Determination of chlorophylls a and b and β-carotene in environmental waters: Diminishing wastes and analysis time by in-tube solid-phase microextraction coupled on-line to nano liquid chromatography

Abstract

Chlorophylls and carotenoids are indicators of water quality. A new method based on in-tube solid-phase microextraction (IT-SPME) coupled on-line to nano-liquid chromatography with diode array detection (NanoLC-DAD) was developed. This paper aims to provide selectivity and sensitivity with a short analysis time of about 10 min and low residues of friendly solvents, 5 µL/run of ethanol:water 95:5 and 250 µL of ethanol for dissolving the pigments retained in a nylon filter (0.45 µm, 13 mm) from 30 mL of water. IT-SPME capillary was a fused silica capillary (10 cm length x 75 µm internal diameter, i.d.) with a coating of tetraethyl orthosilicato (TEOS), triethoximethylsilane (MTEOS) doped with SiO₂ nanoparticles (NPs) and an analytical column Zorbax 300SB-C₁₈ (50 mm x 75 µm i.d., 3.5 µm particle size) was used. The recovery obtained to chlorophyll a, chlorophyll b and β-carotene were 93 ± 8 %, 92 ± 7 % and 94 ± 4 %, respectively. The method shows good linearity in the range up to 300 µg L⁻¹ for chlorophyll a and β-carotene and up to 600 µg L⁻¹ for chlorophyll b. The achieved limits of detection (LODs) in samples were 0.1 µg L⁻¹ to chlorophyll a and β-carotene, and 0.2 µg L⁻¹ to chlorophyll b. Values of relative standard deviations (RSD) expressed in% between 2 and 3 were obtained. Pigments were successfully determined with a short analysis time and minimal residues in real water samples.