Laboratory Exercise In The Validation Of A Purified Water System

Collection of Samples and Counts for TOC, Conductivity and pH

Water is a critical component and an essential raw material in the pharmaceutical industry. It is used in the manufacturing of pharmaceuticals especially the preparation of oral doses of liquid form. Further, it is used in cleaning of equipment, machines and other accessories therefore it contributes directly and indirectly to the quality of pharmaceutical products. Most pharmacopeia have graded water on several quality parameters like TOC, contaminants, conductivity and microbial quality thus validation of purified water is an important process in order to build on its quality. In order to meet the international standards, it is critical to improve the microbial and chemical quality of purified water through the validation protocol. This lab will help us learn the effectiveness, consistency and reproducibility of the water system.

Validation process involves physical, microbiological and chemical collection of measurements from the water system. It is thus a lengthy study which involves monitoring of these measurements in each and every sample collection point. However, microbiological assessment involves expertise and should be done by qualified professionals.  The whole exercise will be to study the microbiological sampling as part of the validation process. Students should begin by touring the water system to acquaint themselves with all the sample collection points.

Students should also study the major units and be directed on how to collect the water samples. Some of the features that students should take note of include the UV lamps, U bends among others which might affect the results from the validation process. Measurement of parameters like TOC and pH have to be done online to reduce risk of contamination from individuals. However, conductivity will be done offline with a conductivity meter. The students should be provided with the diagram for the water system to locate the collection points.

We conducted sampling in a practice and a manner outlined in the protocol. We performed the sampling process in intervals provided and then we recorded the data in table 10 provided. This was the subsequent steps that we followed while collecting the samples:

1. We performed sanitation for each sampling point as well as the collection vessels. This ensured that there was no contamination of the samples by the students.
2. We obtained samples from all the six points provided by the protocol to be used in the water system.

• We sanitized these points by application of 70 % ethanol prior to sample collection.

1. We also drained about 1 liter of water from the taps at these collection points.
2. We then collected 10 ml of tap water at a point preceding the pretreatment zone. We immediately covered this sample and labeled it as required.
3. We then collected another 100 ml of the sample water at the point after the pretreatment zone and poured it into a large sterilized bottle while also covering this sample in an air tight container. We labeled the vessel with the date, time, collection point and our initials.

• After labelling all the samples, we stored them in a refrigerated room while standing upright for a period of 12 hours before performing the assessment.
• We then tested quality parameters to determine whether this pretreated water met the USP criteria. The parameters were pH, TOC and conductivity.

These three parameters are the determining criteria for purified water to be used by pharmacopeia. To start with, pH is the measure of acidity or alkalinity of a substance. Purified water for pharmaceutical use should have a pH range of 5-7 according to the international standards. At this pH range, the growth of microbes is very minimal. We tested it with a pH meter. Our results gave a pH range of 7-8 which is slightly above the accepted criteria.

The other vital parameter that we tested was TOC. There are two reasons why validation system for pharmaceutical water must measure TOC. First, it is a quantity measure for the extent of purification process. TOC is the food source for microbes so it is used to give the bacteria count. A low and a standard TOC imply that reverse osmosis, carbon bed, electro-deionization and downstream filters of the purification process are purifying the water properly. Online TOC test with a TOC meter is recommended for determination of this parameter. This is because online testing reduces the risk of contamination. The online sensors and transmitters used to measure TOC have standards set out by USP and EP which are: limit of detection, system suitability, calibration requirement and effective resolution. In order for water for purified water be approved for pharmaceutical use, it must be less than 500 parts per billion. All the results from all the six sample points had TOC values <500 ppb implying that these water samples meet the acceptance criteria.

Discussion (TOC, Conductivity and pH)

The final parameter that we measured was conductivity which depicts the ionic concentration of the water sample. USP and EP have revised requirements for conductivity and the test is the same for all the categories of pharmaceutical water. We used a conductivity meter to show the level of conductivity in the water samples. Ionic compounds present in water show quantifiable changes when exposed to ultraviolet rays. The validation protocol has given the acceptable criteria for conductivity which should be < 1.3 µs/cm at room temperature. From the results we recorded in table 10, the conductivity values were between 0µS-2µS as required by the USP standards.

• We conducted this assessment by making use of microbial cultivation. We developed a sterile control sample to validate this technique. We began with aseptic technique where we filtered 10 ml of sterilized water sample on a filter membrane. We then placed the filter on a nutrient agar plate. We labeled it as ‘STERILE SALINE CONTROL’. Note that this process was done aseptically!
• We then filtered 10 ml of the sample we obtained from the point preceding pretreatment zone. Again, we placed the membrane aseptically on a nutrient agar plate. We then labeled it with correct details as discussed in the collection of samples section.
• We also filtered 100 ml of the sample we obtained from the point past the pretreatment zone. We then placed the membrane aseptically on a nutrient agar plate and labeled the plate with the correct details i.e. date, collection point and our names.
• We finally placed these labeled samples on an incubator. They were placed inverted at a temperature of 37 °C for a period of 72 hours.
• After this period had lapsed, we removed these plates from the incubator and counted the colonies growing on the membrane surface.
• We then compared the number of colonies on the 10 ml sample plate with that of a 100 ml sample plate.
• Afterwards, we recorded the count on the table and compared the count to that provided in the pharmacopoeia standards. We recorded those that conformed to the standards on table 10 provided on the validation protocol. We recorded those that did not conform to the standards on a log deviation table provided along with the validation protocol.

There were no results for colony forming units on samples 1 to 4. This is because the membrane filter was not placed properly on the agar plate. It is understood that the membrane filter has uniform porosity of approximately 0.45 µm.  This is significantly small to trap the bacteria and during incubation, these colonies grow on the top surface of the membrane. These first 4 samples were taken as deviations since they did not meet the acceptance criteria. However there were colonies on sample 5 and 6.  

Sample 5 was taken for deviation to compare the bacterial impact per volume of the sample and it produced 7 colony forming units for 120 ml and 5.83 colony forming units for 100 ml. sample 6 produced 31 colony forming units implying that there were 31 CFU/100 ml. There were many colony units on sample 6 since the pH of 7.54 favored the growth of the colonies as compared to sample 5 with a pH of 8.10.

From the above results we are required to deduce whether pharmacopeia criteria has been achieved. According to United States pharmacopeia (USP), it has stipulated that coliform forming units should be <100 cfu/ml. From the results we obtained, there were 0.0583 cfu/ml and 0.31 cfu/ml respectively for samples 5 and 6. These counts were below the pharmacopeia specification and therefore we can conclude that these two samples passed the acceptance criteria required by USP. Purified water from this water system should therefore be used for pharmaceutical purposes since there is no threat of infection from the microbes.

Conclusion

From this laboratory, it is advisable to observe the regulatory guidelines while undertaking the validation exercise. However, there are four steps of the validation process which are DQ, OQ, IQ and PQ. Three phases validation is recommended in order to achieve reliability and effectiveness of the water system. If these steps are followed, pharmaceutical water will be of high quality with assurance of high level giving pharmaceuticals the credibility they require.

All in all, we learnt that validation of a purified water system is a very essential process in a pharmaceutical industry. Validation is one of the aspect of quality assurance and it is a programmed process. This process guarantees end products with high quality such as oral dosages. Validation of pharmaceutical water is a mandatory process so that the parameters of water quality are fulfilled. Purification is therefore important since it contributes to the effectiveness, consistency and reproducibility of the water system.  

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