Spectrofluorimetric determination of magnesium (II) with 7-(8-hydroxy-3, 6-disulfonaphthylazo)-8-hydroxyquinoline-5-sulfonic acid

A new fluorescent reagent, 7-(8-hydroxy-3, 6-disulfonaphthylazo)-8-hydroxyquinoline-5-sulfonic acid (HDNHQ) for the determination of magnesium has been developed. It reacted with magnesium to form a 1 : 1 fluorescent complex with λex/λem = 356/495 nm immediately at room temperature in ammonia-ammonium chloride buffer (pH 10.7). A linear relationship was obtained in the magnesium concentration range of 0-160 ng · mL-1 with the detection limit of 0.04 ng · mL-1. The proposed method was simple, rapid and sensitive. It has been successfully applied to the determination of trace magnesium in blood serum with recoveries of 103.75% and 98.16%, respectively.