Supporting information MOF-derived hollow carbon nanocubes for fast solid-phase microextraction of polycyclic aromatic hydrocarbons Xingru Hu, Chaohai Wang, Jiansheng Li,* Rui Luo, Chao Liu, Xiuyun Sun, Jinyou Shen, Weiqing Han and Lianjun Wang* Key Laboratory of Jiangsu Province for Chemical Pollution Control and Resources Reuse, School of Environment and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China *Corresponding author. Tel/Fax: +86-025-84315351 E-mail: lijsh@njust.edu.cn; S-1
1. Investigation of Adsorption Theory Adsorption kinetics. Adsorption kinetic data were fitted using the Lagergren pseudo-first-order kinetic model and the pseudo-second-order model. The model is expressed using the Eqs (1) and (2), respectively. ln( )=ln (1) = + (2) where Q e (mg g -1 ) and Q t (mg g -1 ) is the amount of adsorbate adsorbed per unit mass of adsorbent at equilibrium and any time t (min), respectively. k 1 (min -1 ) is the first-order rate constant adsorption, k 2 (g mg -1 min -1 ) is the rate constant for the pseudo-second-order adsorption kinetics. Adsorption isotherms. Two typical adsorption models, Langmuir and Freundlich models, are used to fit the adsorption isotherms data. The model are depicted using Eqs (3) and (4), respectively. = + (3) ln =ln +( )ln (4) where q e (mg g -1 ) is the amount of adsorbate adsorbed per unit mass of adsorbent at equilibrium, C e (mg L -1 ) is the equilibrium concentration of the adsorbate. K L (L mg -1 ) and q m are the Langmuir constants, K F ((mg g -1 ) (L mg -1 ) 1/n ) and n are Freundlich constants. 2. Optimizations for SPME parameters Extraction time. SPME is an equilibrium extraction technique. The extracted amount of the adsorbates is connection with the extraction time in this process. The extraction time was investigated by exposing the HCNCs-F in the working solutions from 10 to 60 min. As shown in Figure S5a, the peak area achieved the highest point when the extraction time was 30 min, and then decreased slightly, which might attribute to the presence of competitive adsorption. Therefore, the extraction time of 30 min was chosen for the following experiments. Extraction temperature. In this experiment, the extraction temperature was S-2
tested from 20 to 70 o C. As we all known, raising temperature could accelerate the diffusion rate. From the Figure S5b, the extraction efficiencies of six PAHs increased with the extraction temperature increasing. However, after the extraction temperature increased to 50 o C, the extraction amount decreased, which indicated that too high temperature will reduce the partition coefficient of analytes between the coating and the water sample. According to the results, an extraction temperature of 50 o C was chosen as the suitable extraction temperature for the following experiments. Desorption time. In the case of thermal desorption, the time is a main factor that affecting the desorption efficiency of HCNCs-F. The long desorption time can make the analytes desorb thoroughly from the coating, but may shorten the lifespan of the HCNCs-F. Hence, the influence of desorption time was investigated from 1 to 5 min. Based on the result in Figure S5c, the desorption efficiency reached the highest when the desorption time was 2 min. However, to avoid the carry over effect, the best desorption time was set as 3 min. Salt concentration. The partition coefficient of the analyte between the coating and the sample matrix can be raised by increasing the ionic strength of the working solution. Here, different concentrations of NaCl (0-25%, w/v) were added into the sample solution to improve the sensitivity for the proposed SPME. Figure S5d showed that when the salt concentration was 10% (w/v), the best extraction efficiency was obtained. From the results, the concentration of 10% NaCl was applicable for the extraction of PAHs. Abbreviation: OMP, Ordered mesoporous polymers; HMCSs, Hollow mesoporous carbon spheres; OMC, ordered mesoporous carbon; PCA, powdery carbon aerogel; ZSM-5, Zeolite Socony Mobil-5; CBDC, copper 1,4-benzenedicarboxylate; HCP, hyper-cross-linked-polymer; KAPs, knitting aromatic polymers. S-3
Figure S1. Sketch map of sampling sites in Macha River (Nanjing) Figure S2. (a) TEM of ZIF-8 nanocrystals; (b) SEM and (c) TEM of hollow ZIF-8 nanocubes. Figure S3. Powder XRD pattern of the simulated ZIF-8 pattern, ZIF-8 nanocubes and hollow ZIF-8 nanocubes Figure S4. XPS survey spectra of the HCNCs. S-4
Figure S5. Effects of SPME conditions on the extraction efficiencies of the HCNCs-F for PAHs (5 µg L -1 ): (a) extraction time; (b) extraction temperature; (c) desorption time; (d) salt concentration. Figure S6. The experimental data of the analytes adsorbed by SCNCs (solid symbol) and HCNCs (hollow symbol) Figure S7. Extraction time curves of HCNCs-F and SCNCs-F for Nap (a), Ace (b) and Flu (c) in nonaqueous samples. S-5
Figure S8. Langmuir (a) and Freundlich (b) adsorption isotherm of analytes on HCNCs. 6 Peak Area (X10 8 ) 5 4 3 2 1 0 DMP DEPNap Ace FluPhe FlA Pyr Figure S9. Extraction efficiency comparison for the PAHs and esters of HCNCs-F at the same concentration. S-6
Table S1. The pseudo-first-order and pseudo-second-order parameters of analys calculated from experimental data. analyst Coatings Experimental Q e Pseudo-first-order Pseudo-second-order k 1 q e,1 R 1 k 2 q e,2 R 2 Nap SCNCs 87.09 0.0483 57.59 0.8803 7.3 10-4 99.54 0.9896 HCNCs 95.89 0.0689 64.84 0.9655 1.7 10-3 102.04 0.9956 Ace SCNCs 87.84 0.0353 80.37 0.9026 2.2 10-4 101.95 0.9356 HCNCs 98.08 0.0669 84.38 0.9799 8.5 10-4 111.12 0.9805 Flu SCNCs 88.68 0.0415 75.73 0.9599 8.0 10-6 103.64 0.9771 HCNCs 104.61 0.0565 112.30 0.9624 1.8 10-5 117.65 0.9961 o-x SCNCs 47.59 0.1040 107.37 0.7680 8.0 10-4 61.57 0.9562 HCNCs 57.87 0.0570 24.02 0.7998 2.5 10-3 62.54 0.9846 DMP SCNCs 26.81 0.0564 29.42 0.9549 1.4 10-3 34.70 0.9694 HCNCs 32.29 0.0310 26.19 0.8036 2.1 10-3 38.76 0.9706 k 1 and k 2 are the rate constants of the adsorption, q e,1 and q e,2 refer to the simulated equilibrium adsorption amount. R 1 and R 2 are correlation coefficients of the fitted equations. Table S2. The Langmuir and Freundlich parameters and the correlation coefficients calculated from the experimental data on HCNCs-F. analyst Langmuir Freundlich k L q m R L k F n R F Nap 0.0109 277.8 0.5935 6.334 1.442 0.9513 Ace 0.0156 285.7 0.9660 8.363 1.392 0.9869 Flu 0.0218 312.5 0.8545 15.39 1.732 0.9746 k L and q m are Langmuir constants and k F and n are Freundlich constants. R L nd R F are correlation coefficients of the fitted equations. S-7