Each of the raw material used in the preparation of pharmaceutical drug products play a vital role as it directly affect the quality of final drug product so in order to achieve right quality of final product evaluation of all the raw material should be done in a right manner. In the evaluation of raw material, sampling of the subjected raw material is very essential which can directly affect the analytical results of the raw materials. So understand here apart from the right sampling tools what are the other things where we need to focus;As you know if any cross contamination happened into the raw material then exact result of the raw material can not be produce so to avoid any cross contamination an Uni-directional air flow is required which can be achieved by only uni-directional air flow system or booth.UNI-DIRECTIONAL AIR FLOW SYSTEM/BOOTH
As mentioned above uni-directional air flow system are used to avoid any cross-contamination in the raw material with its uni-directional air flow. Apart from to avoid cross contamination UDAF (uni-directional air flow system) are used for the operator safety from materials.Dust containment or uni-directional air flow can be shown through smoke study and through a video recording. Its uni-directional air flow are maintained through a defined air velocity. As per WHO TRS 961 Annex 5, unidirectional air flow system air velocity should be 0.36 to 0.54 m/s, this value of air velocity is required in the UDAF system where grade A environment is required which is generally used to dispense sterile materials. Due to the air velocity weighing balance sensitivity should not be disturbed so if Grade A environment is not required to dispense or sampling the raw materials like in case of oral solid dosages or non-sterile external preparation then air velocity of UDAF booth can be reduce so that weighing balance sensitivity could not be disturbed. Where lower velocity is required then the prescribe limit, uni-directional air flow system can be called as Air protection booth (APB).During dispensing or sampling of raw materials, operator should be stand in a safe zone area where air flow should not be disturbed.
If operator block the path of air flow it could lead contamination to the material which could further affect the final drug product quality.
There should not be any obstruction in the path of air flow so it is suggested that minimum 100 mm gaps is required between return air riser and weighing balance platform so that air can be easily passed and weighing balance reading should not be disturbed.Apart from above uni-directional air flow system a detailed procedure on the sampling of raw material is required which comprises following but not limited to;
Sampling plan and procedure should be defined in a manner so that any non-uniformity within the material can be detected and attention should be paid on any sign of the non-uniformity in the material during sampling of raw material, it can be detected through shape, colour and size of material particles (crystalline, amorphous, granular etc.)
- Sampling tools based on the container size & raw material nature.
- Sampling technique based on the nature of material like some material required shaking/ heating (in case of suspension or material which have some solid material in liquid phase).
- Light sensitive material details and its sampling technique.
- Sampling plan; selection of sample size, sample container etc.
- Labeling procedure on sampled container and other container.
- Representative sample quantity sufficient for testing as per specification requirement.
To avoid the masking the contamination and other quality problem sample pooling from different portion should be avoided.Now understand the sampling plan. As per the WHO technical series no. 929, annex-4 following sampling plan can be followed;The n-sampling Plan
This n-plan of sampling can be used when you know that materials are procured from approved and recognized source and sample considered as uniform. In n-plan sample could be withdrawn from any part of the material container , usually from the top layer of container.Following formula shall be used to decide the sampling plan n= 1 + √N where N mean number of sampling unit in the consignment. suppose if 90 container received in consignment the sampling plan shall be decide as follow n = 1 + √N n = 1 + 9.48 n = 10.48 rounding number 10 n value shall be decide by simple rounding. If total container in consignment is equal to or not more than 4 then sample shall be withdrawn from each of the containers.Identification test of material from each of the sampled container need to be done and once identification test meet requirement against specification then original sample can be combined to make it composite for further analysis and rest can be kept as a retention sample.n-Plan is not suggested to use by laboratories required to analyse and release or reject the consignment which are used in final product processing.The p-sampling Plan
This p- sampling plan is also used when you know that material is procured from approved and recognized source and its main purpose is to test the identity of material. Sampling size for p-plan shall be decide based on the below formula;p = 0.4 √N where N mean number of sampling unit.Suppose if total 25 container received in consignment then sample size shall be calculated as;p = 0.4 x 5p = 2 Figure of p are obtained by rounding up to the next highest integer number, With this plan sample shall be taken from each of the N sampling units of the consignment and keep in separate containers and all these samples visually inspected and tested for identity, if results found compliant then p- final samples are formed by appropriate pooling of the original sample.The r-sampling Plan
As per the WHO-TRS 929 annex-4, r-plan shall be used only when material is suspected as non-uniform and procured from any non-recognized source like ayurvedic or herbal medicinal product used to manufactured product where even therapeutic agent is not equally distributed in any part of herbal plants so in that case r-plan can be used by follow the below formula;r = 1.5 √N where N is sampling units Figure of "r" are obtained by rounding up to the next highest integer number.In this r-plan sample shall be collected from each of the N sampling units of the consignment and keep in separate sample container. All these original sample are transferred to laboratories for identity test and if results are concordant then r-sample are selected randomly and individually tested and if all the results are concordant then all r- samples are combined for retention sample.
Hope above mention all the details will help you to elaborate your raw material sampling procedure w.r.t. sampling plan and precaution during sampling by using uni-directional air flow system/ booth or APB (Air protection booth).
1. WHO technical report series no. 929, 2005 Annex 4 WHO guideline for sampling of pharmaceutical products and related materials
2. WHO technical report series no. 961, 2011 Annex 5 Supplementary guideline on good manufacturing practices for heating, ventilation and air conditioning system for non-sterile pharmaceutical dosages form.