Cleaning of system for dispensing of liquid droplets

Abstract

There is provided a method of cleaning a dispensing assembly for small liquid droplets less than 50 μl and even as low as 10 nl. A purging step with pressurised gas followed by a cleaning step using a suitable cleaning liquid is carried out a number of times.

1 . A method of cleaning a dispensing assembly for small liquid droplets of up to 50 μl in volume, portion of which dispenser is contaminable by liquid used in the dispenser, the method comprising: 
 a purging step of delivering pressurised purging gas through the contaminable portion to expel liquid and fill with the purging gas; and    a cleaning step of delivering pressurised cleaning liquid through the contaminable portion to flush it.    
   
   
       2 . A method as claimed in  claim 1 , in which the purging step is carried out before the cleaning step.  
   
   
       3 . A method as claimed in  claim 1 , in which the final step carried out is a purging step.  
   
   
       4 . A method as claimed in  claim 1 , in which the first and last steps are purging steps.  
   
   
       5 . A method as claimed in  claim 1 , in which during the cleaning step, the flow of liquid is switched on and off to provide pulsed flow.  
   
   
       6 . A method as claimed in  claim 1 , in which during the cleaning step, the flow of purging gas is switched on and off to provide pulsed flow.  
   
   
       7 . A method as claimed in  claim 1 , in which during both the purging and cleaning steps, the flow is switched on and off to provide pulsed flow.  
   
   
       8 . A method as claimed in  claim 1 , in which at least one of the purging and cleaning steps is repeated.  
   
   
       9 . A method as claimed in  claim 1 , in which the purging and cleaning steps are carried out alternately at least twice.  
   
   
       10 . A method as claimed in  claim 1  in which an initial evacuation step is carried out.  
   
   
       11 . A method as claimed in  claim 1 , in which the purging gas is one of air, helium, nitrogen and carbon dioxide.  
   
   
       12 . A method of cleaning a dispensing assembly for small liquid droplets of 100 μl or less, portion of which dispenser is contaminable by liquid used during dispensing, the method comprising: 
 a purging step comprising delivering intermittently pressurised purging gas in a pulsed flow through the contaminable portion to expel liquid; and    a following cleaning step comprising delivering intermittently pressurised cleaning liquid in a pulsed flow through the contaminable portion to flush it.    
   
   
       13 . A method as claimed in  claim 12 , in which the final step carried out is a purging step.  
   
   
       14 . A method as claimed in  claim 12 , in which the purging and cleaning steps are carried out at least four times.  
   
   
       15 . A method as claimed in  claim 12  in which the purging gas is one of air, helium, nitrogen and carbon dioxide.  
   
   
       16 . A method as claimed in  claim 12  in which an initial evacuation step is carried out.  
   
   
       17 . A method of cleaning a dispensing assembly for small liquid droplets of 10 μl or less, portion of which dispenser is contaminable by liquid used during dispensing, the method comprising a purging step of delivering gas through the contaminable portion to expel liquid and fill with the purging gas followed by a cleaning step of delivering pressurised cleaning liquid through the contaminable portion to flush it, the steps being repeated at least four times.  
   
   
       18 . A method as claimed in  claim 17 , in which the final step carried out is a purging step.  
   
   
       19 . A method as claimed in  claim 17 , in which the first and last steps are purging steps.  
   
   
       20 . A method as claimed in  claim 17 , in which during the cleaning step, the flow of liquid is switched on and off to provide pulsed flow.  
   
   
       21 . A method as claimed in  claim 17 , in which during the cleaning step, the flow of purging gas is switched on and off to provide pulsed flow.  
   
   
       22 . A method as claimed in  claim 17  in which an initial evacuation step is carried out.