**Following steps are involved in the swab limit calculation **

**Step 1: **** Calculate MACO with HBEL**

**refer MACO calculation with HBEL(Health-Based Exposure Limits) in cleaning validation**

**Step 1A : Calculate MACO with general Limit **

Establish MACO, based on a general limit, using the following equations.

MACO = MAXCONC x MBS

**MACO Maximum
Allowable Carryover:** acceptable transferred amount from the investigated
product (“previous”). Calculated from general ppm limit.

**MAXCONC** : General
limit for maximum allowed concentration (mg/kg or ppm) of “previous” substance
in the next batch.

**MBS**: Minimum
batch size for the next product(s) (where MACO can end up)

__Example: __

**MAXCON **= 10ppm

MBS= 50 Kg

MACO=10ppmx50kg = 10mg/kg/50 kg = 500mg = 5,00,000Âµg

**Step 2: Calculate the swab limit **

If homogeneous distribution is assumed on all surfaces, a recommended value can be set for the content in a swab.

Target value [Âµg/dm ^{2} ] =MACO [Âµg]/ Total surface
[dm 2 ]

Assume that the total surface area =1500 dm ^{2}

Swab limit = 5,00,000 Âµg/ 1500 dm ^{2 }= 333 Âµg/ dm ^{2}

**Step 3: calculate per swab limit (****Âµg/swab)
**

**Swab sampling Procedure **

**Preparation**

1. Select appropriate swab (see Swab Selection Guide below).

2. Define region/area to be tested.

3. Dampen swab with diluent.

**Sampling**

Step 1: Begin sampling by swabbing the surface using horizontal, unidirectional, parallel strokes

Step 2: Flip the swab over and swab in a perpendicular direction using the same technique

Step 3&4: Repeat procedure with second swab at 45° angles. Flip the swab over for Step 4

Step 5: Swab the perimeter with the swab tip

**Transfer**

1.Snap swab head at the notch along the edge of swab handle

2.Allow swab head to fall into vial

3.Replace the cap, label the sample and transfer for TOC or HPLC analysis

Assume that

Swabbing area = 10x20cm^{2} = 2 dm ^{2 }

Content of residue per 1 dm ^{2 }= 333 Âµg/ dm ^{2}

if 1 dm
^{2} =333 Âµg/ dm ^{2 } then for our 2 dm ^{2 } swabbing area it is 666 Âµg/ dm ^{2 }

Then content per swab =666 Âµg/ dm ^{2 }

**Calculation of sample and standard concentration for analysis of the API in the Swab sample**

**Step 1: Calculate the sample concentration**

**Sample concentration
= **666
Âµg/ dm ^{2 } as given
above

Procedure: collect the swab in 2 dm ^{2 } area and dip the swab in 10 ml solvent and
bring it to the lab for testing.

**Then sample
concentration Limit = swab limit ****Âµg
/sample dilution (ml) **

Our swab limit ==666 Âµg/ dm ^{2 }

Sample dilution volume = 10 ml

=666 Âµg/dm ^{2 }/ 10ml = 66.6 Âµg/ml

**Step 2: Calculate the Standard concentration**

**Standard concentration = sample concentration **

Then we have prepare the standard solution with concentration of 66.6 Âµg/ml

weight accurately about 66.6 mg of the standard into 100 ml and then 10ml of the above to 100 ml (66.6 Âµg/ml)

**Step 3: Calculation**

1000 = Factor to convert result from mg to Âµg

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