Abstract:
An analytical rotor system comprises a rotor and interface. The rotor defines a plurality of chambers configured to process a sample to perform a titration test in response to centrifugal force. The rotor also defines a plurality of capillaries configured to transfer the sample between the chambers in response to the centrifugal force. The interface is configured to couple to the rotor and to an analytical device that spins the rotor to provide the centrifugal force. A plurality of the chambers comprise titration chambers that hold different proportions of a titration reagent and the sample in response to the centrifugal force and wherein-at least one of the titration chambers indicates an event that corresponds to one of the proportions of the sample and the titration reagent.

Description:
RELATED CASES  
       [0001]     This patent application claims the benefit of provisional patent application 60/541,623, filed on Feb. 4, 2004, entitled “User-Configurable Analytical Rotor System”, and that is hereby incorporated by reference into this patent application. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The invention is related to the field of analytical rotors, and in particular, to analytical rotors that perform titration tests.  
         [0004]     2. Statement of the Problem  
         [0005]     An analytical rotor system performs a test on a sample. The test could be the detection of an analyte, such as the detection of a dissolved metal in a fresh water sample. The analytical rotor system includes a plastic disc-shaped rotor. The disc-shaped rotor includes a sample chamber in the center and capillaries and chambers that extend from the sample chamber towards the edge of the rotor.  
         [0006]     To perform the test, the sample is placed in the sample chamber in the center of the rotor, and the system spins the rotor to create centrifugal force. The centrifugal force transfers the sample from the central sample chamber through a capillary to a chamber that typically contains a reagent to interact with the sample. The spin may be accelerated, decelerated, stopped, and reversed to control sample flow through the rotor. Capillary action also draws the sample through the rotor. Thus, a combination of centrifugal force and capillary action transfers a precise amount of the sample to specific locations in the rotor for specific amounts of time.  
         [0007]     In a typical test, the sample is transferred from the central sample chamber to a reagent chamber that contains a reagent to interact with the sample. After the interaction, the sample is then transferred from the reagent chamber to an analytical chamber. A system transmitter transfers an analytical signal through the sample in the analytical chamber to a receiver. The test is completed by analyzing the received analytical signal.  
         [0008]     Current rotors are pre-configured for a single test or set of tests. This condition leads to a series of problems for users and suppliers alike.  
         [0009]     From the user&#39;s perspective, the user must locate and purchase a rotor that is pre-configured for the set of tests that they desire. In many cases, the user cannot locate a single rotor that can perform the entire set of tests that they desire. The user must then purchase multiple rotors. The need to purchase multiple rotors can increase the cost of the tests, especially when the multiple rotors include extra functionality that is paid for but not used.  
         [0010]     In addition, the use of multiple rotors adds unwanted complexity to the testing process. If three rotors are required to complete a desired set of tests, the first rotor is mounted on the analytical device, loaded with a sample, and spun to perform some of the tests. The first rotor is then removed from the analytical device, and the second rotor is mounted on the analytical device, loaded with the sample, and spun to perform some of the tests. The second rotor is then removed from the analytical device, and the third rotor is mounted on the analytical device, loaded with the sample, and spun to perform the rest of the tests.  
         [0011]     More time is required to use the three rotors in sequence than would be required if a single rotor were available to perform all of the tests. In addition to the increased testing time, the sample is handled multiple times to load each rotor. The repeated handling of the sample increases the risk of sample contamination and waste. The repeated loading of the sample may require more sample than is available.  
         [0012]     From the supplier&#39;s perspective, the supplier should minimize the undesirable need for multiple rotors. Thus, the supplier must anticipate the tests that users desire in a single rotor. If the supplier is wrong, then money and time are wasted to pre-configure a rotor that nobody wants. To offer a robust selection of different rotors that each perform a different set of tests, the supplier would have to maintain a rather large rotor inventory. Large inventories are expensive and undersirable for the supplier.  
         [0013]     Thus, current analytical rotor systems do not readily support unique or custom combinations of tests without designing and manufacturing unique and customized rotors. This situation causes problems for both the suppliers and the users of such systems.  
         [0014]     Current analytical rotor systems exhibit other problems. For example, some current analytical rotor systems have analytical chambers where an analytical signal passes through a processed sample. The analytical signal is then processed to characterize the sample. The size and orientation of the analytical chamber defines a distance that the analytical signal passes through the sample—referred to as the analytical signal path. Current analytical rotor systems do not have long enough analytical signal paths to properly perform some tests, such as tests for low concentrations of analytes. Thus, the small size of current analytical signal paths prevents or inhibits rotor systems from performing such tests.  
         [0015]     In addition, the central sample chamber that initially holds the sample and transfers the sample to the rotor may allow the sample to leak while the system is not spinning. Also, rotor technology has not been effectively applied to perform some tests in an automated fashion.  
       SUMMARY OF THE SOLUTION  
       [0016]     Examples of the invention include an analytical rotor system comprising a rotor and interface. The rotor defines a plurality of chambers configured to process a sample to perform a titration test in response to centrifugal force. The rotor also defines a plurality of capillaries configured to transfer the sample between the chambers in response to the centrifugal force. The interface is configured to couple to the rotor and to an analytical device that spins the rotor to provide the centrifugal force. A plurality of the chambers comprise titration chambers that hold different proportions of a titration reagent and the sample in response to the centrifugal force and wherein at least one of the titration chambers indicates an event that corresponds to one of the proportions of the sample and the titration reagent.  
         [0017]     Examples of the invention include a plurality of rotor blocks for selection by a user based tests of interest to the user, wherein an analytical device spins a rotor base to provide centrifugal force. The rotor blocks comprise first and second rotor blocks. The first rotor block is configured for user installation on the rotor base, and in response to the centrifugal force, to receive a first sample portion and perform a first one of the tests of interest to the user on the first sample portion. The second rotor block is configured for user installation on the rotor base, and in response to the centrifugal force, to receive a second sample portion and perform a second one of the tests of interest to the user on the second sample portion simultaneously with the first rotor block performing the first one of the tests. The first rotor block and the second rotor block are physically separate units from one another and from the rotor base. The first one of the tests comprises a titration test and wherein the first rotor block comprises a plurality of titration chambers that hold different proportions of a titration reagent and the sample in response to the centrifugal force. At least one of the titration chambers indicates an event that corresponds to one of the proportions of the sample and the titration reagent.  
         [0018]     Examples of the invention include a method of performing a titration test on a sample. The method comprises: identifying the titration test and the sample; based on the identity of the titration test and the sample, selecting a rotor block configured to perform the titration test on the sample; manually installing the rotor block on a rotor base, wherein the rotor based is mounted on an analytical device; loading the sample into the rotor base; and operating the analytical device to spin the rotor base to provide centrifugal force, wherein in response the centrifugal force; the rotor base transfers the sample to the rotor block, and wherein the rotor block comprises a plurality of titration chambers that hold different proportions of a titration reagent and the sample in response to the centrifugal force and wherein at least one of the titration chambers indicates an event that corresponds to one of the proportions of the sample and the titration reagent. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0019]      FIG. 1  illustrates a perspective view of a rotor base and a rotor block for an analytical rotor system in an example of the invention.  
         [0020]      FIG. 2  illustrates a top view of an analytical rotor system in an example of the invention.  
         [0021]      FIG. 3  illustrates a rotor block for an analytical rotor system in an example of the invention.  
         [0022]      FIG. 4  illustrates a set of rotor blocks for an analytical rotor system in an example of the invention.  
         [0023]      FIG. 5  illustrates a rotor block for an analytical rotor system in an example of the invention.  
         [0024]      FIG. 6  illustrates a rotor base sample chamber for an analytical rotor system in an example of the invention.  
         [0025]      FIG. 7  illustrates a rotor base sample chamber for an analytical rotor system in an example of the invention.  
         [0026]      FIG. 8  illustrates a rotor block to perform a titration for an analytical rotor system in an example of the invention.  
         [0027]      FIG. 9  illustrates a rotor block to perform a method of standard additions for an analytical rotor system in an example of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0028]      FIGS. 1-9  and the following description and Exhibits depict specific examples to teach those skilled in the art how to make and use the best mode of the invention. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these examples that fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. As a result, the invention is not limited to the specific examples described below, but only by the claims and their equivalents.  
         [0000]     Analytical Rotor System with Modular Rotor Blocks  
         [0029]      FIG. 1  illustrates a perspective view of rotor base  100  and rotor block  104  in an example of the invention. Rotor base  100  includes sample chamber  105  and flange  114 . Sample chamber  105  includes sample port  106  that protrudes from sample chamber  105 . Rotor base  100  and rotor block  104  may be comprised of clear plastic.  
         [0030]     Rotor base  100  and rotor block  104  are physically separate units. The user selects and manually installs rotor block  104  on rotor base  100 . Rotor block  104  is configured to perform a test or set of tests when a sample is loaded into sample chamber  105  and rotor base  100  spins. The user would typically select and install additional rotor blocks on rotor base  100  to perform additional tests at the same time, but the additional blocks are not shown on  FIG. 1  for clarity.  
         [0031]     When installed, rotor block  104  couples to a sample port on sample chamber  105  (this sample port is not shown but is like port  106 ). The sample port protrudes from sample chamber  105  through an orifice in rotor block  104 . Flange  114  engages the back and sides of rotor block  104  at the edge of rotor base  100 . Together, flange  114  and the sample port on sample chamber  105  provide a physical interface that secures rotor block  104  to rotor base  100  when rotor base  100  spins, but that also permits easy manual installation and de-installation of rotor block  104  by the user.  
         [0032]     When rotor base  100  spins, it is important to prevent rotor block from sliding off of base  100 . Flange  114  prevents such sliding. In addition, flange  114  prevents rotor block from sliding from side-to-side as the spin stops, starts, or reverses. It is also important to prevent rotor block  104  from tipping upward at the center of block  100  and flying off of base  100 . The protruding sample port (not shown) on sample chamber  105  fits into an orifice on rotor block  104  to prevent such tipping.  
         [0033]     Various alternative physical interfaces could also be used to secure rotor block  104  on spinning base  100 , while allowing easy manual installation by the user. Such alternates include posts extending from base  100  and corresponding holes in the bottom of block  104  or posts protruding from the bottom of block  104  and corresponding holes in block  100 . Instead of a male port on sample chamber  105  and an orifice on block  104 , sample chamber  105  could have the orifice, and block  104  could have the male port. Other physical interfaces that are suitable for securing block  104  to spinning base  100  include adhesive surfaces, Velcro, snaps, and straps. Those skilled in the art will appreciate other physical interfaces that are suitable for securing block  104  to spinning base  100 , but that also allow for easy manual installation and de-installation of block  104  by the user.  
         [0034]      FIG. 2  illustrates a top view of analytical rotor system  120  in an example of the invention. Analytical rotor system  120  includes analytical device  110 , rotor base  100 , and rotor blocks  101 - 104 . Rotor blocks  101 - 104  are each configured to perform a test or set of tests. Thus, the user selects rotor blocks  101 - 104  to perform the tests desired by the user, and manually installs the selected blocks on base  100 . The tests may be the repeated versions of the same test or may be different tests. The tests may be performed on different samples or different portions of the same sample.  
         [0035]     Rotor base  100  includes sample chamber  105  and raised flanges  111 - 114 . Rotor base  100  may include a physical interface that is similar to that used by conventional rotors for attachment to analytical device  110 . Thus, rotor base  100  may be manually installed on analytical device  110  in the same manner that a conventional disc-shaped rotor is manually installed on a conventional analytical device. For example, base  100  may have a pin the fits within a socket on analytical device  110 . Flanges  111 - 114  and protruding sample ports (not shown) secure rotors  101 - 104  to rotor base  100 .  
         [0036]     In operation, the user first selects the tests to perform. The user then selects the necessary rotor blocks (blocks  101 - 104  in this example) to perform the selected tests. The user then installs selected rotor blocks  101 - 104  on rotor base  100  and installs rotor base  100  on analytical device  110 . The user also loads the sample into sample chamber  105 . The user operates analytical device  110  to spin rotor base  100  to generate centrifugal force. The centrifugal force drives the sample from sample chamber  105  into rotor blocks  101 - 104 . The centrifugal force and capillary action force the sample through rotor blocks  101 - 104  to perform the various tests.  
         [0037]     Analytical device  110  carefully controls the spin of base  100 . This control is implemented through a spin profile that specifies when the base spins and when the base is still. For a given spin, the profile specifies the direction, speed, acceleration, deceleration, and duration of the spin. The spin control directs the propagation of the sample through the rotor blocks, including the precise amount of sample that is transferred and how long a transferred sample interacts with a reagent. Those skilled in the art are familiar with spin profiles and spin control.  
         [0038]     Analytical device  110  may use spectrophotometry, fluorescence, electrochemistry, titration, visual detection, kinetic assays, method of standard additions, and/or some other technique to test the sample. Those skilled in the art could adapt conventional analytical devices based on this disclosure to develop analytical device  110 . Abaxis, Inc. of California supplies such analytical devices.  
         [0039]      FIG. 3  illustrates rotor block  104  in an example of the invention. Rotor block  104  includes sample reception chamber  301 , sample overflow chamber  302 , reagent chambers  303  and  304 , analytical chamber  305 , and capillaries  306 - 308 . Rotor block  104  also contains vents that are not shown for clarity.  
         [0040]     In operation, centrifugal force generated by a spinning rotor base (not shown) drives the sample into sample reception chamber  301 . Excess sample overflows into sample overflow chamber  302 . The overflow mechanism loads sample reception chamber  301  with a precise amount of the sample. Using a combination of capillary action and centrifugal force, a precise amount of the sample in sample reception chamber  301  is delivered by capillary  306  to reagent chamber  303 . Reagent chamber  303  contains a reagent that interacts with the sample. After the desired interaction, capillary action and centrifugal force transfer a precise amount of the reacted sample in reagent chamber  303  through capillary  307  to reagent chamber  304 . Reagent chamber  304  also contains a reagent that interacts with the sample. After the desired interaction, capillary action and centrifugal force transfer a precise amount of the reacted sample in reagent chamber  304  through capillary  308  to analytical chamber  305 . The analytical device (not shown) may include a transmitter and receiver to transmit an analytical signal through analytical chamber  305  and receive the analytical signal after it passes through the reacted sample in analytical chamber  305 . Analytical device  110  processes the received analytical signal to complete the test.  
         [0041]     Other rotor block designs could also be used. Typically, rotor blocks would come in various different designs to support various different tests. Some rotor blocks may have no reagent chambers while other blocks may have multiple reagent chambers. Some rotor blocks may have chambers for buffers or diluents.  
         [0042]     On  FIG. 3 , chambers  303 - 305  and capillaries  306 - 308  form a process path from sample reception chamber  301  to the outer edge of block  104 . A rotor block may have multiple parallel process paths from sample reception chamber  301  to the outer edge of block  104 . These parallel paths may placed side-by-side or they may be stacked on top of one another. Multiple paths may merge together, or a single path could diverge into multiple paths.  
         [0043]     The design and manufacture of conventional disc-shaped rotors with chambers, capillaries, and vents to process a sample in the presence of centrifugal force is well known in the art. The same general techniques can be used to implement chambers, capillaries, and vents within the rotor blocks to process a sample in the presence of centrifugal force. One difference between modular rotor blocks and conventional disc-shaped rotors is that a conventional rotor is a single physically integrated unit, but a modular set of rotor blocks are not physically integrated together. Advantageously., the user may select and install the modular rotor blocks to easily customize their own analytical rotor.  
         [0044]      FIG. 4  illustrates a set  400  of rotor blocks  401 - 409  for an analytical rotor system in an example of the invention. Each rotor block is physically separate from the other rotor blocks. Thus, each rotor block is a discreet unit that may be selected and used independently of the other rotor blocks that may be selected and used. Rotor blocks  401 - 409  could be similar to rotor block  104  or could use some other design variation.  
         [0045]     Rotor block  401  is configured to perform test # 1  on sample # 1 . Rotor block  402  is configured to perform test # 2  on sample # 1 . Rotor block  403  is configured to perform test #N on sample # 1 . Thus, rotor blocks  401 - 403  perform three different tests on sample # 1 . Likewise, rotor block  404  is configured to perform test # 1  on sample # 2 . Rotor block  405  is configured to perform test # 2  on sample # 2 . Rotor block  406  is configured to perform test #N on sample # 2 . Thus, rotor blocks  404 - 406  provide multiple blocks for different tests on sample # 2 . Likewise, rotor block  407  is configured to perform test # 1  on sample #N. Rotor block  408  is configured to perform test # 2  on sample #N. Rotor block  409  is configured to perform test #N on sample #N. Thus, rotor blocks  407 - 409  provide multiple blocks for different tests on sample #N.  
         [0046]     It should be appreciated that set  400  provides a robust group of rotor blocks for user-selection based on the samples and tests of interest to the user. The various tests may be as simple as placing a specific amount of the sample in the analytical chamber without any reagent interaction, but the tests may also be relatively complex involving multiple reagent interactions with various reagents.  
         [0047]     The statement that a rotor block performs a test does not mean that the rotor block performs the entire test by itself. The rotor block typically requires the base-and analytical device to generate the centrifugal force, provide the sample, and possibly to transmit, receive, and process an analytical signal. In the context of the invention, a rotor block performs a test by performing at least a part of the test. Other components may perform other parts of the test as well.  
         [0048]     One example of a test is to determine the concentration of an analyte in a sample. Examples of these analytes include manganese, iron, nitrate/nitrite, and copper or some other substance. One example of a sample is a water sample, such as drinking water, fresh water, and sea water. Other tests include aliquating, enzyme-based tests, method of standard additions, and filtration. One example of an enzyme-based test is an Enzyme-Linked Immuno-Sorbent Assay (ELISA).  
         [0049]     Consider a situation where the user desires to test a water sample for concentrations of manganese, iron, nitrate/nitrite, and copper. In prior systems, the user would have had to locate a pre-configured disc-shaped rotor that handles all of these tests or purchase multiple such rotors and perform repeated tests. In contrast, the present system would allow the user to select a first rotor block that tests for manganese detection, a second rotor block that tests for iron detection, a third rotor block that tests for nitrate/nitrite detection, and a fourth rotor block that tests for copper detection. The user would easily install the selected rotor blocks on the rotor base, and perform all tests in a single pass without having to reload the sample or change rotors.  
         [0000]     Analytical Chambers with Longer Analytical Signal Paths  
         [0050]      FIG. 5  illustrates analytical rotor system  120  in an example of the invention. Analytical rotor system  120  includes rotor block  104  that is mounted on rotor base  100 , which is mounted on analytical device  110 . The view on  FIG. 5  is looking from the outside edge toward the center of base  100  and into the end of rotor block  104 . Flange  114  is omitted from  FIG. 5  for clarity. On  FIG. 5 , rotor block  104  includes analytical chambers  305  and  505 .  
         [0051]     In operation, analytical device  110  spins base  100  to process a sample, and eventually, the processed sample is loaded into analytical chamber  305 . Note that sample processing may include multiple reagent interactions or may simply load analytical chamber  305  with the appropriate amount of sample from sample reception chamber  301 . To test the sample in analytical chamber  305 , analytical device  110  spins base  100  to properly position analytical chamber  305  in line with the path of analytical signal  506 . Analytical device  110  then transfers analytical signal  506  through analytical chamber  305  where analytical signal  506  interacts with the sample. Analytical device  110  receives analytical signal  506  after it passes through analytical chamber  305 . Note that flange  114  (see  FIGS. 1-2 ) should be configured to avoid blocking analytical signal  506  as it enters and exits block  104 . Analytical device  110  processes received analytical signal  506  to finish the test. For example, analytical device  110  may process analytical signal  506  to determine the concentration of an analyte in the sample.  
         [0052]     The distance that analytical signal  506  traverses analytical chamber  305  is referred to as the analytical signal path. Note that this analytical signal path is parallel to base  100  and the spin plane, which are horizontal on  FIG. 5 . The length of the analytical signal path can be increased by widening block  104  and analytical chamber  305 . During the design phase, the length of the analytical signal path may be lengthened to support the desired test for the rotor block. For example, possible analytical signal path lengths could start at 1/16 of an inch with additional signal paths at 1/16 inch increments up to a total length of six inches.  
         [0053]     In prior systems, the orientation of the analytical signal path was perpendicular to base  100  and the spin plane. Thus, prior analytical signal paths are vertically oriented with the analytical signal having vertical propagation. This prior signal path could only be increased by increasing the height of the rotor—which has severe practical limitations because of size constraints, such as shipping and storage costs.  
         [0054]     Since the prior vertical analytical signal path is restricted in size, prior rotors are not suitable to determine a low concentration of certain analytes in the sample, because the analytical signal is not exposed to enough of the sample to detect the low concentration. Advantageously, the longer analytical signal path on  FIG. 5  exposes enough sample to analytical signal  506  to allow the analytical device  10  to detect a low concentration of an analyte in the sample.  
         [0055]     In addition, block  104  includes analytical chamber  505  directly below and parallel to analytical chamber  305 . To test a sample in analytical chamber  505 , analytical device  110  transfers analytical signal  507  through analytical chamber  505 , where analytical signal  507  interacts with the sample. Analytical device  110  receives analytical signal  507  after it passes through analytical chamber  505 . Analytical device  110  processes received analytical signal  507  to finish the test. Note that the analytical signal path for chamber  505  is also parallel to base  100  and the spin plane, and thus, provides the same benefits discussed above for chamber  305 .  
         [0056]     In some cases, centrifugal force and capillary action transfer some of the sample from sample overflow chamber  302  (See  FIG. 3 ) to analytical chamber  505 . Thus, an unprocessed portion of the sample can be placed in chamber  505  while a processed portion of the sample is placed in chamber  305 . Advantageously, the analysis of both processed and unprocessed samples may be carried out as described above for comparative purposes. Alternatively, chamber  505  may be loaded with a processed sample like chamber  305 , instead of loading the unprocessed sample.  
         [0057]     Note that  FIG. 5  shows block  104  as having two levels - an upper level having chamber  305  and a lower level having chamber  505 . Each level could have its own chambers and capillaries to support two separate tests on the sample. In addition, sample reception chamber  301  could be placed in the upper level, and sample overflow chamber  302  could be placed in the lower level below sample reception chamber  301 . The analytical signal path is described above with respect to a modular rotor block, but in some examples of the invention, the analytical signal path could also be implemented in an otherwise conventional disc-shaped rotor  
         [0000]     Rotor Base Sample Chambers  
         [0058]      FIG. 6  illustrates sample chamber  105  in an example of the invention. Sample chamber  105  includes sample port  106 , and sample chamber  105  typically includes other similar ports that are not shown for clarity. Sample chamber  105  is tapered, so the bottom is narrower than the top. Note that sample port  106  is located substantially at the top of sample chamber  105 . Sample chamber  105  has an upper barrier with a sample intake port where the user may load the sample into chamber  105 .  
         [0059]     While analytical device  110  is not operating, sample chamber  105  is at rest, and the loaded sample rests at fluid level # 1 . As analytical device  110  operates, sample chamber  105  spins, and the centrifugal force drives the sample to fluid level # 2 , where the sample egresses through sample port  106  to the rotor block. Advantageously, when sample chamber  105  is at rest and the sample is at fluid level # 1 , the sample cannot reach sample port  106 . The sample is provided to sample port  106  at fluid level # 2  only when the system is operating and sample chamber  105  spins. Thus, sample chamber  105  inhibits sample leakage through sample port  106  while analytical device  110  is not operating.  
         [0060]      FIG. 7  illustrates sample chamber  700  in an example of the invention. Sample chamber  700  could be integrated onto base  100  as an alternative to sample chamber  105 . Sample chamber  700  is separated into sample sections  701 - 708 . Sample sections  701 - 708  have respective sample ports  711 - 718 . The sample ports couple to respective rotor blocks when the rotor blocks are installed on base  100 . Sample sections  701 - 708  also have respective sample intakes  721 - 728 . Sample sections  711 - 708  are each configured to receive and dispense its own sample.  
         [0061]     In operation, the user selects the tests and samples of interest, and obtains the corresponding rotor blocks for the selected tests and samples. The user loads the samples into samples sections  701 - 708  and installs the selected rotor blocks to the appropriate sample ports on  711 - 718  When sample chamber  105  spins, sample chambers  701 - 708  dispense the samples to their respective rotor blocks through sample ports  711 - 718 .  
         [0062]     Advantageously, sample chamber  700  facilitates the simultaneous testing of multiple samples with multiple rotor blocks. For example, water samples from eight different locations may be taken and loaded into sample sections  701 - 708 . Eight rotor blocks could be loaded onto base  100 , where each rotor block is designed to determine the concentration of a metal in water. With a single test, the concentration of metal in water samples from eight different locations can be obtained. Eight sample sections are shown on  FIG. 6 , but the number could be increased or decreased as desired. In addition, each sample section could incorporate the tapered design and port location of  FIG. 6  to inhibit sample leakage when sample chamber  700  is at rest.  
         [0063]     In the examples of  FIGS. 6-7 , sample chambers  105  and  700  may be pre-loaded with a substance to interact with the sample prior to transfer to the rotor block. The substance could perform oxidation acid digestion, pH/ ionic strength adjustment, precipitation, or some other operation on the sample. The substances could include a buffer, a masking agent, or some other treatment for the sample. Since these substances may corrode plastic, sample chambers  105  and  700  may be internally lined with glass, ceramic, or some other non-corrosive material. The sample chamber is described above with respect to a modular rotor block, but in some examples of the invention, the sample chamber could also be implemented in an otherwise conventional disc-shaped rotor  
         [0000]     Titration Rotor Block  
         [0064]      FIG. 8  illustrates a titration rotor block  800  in an example of the invention. Rotor block  800  is typically comprised of clear plastic. Rotor block  800  includes sample reception chamber  801 , sample overflow chamber  802 , reagent chambers  803 - 804 , titration chambers  811 - 815 , and capillaries  806 - 808 . Rotor block  800  would also include vents that are not shown for clarity. Rotor block  800  would be selected by the user and mounted on base  100  to facilitate a titration test on a sample of interest to the user.  
         [0065]     In operation, the centrifugal force drives the sample into sample reception chamber  801 . The combination of capillary action and centrifugal force transfer a precise amount of the sample from sample reception chamber  801  to reagent chamber  803  through capillary  806 . Reagent chamber  803  contains a reagent that interacts with the sample. After the desired interaction, capillary action and centrifugal force transfer a precise amount of the reacted sample in reagent chamber  803  through capillary  807  to reagent chamber  804 . Reagent chamber  804  also contains a reagent that interacts with the sample. After the desired interaction, capillary action and centrifugal force transfer precise amounts of the reacted sample in reagent chamber  804  through capillary  808  to titration chambers  811 - 815 . In various alternatives, there may not be any reagent chambers (chamber  801  would directly feed chambers  811 - 815 ), one reagent chamber, or there may be more than two reagent chambers.  
         [0066]     Titration chambers  811 - 815  each contain a titration reagent, so when the sample is loaded into titration chambers  811 - 815 , titration chambers  811 - 815  each contain a different proportion of sample and titration reagent. In a titration, an event such as a color change is looked for to identify the respective proportion of sample and titration reagent that caused the event. Thus, the titration chamber that exhibits the event identifies this proportion. For example, the smallest chamber that changes color can indicate the proportion of interest.  
         [0067]     To obtain the different proportions of sample and titration reagent in titration chambers  811 - 815 , the same amount of a titration reagent could be loaded into titration chambers  811 - 815 , and each titration chamber would receive a different amount of the processed sample, possibly based on the different sizes of titration chambers  811 - 815 . Alternatively, different amounts of titration reagent could be placed in titration chambers  811 - 815 , and each titration chamber would receive the same amount of the processed sample. The titration testing is described above with respect to a modular rotor block, but in some examples of the invention, the titration testing could also be implemented in an otherwise conventional disc-shaped rotor  
         [0000]     Method of Standard Additions Rotor Block  
         [0068]      FIG. 9  illustrates a Method of Standard Additions (MSA) rotor block  900  in an example of the invention. For clarity,  FIG. 9  does not attempt to depict the physical characteristics of the chambers and capillaries as such are depicted for the examples described above. Rotor block  900  is typically comprised of clear plastic. Rotor block  900  includes sample volumes  901 - 903 , sample overflow  904 , chambers  911 - 913 ,  921 - 923 ,  931 - 933 , and  941 - 943 , and capillaries  905 - 907 ,  915 - 917 ,  925 - 927 , and  935 - 937 . Rotor block  900  would also include vents that are not shown for clarity. Rotor block  900  would be selected by the user and mounted on base  100  to facilitate an MSA test on a sample of interest to the user.  
         [0069]     In operation, the centrifugal force drives the sample from the sample chamber on base  100  (not shown) into sample volume  901 . When sample volume  901  is full, sample overflows into sample volume  902 . When sample volume  902  is full, sample overflows into sample volume  903 . When sample volume  903  is full, sample overflows into sample overflow  904 . Thus, sample volumes  901 - 903  each contain a precise amount of the sample as defined by the overflow mechanism.  
         [0070]     The combination of capillary action and centrifugal force transfer a precise amount of the sample from sample volumes  901 - 903  to respective chambers  911 - 913  through respective capillaries  905 - 907 . In some examples, capillaries  905 - 907  have a restricted size to prevent sample flow from sample volumes  901 - 903  until the spin speed reaches a relatively high threshold. Other capillary designs could also be used.  
         [0071]     Chambers  912 - 913  are each pre-loaded with a standard. The standard is typically the analyte of interest. The user may add the standard to chambers  912 - 913 , but alternatively, block  900  may be configured so chambers  912 - 913  are pre-loaded with the standard for the user. In this example, chamber  913  has twice the standard of chamber  912 , and chamber  911  has no standard and only receives the sample. Thus, chamber  911  includes just the sample with some unknown concentration of this analyte. Chamber  912  also includes a portion of the same sample, but this portion of the sample is spiked by the standard to include a higher concentration of the analyte. Chamber  913  also includes a portion of the same sample, and this portion is spiked by the standard to include an even higher concentration of the analyte. Advantageously, the final results may be assessed in light of the standard additions to ensure quality, since a quality result should reflect the spiking that occurs in chambers. For example, quality test results should indicate that chamber  943  has the highest concentration, and chamber  941  has the lowest concentration.  
         [0072]     After standard addition, centrifugal force and capillary action drive the sample from chambers  911 - 913  to respective reagent chambers  921 - 923  through respective capillaries  915 - 917 . Reagent chambers  921 - 923  each contain a reagent to react with the sample. After the reaction, centrifugal force and capillary action drive the sample from chambers  921 - 923  to respective reagent chambers  931 - 933  through respective capillaries  925 - 927 . Reagent chambers  931 - 933  each contain a reagent to react with the sample. After the reaction, centrifugal force and capillary action drive sample from chambers  931 - 933  to respective analytical chambers  941 - 943  through respective capillaries  935 - 937 .  
         [0073]     In some examples, analytical chambers  941 - 943  are vertically stacked in the manner of chambers  305  and  505  on  FIG. 5 , except that there are three stacked chambers in this example as opposed to two stacked chambers in  FIG. 5 . The stacked chambers  941 - 943  provide the beneficial longer analytical signal paths described with respect to  FIG. 5 . Alternatively, analytical chambers could be on the same plane and separated in a radial fashion near the edge of block  900 .  
         [0074]     Analytical device  110  (not shown) transfers analytical signals through respective analytical chambers  941 - 943 , and then receives and processes the analytical signals to determine the concentration of the analyte in the sample. The results should reflect the standard additions, and if they do, the test is validated, and the concentration of the analyte in the sample within chamber  941  (no standard addition) can be trusted with confidence.  
         [0075]     Note that this example may also be varied. There could be one or many process paths that perform standard additions. There could be more stages that add standard. There could be no reagent stages, one reagent stage, or many reagent stages. The three process paths could be horizontally spread across the block or vertically stacked within the block. The three process paths may be separated on three separate blocks. For example, a first block could have no standard addition, a second block could have a 1× standard addition, and a third block could have a 2× standard addition. All three blocks could be mounted on the same base to perform the test at the same time with a shared central sample chamber on the base. Those skilled in the art will appreciate other variations.  
         [0076]     In addition, the same general block design could be used to carry out a spike-recovery assay. The MSA testing is described above with respect to a modular rotor block, but in some examples of the invention, the MSA testing could also be implemented in an otherwise conventional disc-shaped rotor.  
         [0000]     Filtration Rotor Block  
         [0077]     A rotor block could perform filtration. The filtration could be performed by allowing centrifugal force to separate a substance in a chamber, and by providing an orifice or capillary at the point in the chamber that has the filtered portion of the substance. For example, a water sample could be introduced into a chamber, and centrifugal force could drive sediment in the water to the end of the chamber away from the center of the block. The water near the other end of the chamber toward the center of the block would then be sediment- free, and a capillary or orifice near this point could receive the filtered water. Alternatively, a filtration membrane could be placed across a chamber, so that centrifugal force would drive the substance through the membrane to filter the substance. For example, a membrane with pores of a given diameter could be used to filter particles from a sample that are larger than the pores. The sample filtration is described above with respect to a modular rotor block, but in some examples of the invention, the sample filtration could also be implemented in an otherwise conventional disc-shaped rotor