Novel miniaturized sensors for potentiometric batch and flow-injection analysis (FIA) of perchlorate in fireworks and propellants

Three planar miniaturized perchlorate membrane sensors (3×5 mm2) are prepared using a flexible Kaptan substrate coated with nitron-perchlorate (NT-ClO4) [sensor 1], methylene blue-perchlorate (MB-ClO4) [sensor II] and indium-porphyrin (In-Por) [sensor III] as electroactive materials in PVC membranes plasticized with 2-NPPE. Sensors I, II and III display near-Nernstian response for 1.0×10−5–1.0×10−2, 3.1×10−5–1.0×10−2 and 3.1×10−6–1.0×10−2 mol L−1 ClO 4 − with lower detection limits of 6.1×10−6, 6.9×10−6 and 1.2×10−6 mol L−1, and anionic calibration slopes of 50.9±0.4, 48.4±0.4 and 57.7±0.3 mV decade−1, respectively. Methods for determining perchlorate using these sensors offer many attractive advantages including simplicity, flexibility, cost effectiveness, wide linear dynamic response range (0.1–1000 ppm), low detection limit (<1.2×10−6 mol L−1≡0.1 ppm), small sample test volume (100 μL), safety, short response time (<20 s), long life span (~8 weeks), and extended wide working pH range (4.5–8.0). The sensors show high selectivity in the presence of some inorganic ions (e.g., PO 4 3 − , SO 4 2 − , S 2 O 3 2 − , NO 2 − , NO 3 − , N 3 − , CN−, Cl−, Br−, I−) and automation feasibility. Indium-porphyrin based membrane sensor (sensor III) is used as a detector in a wall-jet flow injection set-up to enable accurate flow injection analysis (FIA) of perchlorate in some fireworks without interferences from the associated reducing agents (sulfur and charcoal), binders (dextrin, lactose), coloring agents (calcium, strontium, copper, iron, sodium), color brighten (linseed oil) and regulators (aluminum flakes) which are commonly used in the formulations. The sensor is also used for perchlorate assessment in some propellant powders. The results fairly agree with data obtained by ion-chromatography.