Dissolution testing sample collection

Most manufacturers of dissolution testing devices offer semi-automated systems that can perform sampling, filtration, and UV reading or data collection. These systems automate only a single test at a time. Fully automated systems typically automate entire processes including media preparation, media dispensing, tablet or capsule drop, sample removal, filtration, sample collection or analysis (via direct connection to spectrophotometers or HPLCs), and wash cycles. A fully automated system allows automatic performance of a series of tests to fully utilize unused night and weekend instrument availability. 

Dissolution testing involves a two-step process sample preparation and sample analysis. In this chapter sample preparation denotes the actual sample dissolution procedure, including sample collection. The samples collected from the dissolution apparatus may be analyzed directly or may be subject to further manipulation (e.g., dilution) to give the final sample solutions. 

Flow analysis is associated with wet chemical methods and samples are generally collected and transported to the laboratory for analysis. After optional preparative step(s), e.g., dilution, dissolution, extraction, depro-teinisation, or analyte separation/concentration, the resulting aqueous test sample is accommodated in a cup in the sampler tray of the flow analyser for further handling. This practice has been adopted since the appearance of the first commercially available flow analysers, as shown in Fig. 2.3. 

Fully automated workstations can automatically fill vessels with dissolution medium, drop the tablets or capsules, collect multiple samples, and clean vessels. Zymark MultiDose Automated Dissolution Workstation (Zymark Corporation, Hopkinton, MA), Sotax AT70 Smart (Sotax Corporation, Horsham, PA), and AUTO DISS systems (Pharma Test GmbH, Hainburg, Germany) are several popular automated systems used within the pharmaceutical industry. 

Chemical leach tests on the bulk settled dust samples showed that the dusts are quite chemically reactive. Leach solutions have high alkali-nities, due to the rapid partial dissolution of calcium hydroxide from concrete particles. Indoor dust samples produced higher pH levels (11.8-12.4) and alkalinities (—600 mg CaCOa) than outdoor dusts (pH 8.2-10.4 alkalinity —30mgL CaCOa), indicating that outdoor dust samples had reacted with rainfall or other water prior to collection. Thurston et al (2002) found that the leachate pH of the dusts decreased with decreasing particle size. Some metals or metalloids in the dusts (aluminum, chromium, antimony, molybdenum, barium, copper, zinc, cobalt, nickel) are readily leached by deionized water many of these form oxyanion species or carbonate complexes that are most mobile at the alkaline pH s generated by the leachates. 

The flow method ts the simplest and the most straightforward. In the flow method, the solvent fluid is supplied to a compressor by a pressure cylinder. At the desired pressure, the fluid passes into the thermostatted extractor cell that contains the solute present in appropriate matrix (e.g., multiple layer of glass wool). The fluid dissolves the solute in the extractor and, on expansion through a heated metering valve, precipitates solute into a series of collection vessels to be measured gravimetrically. The volume of the decompressed fluid is totaled by a wet or dry gas test meter. Static or equilibrium solubility measurement methods are used to eliminate the need to sample the supercritical fluid solution. A high-pressure flow cell is placed in the flow circuit to monitor the dissolution process by spectrophotometry. 

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