Generally, surface characteristics of the hollow fiber influence the extraction of analytes on HF LPME. To choose an appropriate hollow fiber membrane for the online HF LPME enrichment of alachlor and 2,6 DEA, two different hollow fibers, namely, cellulose acetate and regenerated cellulose acetate, were examined under different flow rates of perfusion in the fortified culture medium sample solutions. Experimental results, as shown in Figure 1c, revealed that the RCA fiber offers higher extraction efficiency for alachlor and 2,6 DEA than the CA fiber, especially in the low flow rate of perfusion. The RCA hollow fiber was used herein. Selection of the Perfusion Solvent. In conventional LLE, the polarity of the extraction solvent is one of the main factors affecting the extraction efficiency.

The dialysis could be achieved not only by the concentration gradient but also by appropriate selection of perfusion solvent. To achieve high extraction efficiency in the online HF LPME method, perfusion solvent selection is essentially based SNDX-275 on polarity, viscosity, and its retention behavior in the chromatographic column. In this study, acetonitrile, acetone, ethyl acetate, methanol, and hexane were selected, and the relative concentration abilities of these solvents were examined in online HF LPME for alachlor and 2,6 DEA in the fortified sample solution. Figure 2a indicates that hexane has the highest enrich ment potential among the test solvents, followed by acetone and ethyl acetate. In addition, the polarity difference between hexane and culture medium simplified the diffusion of species into perfusate and, thus, gave at better baseline of chromato grams.

Hexane was thus used as the perfusion solvent. Effect of Sample pH. Normally, sample pH is adjusted to improve the extraction efficiency of LLE, LPME, SPE, and SPME, which enables the favorable partition of analytes in their molecular forms into the extraction solvent. The enrich ment of analytes from a dialysis system depends on the pH of sample solution, thus affecting online MLN8237 HF LPME efficiency. Figure 2b shows the concentrations of alachlor and 2,6 DEA in perfusate under different pH values of fortified sample solution. The dialysis efficiency of 2,6 DEA increased with the increase of pH until pH 7. 0, and alachlor did not change over the pH range of 3_8.

This depicts that only the neutral molecular 2,6 DEA and alachlor were favored to diffuse through the fiber membrane. To obtain good HF LPME efficiency, the pH of the sample solution was re commended at 7. 0. Hence, pH 7 was utilized in the following experiments. Effect of Salt Addition in Sample Matrix. A salting out effect is frequently employed PI3K Inhibitors to improve the recovery in extraction processes such as LLE, LPME, and SPME. culture medium, the recovery of 2,6 DEA in the dialysis process increased slightly with the NaCl addition and went to flatness after 1. 0 M addition, but it was not significant for alachlor, as shown in Figure 2c. In the PDB culture medium, no significant change of dialysis efficiency for either 2,6 DEA or alachlor occurred due to the PDB culture medium comprising some inorganic salts.

Thus, it was not required to add NaCl in the sample solution. Effect of Fiber Length and Perfusion Flow Rate. As re ported in the literature, diffusion efficiency and extraction PI3K Inhibitors time depend on the length of the hollow fiber and perfusion flow rate. In this study, the extraction efficiency of HF LPME increased with the length of fiber when 30 and 40 cm were studied. Figure 3a shows that the extraction efficiency of alachlor and 2,6 DEA increased gradually with increase in the length of fiber under the fortified sample solution of 10 L/mL of alachlor and 2,6 DEA by using hexane as the perfusion solvent at the flow rate of 4 L/min. A series of tests were carried out under various flow rates from 0. 1 to 8 L/min using hexane as perfusion solvent and 20 cm of hollow fiber in 50 mL of fortified sample solution.

Experimental results as shown in Figure 3b revealed that significant enrichment occurred in a low flow rate of perfusion, and enrichment factors could be controlled by the flow rate of perfusion and the length of hollow fiber depending on the requirement of detection sensitivity. The higher the flow FDA rate of perfusion, the lower the recovery obtained because of a dilution effect and the increased pressure that reduced the diffusion tendency from the sample solution. Although a low perfusion flow rate increased the diffusion recovery, it took time to collect enough perfusate to clear the eluent in the sample loop and be injected into the chromatographic system. Therefore, the optimal flow rate of perfusion of 4 L/min and a hollow fiber length of 20 cm were selected. Validation of the Method. The applicability of the proposed method was examined for the quantitative determination of alachlor and 2,6 DEA using HPLC UV by spiking standard solutions of alachlor and 2,6 DEA into the sample matrix under the optimum online HF LPME conditions.