Researchers in the US have developed a semi-automated method to generate ions for calibration-free titrations.  

Eric Bakker at Purdue University, Indiana, and colleagues have used an ion-selective polymeric membrane (usually used to detect ions) to generate ions.  The researchers say that applying a pulse of current across the membrane causes a defined amount of ions to be released.

The released ions were then detected by a similar polymer-electrode. The researchers showed that the system could be used for various types of electrochemical titrations and is capable of nanomolar detection limits. 

The researchers say that with some adaptation, the method could be used to electro-release a range of ions, and might prove to be more practical than existing reagent delivery systems.  In particular, it may make traditional chemical titrations redundant, since stock solutions would no longer be needed and small sample sizes would not be a problem, said Bakker.

According to Bakker, the system could be used to develop a miniature, calibration-free titration device. This could be used in medical applications including generating and detecting metal ions such as magnesium, and human nuclear proteins such as heparin (important for blood clotting).

Frank Davies, a specialist in bioelectrochemistry at Cranfield University said the ion release method could be very useful in electrochemical titrations. 'This technique could prove of interest due to its inherent lack of the need for calibration,' said Davies.

Emma Lawrence