A chemometrically validated, field-portable wet-chemical protocol for rapid triage of 15 white powder substances

Reliable field identification of unknown white powder substances is a persistent analytical challenge in security screening, forensic science, and environmental emergency response. We report an eight-step sequential chemical protocol that generates fourteen orthogonal descriptors for the rapid, kit-based, instrument-free triage of fifteen common white powder substances spanning organic materials (wheat flour, starch, sucrose, urea, monosodium glutamate, baking powder) and inorganic compounds (NaCl, alum, (NH₄)₂SO₄, CaCO₃, Na₂CO₃, Ca(OH)₂, NaOH, bleaching powder, CaC₂). The protocol operates within a compact portable kit (30 × 20 × 10 cm; <50 USD) and completes identification within 15-20 min without electricity or specialised instrumentation. Principal component analysis (PCA) resolved all fifteen substances into four chemically coherent clusters, capturing 63.5% of total variance in two components. The fifteen substances yield fifteen distinct descriptor profiles that a transparent decision rule separates without overlap under the controlled conditions examined. The transparent decision rule resolves all fifteen substances using nine of the fourteen descriptors, and feature-importance analysis identifies aqueous pH (step 3) as the dominant discriminator. The protocol provides a low-cost analytical workflow with strong potential for field triage, demonstrated on a representative panel of substances frequently encountered in operational casework; positive identifications are provisional and intended for triage rather than confirmatory analysis.