The leading providers of continuous water quality monitoring instrumentation frequently claim similar levels of performance, so it can be challenging to choose the best measurement technology with which to entrust critical manufacturing processes. In this article, Russell Culver from Swan Analytical explains why some of the key differentiators are not shown in specification sheets.
Background.
Continuous monitoring equipment plays an essential role in most manufacturing processes, protecting product quality, lowering costs, avoiding waste and ensuring regulatory compliance. For the purposes of this article, we will study the monitoring of total organic carbon (TOC) in purified water systems.
The quality of purified water is particularly important for most manufacturers, but especially so for the manufacturers of pharmaceuticals, medicines and personal care products. Cutting-edge measurement technology is therefore essential to ensure the quality and reliability of purified water systems.
TOC is a particularly important measurement in pure water systems because it provides a failsafe method to immediately detect any unwanted organic content. Contamination may result from sources present in the supply water and not removed by the purification process. However, contamination may also arise from within the high purity water system itself. Sources include piping, filters, valves, biofilm buildup, system leaks, adhesives, process gases, ion-exchange resins and thermoplastic breakdown products created during sterilisation procedures. Continuous monitoring, a fast response time and reliability are therefore essential – to monitor trends and raise alarms.
The Pharmacopeia regulations.
TOC is one of the four critical parameters defined by the Pharmacopeia to ensure the quality of purified water (PW) and water for injection (WFI).
The objectives of the United States Pharmacopeia standard USP <643> are to ensure the accurate measurement of TOC and to provide guidance on how to achieve that goal. USP <643> does not specify a particular analytical method, however it does specify the criteria for qualifying TOC instrumentation and for the interpretation of results. For example, instruments should be able to distinguish between organic and inorganic carbon, and must have a detection limit specified by the manufacturer of 0.05 mg/L (equivalent to 0.05 ppm or 50 ppb). Also, instruments must be calibrated according to the manufacturer’s instructions and regularly subjected to a System Suitability Test (SST). USP <643> intentionally says nothing about how often the SST should be run, because the frequency depends on the stability of the TOC instrument response and other factors associated with water quality and risk.
USP <643> states that TOC must not exceed the defined limit, which is the response of the TOC analyzer to a 500ppbC standard made from USP-traceable sucrose. This means that the value which a specific TOC analyser gives for USP-traceable 500ppbC sucrose becomes the limit value.
Continuous TOC monitoring is also specified in European standards. For example, the EU GMP Annexe 1 requires water for injection systems to include continuous monitoring systems such as TOC and conductivity, (unless justified otherwise) as these may give a better indication of overall system performance than discrete sampling. Sensor locations should be based on risk and the outcome of qualification.
Spec sheet conundrum.
One of the key challenges facing process managers is how to choose instrumentation when all the spec sheets look the same! This is because measurement instrumentation frequently employs the same or similar detection technology, so performance measures such as accuracy and resolution are inevitably similar. The key differences between different manufacturers therefore mainly relate to issues such as measurement stability, reliability, and ease of use. However, these characteristics are difficult to define on specification sheets, but feature prominently in the minds of existing users.
Case study - pharmaceutical manufacturer.
One of
Swan Analytical’s customers is a well-known global brand in the body care and fragrance sectors with a British manufacturing facility using purified hot and cold water for both manufacturing and cleaning purposes. The level of purification is critical for the quality of their products, so a comprehensive continuous water quality monitoring network has been established for quality control and regulatory compliance.
The company takes an uncompromising approach to quality, covering every stage of the development and manufacture of its products, with rigorous compliance to some of the strictest regulations in the world. In addition, the company’s state-of-the-art manufacturing facilities feature the most advanced testing equipment to guarantee product quality. All manufacturing equipment is tested and certified, and every production process is validated.
Local engineering staff have commented that most reputable instruments can be relied on to deliver accurate results, but they believe that the key differentiators are the ease and cost of maintenance procedures such as service and calibration. These are not issues that can generally be assessed in product literature, so it is necessary to learn from the experience of existing users. However, in this example, the user already had the prior benefit of an existing Swan chlorine analyser which was employed to continually check the performance of a carbon filtration system. This provided the level of confidence necessary to subsequently deploy a Swan analyser for the measurement of TOC. Importantly, the client chose Swan, not because it was more accurate than its predecessor, but because it was so much easier to manage.
Swan analysers are simpler to maintain because they have a modular design. This means that the footprint is very slightly larger, but importantly, service and calibration work is improved, because it is easier and less costly to work on or replace individual modules. In addition, the Swan analysers come with a 3-year warranty, which is quite unusual in this market.
To further extend confidence and reliability in continuous monitoring systems, many UK customers are covered by a service contract under which Swan engineers conduct a preventative maintenance and SST/calibration check every 6 months. The resulting service report and calibration certificate can form part of an internal audit procedure, as well as external audits by organisations such as the US Food & Drug Administration (FDA).
Summary.
The accuracy and performance of Swan’s AMI LineTOC analysers are equivalent to other leading manufacturers, but for many users a key point of differentiation is the ease of maintenance. This generally results in lower operational costs, but in comparison with other continuous monitors, Swan instruments also represent a lower capital cost.
In addition to online monitoring, many customers take water samples from multiple locations for laboratory analysis. This enables the measurement of a wide variety of parameters, but lacks the advantages of continuous monitoring. For example, online instruments provide 24/7 reassurance that processes are in perfect condition and fully compliant with pharmacopoeia and all applicable regulations. These continuous measurements are extremely important, not just for regulatory compliance, but also to provide fast alerts to prevent any possibility of product contamination.
In conclusion, most instrument manufacturers publish high levels of performance for their monitors, so it can be difficult to choose one over another. It is therefore important to seek the views of existing users, most of whom will emphasise the importance of maintenance ease and cost.
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