Kang Yan,Li Long,Chen Wanchao,Zhang Feiyu,Du Yiping,Wu Ting
A structure of polyurethane micelle/Ag nanoparticle (Ag NP) cluster was fabricated as surface-enhanced Raman scattering (SERS) substrate for in situ extracting organic compounds on the surface of different matrixes, in which polyurethane micelles acted as the host material to capture target molecules and stabilize nanoparticle cluster. This method provided stable aqueous suspensions of Ag NP cluster due to the amphiphilic properties of polyurethane. We demonstrated SERS-based in situ detection of pesticides on vegetables and fruit skin, by simply dropping polyurethane micelle/Ag NPs substrate on the sample surface where the target molecules could be detected without a previous elution and extracting. The obtained results showed that this polyurethane micelle/Ag NP cluster substrate had excellent SERS performance for pesticide molecules with ideal stability and reproducibility. With further optimization, the limit of detection of 0.03 μg/mL acetamiprid, 0.08 μg/mL phosmet, and 0.002 μg/mL thiabendazole was obtained, respectively.
TingTing Yu,FuRong Yang,Fang Wang,YongMei Chen,Yi Liu,Nan Hu
This study investigated the chain length-dependent extraction efficiency of two cationic surfactants—dodecyltrimethylammonium bromide (C12, 12-carbon chain) and cetyltrimethylammonium bromide (C16, 16-carbon chain)—for reverse micelle extraction of prolamins from Baijiu Jiuzao (Chinese Baijiu distillers' grains). Although pH variations (4.0–9.0) had negligible effects, ethanol, ionic strength, and chaotropic agent demonstrated distinct chain length-dependent behaviors: ethanol increased C12's forward extraction efficiency by 10.6% (absolute) while enhancing C16's backward efficiency by 8.7%. Potassium chloride enhanced C16's forward efficiency by 4.7%, while potassium bromide significantly improved C12's backward efficiency by 15.9%. Guanidine hydrochloride consistently promoted C16 in both extraction phases. Dynamic light scattering demonstrated significant differences ( p < 0.05) in reverse micelle sizes: C12 formed smaller empty reverse micelles (1.5 ± 0.2 nm) compared to C16 (2.5 ± 0.5 nm). During forward extraction, reverse micelles expanded significantly to 217.9 ± 6.3 nm (C12) and 311.2 ± 43.2 nm (C16). Backward extraction released prolamin particles of 449.0 ± 16.2 nm (C12) and 650.4 ± 29.7 nm (C16), confirming the size-exclusion-driven release mechanism. The more compact C12 reverse micelles correlated with lower total prolamin yield (26.6 ± 0.1% vs. 32.2 ± 0.1% for C16, p < 0.01) and substantially diminished bovine serum albumin recovery (5.2 ± 0.2% vs. 45.3 ± 2.5%, p < 0.01). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis corroborated these findings, further demonstrating that reverse micelle-extracted prolamins formed thermally stable dimers resistant to reductive cleavage. Combined with dynamic light scattering data (particle size range: 400–700 nm in the backward-extraction aqueous phase), these findings demonstrate that prolamin aggregates after reverse micelle extraction. These findings demonstrate that surfactant chain length as a key parameter for optimizing reverse micellar systems, where shorter-chain surfactants facilitate selective extraction, whereas longer chains enhance yields.
Jiechun Yu,Jianhao Huang,Fei Long,Ande Ma,Jialiang Pan
The efficient isolation of trace hydrophilic compounds from complicated aqueous-rich samples remains a daunting challenge. Herein, to address the analytical bottleneck, a novel inverse cloud-point extraction (ICPE) strategy was proposed based on the extraction principle opposite to that used in traditional CPE. Then, an original large-volume injection ion-pair chromatography (LVI-IPC) method was developed and systematically investigated based on the retention mechanism of the dynamic ion-exchange model. The combined ICPE-LVI-IPC method integrated extraction, challenging sample cleanup, and (on-column) concentration in a fast, simple phase-separation and injection operation. This method was successfully applied to the determination of melamine in dairy samples, including milk, yogurt and milk powder. The organic-solvent-free and sorbent-free sample preparation process could be accomplished within 11 min, requiring only 1.2 mL of water solution per sample. As an efficient on-column concentration strategy, LVI significantly improved the sensitivity. The obtained limit of detection of 0.0028 mg kg −1 was far below the limits established by the Codex Alimentarius Commission . Good recoveries were obtained from samples spiked at four concentration levels (92.6–95.8%), with satisfactory intraday and interday precisions of 1.9–3.9% and 1.6–5.2%, respectively. Further evaluation of the accuracy, by analyzing a certified milk reference material gave a small relative error of 2.2%. Comparisons with a variety of efficient methods showed the superiority of the proposed method in terms of sensitivity, speed, sample and solvent consumption, practicability, and throughput.
危险品化学品经营许可证（带存储）