Chain-Shattering Polymers as Degradable Microdispersive Solid-Phase Extraction Sorbents

A chain-shattering polymer (CSP) has been proposed as a microdispersive solid-phase extraction (μdSPE) sorbent in a proof-of-concept study of degradable materials for analytical purposes. The responsive CSP was synthesized from 1,3,5-tris(bromomethyl)-2-nitrobenzene acting as the self-immolative trigger responsive unit and 2,6-naphthalenedicarboxylic acid as aromatic linker to enhance noncovalent aromatic interactions with the analytes. The CSP was characterized and applied as a μdSPE sorbent of a group of plasticizers, which were selected as model analytes, from different types of environmental water samples (tap, waste, and spring waters). Gas chromatography coupled to mass spectrometry detection was used for analyte determination. Mean recovery values were in the range of 80%–118% with RSD values below 22%. After the extraction, the polymer could be efficiently degraded by UV irradiation or by chemical reduction, recovering the aromatic linker. This work has proved the potential of CSPs as recyclable sorbents, paving the way to more environmentally benign analytical procedures.


TABLE OF CONTENT
.-Chemical structure and properties of the studied PAEs and DEHA (pages S3-S4). Table S2.-GC-MS retention times, quantifier and qualifier m/z values of DEHA and the selected PAEs and ISs (page S5). Table S3.-Langmuir and Freundlich parameters of the adsorption isotherms of BBP onto the synthesized polymer (page S6). Table S4.-Internal instrumental calibration data of the target analytes (page S7). Table S5.-Relative recovery and RSD values of the target analytes in tap, waste and spring water (pages S8-S9). Table S6.-Matrix-matched calibration data of the target analytes in tap, waste and spring water (pages S10-S11). Table S7.-pH and conductivity data of the water samples analyzed in this work (page S12). Table S8.-Previous studies in which a dSPE procedure has been applied for the extraction of plasticizers from water samples (pages S13-S15).

Compound (4): 1,3,5-tris(bromomethyl)benzene
According to the literature, 8 triester 2 (3.6 g, 14.3 mmol) was dissolved in THF (75 mL) and it was added dropwise over a solution of LiAlH 4 (2.56 g, 64.4 mmol) in THF at 0 o C. The reaction was refluxed during 24 h before being allowed to cool. Upon cooling, H 2 O was carefully added (50 mL) and the mixture was filtered through a celite pad, and the filter cake was washed with DCM. The volatiles were concentrated under reduced pressure. After that, the crude of alcohol 3 was mixed with 20.9 mL of HBr in HAc solution (33% w/v) and stirred over night to obtain a needle-like off-white solid that was filtered, generously washed with water and dried under reduced pressure. 9 4.03 g, 79% yield. NO 2 -polymer: compound 5 (0.84 g, 3.9 mmol), K 2 CO 3 (1.25 g, 9.1 mmol) and commercially available 6 (1.04 g, 2.6 mmol) were placed in a round bottom flask under N 2 atmosphere with a magnetic stirrer. Dry DMF (13 mL, 0.2M) was added and the solution was heated for 18 h at 80 o C. The mixture was cooled to room temperature and 20 mL of Milli-Q H 2 O were added appearing a white solid. The mixture was let to stir for 1 additional hour and the solid was filtered, washed with Milli-Q H 2 O (2x20 mL), MeOH HPLC grade (2x15 mL) and ACN HPLC grade (2x15 mL). Finally, the white solid was dried in high vacuum. 1.17 g, 93% yield.
Before use, if necessary, the polymer was washed with an appropriate volume of different organic solvents (i.e., ACN, MeOH or AcOEt) to remove any impurities or plasticizers. Then, it was dried under vacuum and acidified with a 0.1 M HCl solution and subsequently washed with Milli-Q water until neutral pH. Finally, it was completely dried under vacuum.

Photodegradation:
1.4 mg of the polymer (2.89 mmol) was added to a quartz NMR tube, followed by 0.17 mL of a 0.0145 M solution of hexamethyldisilane in DMSO-D 6 (as IS). The volume of the tube was adjusted to 0.7 mL and exposed to UV light with an ACE-Hanovia photochemical lamp 7830-60 (450W) and monitored by 1 H-NMR experiment.
To obtain the concentration of the carboxylic acid, 1 peak of IS and 1 signal of the acid were deconvolutionated to obtain the areas. With those values, a quotient of both was done to obtain the concentration.