From: michalp717@gmail.com   
      
   I'm working on detecting a particular metal ion using fluorescent dyes in   
   conjunction with absorbance and emission spectroscopy, and I need to test the   
   chosen dye over a range of pH values (i.e. 10-14). I first create the dye   
   solution in a beaker and    
   adjust its pH using NaOH (lets say one dye solution at 12.5 and one at 13.0),   
   then I add 1.9 mL of this to a cuvette along with 0.1 mL of a metal ion in   
   acid solution. However, the cuvette's pH always drops to the same value   
   (typically 12.3) once I add    
   my 0.1 mL metal ion in acid solution. I'm assuming this is because pH is   
   logarithmic, to reiterate the proportions are 1.9 mL of the dye solution to   
   0.1 mL of the metal ion in acid solution.    
      
   Any suggestions on resolving this? I cannot titrate a solution in a small, 2.5   
   mL cuvette. I've considered using a buffer from what I've read but I do not   
   know how to select one, or if they affect absorbance/emission data.    
      
   I do not have a background in chemistry but I've been on this project and am   
   now hitting a brick wall. Any advice or guidance is much appreciated.   
      
   Thanks   
      
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