Gold-coated capillary based 2,4-dichlorophenoxyacetic acid chemi-luminescent assays: possibilities towards multianalysis.

The application of gold-coated glass capillaries for the design of a sensitive chemiluminescent immunoassay for 2,4-dichlorophenoxyacetic acid (2,4-D) is reported. The gold coating on the glass capillaries has been partially characterized and its effect on enhancing the signal intensity has been measured. A simple photo-multiplier tube-based photon detector is used for this purpose. At least three times improvement in the signal intensity is observed compared to uncoated glass capillaries, with a consequent improvement in the sensitivity of detection. Using such gold-coated glass capillaries, 2,4-D in the range 10−9 to 10−13 mol/l is detectable at a precision of ±15% (CV%) and a limit of detection of 10−15 mol/l is achievable. The possibility of using such gold-coated capillaries with a portable multianalytical set-up for field studies is also demonstrated.