Chitosan-Ni/Fe layered double hydroxide composites as an efficient solid phase extraction sorbent for HPLC-PDA monitoring of parabens in personal care products

Highlights

• CS-Ni/Fe-LDH composites were synthesized to monitor parabens.

• Optimization of LDH-SPE was performed before HPLC-PDA analysis.

• LDH-SPE-HPLC method exhibited high sensitivity, reproducibility, and recovery.

• CS-Ni/Fe-LDH was an efficient sorbent for trace level extraction of parabens.

Abstract

There is a dire need for development of efficient and sensitive methods to efficiently screen parabens. In this research, we focused on quantification of four parabens (i.e., methylparaben (MP), ethylparaben (EP), propylparaben (PP), and butyl paraben (BP)) using chitosan intercalated nickel/iron layered double hydroxide (CS–Ni/Fe-LDH) composites as solid phase extraction sorbent prior to HPLC-PDA analysis. CS-Ni/Fe LDH composites with a heterogeneous, porous texture, and coral reef-like structure exhibit appealing extraction efficiency for the target parabens due to the enhanced possibility for the formation of hydrogen bonding and hydrophobic interactions. The performance of the composites was assessed and optimized for solid phase extraction of parabens from standard samples and real samples (rose water, cream, toothpaste, hair serum, and sunscreen). The LDH-SPE-HPLC method exhibited a wide linear range (e.g., 100–50,000 ng L⁻¹), good linearity (R² ≥ 0.999), and good precision (relative standard deviation (RSD) < 3%). This method successfully enriched selected parabens with remarkable recovery above 85.95% and a good RSD (0.01–2.90%). The quantitation of MP, EP, PP, and BP was made at detection range (and limits of detection (LOD)) of 5–15 (9.8), 11–21 (16.2), 6–18 (12.4), and 10–20 (15.6) ng L⁻¹, respectively. The prepared composites also displayed excellent performance with enhanced reusability/durability (n = 30 cycles) and reproducibility (n = 5).

Introduction

Parabens are esters of p-hydroxybenzoic acid that are widely used as preservatives and antimicrobial agents in food (such as fruits, cereals, sea food, dairy products, beverages, condiments, cookies, vegetables, breadstuffs, and cooking oils), pharmaceuticals, and personal care products (Raza et al., 2018; Liao et al., 2013). Some of the commonly used parabens are methyl paraben (MP), ethyl paraben (EP), propyl paraben (PP), and butyl paraben (BP) (Chen et al., 2018). Parabens possess unique biological and physicochemical characteristics (e.g., they have neutral pH and are odorless, colorless, tasteless, resistant to hydrolysis in aqueous and acidic solutions, have good persistence in air, and show antimicrobial activity) that allow them to be used as preservatives (Ito et al., 2015; Seidi et al., 2019). The antimicrobial activity of parabens can be greatly improved by synergistic effects if used as a mixture of two or more parabens (Gholami et al., 2019; Błędzka et al., 2014; Andersen, 2008). The worldwide production of MP is estimated between 1000 and 10,000 tons per year (Assessment–Parabens, 2013). EP and PP production is 10–1000 tons per year based on data provided by the European chemical substances information system (Assessment–Parabens, 2013). In the United States, the estimated daily dermal intake of key parabens (e.g., MP, EP, and PP) ranged between 58.6 and 766 μg/kg-body weight/day for children up to three years of age (Guo and Kannan, 2013).

Parabens have been categorized as endocrine disrupting chemicals. Numerous health concerns and research efforts have been established by the European Union to set permissible concentrations of parabens in cosmetics (Czarczyńska-Goślińska et al., 2017). The suggested acceptable limit in cosmetics for MP and EP is 0.4% (w/w). Likewise, the allowable limit for the sum of PP and BP (acid form) is 0.19% (w/w). The content of a mixture of parabens should not exceed 0.8% (w/w) in cosmetics (Buzek and Ask, 2009; Commission Regulation, 2014). Their exposure above permissible concentrations and over extended durations has been linked to many life threatening disorders such as breast cancer (Nowak et al., 2018), detrimental reproductive functions (Aker et al., 2016; Harley et al., 2018; Meeker et al., 2010; Smarr et al., 2016), hypothyroidism in neonatal babies (Berger et al., 2018b), adverse impacts on human metabolism (Esimbekova et al., 2017; Lennerz et al., 2015), pediatric respiratory disorders (Quirós-Alcalá et al., 2019; Berger et al., 2018a), adipocyte differentiation (Prapainop et al., 2019), and skin diseases (Dubey et al., 2017).

A survey conducted in different regions of China showed that about 97% of pharmaceutical products contained at least one type of paraben (Wang et al., 2013). Further, presence of parabens has been reported in urine samples from males and females (age range 20–30 years) in Europe (Moos et al., 2017), couples (females 18–40 years and males ≥18 years) in North America (Smarr et al., 2016), and subjects (3–69 years) in Asian countries (Kang et al., 2016). A thorough investigation of urinary paraben level can provide insight into health risks and related exposure levels. A study of 52 personal care product samples collected from Tianjin, China confirmed that the most commonly detected parabens were MP (77%), PP (73%), EP (46%), and BP (25%) (Guo et al., 2014). MP, EP, PP, and BP have also been detected in 196-paired urine/blood samples collected from Chinese university students. These data were then used to derive their estimated daily intake (EDI). It was observed that EDI_MP, EDI_EP, and EDI_PP were higher in female (53.7, 8.65, and 5.22 μg kg⁻¹ bw day⁻¹, respectively) than in males (8.41, 0.85, and 2.57 μg kg⁻¹ bw day⁻¹, respectively) (Zhang et al., 2020). These results suggest that the female students should use personal care products more frequently and with larger amounts than the male students. Another survey determined that EDI of parabens were 18.1 and 9.79 mg kg⁻¹-bw day⁻¹ for kindergarten children and elementary school students, respectively from South China (Lu et al., 2019). Their urinary concentrations of MP, EP, and PP were detected as 2.25, 0.33 and 0.50 μg L⁻¹, respectively. In view of the potential hazards of parabens, numerous efforts have been made to develop rapid and efficient extraction methods for parabens (Shahvar et al., 2018; Tartaglia et al., 2019; Becerra-Herrera et al., 2018; Chen et al., 2018; Pastor-Belda et al., 2018). The major challenges in paraben quantification from real samples are sample isolation (followed by pre-treatment of complex sample matrices) and low sensitivities of the detecting instruments (Ostovan et al., 2017; Tang et al., 2015). Among numerous preconcentration techniques, solid phase extraction (SPE) has been used extensively for extraction of parabens due to its appreciable sensitivity, rapid phase separation, user friendliness/easy handling, high extraction efficiency, environmentally benign operation, and elimination of concomitant substances from complex matrices (Wang et al., 2018). For the efficient extraction of analyte, the promising role of solid phase sorbent approaches has been recognized. Hence, the proper selection of a sorbent should be done to effectively achieve the final detection of targets with confidence.

Efforts were made to assess the potential utility of various forms of sorbents such as MCM-41 (Kharbouche et al., 2020), quantum dots (Prapainop et al., 2019), graphene (Ye et al., 2013), Lichrolut RP-18 (Zotou et al., 2010), moleculary imprinted polymers (Mohiuddin et al., 2020), covalent organic framework polymers (Wen et al., 2020), and microporous organic networks (Li et al., 2020) for SPE-based assays of emerging pollutants in diverse media. Layered double hydroxides (LDHs) are fascinating sorbents in solid-based extraction due to their chemical multi-functionality, layered structure, high porosity, large surface area, water resistance, good thermal stability, potential ion exchanger behavior, biocompatibility, and low synthesis cost (Wang et al., 2018; Sansuk et al., 2015; Tang et al., 2014; Sajid and Basheer, 2016; Yao et al., 2015). Recently, the utility of various LDHs has been utilized as an effective option for the potential application towards environmental remediation. Fe₃O₄@ZnAl-LDH has been recognized as an excellent dispersive soild phase extraction (DSPE) sorbent to preconcentrate and clean phenoxy acid herbicides from water samples prior to their identifications by HPLC-UV (Guo et al., 2020). Likewise, NiFe₂O₄@polydopamine@Mg/Al-LDH composite was prepared and applied for magnetic solid phase extraction of organophosphorus pesticides in fruit juice samples (Du et al., 2019). Trace level tetracyclines were efficiently extracted from water and milk samples by utilizing Mg/Al LDH as in situ-SPE sorbent (Phiroonsoontorn et al., 2017). Further, graphene oxide/LDHs@ sulfonated polyaniline was synthesized as ultrasonic-assisted-DSPE for the isolation and pre-concentration of phthalates in drinking water and distilled herbal beverages before GC-MS analysis (Otoukesh et al., 2020).

Similarly, this study describes the preparation of chitosan-Ni/Fe-LDH (CS–Ni/Fe-LDH) composites through a co-precipitation method and evaluation of their performance for SPE-HPLC-PDA applications. The main focus of our work was to (1) provide a reliable LDH composite with superior potential for sorbent extraction with sufficient sensitivity, good thermal/chemical stability, environmental friendliness, and reusability and (2) demonstrate an application toward sensitive quantification of parabens in real samples using the synthesized LDH composites.

In order to develop a well-designed composite structure, combination between different building blocks can be an appropriate idea since it takes advantage of all of them. Herein, we report a strategy to synthesize new CS-Ni/Fe-LDH composites for pre-concentration applications. CS is recognized as a versatile biomaterial with various beneficial properties such as porous structure, large surface area, biodegradability, non-toxic nature, and easy availability (Elanchezhiyan et al., 2016; Ngah et al., 2011). Moreover, Ni/Fe-LDH composites with large surface area possess high adsorption capacity for extracting and pre-concentrating trace level target analytes (Zhou et al., 2015). As such, efforts have been made to intercalate CS into Ni/Fe LDH composites for efficient sorption of target analytes with remarkably high extraction capability (per unit mass of LDH). This developed material is advantageous as CS-Ni/Fe LDH composites is synthesized by a facile and green approach. To the best of our knowledge, this study is the first report to measure parabens in personal care products with the aid of CS-Ni/Fe LDH composites through the sorptive extraction and subsequent quantitation by HPLC-PDA. Due to their noticeable analytical benefits, CS-Ni/Fe LDH composites can effectively replace other conventional sorbents for extraction and monitoring of diverse target analytes including parabens in diverse complex matrices.