Ultrasound assisted extraction combined with dispersive liquid–liquid microextraction (US-DLLME)—a fast new approach to measure phthalate metabolites in nails

Abstract

A new, fast, and environmentally friendly method based on ultrasound assisted extraction combined with dispersive liquid-liquid microextraction (US-DLLME) was developed and optimized for assessing the levels of seven phthalate metabolites (including the mono(ethyl hexyl) phthalate (MEHP), mono(2-ethyl-5-hydroxyhexyl) phthalate (5-OH-MEHP), mono(2-ethyl-5-oxohexyl) phthalate (5-oxo-MEHP), mono-n-butyl phthalate (MnBP), mono-isobutyl phthalate (MiBP), monoethyl phthalate (MEP), and mono-benzyl phthalate (MBzP)) in human nails by UPLC-MS/MS. The optimization of the US-DLLME method was performed using a Taguchi combinatorial design (L9 array). Several parameters such as extraction solvent, solvent volume, extraction time, acid, acid concentration, and vortex time were studied. The optimal extraction conditions achieved were 180 μL of trichloroethylene (extraction solvent), 2 mL trifluoroacetic acid in methanol (2 M), 2 h extraction and 3 min vortex time. The optimized method had a good precision (6-17 %). The accuracy ranged from 79 to 108 % and the limit of method quantification (LOQm) was below 14 ng/g for all compounds. The developed US-DLLME method was applied to determine the target metabolites in 10 Belgian individuals. Levels of the analytes measured in nails ranged between <12 and 7982 ng/g. The MEHP, MBP isomers, and MEP were the major metabolites and detected in every sample. Miniaturization (low volumes of organic solvents used), low costs, speed, and simplicity are the main advantages of this US-DLLME based method. Graphical Abstract Extraction and phase separation of the US-DLLME procedure.

A Review of Biomonitoring of Phthalate Exposures

“…It should be noted, however, that some phthalates, especially DBP, are used in nail polishes and that care should be exercised in interpreting such measurements. MEHP, MBP, and MEP were the major metabolites detected in every nail sample, with a median concentration of 138, 74, and 64 ng/g, respectively [135]. Another study of nail samples from Oslo, Norway, showed the presence of monoesters, such as MMP (geometric mean 89.7 ng/g), MEP (104.8 ng/g), and MBP (89.3 ng/g) [112].…”

Case Study on Screening Emerging Pollutants in Urine and Nails

“…Similarly to Giovanoulis et al 33 in which the same urine and finger nail sample extracts were used for the quantification of phthalate and DINCH metabolites, field (n 1 = 10) and procedural blanks (n 2 = 5) were analyzed for each extraction method without any phthalate contamination problems. 25,26,31 2.5. LC/ESI-Orbitrap-MS Analysis.…”

“…Until analysis all samples were stored at −20 °C. Before the extraction, residues of nail polish and dirt were cleaned from the nails using acetone, as previously described. − , …”

“…Previously optimized methods were used for extraction of the target plasticizers, V6, and their metabolites in nails and urine. ,, For nails, 30 mg of cut pieces were weighed into glass vials followed by extraction of the target analytes using ultrasound-assisted dispersive liquid–liquid microextraction (US-DLLME) as described by Alves et al , Urine samples were extracted following a method involving deconjugation of the phthalate glucuronide, validated by Servaes et al Since no internal standards and individual standards of the metabolites were commercially available, only qualitative analyses (screening) were possible. Similarly to Giovanoulis et al in which the same urine and finger nail sample extracts were used for the quantification of phthalate and DINCH metabolites, field ( n 1 = 10) and procedural blanks ( n 2 = 5) were analyzed for each extraction method without any phthalate contamination problems. ,, …”

“…Therefore, nails have the advantage to indicate long-term exposure. In addition, due to sampling advantages (e.g., cost reduction, less storage, and sample stability), finger nails were considered as an alternative matrix for human biomonitoring (HBM). − …”