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171.
Sung Joong Lee Semin Park Jin Young Choi Jae‐Han Shim Eun‐Ho Shin Jeong‐Heui Choi Soo Taek Kim A. M. Abd El‐Aty Jong Sung Jin Dong Won Bae Sung Chul Shin 《Biomedical chromatography : BMC》2009,23(7):719-731
It would be preferable for pesticide residues substituted by hydrolyzable functionality to be analyzed after cooking because their structures are apt to degrade during boiling and/or heating. A liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method for the quantitative determination of 44 pesticide residues with hydrolyzable functional group in five typical vegetable widely consumed in Republic of Korea is described. The sample clean‐up was carried out according to the method of Food Code No. 83 established by the Korea Food and Drug Administration (KFDA). Zorbox XDB‐C18 column was selected for the analysis because of the best peak separation. The LC mobile phase consisted of water and 5 mm methanolic ammonium formate, which resulted in a peak shape with good symmetry at each run. Tandem mass spectroscopic (MS/MS) experiments were performed in ESI positive mode and the multiple reaction monitoring modes. A conventional matrix effect was modified to more comprehensive form 100γij (%). A high matrix effect (30%) was detected for the seven polar pesticides, namely thiamethoxam, clothianidin, acetamiprid, aldicarb, thiacloprid, pirimicarb and methabenzthiazuron. The limits of detection were in the range of 0.1–8.1 µg/kg, indicating a good sensitivity. Most of the recoveries ranged from 70 to 131% with RSDs ≤ 20%. The current method allowed rapid quantitation and identification of low pesticide levels in the cooked vegetable samples. Of the screened pesticide residues, only fluquinconazole and dimethomorph below the maximum residue levels established by the KFDA were detected in onion and cucumber samples. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
172.
A series of crosslinked polymer electrolyte membranes were prepared by blending cellulose and sulfosuccinic acid (SA) for
fuel cell applications. The crosslinking reaction of membranes occurred via the esterification between –OH of cellulose and
–COOH of SA, as confirmed by FT-IR spectroscopy. Both the ion exchange capacity and the proton conductivity increased in proportion
to the increase of SA concentrations due to the increasing portion of charged groups in the membrane. In contrast, the water
uptake linearly increased up to 25 wt.% of SA concentration, above which it decreased abruptly. The maximum behavior of water
uptake may be a result of competitive effect between the increasing number of ionic sites and the increasing degree of crosslinking
with the SA concentrations. Wide angle X-ray scattering also showed that the crystalline structures of cellulose disappeared
upon the introduction of SA. The mechanical properties of cellulose/SA membranes, i.e., tensile strength at break and Young’s
modulus, showed a maximum at 15 wt.% of SA, as revealed by universal testing machine. These membranes exhibited good thermal
stability up to 250 °C, as revealed by thermal gravimetric analysis. 相似文献
173.
Transducer safety encompasses a wide spectrum of topics. It may range from mechanical construction reliability to biological effects created by ultrasound radiation. In this Paper the electrical and acoustical safety aspects are summarized and initial experience with sterilization of echocardiographic transducers for peroperative cardiac scanning is mentioned. 相似文献
174.
Theo de Jong 《Abhandlungen aus dem Mathematischen Seminar der Universit?t Hamburg》1999,69(1):271-281
In this paper we give explicit equations for quasi-determinantal rational surface singularities, extending previous results
for determinantal rational surface singularities. 相似文献
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In this paper, we study the decay property of the solutions to the Bernoulli–Euler-type equation with a local degenerate dissipation. 相似文献
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