Combined titration and pH electrode for the preparation of liquid samples in particular for NMR spectroscopy

Abstract

An electrode rod ( 1;21 ) for a pH meter, comprising a measuring end ( 2; 22 ) for immersion into a liquid test sample ( 31 ), wherein the measuring end ( 2; 22 ) has a pH measuring element, and wherein electrical feed lines ( 5 ) in the electrode rod ( 1;21 ) extend towards the pH measuring element, is characterized in that at least one capillary ( 8, 9, 10; 23 ) for feeding a liquid into the test sample ( 31 ) extends in the electrode rod ( 1; 21 ), and the at least one capillary ( 8, 9, 10; 23 ) has an outlet opening ( 11, 12, 13; 24 ) in the area of the measuring end ( 2; 22 ). The inventive electrode rod facilitates and accelerates preparation of liquid test samples, in particular, adjustment of a pH value for small amounts of test samples or narrow sample containers.

1 . An electrode rod for a pH meter, the electrode rod for immersion into a liquid test sample, the rod comprising: 
 a measuring end for immersion into the liquid sample;    a pH measuring element disposed in said measuring end;    electrical feed lines extending in the electrode rod to said pH measuring element; and    at least one capillary extending within the electrode rod for feeding a fluid into the sample, said capillary having an outlet opening proximate said measuring end.    
   
   
       2 . The electrode rod of  claim 1 , wherein several,  2 ,  3 , or  4  capillaries are provided in the electrode rod, each having an outlet opening in an area of said measuring end.  
   
   
       3 . The electrode rod of  claim 1 , wherein said capillary is made from glass, quartz glass of high purity, “fused silica”, metal, stainless steel, plastic material, PTFE (polytetrafuoroethylene), or PEEK (polyetheretherketone).  
   
   
       4 . The electrode rod of  claim 1 , wherein said pH measuring element has a sensor chip or an ISFET (ion sensitive field effect transistor) and a reference electrode.  
   
   
       5 . The electrode rod of  claim 1 , further comprising a temperature sensor disposed in an area of said measuring end.  
   
   
       6 . The electrode rod of  claim 1 , wherein the electrode rod has an outer diameter of between 2 mm and 7 mm in an area of said measuring end.  
   
   
       7 . The electrode rod of  claim 1 , wherein said capillary has an inner diameter of between 50 μm and 500 μm.  
   
   
       8 . The electrode rod of  claim 1 , wherein said measuring end is pointed or bevelled.  
   
   
       9 . The electrode rod of  claim 1 , wherein an outlet opening of a lower capillary is closer to an end of the electrode rod than said pH measuring element.  
   
   
       10 . The electrode rod of  claim 9 , wherein outlet openings of other capillaries are further away from an end of the electrode rod than said outlet opening of said lower capillary.  
   
   
       11 . Use of the electrode of  claim 1  for adjusting a pH value of a liquid test sample, wherein a titration liquid is supplied through said at least one capillary.  
   
   
       12 . The use of  claim 11 , wherein an acid is supplied through a first capillary and a base is supplied through a second capillary.  
   
   
       13 . The use of  claim 12 , wherein a gas, an inert gas, nitrogen, a noble gas, or air is supplied through a third capillary or through a lower capillary.  
   
   
       14 . The use of  claim 12 , wherein a buffer solution is supplied through a fourth capillary.  
   
   
       15 . A titration unit having the electrode rod of  claim 2 , the titration unit further comprising: 
 a pH meter connected to said pH measuring unit;    an acid reservoir;    an acid pump connected to said acid reservoir to pass acid to one of said capillary outlet openings;    a base reservoir;    a base pump connected to said base reservoir to pass base to an other one of said capillary outlet openings; and    means for controlling said acid pump and said base pump to supply defined amounts of acid and base to the sample.    
   
   
       16 . The titration unit of  claim 15 , wherein said controlling means is designed to automatically, iteratively adjust a pH value of the liquid test sample.  
   
   
       17 . The titration unit of  claim 15 , further comprising a gas pump to supply gas through a capillary or through a lower capillary, wherein said controlling means drives said gas pump in such a manner that gas can be supplied during and/or after supplying acid and/or base.  
   
   
       18 . The titration unit of  claim 15 , further comprising a buffer reservoir and a buffer pump for supplying buffer solution from said buffer reservoir through a capillary.