the measuring cell are clean before each measurement.
Insufficient cleaning leads to remains on the prism and, therefore, incorrect
results.

2.1.1
Check the sample for chemical resistance of the following materials :

·        
Prism :                                          Glass
(Refracto 30 GS : gold )

·        
Measuring cell :                          Stainless steel SUS
316 (Refracto 30 GS : gold)

·        
Housing :                                     PBT (
Polyester )

2.1.2
Ensure that the samples to be measured

·        
Have reached more or less
ambient temperature

·        
Are homogeneous. Viscous and
highly concentrated liquids have to be mixed        thoroughly before a sample is taken or
a measurement is carried out.

·        
Can be dissolved with a
solvent suitable for cleaning the measuring cell

2.1.3 Adjust the instrument with water
before performing the analysis.

3.0
Pipetting the sample onto the measuring cell.

3.1
Pipette the sample onto the measuring cell. The measuring cell has to be filled
up to 
inner circle of the cell.

4.0
Dipping the measuring cell into the sample

4.1
Immerse the measuring cell completely in the sample.

Caution
: Never immerse the instrument deeper into the sample than the indicated line
(about 1.8 inch). The instrument is only resistant to splashed water.

5.0  
Measurements

The
procedure is dependent upon the setting in the menu

Measurements
without temperature – compensation coefficient (
α).

Configuration
of sample identification and method of data storage.

Sample Name Sample
identification 

A
letter ( A… Z or space ) can be set for the identification of
 samples)

Mode
Method
of data storage.

Labo           By
pressing the
ok/measure key the result is saved and transferred ( pinter, PC).

Filed           By pressing the ok/measure key
the result is saved 
Customer
User-defined setting.

Memory
in
    Save results.

Auto                Save result automatically

Manu
             result saved by pressing 
ok/measure
key.

Memory
out
   Transfer result to PC or printer.

Auto                Save result automatically

Manu
             result saved by pressing  key.

Measurements
with temperature – compensation coefficient (
α).

( nDT or conc. on the
display ).

  • Press key
    until a previously saved temperature – compensation coefficient appears in
    the display, eg.
    a0= 0.091
  • Select the desired
    coefficient using the ↓ and ↑ keys.
  • Confirm the selected
    coefficient with the ok/measure key.

  • Press the ok/measure
    key to start the measurement. 

6.0    
Saving the results


The
instrument can save up to 1100 results internally. Each time a results is
saved, the sample number increase by one. 

The Down symbol appears in the display : Savings all results automatically.

The
instrument saves 
all results
automatically, After the measurement, as soon as the results are is saved,
Ready appears on the display.

The
Down symbol does not appear in the display
: savings selected result manually

After
the measurement, the result appears in reverse display 
Save
the result :


Press the
ok/measure key.

Do
 not save the result :


Press the
esc key.

Ready
appears on the display and the instrument is ready for the next measurement.

 

7.0   Displaying
and marking saved result

Display
saved result

– Press the ← key.

  The sample number flashes and the symbol appears.


Scroll through the saved result using the ↑ and ↓ key.

Marking results

For the identification of invalid or
incorrect results or for marking a sample change.

– Select the desired sample
number using the
   ↑ and ↓ keys.

– Press the ok/measure key.

The selected sample number is marked with
asterisk.

Note :The
marking is removed if the sample has already been marked.

8.0        
Printing and transferring results

Check the interface and
peripheral device are configured properly

For PRN and RS
interface, the infrared adapter must be connected to the printer / PC.

The
procedure for printing and transferring result is dependent upon the setting in
the menu as specified in the section measurements.

To
transfer or print result, hold the instrument in the direction of the infrared
adapter at a maximum distance of approx. 20 cm. 

The Up symbol appears in the display :  printing or transferring results automatically

Every display result is transferred automatically.

9.0 Adjustment

9.1 Adjusting the measuring cell with water

–     Ensure that the measuring cell and surface of the prism are clean.

          Transfer pure distilled water onto the measuring cell by means of the pipette which comes with the instrument. The measuring cell has to be filled up to the mark.

–     Wait until the water has reached more or less ambient temperature .

–     Press and hold the ↓ key, until CALIB (water) appears in the display

.          The instrument adjust automatically ( duration : several seconds ). After adjustment is completed, the measured deviation from the theoretical value and Execute ? (No) appears.

Measured deviation < 0.0005

– Press the 
↓ or ↑ key.

– Execute ? (Yes) appears .

– Press the ok/measure key.

The adjustment is confirmed.

Measured deviation >  0.0005

– Check whether the measuring
cell and the surface of the prism are clean.

 Measuring cell and the surface of the prism
are clean.

– Press the ↓ or ↑ key.

– Execute ? (Yes) appear.

– Press the ok/measure key.

     Measuring
cell and / or the surface of the prism are dirty.

    Confirm
Execute ? (No
) by pressing the ok/
measure
key.

    Clean
the cell and the surface of the prism and repeat the adjustment.

9.2    Adjusting the measuring cell with air

The
Refractometer measures with specified accuracy if the measuring cell is
correctly adjusted with distilled water. An adjustment with air is only
necessary if the error message E-01 appears frequently during measurement or
adjustment.

Preparing
the measuring cell.

         
Clean the
measuring cell and the surface of the prism thoroughly with a cleaning tissue.
Wait until the surface of the prism is completely dry.

Adjusting

– Press the ↓ or ↑ key.
Simultaneously. CALIB (Air) 
appears in the display. The instrument adjust the measuring cell automatically.

Adjustment is complete when CALIB (Air) disappears.

  Adjust measuring cell with distilled water

If
the error message E-01 appears in the display during the adjustment with air
call inform service engineer.
  

10.0    CLEANING :

10.1    Before cleaning, disconnect the balance from
the power supply.

10.1.1 Do not use any aggressive cleaning agents or
strong solvents.

10.1.2 Use a piece of cloth, which has been wet with a
mild detergent (Soap) to clean the weighing pan and balance housing.

10.1.3 Make sure that no liquid enters the balance
housing.

10.1.4
After cleaning, wipe down the balance with a soft, dry piece of cloth.

10.1.5
Carefully remove any sample residue / spilled powder by using a brush that is
placed with the balance.

CALIBRATION PROTOCOL

 

Calibration
frequency : Once in three months

Perform
the calibration of the instrument by the following solvents:

 

Sr. No.

Solvents

Refractive
Index

Tolerance
Limits

1.

PURIFIED WATER

1.3330
at 20°C

1.3330
±
0.001

2.

PURIFIED WATER

1.3325
at 25°C

1.3325
±
0.001

3.

CARBON TETRA
CHLORIDE

1.4603
at 20°C

1.4603
±
0.001

4.

TOLUENE

1.4969
at 20°C

1.4969
±
0.001


Temperature
Calibration:

Procedure:
Perform
the temperature calibration using calibrated thermometer at a temperature at
20°C and 25°C using purified water maintained at 20°C and 25°C respectively.

Tolerance
Limits:
±
0.5°C of the specified temperatures.

Note:   If
instrument does not comply with any of the calibration parameters, then follow
the relevant procedure of instrument breakdown.

MAJOR BREAKDOWN: Following are the major breakdown
of the instrument

a)   
Change in electronics

REFERENCES:

Manufacturers
Operation Manuals

Indian
Pharmacopoeia (IP).

ANNEXURE:

Instrument
calibration data sheet

Instrument
calibration summary sheet

DISTRIBUTION:                       

Master Copy                          : Quality Assurance

Control Copy                        : 10 : Quality control

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