Chemical apparatus and process disinfecting – deodorizing – preser – Analyzer – structured indicator – or manipulative laboratory... – Means for analyzing liquid or solid sample
Reexamination Certificate
2001-11-07
2004-07-20
Gakh, Yelena G. (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Analyzer, structured indicator, or manipulative laboratory...
Means for analyzing liquid or solid sample
C422S082050, C422S082070, C422S082080, C422S082090
Reexamination Certificate
active
06764651
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the preparation, sampling and analyzing of soluble materials. More particularly, the present invention relates to apparatus and methods for implementing flow-through techniques and the use of fiber optics in connection with the testing of soluble materials.
BACKGROUND OF THE INVENTION
Dissolution testing is often performed as part of preparing and evaluating soluble materials such as pharmaceutical dosage forms (e.g., tablets consisting of a therapeutically effective amount of active drug carried by an excipient material). Typically, dosage forms are dropped into test vessels that contain dissolution media of a predetermined volume and chemical composition. For instance, the composition can have a pH factor or acidic concentration suitable for emulating a gastro-intestinal environment. Dissolution testing can be useful, for example, in studying the drug release characteristics of the dosage form or in evaluating the quality control of the process used in forming the dose. In order to ensure validation of the data generated from dissolution-related procedures, dissolution testing is often carried out according to guidelines approved or specified by certain entities such as Unites States Pharmacopoeia (USP), in which case the testing must be conducted within various parametric ranges. Important parameters include dissolution media temperature, the amount of allowable evaporation-related loss, and the use, position and speed of agitation or dosage-retention devices. Recent developments in robotics and other automating means have been applied to dissolution media preparation and sample analysis technology, and have resulted in improved procedural efficiency and data quality.
As a dosage form is dissolving in the test vessel of a dissolution system, samples of the solution can be taken at predetermined time intervals and transported through a pumping system to the cuvette or sample vial of analytical equipment. The analytical equipment determines drug concentration and other properties. The dissolution profile for the dosage under evaluation—i.e., the percentage of drug dissolved in the test media at a certain point in time or over a certain period of time—can be calculated from the measurement of analyte concentration in the sample taken. The types of analytical equipment commonly provided include those adapted for effecting analytical techniques such as high-performance liquid chromatography (HPLC) and spectral analysis. HPLC entails separating the chemical compounds of the sample for discrete analysis by a detection device (which may be a simply designed UV spectrometer). Flow cells can be used in conjunction with HPLC as shown, for example, in U.S. Pat. No. 4,886,356 wherein Z-type flow cells are disclosed. As one example for implementing spectral analysis, a spectrophotometer uses ultraviolet (UV) and/or visible light to scan the sample and calculate light absorbance values. In one specific method involving the UV or UV-vis spectrophotometer, the UV sipper method, the sample is transferred to a flow cell contained within the spectrophotometer, is scanned while residing in the flow cell, and is then returned to the test vessel. The sample return step is advantageous in that it significantly reduces any analytical errors potentially resulting from a volumetric reduction in the solution still being developed in the test vessel. In general, spectrophotometric techniques are considered to be easier to implement than HPLC techniques for many applications.
The concentration of a given analyte in a sample through spectrochemical determination typically involves several steps. These steps can include (1) acquiring an initial sample (e.g., providing a dissolution testing apparatus with a dosage form such as a drug tablet that has been manufactured from a bulk material, or conducting chromatography, dialysis, and so on); (2) performing sample preparation and/or treatment to produce the analytical sample (e.g., dissolving the dosage from in dissolution media, and possibly adding reagents or pH factor-modifying agents, thereby creating a formulation suitable for measurement or detection by certain instruments); (3) using a sample introduction system to present the analytical sample to the sample holding portion of a selected analytical instrument (e.g., transferring the sample to the sample-holding portion of a UV spectrophotometer); (4) measuring an analytical signal (e.g., an optical signal) derived from the analytical sample; (5) establishing a calibration function through the use of standards and calculations; (6) interpreting the analytical signal; and (7) feeding the interpreted signal to a readout and/or recording system.
Conventional equipment employed in carrying out the above processes are generally known in various forms. Measurement of the analytical signal involves employing a suitable spectrochemical encoding system to encode the chemical information associated with the sample, such as concentration, in the form of an optical signal. In spectrochemical systems, the encoding process entails passing a beam of light through the sample under controlled conditions, in which case the desired chemical information is encoded as the magnitude of optical signals at particular wavelengths. Measurement and encoding can occur in sample cells, cuvettes, flow cells, and other sample containers of various designs. Flow cells permit increased sample throughput and facilitate the automation of filling and cleaning procedures. Test media and calibration media can be pumped or otherwise transferred into the flow cell, and the flow stopped for conducting an absorption measurement. After the measurement is taken, the pumping rate can be adjusted, and the liquid flow adjusted or reversed as needed, so as to remove the entire sample from the flow cell. The flow cell and associated liquid conduits can then be rinsed and another sample introduced into the flow cell. Flow cells can also be utilized to take absorption measurements on flowing streams of analyte-containing media, thereby making the measurement or analysis time-dependent. In this latter case, the flow rate and data acquisition time are controlled to ensure that the absorbance value is obtained for the sample at the proper time.
In addition, a suitable optical information selector must be used to sort out or discriminate the desired optical signal from the several potentially interfering signals produced by the encoding process. For instance, a wavelength selector can be used to discriminate on the basis of wavelength, or optical frequency. A radiation transducer or photodetector is then activated to convert the optical signal into a corresponding electrical signal suitable for processing by the electronic circuitry normally integrated into the analytical equipment. A readout device provides human-readable numerical data, the values of which are proportional to the processed electrical signals.
Considering all of the physical events that must occur over the course of sample preparation and analysis, adequate procedures for calibration or standardization of the system are usually required. For example, standards of known concentration can be introduced at one or more points along the liquid flow circuit of the system. Calibration data can thus be generated, stored and used as part of the analyzing process. Modern calibration procedures are often controlled by computer software. Indeed, a computer-controlled system can be provided to interface with many of the various components of the sample preparation and analysis systems. Such programmable systems are useful for monitoring and coordinating the various hardware operations, as well as for processing both the test data and the calibration data.
For spectrophotometers operating according to UV-vis molecular absorption methods, the quantity measured from a sample is the magnitude of the radiant power or flux supplied from a radiation source that is absorbed by the analyte species of the sample. Ideally, a value for the absorban
Fernando C. J. Anthony
Hofer Henry Z.
Swon James E.
Fishman Bella
Gakh Yelena G.
Gloekler David
Varian Inc.
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