Fast methodology for the reliable determination of nonylphenol in water samples by minimal labeling isotope dilution mass spectrometry

Isomer-specific analysis of nonylphenol and their transformation products in environment: A review

Nonylphenols (NPs) are crucial fine chemicals widely employed in producing industrial and consumer surfactants that ultimately enter the environment through various pathways, leading to environmental pollution. NPs are suspected endocrine-disrupting chemicals that may accumulate in the body over time, resulting in unusual reproductive function. Due to limitations in analytical methods, NPs have typically been quantified as a whole in some studies. However, NPs are a mixture of multibranched structures, and different NP isomers exhibit distinct environmental behaviors and toxic effects. Therefore, it is critical to analyze environmental and human biological samples at the isomer-specific level to elucidate the contamination characteristics, human exposure load, and toxic effects of NPs. Accurately analyzing NP samples with various isomers, metabolites, and transformation products presents a significant challenge. This review summarizes recent advances in analytical research on NPs in technical products, environmental, and human biological samples, particularly emphasizing the synthesis and separation of standards and the transformation of NP homolog isomers in samples. Finally, the review highlights the research gaps and future research directions in this domain.

Simultaneous determination of the free and total forms of nonylphenol, nonylphenol monoethoxylate, and nonylphenol diethoxylate in human urine by gas chromatography-mass spectrometry

Nonylphenol (NP), nonylphenol monoethoxylate (NP1EO), and nonylphenol diethoxylate (NP2EO) are widely used in various daily products and have been cataloged as endocrine-disrupting chemicals. Due to their high lipophilicity and low biodegradability, these compounds remain in the environment and enter the human body through the food chain. Growing concerns regarding the potential negative effects of NP, NP1EO, and NP2EO on human health have raised the need for biomonitoring to investigate human exposure to these compounds. In this study, a simultaneous analysis method using solid-phase extraction (SPE) combined with gas chromatography-mass spectrometry (GC-MS) was established by controlling the background contamination of NP, NP1EO, and NP2EO, which are ubiquitous in laboratory environments. The proposed method showed proper linearity of over 0.999 and a recovery greater than 85.8% for all analytes. Accuracy and precision were verified in ranges of 92.97-116.30% and 0.65-9.29%, respectively. The detection limits for NP, NP1EO, and NP2EO were 0.0363 μg L-1, 0.0401 μg L-1, and 0.0364 μg L-1, respectively, which were suitable for determining the trace analytes in human urine. Therefore, this simple and integrated analytical method was applied to measure the free and total forms of the target analytes in 25 human urine samples collected in Korea. Overall, free NP, NP1EO, and NP2EO were detected with average contents of 3.94 ± 4.14 μg L-1, 4.63 ± 2.62 μg L-1, and 0.293 ± 0.638 μg L-1, respectively, and with total NP, NP1EO, and NP2EO contents of 6.14 ± 8.24 μg L-1, 5.99 ± 2.91 μg L-1, and 0.806 ± 1.10 μg L-1, respectively. These data showed that these compounds are prevalent in human urine, and indicate the need for further studies.

Preparation of sheet-like covalent organic frameworks and their application for efficient preconcentration of 4-(tert-octyl)-phenol and 4-nonylphenol in textiles

In the design of highly ordered (covalent organic frameworks) COFs with "ordered domains size and orientation" construction in a well-defined arrangement, the molecular monomers are the key factors. Here, the effect of molecular monomers on the construction of COFs has been studied, and two kinds of molecular monomers, i.e., ethanediamine (flexible amine ligand) and 4,4'-diaminobiphenyl (rigid amine ligand) have been used for developing sheet-like COFs-I and sheet-like COFs-II, respectively. Furthermore, they have been evaluated in the dispersive solid phase extraction (dSPE) procedure for textiles prior to the analysis of alkylphenol by liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS). The results showed that, the optimal usage amount of sheet-like COFs-II used in the dSPE procedure was less than that of sheet-like COFs-I, which may be explained by much higher adsorption capacity of sheet-like COFs via hydrogen-bonding and π-π stacking interactions. Rectilinear calibration graphs were obtained for 4-(tert-octyl)-phenol (4-tOP) and 4-nonylphenol (4-NP) in the range 0.2-20 µg/kg with determination coefficient (r²) higher than 0.9990, and the limits of detection (LODs) of 4-tOP and 4-NP were 0.039 µg/kg and 0.048 µg/kg, respectively. The developed method has been successfully applied to analysis of 50 textile samples, in which 4-tOP and 4-NP were found in six samples with concentrations in the range of 1.6 μg/kg-20.9 μg/kg.

Determination of selected endogenous anabolic androgenic steroids and ratios in urine by ultra high performance liquid chromatography tandem mass spectrometry and isotope pattern deconvolution

An isotope dilution mass spectrometry (IDMS) method for the determination of selected endogenous anabolic androgenic steroids (EAAS) in urine by UHPLC-MS/MS has been developed using the isotope pattern deconvolution (IPD) mathematical tool. The method has been successfully validated for testosterone, epitestosterone, androsterone and etiocholanolone, employing their respective deuterated analogs using two certified reference materials (CRM). Accuracy was evaluated as recovery of the certified values and ranged from 75% to 108%. Precision was assessed in intraday (n=5) and interday (n=4) experiments, with RSDs below 5% and 10% respectively. The method was also found suitable for real urine samples, with limits of detection (LOD) and quantification (LOQ) below the normal urinary levels. The developed method meets the requirements established by the World Anti-Doping Agency for the selected steroids for Athlete Biological Passport (ABP) measurements, except in the case of androsterone, which is currently under study.

Occurrence, distribution and bioaccumulation of endocrine disrupting compounds in water, sediment and biota samples from a European river basin

The occurrence, distribution and bioaccumulation of five endocrine disrupting compounds (4-tert-octylphenol, 4-n-octylphenol, 4-n-nonylphenol, nonylphenol and bisphenol A) in water, sediment and biota (Corbicula fluminea) collected along the Minho River estuary (NW Iberian Peninsula) were examined. Samples were collected in two campaigns (May and November, 2012) and analyzed by different extraction procedures followed by liquid chromatography tandem mass spectrometry determination. The presence of linear isomers (4-n-octylphenol and 4-n-nonylphenol) was scarcely observed whereas branched isomers (4-tert-octylphenol and nonylphenol) were measured in almost all samples. Wastewater treatment plant effluents and nautical, fishing and agricultural activities are considered the primary source of pollution of the river by alkylphenols. The presence of bisphenol A in the river could be mainly associated to punctual sources of contamination from industrial discharges. A decrease in the total concentration of phenolic compounds in water was observed from spring to autumn (from 0.888 μg L(-1) in May to 0.05 μg L(-1) in November), while similar values were shown in C. fluminea samples from the two campaigns (1388 and 1228 ng g(-1) dw in spring and autumn, respectively). In sediments, the total concentration of the target compounds varied between 13 and 4536 ng g(-1) dw (average of 1041 ng g(-1) dw). Sediment-water partition coefficient (Kd), bioaccumulation factor (BAF) and biota-sediment accumulation factor (BSAF) were estimated and highest values were obtained for nonylphenol. Calculated risk quotients showed low and moderate risk for the aquatic environment from the presence of the target compounds at all sampling points. The estimation of the daily intake of the studied compounds via water and biota ingestion indicated no risk for human health.

Magnetic Molecularly Imprinted Polymers Based on Poly[2,2’-(p-oxidiphenylene)-5,5’-bibenzimidazole] (OPBI) for Selective Detection of Nonylphenol in Water Samples

Magnetic molecularly imprinted polymers (MMIPs) based on poly [2,2’-(p-oxidiphenylene)-5,5’-bibenzimidazole] (OPBI) composites were synthesized for the selective adsorption and detection of nonylphenol (NP) from water samples. During polymerization, Fe3O4@C was used as supporter and magnetic substance and OPBI not only was used as crosslinking agent but also functional monomer. Morphology of Fe3O4@C and MMIPs were investigated by scanning electron microscopy (SEM). The kinetics of adsorption followed the pseudo-first-order model. Selectivity of MMIPs was further demonstrated through HPLC analysis of the water samples, in which bisphenol A (BPA), phenol, 4-nitrophenol (4-NP) and tetrabromobisphenol (TBBPA) were dissolved respectively. The result showed that MMIPs had more effectively recognition capability of NP than other contrasts.

Determination of the enrichment of isotopically labelled molecules by mass spectrometry

A general method for the determination of the enrichment of isotopically labelled molecules by mass spectrometry (MS) is described. In contrast to other published procedures, the method described here takes into account and corrects for measurement errors such as the contribution at M - 1 due to loss of hydrogen or lack of spectral resolution and provides an uncertainty value for the determined enrichment. The general procedure requires the following steps: (1) evaluation of linearity in the mass spectrometer by injecting the natural abundance compound at different concentration levels, (2) determination of the purity of the mass cluster using the natural abundance analogue, (3) calculation of the theoretical isotope composition of the labelled compound using different tentative isotope enrichments, (4) calculation of 'convoluted' isotope distributions for the labelled compound taking into account the purity of the mass cluster determined with the natural abundance analogue and (5) comparison of the isotope distributions measured for the labelled compound with those calculated for different isotope enrichments using linear regression. The method was applied to a series of commercially available (13)C- and (2)H-labelled compounds and to a suite of singly (13)C-labelled β2-agonist prepared in-house both by gas chromatography (GC)-MS, GC-tandem MS (MS/MS) and liquid chromatography-MS/MS with satisfactory results. It was observed that the main uncertainty source for the isotope enrichment was the uncertainty in the purity of the measured cluster as determined with the natural abundance compound.

Application of screening experimental designs to assess chromatographic isotope effect upon isotope-coded derivatization for quantitative liquid chromatography-mass spectrometry

Isotope effect may cause partial chromatographic separation of labeled (heavy) and unlabeled (light) isotopologue pairs. Together with a simultaneous matrix effect, this could lead to unacceptable accuracy in quantitative liquid chromatography-mass spectrometry assays, especially when electrospray ionization is used. Four biologically relevant reactive aldehydes (acrolein, malondialdehyde, 4-hydroxy-2-nonenal, and 4-oxo-2-nonenal) were derivatized with light or heavy (d3-, (13)C6-, (15)N2-, or (15)N4-labeled) 2,4-dinitrophenylhydrazine and used as model compounds to evaluate chromatographic isotope effects. For comprehensive assessment of retention time differences between light/heavy pairs under various gradient reversed-phase liquid chromatography conditions, major chromatographic parameters (stationary phase, mobile phase pH, temperature, organic solvent, and gradient slope) and different isotope labelings were addressed by multiple-factor screening using experimental designs that included both asymmetrical (Addelman) and Plackett-Burman schemes followed by statistical evaluations. Results confirmed that the most effective approach to avoid chromatographic isotope effect is the use of (15)N or (13)C labeling instead of deuterium labeling, while chromatographic parameters had no general influence. Comparison of the alternate isotope-coded derivatization assay (AIDA) using deuterium versus (15)N labeling gave unacceptable differences (>15%) upon quantifying some of the model aldehydes from biological matrixes. On the basis of our results, we recommend the modification of the AIDA protocol by replacing d3-2,4-dinitrophenylhydrazine with (15)N- or (13)C-labeled derivatizing reagent to avoid possible unfavorable consequences of chromatographic isotope effects.

Development and validation of a liquid chromatography isotope dilution mass spectrometry method for the reliable quantification of alkylphenols in environmental water samples by isotope pattern deconvolution

We present here a new measurement method for the rapid extraction and accurate quantification of technical nonylphenol (NP) and 4-t-octylphenol (OP) in complex matrix water samples by UHPLC-ESI-MS/MS. The extraction of both compounds is achieved in 30min by means of hollow fiber liquid phase microextraction (HF-LPME) using 1-octanol as acceptor phase, which provides an enrichment (preconcentration) factor of 800. On the other hand we have developed a quantification method based on isotope dilution mass spectrometry (IDMS) and singly (13)C1-labeled compounds. To this end the minimal labeled (13)C1-4-(3,6-dimethyl-3-heptyl)-phenol and (13)C1-t-octylphenol isomers were synthesized, which coelute with the natural compounds and allows the compensation of the matrix effect. The quantification was carried out by using isotope pattern deconvolution (IPD), which permits to obtain the concentration of both compounds without the need to build any calibration graph, reducing the total analysis time. The combination of both extraction and determination techniques have allowed to validate for the first time a HF-LPME methodology at the required levels by legislation achieving limits of quantification of 0.1ngmL(-1) and recoveries within 97-109%. Due to the low cost of HF-LPME and total time consumption, this methodology is ready for implementation in routine analytical laboratories.