Quality Control: CONTAMINATION CONTROL
Automate Your Sample Prep
Save time and money by automating this important, yet tedious, task
S ample preparation is one of the single most time consuming activities for analytical scientists working in pharmaceutical laboratories today. In the pharmaceutical development process, large numbers of samples are prepared and analyzed as part of stability and impurity studies. In a quality control environment, assay and content uniformity testing is a requirement of the pharmacopeia. In addition, increasingly complex controlled release dose forms are creating real challenges for traditional sample preparation techniques and technologies.
This article will review the need for analysis, current approaches to tablet and solid dose sample preparation, and explore how innovative technology and techniques can be applied to achieve faster and more effective sample preparations. The challenges of reducing solvent consumption and waste, processing "difficult" pharmaceutical dose forms, and the hidden costs of analysis will also be examined.
The Need for Analysis
Tablets are manufactured using batch production techniques. The production process facilitates the combination of the bulk components and active ingredients within the formulation and results in the dosage form presented to the patient. Regulations require pharmaceutical companies to test the tablets they produce for a number of important reasons:
The ratio of active ingredient to bulk components within most tablets is small. This makes the production of a uniformly distributed mixture very challenging.
The process steps used to manufacture the components and the batch production process can potentially introduce contaminants to the finished tablets.
Variations in the manufacturing process can lead to changes in the final tablet properties.
The effects of storage conditions and environmental factors such as temperature, humidity, and light need to be understood to provide evidence on how the stability and quality of a pharmaceutical product varies with time.
Tests for dose content uniformity and impurity content are a vital part of the work carried out by pharmaceutical companies to ensure the efficacy of their formulations. During research and development these tests enable the formulation, packaging, and manufacturing process to be optimized for consistent product quality. Once a product reaches the market the tests continue within a quality control environment to ensure that the manufactured product remains within its specification.
High Performance Liquid Chromatography (HPLC) is the most common analytical technique used for the purpose of tablet analysis. HPLC analysis is used to separate, identify, and quantify compounds within a target sample. Before using HPLC analysis or other comparable analytical techniques, the solid dosage form must be prepared as a suitable solution, by breaking down the tablet in a solvent and extracting the soluble components of interest.
Current Manual Methods
In theory the extraction of a substance from a tablet should be a simple and straightforward process-simply place the tablet in a suitable quantity of solvent and wait for it to dissolve. The reality is somewhat different.
In most cases tablet formulations are designed to allow them to be easily handled by the patient, swallowed, and then passed into the stomach without them breaking up. These characteristics provide the tablets with some inherent resistance to dissolution. Speciality "enteric" coatings may be used to control the location in the digestive system where a drug is delivered and absorbed. Modified and controlled release tablets take this concept further, and are designed to deliver their active ingredients with a controlled dosing profile, in some cases releasing the active ingredient slowly over a period of 24 hours. Consequently, such formulations are the most challenging to put into solution.
Laboratory analysts typically employ a number of techniques to assist the dissolution of a tablet, thereby reducing the time required to achieve liquid-solid extraction. The following techniques are among the most widely adopted manual methods used for sample preparation.
Stirrers and shakers: When using a shaker bath the analyst places the tablets into a volumetric flask together with a suitable volume of solvent, typically in the range 250 ml to 500 ml. The equipment agitates the solution to encourage the tablets to dissolve. Stirrers and shakers are relatively cost effective and easy to use. However, they require a large amount of space, as multiple units are usually required. Extended run times are also required for many formulations.
Sonication baths: Sonication baths are used in much the same way as stirrer baths. However, rather than a gentle stirring action, the sonication bath uses ultrasonic energy to disrupt the physical structure of the tablets. Sonication baths can get the job done more quickly than stirrer baths, but care must be taken to avoid the formation of local hot spots within the solution that can lead to accelerated degradation of the formulation. Sonication baths can also be very noisy devices and thus need careful placement in the laboratory.
External homogenization: External homogenization requires the introduction of a homogenizer into the flask or beaker containing the tablets. Homogenizers are noisy and potentially dangerous devices that typically use bladed tips to mechanically break up tablets. The introduction of an external tool of this type also introduces the need for careful method development around the cleaning of the tool. Failure to address this point can result in unacceptable recovery levels or potential cross sample contamination through the carryover of analytes.
There are a number of hidden costs associated with the current manual methods of sample preparation. One is finding and cleaning the glassware needed for the method. This factor is often overlooked when the cost of analysis is assessed. Typically, content uniformity testing is performed in batches of 10, requiring 10 sets of glassware to be available and cleaned after use. It is often cited that laboratory analysts may walk several miles in the course of a typical working day moving between equipment stations in the lab and their desks, seeking out reagents and equipment. Reducing the time spent searching for laboratory glassware can thus provide a significant benefit.
There are a number of hidden costs associated with the current manual methods of sample preparation. One is finding and cleaning the glassware needed for the method. This factor is often overlooked when the cost of analysis is assessed.
Another hidden cost is the large volume of solvent required in sample preparation. In most cases the solvents cost even more to dispose of than they do to supply. The environmental impact of solvent usage is also an increasingly topical issue for laboratories.
Automated Sample Preparation
For the higher throughput associated with quality control/batch release environments, pharmaceutical companies often look for automated solutions to perform sample preparation activities. Examples of systems currently designed for this purpose are TPW from Caliper and CTS from Sotax.
Automating sample preparation reduces manual working time and helps control inconsistencies in the preparation methods by using robots or automation in place of the operator. This approach helps control sources of analytical variability because environment, method, or operator factors are removed, measured, or controlled. Automated workstations offer the benefits of unattended operation and allow the analyst to focus on other more value-added activities, thus providing an associated cost and time saving. In addition, methods developed in one laboratory can more easily be transferred to similar qualified apparatus in another laboratory.
The adoption of automated technology is not without challenges (see references 4-6). Most automation systems have taken the existing benchtop paradigms and introduced robots and software to perform the task an operator would usually perform. This means that the limitations previously described for manual methods are still inherent in such systems, with the automation itself introducing additional complexity in the forms of software and compliance issues and additional points of failure and failure modes.
Transferring existing manual methods to an automated system is also a considerable challenge. Proving equivalence to current manual techniques is often a prerequisite and is inevitable in the case that manual testing has been used to establish the registration or product specification. This method transfer can be especially problematic if the automated equipment uses technology that is not available in benchtop form to allow a phased transfer to the automation.
Alternative to Conventional Methods
In response to the numerous challenges the industry faces with tablet sample preparation, RTS Life Science (Manchester, England), a major supplier of drug delivery automation systems, has developed a new sample preparation instrument which aims to overcome these challenges. RTS has focused a large part of its effort on achieving the fastest possible processing time for one of the most important and time-consuming steps in the process, namely the sample homogenization and associated solid-liquid phase extraction.
The new sample preparation instrument, RTS SolidPrep, uses novel technology to deliver fast liquid-solid extraction for tablet preparation. The short process times achieved by this technology offer radical improvements in throughput compared to traditional manual methods. The instrument is bench mounted and requires the same amount of space as a single stirrer bath. The instrument accommodates five 50 ml centrifuge tubes within its standard processing head, with each tube containing a crushing matrix.
To operate the instrument the analyst first places the tablets into each of the centrifuge tubes together with a suitable volume (typically 40 ml) of solvent. The analyst then places the caps onto the tubes before inserting them in the sample preparation instrument. The protective cover of the instrument is then closed to enable the unit. Once the instrument is started the vigorous action of the processing head agitates the crushing matrix within each tube. The action of the crushing matrix and solvent quickly places tablets into solution.
A large pharmaceutical company tested this tool to determine its reliability. The data collected by the independent third party provides compelling evidence to support claims for the efficiency of the instrument.
The main advantages of this instrument compared to traditional methods include:
The fast homogenization action combined with the parallel processing capacity of the five tube head reduces processing time and increases throughput.
The use of closed processing vessels eliminates issues of cross contamination and low recovery through product loss and reduces the exposure of analysts to undesirable vapors or aerosolized drug particles.
The use of low solvent volumes reduces overall solvent usage requirements and reduces solvent disposal costs.
The homogenization technology provides a uniform thermal environment (without hotspots) and does not increase the degradation of drug products.
The unit is compact and quiet in operation making it unobtrusive in the laboratory environment.
The processing tubes are disposable and supplied in close pack trays of 50 tubes that are easily stored and take up little space. The tubes are preloaded with an optimized quantity of crushing matrix for ease of use.
Automating sample preparation reduces manual working time and helps control inconsistencies in the preparation methods by using robots or automation in place of the operator. This approach helps control sources of analytical variability because environment, method, or operator factors are removed, measured, or controlled.
As with all new technology, there are aspects of the new instrument that need to be carefully considered. For example, existing sample preparation methods will be based around alternative technology. Consequently, the ability of the system to deliver comparable results needs to be established before the technology can be widely adopted. Fortunately, existing methods can in most cases be easily adapted to work with the equipment. Special attention needs to be paid to the smaller working volume, and in some cases, the solvent systems themselves may require adjustment or optimization to work within a lower volume window. Dilution may also be required prior to analysis to realize the same target analyte concentrations as established sample preparations.
Also, with most new instruments there is a lack of documentary evidence to support reliability claims. However, in the case of this development, the core technology used by the instrument has been used in other, non-pharmaceutical, sample preparation methods for several years. As demonstrated earlier, the company has also done extensive laboratory testing with the equipment to establish and optimize its performance with a variety of tablet dosage forms.
The company will also be introducing an automated workstation version of the equipment later this year. This will facilitate batch processing of samples and automate the stages of sample homogenization and sample clarification prior to analysis. By using a novel homogenization process and simplifying downsteam processing, the automated system is a high throughput parallel processing system that avoids many of the complications and problems of alternative benchtop and automated technologies. At the same time, it delivers the benefits of the benchtop system in an automated form.
In researching new technology for more effective sample preparation, RTS Life Science realized that a new technique was required for sample homogenization and drug product extraction. This technology needed to be robust and cover the full range of available dosage forms. The result of this work was an advanced sample preparation bench-top instrument.
Existing methods can be easily adapted to the new equipment, allowing companies to test the effectiveness of the process and technology with their specific drug products in a very cost effective format. Having the system available as benchtop components reduces the risk and complexity of method transfer, paving the way to the adoption of automated technology.
The automated version of the innovative technology is based on modular, upgradable technology, and fully automates the stages of sample homogenization, drug product extraction, and sample clarification prior to analysis. Planned future enhancements include integrated liquid handling and in-line analytical instrumentation. �
Pollard is the technical sales manager and Fish is the business unit director in drug delivery automation at RTS Life Science.
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