The Rainbow Dynamic Dissolution Monitor® System (RDDM) is a powerful tool that has been designed to aid drug developers requiring multiple, accurate dissolution analyses performed with minimal operator involvement. The RDDM is easy to operate, and the only required maintenance is replacement of the light source after 2,000 hours of use. Also, the RDDM system does not generate any waste and it occupies minimal laboratory bench space, although it should be placed next to a dissolution bath. The Rainbow requires a PC to perform calculations and store the generated data. The PC can be located remotely from the RDDM.
The RDDM system utilizes a dip type UV probe to measure the amount of active drug released from a solid dosage form.
For most measurements, six UV transflectance probes are placed into separate vessels and reside in situ for the duration of the dissolution test. Each probe is connected to its own miniature photo diode array (PDA) spectrometer via a fiber optic light guide.
The RDDM utilizes a series of Zeiss PDA spectrometers interfaced to a dip probe to generate real time dissolution curves. Each of the probes is placed into a dissolution vessel at the start of the dissolution experiment and remains in situ during the entire dissolution test. Energy from a source lamp is split by a fiber optic furcation cable with individual fibers coupled to one of a series of dip probes. The energy thus directed, transits a calibrated gap in the probe body. The gap, which is in the dissolution bath, has a reflecting surface on the opposite side that sends the energy, which has passed through the media into a return fiber. The energy transmitted by this return fiber is then analyzed by one of the Zeiss PDA spectrometers and converted to absorbance values.
The sample taken is an "optical sample"; that is, no material is removed from the dissolution bath. This allows rapid acquisition of a full UV spectrum (235 nm - 390 nm) from all vessels. For a controlled-release formulation, measurements would be recorded every 10 minutes for 24 hours, or every 5 seconds for an immediate-release formulation. Faster sampling rates are possible if fewer vessels are sampled. If a single probe is used, the scan rate can approach one scan per second.
A dissolution curve is generated in real time by the Rainbow Dissolution SmartWare® software using the measured absorbance data and relating it to a set of previously analyzed standards to determine the percent the active ingredient dissolved as a function of time. The data that is generated is automatically stored in a secured database.
Optical Specification. The Zeiss MMS spectrometer exhibits excellent analytical performance in the absorbance range of 0.02 Au up to 1.00 Au. Because of its low thermal expansion properties, the titanium body of the Zeiss spectrometer minimizes drift due to heating and cooling. The patented design of the Zeiss MMS eliminates moving parts to ensure wavelength accuracy.
Optical entrance. The fiber optic cable consists of approximately 15 quartz glass fibers with 70µm core diameter each, designed as cross section converter. Fiber bundle input round: diameter 0.4 mm NA = 0.2 mounted in SMA-coupling mechanical tubes centric to the optic axis diameter outside: 25 mm diameter inside: 16 mm NA = 0.2 70, µ X 1250 Am.
Grating. Flat-field, 1084 I/mm (center) blazed for approximately 220 nm.
Spectral Range. 200 nm - 390 nm (190 nm - 380 nm slit version) specifications for the range 235 nm - 390 nm
Resolution. Rayleigh-criterion: \Rayleigh ~ 3 nm. Sensitivity: 1011 - 1012 Counts/VVS (using 14-Bit conversion).
Wavelength accuracy absolute: 0.2 nm (CSC version)
Temperature-induced drift: < 0.005 nm / °C (CSC version)
Spectral distance of pixel: ~ 0.8 nm
Dissolution Baths
