Automated tablet dissolution apparatus

In a preferred embodiment, the apparatus includes a dissolution vessel removably seated within an aluminum platen. The apparatus also includes an assembly for automatically measuring a desired volume of media, heating and degassing the volume of media and then dispensing the volume of media into the dissolution vessel. In addition, the apparatus includes a carousel having a plurality of compartments, the carousel being rotatably mounted on a stage, the stage being alignable with the vessel. According to one mode of operation, an open-top, cage-type basket is placed in one or more compartments of the carousel, each basket containing a tablet intended for dissolution. The apparatus additionally includes a shaft aligned with the vessel, the bottom end of the shaft being adapted to frictionally fit together with a basket. The shaft is rotatable and vertically movable so that it can fit together with a basket, pick the basket up out of the carousel, lower the basket into the vessel, rotate the basket within the media and remove the basket from the media. The apparatus further includes a catheter automatically movable in and out of the vessel for sampling the media at desired times, an automated mechanism for loading and replacing a depth filter on the input end of the catheter, an automated mechanism for removing the basket from the end of the shaft after testing has been completed and an automated mechanism for removing media from the vessel after testing has been completed. The apparatus also includes a paddle shaft which may be used interchangeably with the basket shaft if tablets are placed directly in the compartments of the carousel and are then dispensed from the carousel into the vessel through an opening in the bottom of each carousel that is alignable with an opening in the stage.

BACKGROUND OF THE INVENTION 
The present invention relates generally to tablet dissolution testing and 
more particularly to a novel tablet dissolution apparatus. 
In the pharmaceutical industry, it is commonplace, during pharmaceutical 
formulation development, stability determination, analytical development, 
quality control, or otherwise, to ascertain the rate at which a drug in 
solid form (hereinafter referred to as a "tablet") dissolves under certain 
well-defined conditions. In this manner, one can gauge or predict the 
dissolution rate of the tablet in the human stomach. Historically, tablet 
dissolution testing has been performed largely manually and has required a 
person to perform the following type of procedure: First, the person pours 
a defined volume (e.g., approximately 500-1000 ml) of an appropriate 
medium, such as water or a pH-adjusted buffer, into a 1 liter vessel 
positioned in a water bath, the water bath typically being heated to about 
37.degree. C. The person then drops a tablet to be tested into the media 
and lowers a mechanically-rotating paddle (rotating at approximately 
50-150 rpm) into the media to stimulate dissolution of the tablet. (As an 
alternative to dropping the tablet into the media and using a paddle to 
stimulate dissolution, the person may place the tablet inside a cage-type 
basket, which is then lowered by the person into the media and 
mechanically rotated at about 50-150 rpm.) At one or more defined times 
(typically between about 0.5-2 hours after the tablet is dropped into the 
media), the person withdraws and filters one or more samples of the media 
from the vessel (typically using a depth filter fitted on the end of a 
suctioning sampling tube inserted into the media). The person then 
analyzes each filtered sample (e.g., using UV spectrophotometry, high 
performance liquid chromatography (HPLC), etc.) to detect the level of 
drug dissolved therein. 
Frequently, it is necessary for the person to repeat the aforementioned 
dissolution procedure for a plurality of tablets, it therefore being 
further necessary, between successive tests, for the person to empty and 
to wash the vessel, to wash the paddle and to replace the media in the 
vessel. 
To enable several tablets to be dissolved at the same time (i.e., in a 
batch mode), semi-automated dissolution equipment has been developed. Such 
equipment (e.g., VanKel, Edison, N.J ; DISTEK, New Brunswick, N.J.; 
Hanson, Chatsworth, Calif.) typically includes a plurality of vessels 
(e.g., six) positioned in a water bath and a corresponding plurality of 
rotatably-driven paddles or baskets positionable in the vessels. (Instead 
of employing a water bath to heat the media-filled vessels, the 
dissolution equipment may alternatively use one or more ceramic platens 
fixed to the outside of each vessel-DISTEK, New Brunswick, N.J.) 
Nevertheless, as can readily be appreciated, even the above-described 
equipment requires a great deal of manual labor, as the sampling step, as 
well as the vessel emptying, filling and washing steps, among other 
things, are still performed manually. 
Consequently, dissolution testing has traditionally been labor-intensive, 
slow and prone to the commission of errors. Recently, however, efforts 
have been undertaken to automate as many aspects of dissolution testing as 
possible. An example of such efforts is the MultiDose.TM. workstation of 
Zymark Corporation, Hopkinton, Mass. The MultiDose.TM. workstation, which 
is adapted for integration with commercially-available, multi-vessel, 
dissolution testing equipment of the type described above, includes a 
plurality of rotatably-driven carousels which are positioned over a 
corresponding plurality of vessels. Each carousel is adapted to hold a 
plurality of tablets. The workstation further includes automated means for 
dispensing a gravimetrically-measured quantity of media into each of the 
vessels, automated means for causing each of the carousels to drop a 
tablet into its corresponding vessel at a desired time, automated means 
for causing each of the paddles to rotate within its respective vessel, 
automated means for sampling the media from each of the vessels at one or 
more desired times, automated means for filtering the sampled media prior 
to analysis and automated means for emptying and washing the vessels 
between successive tests. 
Although the above-described MultiDose.TM. workstation represents an 
advance in the art of dissolution testing technology, the present 
inventors have identified certain shortcomings in the MultiDose.TM. 
workstation. One such shortcoming is that the MultiDose.TM. workstation is 
designed for use in combination with pre-existing, commercially-available, 
six-vessel dissolution equipment of the type described above. The present 
inventors believe that this is a shortcoming for the following reasons: 
First, the combination of the MultiDose.TM. workstation and the 
above-described six-vessel dissolution equipment is rather expensive and 
occupies a considerable amount of laboratory space; consequently, certain 
small laboratories may be unable to use such equipment due to price and/or 
space considerations. In addition, even though there are instances where 
less than all six vessels need to be used at the same time for dissolution 
testing, certain components of the six-vessel dissolution equipment are 
not capable of being operated independently for each of the six vessels; 
consequently, some of the equipment must be used even when not needed. 
Moreover, because the MultiDose.TM. workstation performs the emptying, 
washing and filling steps for all six vessels at the same time, a second 
batch of tablets cannot be tested until all of the testing for the first 
batch of tablets has been completed. Furthermore, whereas approximately 
50% of dissolution testing in the art is currently performed using the 
above-mentioned basket method (as opposed to the paddle method), the 
MultiDose.TM. workstation is adapted for use only with paddle-type 
systems. Other shortcomings will be described or will be apparent from the 
discussion below. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a novel tablet 
dissolution apparatus. 
It is another object of the present invention to provide a tablet 
dissolution apparatus that overcomes at least some of the shortcomings 
inherent in existing tablet dissolution apparatuses. 
It is still another object of the present invention to provide a tablet 
dissolution apparatus that is compact in size and easy to use. 
According to one aspect of the invention, there is provided a tablet 
dissolution apparatus that is alternately configurable for either 
paddle-type or basket-type dissolution of a tablet. 
According to another aspect of the invention, there is provided a tablet 
dissolution apparatus that includes automated means for volumetrically 
measuring and dispensing a quantity of dissolution media into a 
dissolution vessel. 
According to yet another aspect of the invention, there is provided a 
tablet dissolution apparatus that includes automated means for preheating 
dissolution media to a temperature approximating that desired for 
dissolution and for dispensing such preheated dissolution media into a 
dissolution vessel. 
According to still another aspect of the invention, there is provided a 
tablet dissolution apparatus that includes a dissolution vessel and a 
metal platen, the metal platen being used, instead of a water bath, to 
heat the contents of the dissolution vessel. 
According to still yet another aspect of the invention, there is provided a 
tablet dissolution apparatus that includes a dissolution vessel and a 
platen for heating the contents of the dissolution vessel, the platen 
being sized and shaped to removably receive the dissolution vessel. 
According to a further aspect of the invention, there is provided a tablet 
dissolution apparatus that includes fully-automated means for withdrawing 
and filtering a sample from a dissolution vessel, said fully-automated 
means including a depth filter positioned on the end of a sampling tube 
inserted into the dissolution vessel. 
According to yet a further aspect of the invention, there is provided a 
tablet dissolution apparatus that enables the fully-automated, serial, 
basket-type dissolution of a plurality of tablets in the same dissolution 
vessel. 
According to still yet a further aspect of the invention, there is provided 
a tablet dissolution apparatus that includes camera means for imaging the 
contents of a dissolution vessel for purposes of enabling verification of 
proper placement of the tablet and the paddle or basket within the vessel. 
According to even yet a further aspect of the invention, there is provided 
a tablet dissolution apparatus that includes a media removal assembly 
comprising the combination of a comparatively large-diameter media removal 
tube and a comparatively-small diameter media removal tube. 
According to still even yet a further aspect of the invention, there is 
provided a tablet dissolution apparatus that includes a first dissolution 
vessel, a second dissolution vessel and commonly-controlled automated 
means for causing the dissolution of a first tablet in said first 
dissolution vessel and for causing the dissolution of a second tablet in 
the second dissolution vessel wherein the respective dissolutions of the 
first and second tablets are operable completely independently of one 
another. 
Additional objects, as well as features, advantages and aspects of the 
present invention, will be set forth in part in the description which 
follows, and in part will be obvious from the description or may be 
learned by practice of the invention. In the description, reference is 
made to the accompanying drawings which form a part thereof and in which 
is shown by way of illustration specific embodiments for practicing the 
invention. These embodiments will be described in sufficient detail to 
enable those skilled in the art to practice the invention, and it is to be 
understood that other embodiments may be utilized and that structural 
changes may be made without departing from the scope of the invention. The 
following detailed description is, therefore, not to be taken in a 
limiting sense, and the scope of the present invention is best defined by 
the appended claims.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring now to FIGS. 1 through 5, there are shown various views of one 
embodiment of an automated tablet dissolution apparatus constructed 
according to the teachings of the present invention, the automated tablet 
dissolution apparatus being represented generally by reference numeral 11. 
Those aspects of apparatus 11 not pertinent to the present invention are 
neither shown in the drawings nor described herein for clarity. 
Apparatus 11 includes a housing 13, which may be made of metal or a 
similarly suitable structurally-durable material. Housing 13 includes an 
upper portion 15 and a lower portion 17, upper portion 15 and lower 
portion 17 being separated by a platform 19. A drawer 21 is mounted within 
lower portion 17 of housing 13, drawer 21 being manually slidabllle 
forwards and backwards within lower portion 17 in the directions indicated 
by arrows A and A', respectively, for reasons hereinafter to become 
apparent. 
Apparatus 11 also includes a dissolution vessel 23 (seen best in FIG. 6). 
In the present embodiment, vessel 23 is a 1 liter transparent glass vessel 
of the type conventionally used in tablet dissolution apparatuses. 
Apparatus 11 additionally includes means for heating the contents of 
dissolution vessel 23. Referring now to FIGS. 7 and 8, in the present 
embodiment, said means for heating the contents of dissolution vessel 23 
can be seen to include a metal platen 25. Platen 25, which is preferably 
made of aluminum or a similarly suitable heat-conductive material, is 
appropriately sized and shaped to removably receive vessel 23. A plurality 
of heat-conductive fingers 24 used to promote heat transfer from platen 25 
to vessel 23 are affixed to the interior surface of platen 25 and are 
adapted for contact with vessel 23 when vessel 23 is seated within platen 
25. A plurality of resistive heating elements 27 are disposed within 
platen 25 to heat platen 25. The outputs of elements 27 are controlled by 
a computer 29 (see FIG. 1). (For convenience and clarity, certain 
connections between computer 29 and other components of apparatus 11 are 
not shown.) A thermistor 31, which is also connected to computer 29, is 
also disposed within platen 25 to determine the temperature of platen 25. 
In this manner, using suitable calibration curves, computer 29 can be used 
to control the temperature at which the contents of vessel 23 are 
maintained by monitoring the temperature of platen 25 with thermistor 31 
and accordingly adjusting the outputs of heating elements 27. Typically, 
the contents of vessel 23 are maintained at a temperature of 37.degree. C. 
Referring back now to FIGS. 1 through 3, vessel 23 and platen 25 can be 
seen to be positioned within the rear of drawer 21. Vessel 23 can be 
removed from apparatus 11 (e.g., for washing or replacement) by pulling 
drawer 21 forwardly in the direction of arrow A and lifting vessel 23 out 
of platen 25. 
An opening 33 is provided in the bottom of platen 25. A camera 34, which is 
controlled by and whose output is fed to computer 29, is aligned with 
opening 33 so that one or more images, as desired, may be taken of the 
contents of vessel 23. Such images may be stored in computer 29 (and, if 
desired, printed out by a printer (not shown) connected to computer 29) 
and may be used, for example, to verify that a tablet was dropped 
correctly into vessel 23 and/or that the tablet was dissolved properly. 
Although not shown, one or more openings like opening 33 may be provided 
in the side wall of platen 25 to permit an additional camera to be 
deployed from a different vantage point than that of camera 34 or to 
permit an individual to visually inspect the contents of vessel 23. 
Apparatus 11 further comprises a stage 35 disposed within drawer 21. Stage 
35 is mechanically coupled to an air cylinder 37. Air cylinder 37, which 
is controlled by computer 29, moves stage 35 forwards and backwards within 
drawer 21 in the directions indicated by arrows B and B', respectively. A 
carousel 39 is rotatably mounted on top of stage 35. Rotation of carousel 
39 in the directions indicated by arrows C and C' is caused by a motor 41, 
which is controlled by computer 29. Referring now to FIGS. 9 through 12, 
additional details of stage 35 and carousel 39 are shown. As can be seen, 
carousel 39 is shaped to include a plurality of compartments 43. Each 
compartment 43 is appropriately dimensioned to removably receive a 
cage-type, open-top basket 45 (see FIG. 11) adapted to hold a tablet T (to 
enable apparatus 11 to be used for basket-type dissolution). In addition, 
the bottom of each compartment 43 is provided with an opening 47 
sufficiently large to permit a tablet T to pass therethrough but small 
enough to prevent basket 45 from passing therethrough. An opening 49 
appropriately dimensioned to permit tablet T to pass therethrough is also 
provided in stage 35. Opening 49, which is aligned with vessel 23 when 
stage 35 is in its rearwardmost position within drawer 21, may be aligned 
with opening 47 of each compartment 43 by rotating carousel 39. In this 
manner, as can be seen in FIG. 12, when a basket-less compartment 43 
containing a tablet T is aligned with opening 49, tablet T can drop 
through openings 47 and 49 (and into vessel 23) to enable apparatus 11 to 
be used for paddle-type dissolution. 
Referring back now to FIGS. 1 through 3, apparatus 11 further comprises 
means for dispensing a volumetrically-measured quantity of pre-heated, 
sparged (i.e., de-gassed) media into vessel 23. As can best be seen in 
FIGS. 13 and 14, said dispensing means comprises, in the present 
embodiment, a cylindrical platen 51, which is preferably made of aluminum 
coated with TEFLON (synthetic resin polymer) or a similarly suitable 
heat-conductive, non-stick surface. A plurality of resistive heating 
elements 53, connected to and controlled by computer 29, are disposed 
within platen 51. Platen 51 is mounted on top of a base member 57, and a 
cover 59 is mounted on top of platen 51. Platen 51, bas e m ember 57 and 
cover 59 jointly define a media chamber 61. Media is introduced into 
chamber 61 from an external source (not shown) through tubing 63 inserted 
into a media input channel 65 formed in base member 57. Once in chamber 
61, the media is pre-heated via platen 51 to a temperature slightly higher 
than that desired for dissolution (e.g., about 38.degree. C.) so that, 
during transport from chamber 61 to vessel 23, the media may cool to the 
appropriate dissolution temperature. Helium, which is added to the media 
in order to sparge (i.e., de-gas) the media, is introduced into chamber 61 
from an external source (not shown) through tubing 67 inserted into a 
helium input channel 69 formed in base member 57. 
A section of clear tubing 71 is mounted within cover 59 so that one end 
thereof is placed in fluid communication wit h chamber 61 and so that the 
other end thereof extends upwardly a short distance beyond the top of 
cover 59. A pair of media detectors 73-1 and 73-2, which are connected to 
computer 29, are mounted on a bracket 75 extending parallel to tubing 71. 
Detector 73-1 is appropriately vertically positioned on bracket 75 so 
that, when detector 73-1 detects media at a corresponding height in tubing 
71, a signal is sent to computer 29 indicating that a desired volume of 
media (e.g., about 900 ml) is present within chamber 61 and tubing 71. 
Computer 29 then s huts down the flow of additional media into chamber 61 
through tubing 63 (by means of a valve not shown). Detector 73-2, which is 
vertically positioned higher on bracket 75 than is detector 73-1, detects 
when the aforementioned volume of media has expanded due to having been 
pre-heated to a desired temperature, e.g., about 38.degree. C. When 
detector 73-2 detects media at the appropriate level, it sends a signal to 
computer 29. Computer 29 then causes a motor 79 to drive a piston 81 
upwardly and away from an O-ring 83 located at the entrance of a media 
egress channel 85 formed in base member 57. With piston 81 spaced apart 
from O-ring 83, media is then allowed to escape from chamber 61 and is 
conducted through channel 85 into vessel 23 via a media dispensing tube 
87. 
As can readily be appreciated, the above-described media dispensing means 
can be modified to measure varying volumes of media by providing a movable 
piston within chamber 61 that effectively varies the usable volume of 
chamber 61. 
Referring back now to FIGS. 1 through 5, apparatus 11 further comprises a 
basket shaft 91. Basket shaft is vertically aligned with vessel 23 and 
with opening 49 of stage 35 (when stage 35 is in its rearwardmost 
position) and has a bottom end in the form of a basket lid 93. Lid 93 is 
appropriately dimensioned to engage a basket 45 from the top by 
friction-fit. Near its top end 95, basket shaft 91 is removably attached 
by walking collars (not shown) to a carriage 97, shaft 91 being 
mechanically coupled to carriage 97 for vertical movement into and out of 
vessel 23 but being free to move rotationally relative to carriage 97. 
Rotation of shaft 91 is provided by a motor 99 controlled by computer 29. 
Carriage 97 is slidably mounted on a pair of posts 101-1 and 101-2. 
Vertical movement of carriage 97 along posts 101-1 and 101-2 is achieved 
by means of a threaded drive shaft 103 mechanically coupled to a motor 105 
controlled by computer 29. 
As discussed elsewhere in the present specification, apparatus 11 can be 
used either for basket-type or paddle-type dissolution of tablets. When 
apparatus 11 is intended for basket-type dissolution, tablet-containing 
baskets 45 are loaded into carousel 39 and basket shaft 91 is attached to 
carriage 97. When apparatus 11 is intended for paddle-type dissolution, 
tablets are placed directly into compartments 43 and basket shaft 91 is 
replaced with a paddle shaft 111 having a paddle 112 at the bottom end 
thereof (see FIG. 15). 
An opening 113 is provided in platform 21, opening 113 being aligned with 
basket shaft 91 (or paddle shaft 111) and having a shape appropriate for 
insertion of basket shaft 91 (or paddle shaft 111) therethrough. 
Referring now to FIGS. 4 and 5, apparatus 11 further comprises a 
temperature sensor 117 and a media sampling cannula 119. Sensor 117 is 
connected to computer 29 so as to provide computer 29 with temperature 
readings of the dissolution media within vessel 23. Cannula 119 is used to 
withdraw samples of the media within vessel 23 for external analysis 
(e.g., chromatography, spectroscopy, etc.) and is connected to a 
peristaltic pump 121 through a length of flexible tubing 123. Pump 121 is 
controlled by computer 29. Sensor 117 and cannula 119, both of which are 
vertically aligned with vessel 23, are fixedly attached near their 
respective top ends to a carriage 125. Carriage 125, in turn, is slidably 
mounted on a pair of posts 127. Vertical movement of carriage 125 along 
posts 127 to permit sensor 117 and cannula 119 to be moved into and out of 
vessel 23 is achieved by means of a threaded drive shaft 129 mechanically 
coupled to a motor 131 controlled by computer 29. 
As seen in FIGS. 4 and 5, a disposable depth filter 133 is mounted on the 
bottom end of cannula 119. Filter 133, which may be a conventional depth 
filter of the type used in tablet dissolution, is used to remove 
pharmacologically-inactive excipients from the sample collected for 
analysis using cannula 119. Filter 133 preferably has a pore size of 
approximately 2 microns. 
Referring now to FIGS. 1 through 3 and 16(a) through 16(e), apparatus 11 
can be seen to further include means for feeding a filter 133 onto the 
bottom of cannula 119 and for ejecting from cannula 119 a filter 133 that 
has been loaded thereonto and no longer needed. In the present embodiment, 
said feeding and ejecting means comprises a tube 151 into which a 
plurality of filters 133 have previously been stacked, either manually or 
otherwise. As seen best in FIGS. 16(a) through 16(e), filters 133 are held 
in place by an air cylinder 153 (controlled by computer 29) which 
releasably engages the bottom filter 133 of the stack within tube 151. 
Said feeding and ejecting means also comprises a carriage assembly 155. 
Carriage assembly 155 includes a filter receiving member 157. Member 157 
is provided with a transverse bore 159 alignable with tube 151 and 
appropriately dimensioned to receive a filter 133. Member 157 is also 
provided with a longitudinal slot 161 (see FIG. 19) which extends 
rearwardly from the front of member 157 into bore 159 and which is 
appropriately dimensioned, for reasons to become apparent below, to 
accommodate cannula 119 extending transversely therethrough. 
Carriage assembly 155 also includes a base 167, member 157 being mounted on 
base 167. Base 167 is provided with a transverse bore 168 aligned with 
bore 159 of member 157 and similarly dimensioned to receive filter 133. As 
seen best in FIGS. 17(a) and 19, base 167 is also provided with a 
longitudinal slot 169, which extends rearwardly from the front of base 167 
into bore 168 and which is also appropriately dimensioned to accommodate 
cannula 119 extending transversely therethrough. Carriage assembly 155 
also includes a filter stop 171 (shown in isolation in FIGS. 18(a) and 
18(b)), which is slidably mounted within longitudinal slot 169 of base 
167. Movement of stop 171 within slot 169 is achieved by means of an air 
cylinder 173, one end of which is inserted into an opening 175 formed in 
stop 171. Stop 171 is shaped to include a platform 181 which, when 
positioned between bore 159 of member 157 and bore 168 of base 167, 
prevents a filter 133 from passing therebetween. 
As seen best in FIGS. 1 through 3, 17(a), 17(b) and 19, carriage assembly 
155 further includes a block 183 to which base 167 and member 157 are 
fixedly attached. Block 183, in turn, is slidably mounted on a pair of 
posts 185. Movement of block 183 along posts 185 is achieved by means a 
threaded drive shaft 187 mechanically coupled to a motor 188 controlled by 
computer 29. 
Referring back now to FIGS. 16(a) through 16(e), there is illustrated the 
manner in which the filter feeding and ejecting means ensures that a 
filter 133 is properly positioned for feeding onto the end of cannula 119. 
As seen in FIG. 16(a), the temporary retraction of air cylinder 153 allows 
the bottom filter 133 in tube 151 to drop into bore 159 of member 157. 
Because stop 171 is positioned so that platform 181 is located between 
bores 159 and 168, filter 133 is retained within bore 159. In FIG. 16(b), 
carriage assembly 155 moves laterally in the direction of cannula 119 
until bores 159 and 168 are in alignment with a probe 191. Probe 191, 
which is used to determine whether filter 133 has been loaded into bore 
159 correctly (i.e., with its cannula opening 195 facing upwardly) or 
incorrectly (i.e., with its cannula opening 195 facing downwardly or not 
loaded at all), is vertically movable by means of an air cylinder 193 
controlled by computer 29. Probe 191 is provided with an opening 197, 
which is detected by an optic sensor 199 if probe 191 extends downwardly 
to an appropriate depth (see FIG. 16(c)). If, however, as is the case 
shown in FIG. 16(b), filter 133 is positioned upside down in bore 159, 
probe 191 will not be able to extend down far enough for sensor 199 to 
detect hole 197. In such a case, as seen in FIG. 16(d), filter stop 171 
will then be retracted and filter 133 will be ejected through bores 159 
and 168 into a filter refuse receptacle (not shown). As seen in FIG. 
16(e), if no filter has been loaded into bore 159, probe 191 will pass 
through an opening 200 (see FIG. 18(a)) in filter stop 171 and will move 
downwardly too far for hole 197 to be detected by sensor 199. 
Assuming that filter 133 is properly positioned within bore 159, filter 133 
is fed onto cannula 119 as follows: Carriage assembly 155 moves laterally 
from the aforementioned testing area to a point where cannula hole 195 of 
filter 133 is aligned with cannula 119. Cannula 119 moves downwardly 
through an opening 201 in platform 21 into cannula hole 195 until it 
frictionally engages filter 133 and then moves upwardly a sufficient 
distance to remove filter 133 from member 157. Carriage assembly 155 then 
retracts, leaving filter 133 on the bottom end of cannula 119. 
Filter 133 is removed from cannula 119 (e.g., after the media has been 
sampled) as follows: With cannula 119 and filter 133 remaining lowered 
beyond the height of carriage assembly 155, carriage assembly 155 is moved 
back to the aforementioned filter loading position, thereby causing 
cannula 119 to pass through slots 161 and 169 of member 157 and base 167, 
respectively, until it extends through bores 159 and 168. Cannula 119 is 
then raised, causing filter 133 to be drawn upwardly through bore 168. As 
filter 133 moves upwardly through bore 168, however, it becomes wedged in 
bore 168 against a flange 204 of filter stop 171 and cannot continue 
upwardly any further. Upward movement of cannula 119, however, is 
unimpeded; consequently, cannula 119 slips out of filter 133 and is 
retracted to its initial position. Carriage assembly 155 then moves back 
over to the filter testing area. Probe 191 then moves downwardly, pushing 
filter 133 down through bore 168 where it is discarded into the filter 
refuse receptacle (not shown). 
Referring now to FIGS. 17(a), 17(b) and 19, base member 167 can also be 
seen to be shaped to include an arcuate groove 205 adapted to receive a 
bottom lip 206 of basket 45. Consequently, basket 45 can be detached from 
shaft 91 by moving base member 167 relative to basket 45 until lip 206 is 
inserted into groove 205 and then pulling shaft 91 upwardly until lid 93 
disengages from basket 45. Carriage assembly 155, with basket 45 in tow, 
is then moved laterally to the filter testing position, where an ejector 
rod 207 pushes basket 45 out of groove 205 into a basket receptacle (not 
shown). 
Referring back now to FIGS. 1 through 3, apparatus 11 further comprises 
means for emptying media from vessel 23. In the present embodiment, said 
vessel emptying means comprises a relatively large diameter tube 211 and a 
relatively small diameter tube 213, tube 213 being fixedly mounted within 
tube 211 and extending a short distance out from the bottom of tube 211. 
The top ends of tubes 211 and 213 are connected to a pump motor (not 
shown) through a pair of pump heads (not shown). Tube 211 is mechanically 
coupled to an air cylinder 215, which is controlled by computer 29. Air 
cylinder 215 serves to move tube 211 into and out of vessel 23. Tube 211 
is capable of quickly removing large quantities of media from vessel 23 
whereas tube 213 is capable of removing small quantities of media from 
vessel 23 that tube 211 may leave behind. 
Although not shown, apparatus 11 also comprises means, controlled by 
computer 29, for dispensing a washing solution into vessel 23. Washing 
solution may also be emptied from vessel 23 using the aforementioned 
vessel emptying means. 
To use apparatus 11 for basket-type dissolution, a user places one or more 
baskets 45 into compartments 43 of carousel 39 and places a tablet inside 
each basket 45. The user also mounts basket shaft 91 on carriage 97. In 
addition, the user inputs information into computer 29 regarding several 
dissolution testing parameters, such as the number of tablets to be 
tested, whether the dissolution is a basket-type dissolution or a 
paddle-type dissolution, the time duration of each dissolution, the number 
of samples to be drawn from each dissolution, the times at which said 
samples are to be taken, the temperature at which dissolution is to be 
performed, etc. The dissolution testing parameters may be either the same 
or different for multiple tablets tested sequentially. 
From this point onward, no more human intervention is necessary as 
apparatus 11 automatically performs the following steps, among others: The 
media dispensing means volumetrically measures the desired quantity of 
media, pre-heats and sparges said quantity of media and then dispenses the 
pre-heated and sparged quantity of media into vessel 23. The media within 
vessel 23 is then maintained at the appropriate dissolution temperature by 
platen 25. Carousel 39 is positioned so that a compartment 43 holding a 
tablet-containing basket 45 is situated directly under shaft 91. Shaft 91 
is then lowered until lid 93 engages basket 45. Shaft 91 is then raised, 
thereby removing basket 45 from carousel 39. Carousel 39 is then moved to 
its forwardmost position, and shaft 91 is lowered until basket 45 is 
positioned approximately 1 inch from the bottom of vessel 23. Basket 45 is 
then rotated at approximately 50-150 rpm for the dissolution period 
specified (see FIG. 2). A filter 133 is fitted onto cannula 119 and, at 
the time specified, a sample is withdrawn from vessel 23. Where multiple 
samples are taken during the dissolution period, either the same filter 
133 or different filters 133 may be used. After use, the filter 133 is 
removed from cannula 119 and discarded. At the conclusion of the 
dissolution period, rotation of basket 45 is halted and shaft 91 is raised 
until lip 206 of basket 45 is vertically aligned with groove 205 of base 
member 167. Base member 167 is then moved laterally towards basket 45 
until lip 206 is inserted into groove 205. Shaft 91 is then raised, 
thereby detaching shaft 91 from basket 45. Base member 167 then moves back 
laterally, causing ejector rod 207 to eject basket 45 from base member 167 
into a used basket receptacle. At the same time that basket 45 is being 
detached from shaft 91, tubes 211 and 213 are lowered into vessel 23 and 
are used to remove the media from vessel 23 (see FIG. 3). While this is 
being done, a washing solution is dispensed into vessel 23, tubes 211 and 
213 similarly being used to remove the washing solution from vessel 23. 
Lid 93 of shaft 91 may be lowered into vessel 23 to also be washed by the 
washing solution. At the conclusion of the above-described procedure, 
shaft 91 and carriage assembly 155 are returned to their initial 
positions. Where a second dissolution is to be performed, carousel 39 is 
then positioned so that a second basket 45 is aligned with shaft 91 and 
the foregoing procedure is repeated. 
To use apparatus 11 for paddle-type dissolution, the above-described 
procedure is performed with the following exceptions: Instead of attaching 
shaft 91 to carriage 97, the user attaches paddle shaft 111 to carriage 
97. Moreover, instead of placing tablets inside baskets 45 that are, in 
turn, inserted into carousel 39, the user places the tablets directly into 
compartments 43 of carousel 39. The tablets are then dispensed from 
carousel 39 into vessel 29 in the manner shown in FIG. 12. Because the 
same paddle 112 and paddle shaft 111 are used for each dissolution, the 
basket-basket shaft detachment procedure described above is not 
applicable. 
As can readily be appreciated, two or more independently operable 
apparatuses 11 can be hooked up to same computer 29. 
The embodiments of the present invention recited herein are intended to be 
merely exemplary and those skilled in the art will be able to make 
numerous variations and modifications to it without departing from the 
spirit of the present invention. All such variations and modifications are 
intended to be within the scope of the present invention as defined by the 
claims appended hereto.