DISSOLUTION SYSTEM SS 231 (FOR HPLC)

INTRODUCTION

The majority of systems used in the tablet dissolution field employ UV/VIS as the chosen form of analysis. Such systems are simple, clean, easy to set up and maintain.  Valuable as these systems are, they cannot in themselves provide a satisfactory solution to all the problems experienced in dissolution testing.

Although UV Analysis adapts to the analysis of a high proportion of drugs which exhibit active chromopore activity, in the case of certain dosage forms this approach is not practical. Furthermore, many formulations, for example, contain multiple components or excipients or coatings that interfere with UV analysis.

In these cases, high pressure liquid chromatography (HPLC) may well provide the solution. The excellent specificity of HPLC makes it more sensitive than UV/VIS techniques for the analysis of sustained release products and of low dosage formulations.  However, these techniques tend to bring a new set of problems to the systems engineer charged with their design. Many of these problems emanate from the fact that the samples are collected in multiples of 6, 7 or 8 simultaneously whereas the HPLC detector will only accept samples one at a time.

Furthermore, the time taken to perform the test may prohibit the immediate ‘on-line’ analysis of the collected samples, that is to say, there is insufficient time between the dissolution sampling intervals to allow for the analysis of 6-8 samples.

The Dissolution System SS 231 has been specifically designed for this eventuality in so much that the sampling station acts simply as a temporary storage vehicle for the dissolution samples: the collected samples are then aspirated sequentially to the appropriate detector.  This system provides for maximum flexibility in the sample/inject control sequence allowing separate timing of sample withdrawal and analysis whilst optimising throughput.

SYSTEM COMPONENTS

The system comprises four main elements:

1.  The ‘Sample Station’ itself having a capacity of 120 open or sealed septum vials (20 rows of 6) 
2.  The Peristaltic Pump which provides the motive force to transport the samples from the Dissolution Tester to the Sampling Station 
3.  The Syringe Pump which serves to transfer the samples from the flow-through vials to the collection vials and then to the HPLC loop 
4.  The Control Module which serves to control all the various components during operation
    

 
PRINCIPLE OF OPERATION

The principle of operation is similar to the SS 8000 described on the link above.

In this case however, the media from each of the six test vessels is circulated continuously via a 6-line peristaltic pump through 6 flow through vials located on the sampling station before returning back to the dissolution vessels.

At user defined intervals, each of the flow through vials is sampled in  turn by a needle probe and the sample then aspirated into a collection vial in the sampling station. A wash cycle is provided between samples to avoid carryover between samples.

Three modes of operation are possible:

• 1. Collect Only

In this mode, the sampling station behaves solely as a fraction collector. Samples are collected and stored in sealed HPLC vials in the rack and can then be analysed by an appropriate post run technique.

• 2. Collect then Inject

As Collect mode but then depending on the amount of time remaining before the next collection, HPLC injections of standards and samples will commence. The analysis sequence will proceed until all the vials have been injected and then wait until the next collection time point. In the event of insufficient time remaining to inject all the samples prior to the next collection point, the HPLC injections will be halted until the collection has taken place whereupon injections will recommence.

• 3. Immediate Inject

In this mode, no samples are collected. HPLC injections are made directly from the flow vials and standard vials onto the HPLC system. This presupposes that all the samples can be injected before the next dissolution collection cycle.

KEY FEATURES

•  Dedicated Dissolution System for HPLC analysis   
•  Intelligent scheduling software controls when to sample and inject 
•  Independent control module - no PC required 
•  Easy menu-lead operating procedure via membrane keypad 
•  Accommodates up to 20 rows of 6 samples plus standards

 
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