Determining the presence or amount of a metal-labelled species

1. A method for determining the presence or amount of a silver-labelled species in a sample, the method comprising:

applying the sample to a test device in a dry state, the test device comprising dried reagents;

causing the metal of the silver-labelled species in the sample to form a soluble electrochemically-active complex which is stable relative to moieties present or potentially present in the sample which moieties will form an insoluble and/or electrochemically-inactive complex with the silver, wherein the electrochemically-active complex is formed by oxidising the silver to form a silver ion and reacting the silver ion with a complexing agent according to the following reaction: Ag + +m(NH4) + +n(SCN) − →[Ag(NH4) + m(SCN − )n] m-n+1 ; and

electrochemically measuring the formed complex to provide an indication of the presence or amount of the silver-labelled species.

2. A method as claimed in claim 1 , wherein the metal label is particulate.

3. A method as claimed in claim 1 , wherein measurement of the electrochemically active complex is carried out by anodic stripping voltammetry.

4. A method as claimed in claim 1 , wherein the metal-labelled species is formed by the binding of an analyte to be detected with a metal-labelled binding partner.

5. A method as claimed in claim 1 , wherein the metal-labelled binding partner is an antibody or antigen binding fragment thereof.

6. A method as claimed in claim 1 , wherein the sample is a biological sample.