Systems and methods for generating fluid samples having select concentration of particles

Abstract

Instruments and processes according to the invention provide for the preparation of a fluid sample that has a substantially known concentration of a select particulate matter. In one aspect, the invention is understood as laboratory instruments for sample preparation. These instruments can include a filter that is submersible within a fluid suspension of particulate matter. To collect particulate matter from the fluid suspension, the instruments can cause a fluid flow that pulls fluid across the filter to trap particulate matter against one surface of the filter. The instruments can then remove the filter from the fluid suspension and dispose the filter above a collection vessel such that the side of the filter that is carrying particulate matter is positioned above the opening of the collection vessel. The laboratory instruments can then send a collection fluid through the filter in a direction opposite to the original fluid flow, thereby washing the particulate matter off the filter and into the collection vessel. The laboratory instruments according to the invention can provide samples having a known concentration by passing a known volume of collection fluid through the filter, thereby trapping the collected particulate matter within a known volume of collection fluid.

What is claimed is:  
     
         1 . A method for collecting a fluid sample having a select concentration of particles, comprising the steps of 
 providing a fluid suspension of dispersed particles,    disposing a filter having a first side and a second side within said fluid suspension and flowing said fluid suspension across said filter from said first side to said second side such that a substantially known quantity of particles collect onto said first side of said filter,    removing said filter and said particles collected thereon from said fluid suspension, and    passing a known volume of collection fluid through said filter, to remove substantially said particles collected on said first side, and to collect said particles within said known volume of collection fluid.    
     
     
         2 . A method according to  claim 1  wherein said step of disposing a filter includes the step of 
 providing a particle collection device having an intake port and an evacuation port and having said filter spanning said intake port.  
 
     
     
         3 . A method according to  claim 2  wherein said step of flowing said fluid includes the step of 
 evacuating said particle collection device to draw fluid across said filter and through said intake port and into said collection device.  
 
     
     
         4 . A method according to  claim 1  wherein said step of passing a known quantity of collection fluid through said filter includes the step of 
 applying a select fluid pressure within said collection device to force fluid collected therein back across said filter.  
 
     
     
         5 . A method according to  claim 4  wherein said step of passing a known volume of collection fluid through said filter includes the step of 
 disposing said filter collection device at a select angle and to generate thereby a drip of said collection fluid having said particles collected therein.  
 
     
     
         6 . A method according to  claim 1  comprising the further step of 
 selecting a filter having a pore size adapted for collecting particles of a predetermined size.  
 
     
     
         7 . A method according to  claim 1  including the further step of 
 lysing said collected particles.  
 
     
     
         8 . A method according to  claim 1  comprising the further step of 
 providing a portion of said collected particles in said known volume of collection fluid as a sample for a diagnostic assay.  
 
     
     
         9 . A method according to  claim 1  wherein said step of flowing said fluid suspension includes the step of 
 measuring a characteristic representative of the quantity of particles collected against said filter.  
 
     
     
         10 . A method according to  claim 9  including the further step of 
 interrupting said step of flowing said fluid suspension responsive to a measured characteristic representative of a pre-selected quantity of particles.  
 
     
     
         11 . A method according to  claim 1  wherein said step of flowing said fluid suspension includes the further step of 
 applying a known pressure to said fluid suspension.  
 
     
     
         12 . A method according to  claim 1  wherein said step of flowing said fluid suspension includes the further step of 
 applying a succession of known pressures to said fluid suspension.  
 
     
     
         13 . A method according to  claim 11  wherein said step of flowing said fluid suspension includes the further step of 
 measuring a characteristic representative of a rate of change of pressure.  
 
     
     
         14 . A method according to  claim 1  wherein said step of providing a fluid suspension of dispersed cells includes the step of 
 providing said collected particles within said known volume of fluid, for incrementally increasing the concentration of said particles within said known volume of fluid.  
 
     
     
         15 . A method according to  claim 1  wherein said step of providing a fluid suspension of dispersed cells comprises the further steps of 
 actuating a fluid having a sample material disposed therein.  
 
     
     
         16 . Apparatus for reproducibly collecting a sample having a select concentration, comprising 
 a filter having a first side and a second side and being submersible within a fluid that contains a quantity of particles,    a source of fluid pressure coupled to a pressure monitor for providing a flow of said fluid across said filter from said first side to said second side such that a substantially known quantity of particles collect onto said first side of said filter,    an actuator for removing said filter and said particles collected thereon from said fluid suspension, and    a source of fluid having volumetric control for passing a known volume of collection fluid through said filter, to remove substantially said particles collected on said first side, and to collect said particles within said known volume of collection fluid.    
     
     
         17 . A method for determining a concentration of a fluid sample, comprising the steps of 
 providing a fluid suspension of dispersed particles to a particle collection element,    generating a flow of said fluid suspension into said particle collection element,    measuring a flow characteristic of said flow of fluid suspension being representative of a quantity of said dispersed particles,    determining a volume of said fluid flow having flowed to said particle collection element, and    determining, as a function of said flow characteristic and said volume, said concentration of dispersed particles within said fluid sample.    
     
     
         18 . A method according to  claim 17  wherein said step of generating said flow of said fluid suspension includes the step of 
 flowing substantially all of said fluid sample to said particle collection element, to collect substantially all of said disposed particles from said fluid sample.  
 
     
     
         19 . A method according to  claim 18  including the further step of 
 removing said collected dispersed particles from said fluid sample.  
 
     
     
         20 . A method according to  claim 19  including the further step of 
 testing said fluid sample to detect a presence of said dispersed particles within said fluid sample.  
 
     
     
         21 . A method according to  claim 17  wherein said step generating said flow of said fluid suspension includes the step of 
 generating a flow of a known volume of said fluid suspension.  
 
     
     
         22 . A method according to  claim 21  wherein said step of determining a volume of said fluid flow having passed to said particle collection element includes the step of 
 recording said known volume of said fluid suspension.  
 
     
     
         23 . A method according to  claim 17  including the further step of 
 comparing said concentration to a threshold value representative of a threshold concentration for achieving a valid test of said fluid sample.  
 
     
     
         24 . A method according to  claim 17  where said step of measuring a flow characteristic includes the step of 
 measuring a rate of flow of said fluid suspension.