Smartphone-Assisted Fluorescence Determination of Inorganic Phosphorus Using a Samarium Metal–Organic Framework

Inorganic phosphori are widely used in food, whose quantitative detection method is of significance. This work presents a Sm-DDB (H4DDB = 1,3-di(3′,5′-dicarboxylphenyl)benzene), which acts as a ratiometric fluorescence sensor to monitor PO43–, H2PO4–, and (PO3)66– with high sensitivity. The determination factors of pH, MOF dosage, and fluorescence response time are optimized as 7.35, 1 mg, and 2 min, respectively. The sensitivity tests show the linear fitting equations of I465/I598 = 0.00363·CP + 1.49183 (I465 and I598: the emission intensities at 465 and 598 nm; Cp = inorganic phosphorus concentration) for PO43–, I465/I598 = 0.00272·CP + 1.55944 for H2PO4–, and I465/I598 = 0.00957·CP + 1.55122 for (PO3)66– with LODs being 1.00 μM for PO43–, 1.33 μM for H2PO4–, and 0.38 μM for (PO3)66–. The detection method was applied in frozen shrimp, marine fish, and bacon, whose fluorescence recoveries of around 100% demonstrate its reliability. The analytical results are close to those determined by the phosphomolybdenum blue method. The Sm-DDB test paper shows an obvious emission color change, whose blue/red (B/R) values can be recognized by a smartphone APP. This work provides a smartphone-assisted visualization detection method for PO43–, H2PO4–, and (PO3)66–.