Method for authentication of an item

This invention relates to a method to authenticate an item comprising:combining a chelated compound with the item and thereafter detecting the presence of the chelated compound, wherein the chelated compound is present at 10 ppb to 5000 ppm and is the result of the combination of a lanthanide metal halide compound with a macrocycle compound comprising at least one pyridine moiety.

EXAMPLE 1 Five moles of terbium trichloride were combined with 5 moles of 3 in 10 ml of tetrahydrofuran. Two drops (about 10 &mgr; liters) of the solution were then painted onto a five dollar bill. The bill was allowed to dry and then placed under an ultraviolet light source. The painted area fluoresced brightly. 
 EXAMPLE 2 Five moles of samarium trichloride is combined with 5 moles of 4 in 10 ml of tetrahydrofuran. Two drops (about 10 &mgr; liters) of the solution is then painted onto a five dollar bill. The bill is allowed to dry and then placed under a heat lamp or sufficient electrical current is applied and the responsive infrared emission is measured with a calorimeter or spectrometer. The painted area exhibits an infrared response. 
 EXAMPLE 3 Five moles of gadolinium trichloride is combined with 5 moles of 5 in 10 ml of tetrahydrofuran. Two drops (about 10 &mgr; liters) of the solution is then painted onto a five dollar bill. The bill is allowed to dry and then placed under a Teslameter with an electric current applied across either end of the painted area. The painted area shows a magnetic response.