SOP on Sampling Plans (Scale of Sampling)
SOP on Sampling Plans
1.0 Purpose: This SOP describes a procedure to draw a sample by selecting sampling units.
2.0 Scope: This SOP is applicable to all the vendors or the suppliers with a high confidence level.
3.0 Responsibility: Quality Control Chemist to ensure that the procedure is followed
4.0 Materials and Equipment: None
5.0 Procedure: The object of the sampling is to find out the quality of materials at different points in a container. The consignments received from approved suppliers with a high confidence level may be sampled by selecting sampling units on random basis. For random sampling, each sampling unit is consecutively numbered and required number of sampling units depends on the following assumptions –
5.01 The “n plan”: In this plan, samples can be withdrawn from any part of the container
(Usually from the top layer). It is based on the formula:
n = √ N
Where, N= number of sampling units in the consignment.
The value of n is rounded off to the next higher integer. According to this plan, original samples are taken from n sampling units selected at random and they are placed in separate sample containers. Each sample is examined for appearance and identity test according to the specifications. If the result on these samples are concordant, the original samples are pooled into final sample from which analytical sample is prepared and is tested for complete analysis. The remaining sample is kept as retention sample. The “n plan” should be used only when the material is considered uniform (e.g. same batch) and is supplied by a well known supplier.
5.02 The “p plan”: This plan is used when the material is uniform and has been received from a well known & time tested supplier. It may be used when the main aim is to check identity. This plan is based on the formula –
p = 0.4√ N
Where, N= number of sampling units in the consignment
Under this plan, samples are taken from each of the N sampling units of the consignment and are placed in separate sample containers. These samples are individually examined for appearance and identity. If the result of samples are concordant, p final sample, are formed by appropriate pooling of the original samples.
5.03 The “r plan”: This plan may be used when the material is either suspected to be non-uniform or has been received from a supplier who is not well known. This plan is based on the formula:
r = 1.5√ N
Where, N= number of sampling units in the consignment
Under this plan, samples are taken from each of the N sampling units of the consignments. The samples are collected in separate containers. All the samples are tested individually for identification as per specification. If the results of testing are concordant, r samples are randomly selected and individually subjected to complete testing. If the result of r samples are concordant, pooled sample may be kept at retention sample.
Table – Values of n, p or r for N sampling units
|
Value of n, p or r |
Values of N |
||
|
n plan |
p plan |
r plan |
|
|
2 |
Upto 4 |
Upto 25 |
Upto 2 |
|
3 |
5-9 |
26-56 |
3-4 |
|
4 |
10-16 |
57-100 |
5-7 |
|
5 |
17-25 |
101-156 |
8-11 |
|
6 |
26-36 |
157-225 |
12-16 |
|
7 |
37-49 |
|
17-22 |
|
8 |
50-64 |
|
23-28 |
|
9 |
65-81 |
|
29-36 |
|
10 |
82-100 |
|
37-44 |
Also, Visit:
B. Pharma Notes | B. Pharma Notes | Study material Bachelor of Pharmacy pdf