Covalent binding and fluorimetric determination of dialdehydes using aminated silica nanoparticles and ethylenediamine fluorescein

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The possibility of formation of a ternary (sandwich) compound of a dialdehyde (malondialdehyde, glutaraldehyde, or glyoxal) with ethylenediamine fluorescein thiocarbamyl (EDF) and silica nanoparticles noncovalently modified with polyethyleneimine (SiO₂/PEI) with the subsequent fluorimetric determination of the dialdehyde was demonstrated. The mixed Schiff base SiO₂/PEI–dialdehyde–EDF (sandwich) is formed in an acetic acid solution on heating in a water bath. The sandwich and the excess of SiO₂/PEI were separated from the unreacted fluorophore by centrifugation; the precipitate was washed and resuspended in water, and the fluorescence of solution was measured (λ_ex = 470 nm, λ_em = 520 nm). The duration of an analytical cycle was no longer than a half-hour. The limit of detection of dialdehydes in pure water is 1 × 10^–5 M, and the analytical concentration range is 2 × 10^–5–3 × 10^–4 M (for malondialdehyde). The repeatability RSDs in this concentration range were 3–5% (n = 3). The comparable concentrations of sulfamethoxazole, sulfadiazine, pyracetam, and chloramphenicol and 1 × 10^–5 M of ceftriaxone, ceftazidime, metamizole (analgin), isoniazid, and amikacin caused no interference with the determination of 3 × 10^–4 M malondialdehyde; protein noticeably interfered. The determination of glyoxal and glutaraldehyde in disinfectants was carried out.