Optimization of a Multi-Residue Analytical Method during Determination of Pesticides in Meat Products by GC-MS/MS

In this study, a multi-residue analysis was developed for 32 compounds, including pesticides and metabolites, in five meat products using gas chromatography-tandem mass spectrometry (GC-MS/MS). The validation of the developed analytical method was also evaluated in accordance with Codex Alimentarius guidelines. Aminopropyl (NH2), C18, and florisil solid phase extraction (SPE) cartridges were used to evaluate and optimize the cleanup procedure of the tested samples prior to GC-MS/MS analysis. Based on the analytical performance, the C18 SPE cartridge was deemed to be the most suitable among the examined SPE cartridges. The optimized method demonstrated that 29 out of 32 tested compounds acquired good linearity (R2 ≥ 0.99), and 25 tested compounds displayed the method limit of quantification (MLOQ) ≤ 0.01 mg/kg. Out of the 32 tested compounds, only 21 compounds met the acceptable analytical criteria for the lard and tallow samples, compared to 27 compounds in the beef, pork, and chicken samples that falls within the acceptable standards for recovery (70–120%) and analytical precision (relative standard deviation RSD ≤ 20%). The average matrix effect was widely varied (20.1–64.8%) in the studied meat samples that were affected by either ion enhancement or suppression. In particular, in the lard sample, 13 compounds showed poor recovery and analytical precision due to ion suppression. Thus, the matrix effect (ME) was considered a critical factor during multi-residue pesticide analysis in different meat products. In conclusion, this developed analytical method can be used as a routine monitoring system for residual pesticide analysis in livestock products with acceptable analytical standards. Further meticulous analytical studies should be optimized and validated for multi-residue pesticide analysis in diversified meat products

Enhanced Optical Output Power of Tunnel Junction GaN-Based Light Emitting Diodes with Transparent Conducting Al and Ga-Codoped ZnO Thin Films

High quality Al and Ga-codoped ZnO (AGZO) thin films were successfully deposited both on sapphire substrates and GaN-based light emitting diodes (LED) with a tunnel junction (TJ) layer by using the radio frequency magnetron sputtering technique at room temperature. The AGZO thin films grown on sapphire substrate showed high transparency (96.3% at 460 nm) and low resistivity (6.8 x 10(-4) Omega cm). The AGZO thin films deposited on the GaN-based LED with a TJ layer exhibited weak ohmic behavior although it improved slightly with the annealing. The optical output power of the TJ GaN-based LED with an AGZO transparent conducting layer was about 12.6mW at 20 mA, and the external quantum efficiency was 23.0%. These values are approximately 1.7 times larger than that of the TJ GaN-based LED with a conventional Ni/Au layer. (C) 2010 The Japan Society of Applied Physicclose3

Characteristics of ALD tungsten nitride using B2H6, WF6, and NH3 and application to contact barrier layer for DRAM

Tungsten nitride (WNx) thin films were grown by atomic layer deposition (ALD) within the temperature range of 200-350 degrees C from diborane (B2H6), tungsten hexafluoride (WF6), and ammonia (NH3) for application to a contact barrier layer in dynamic random access memory (DRAM). Herein, B2H6 was used as an additional reducing agent to produce a low-resistivity ALD-WNx film, and its resistivity was in the range of 300-410 mu Omega cm, depending on the deposition conditions for the similar to 10 nm thick film. An increase in the growth rate was observed with increasing deposition temperature, but an almost constant growth rate of similar to 0.28 nm/cycle was obtained in the temperature range from 275 to 300 degrees C. The properties of the as-deposited film, including the resistivity, W/N ratio, density, B and F impurity content, and phase, were affected by the deposition temperature and B2H6 flow rate during the process. As the deposition temperature and B2H6 flow rate increased, the W/N ratio and film density increased and the impurity content decreased, leading to a reduction in the resistivity of the film. An increased W/N ratio was found to be favorable to the formation of a face-centered-cubic beta-W2N phase. Excellent step coverage was obtained even on a 0.14 mu m diameter contact hole with an aspect ratio of 16:1. The ALD-WNx film in this study was thermally stable to annealing at 800 degrees C for 30 min, but after annealing at 900 degrees C, it converted to body-centered-cubic alpha-W with the accompanying release of N. The ALD-WNx film was evaluated as a barrier layer for W-plug deposition for 70 nm design-rule DRAM. The results showed that the integration scheme with ALD-WNx showed lower contact resistance than metallorganic chemical vapor deposition TiN or TiCl4-based chemical vapor deposited TiN. (c) 2007 The Electrochemical Society

ZnO film thickness effect on surface acoustic wave modes and acoustic streaming

Surface acoustic wave(SAW) devices were fabricated on ZnO thin films deposited on Si substrates. Effects of ZnOfilm thickness on the wave mode and resonant frequency of the SAWs have been investigated. Rayleigh and Sezawa waves were detected, and their resonant frequencies decrease with increase in film thickness. The Sezawa wave has much higher acoustic velocity and larger signal amplitude than those of Rayleigh mode wave.Acoustic streaming for mixing has been realized in piezoelectric thin filmSAWs. The Sezawa wave has a much better efficiency in streaming, and thus is very promising for application in microfluidics