FaPEx® Multipesticide Residues Extraction Kit for Minimizing Sample Preparation Time in Agricultural Produce.

Background: The quick, easy, cheap, effective, rugged, and safe method, generally applied to the determination of pesticide residues in food, has been recently modified and adopted for the analysis of pesticide residues worldwide, including Taiwan. Objective: The method still needs to be improved, particularly in efficiency and normalization, because the time costs 20-30 min for extraction and cleanup of multiple pesticides in every food. Methods: In this study, we present a highly efficient and simple sample preparation method that was developed for the determination of 380 pesticide residues in food, including mangoes, scallions, bok choy, apples, carrots, and pea seedlings. The homogenized 1 g samples mixed with 5 mL 1.0% acetic acid in acetonitrile were pushed through the FaPEx® (fast pesticide extraction) kits in a dropwise manner to obtain sample extracts. The total processing time was less than 15 min. The extracts were subject to chromatographic separation followed by GC-tandem MS (MS/MS) and LC-MS/MS analysis. Results: For more than 270 pesticide residues in these foods, the test gave acceptable mean recoveries, ranging between 70 and 120%, and relative SDs below 20%. The LOQ was at least 0.01 mg/kg for 380 pesticides. Conclusions: The developed method can greatly reduce the time needed for multiple pesticide residues analysis. Highlights: FaPEx is used for the extraction of pesticide residues that relies on single-use pre-filled sealed cartridges. FaPEx diminishes operation time, glassware demand, and laboratory space requirement. It also significantly decreases the amount of chemical solvents.

Effect of different radial hole designs on pullout and structural strength of cannulated pedicle screws.

Cannulated pedicle screws are designed for bone cement injection to enhance fixation strength in severely osteoporotic spines. However, the screws commonly fracture during insertion. This study aims to evaluate how different positions/designs of radial holes may affect the pullout and structural strength of cannulated pedicle screws using finite element analysis. Three different screw hole designs were evaluated under torsion and bending conditions. The pullout strength for each screw was determined by axial pullout failure testing. The results showed that when the Von Mises stress reached the yield stress of titanium alloy the screw with four radial holes required a greater torque or bending moment than the nine and twelve hole screws. In the pullout test, the strength and stiffness of each screw with cement augmentation showed no significant differences, but the screw with four radial holes had a greater average pullout strength, which probably resulted from the significantly greater mean maximum lengths of cement augmentation. Superior biomechanical responses, with lower stress around the radial holes and greater pullout strength, represented by cannulated pedicle screw with four radial holes may worth recommending for clinical application.

Biomechanical study of expandable pedicle screw fixation in severe osteoporotic bone comparing with conventional and cement-augmented pedicle screws.

Pedicle screws are widely utilized to treat the unstable thoracolumbar spine. The superior biomechanical strength of pedicle screws could increase fusion rates and provide accurate corrections of complex deformities. However, osteoporosis and revision cases of pedicle screw substantially reduce screw holding strength and cause loosening. Pedicle screw fixation becomes a challenge for spine surgeons in those scenarios. The purpose of this study was to determine if an expandable pedicle screw design could be used to improve biomechanical fixation in osteoporotic bone. Axial mechanical pull-out test was performed on the expandable, conventional and augmented pedicle screws placed in a commercial synthetic bone block which mimicked a human bone with severe osteoporosis. Results revealed that the pull-out strength and failure energy of expandable pedicle screws were similar with conventional pedicle screws augmented with bone cement by 2 ml. The pull-out strength was 5-fold greater than conventional pedicle screws and the failure energy was about 2-fold greater. Besides, the pull-out strength of expandable screw was reinforced by the expandable mechanism without cement augmentation, indicated that the risks of cement leakage from vertebral body would potentially be avoided. Comparing with the biomechanical performances of conventional screw with or without cement augmentation, the expandable screws are recommended to be applied for the osteoporotic vertebrae.