A slurry sampling method has been developed for the determination of Pb in marine plankton by ETAAS using a freshwater plankton certified reference material (CRM 414). Slurries were prepared in 1–3% m/v range with 1% v/v HNO3 by ultrasonic agitation for 5 min. The effects of several chemical modifiers, including Ir(NO3)2, Mg(NO3)2, Pd(NO3)2, Pd(NO3)2 + Mg(NO3)2, and Mg(NO3)2 + NH4H2PO4, were investigated for the stabilization of Pb during thermal pretreatment. Lead in slurries was effectively stabilized up to 1000 °C with Ir, Pd and Pd + Mg modifiers among which Pd + Mg provided the best results with complete atomization at 1850 °C. Firings in the presence of Ir were, problematic due to ash formation inside the atomizer. Water, dilute HNO3 and HF were examined as suspension medium. Dilute HNO3 (1–2% v/v) proved to be advantageous over water as it afforded extraction of Pb from plankton almost quantitatively in 5 min agitation. Hydrofluoric acid was the least suitable medium. Increasing HF concentration up to 5% v/v resulted in inaccuracy and substantial background absorption. Fast-heating furnace method provided comparable accuracy and precision to that of conventional-heating in slurries of CRM 414. Detection limits and characteristic masses were, respectively, 0.49 μg L− 1 and 32 pg for the conventional method and 0.62 μg L− 1 and 37 pg for the fast-heating method. However, fast-heating approach suffered from distorted peaks at high temperatures and incomplete pyrolysis of matrix at lower temperatures. Analysis of marine plankton samples for Pb was performed by using the conventional furnace program. The results showed a high correlation with those obtained by solution ICP-MS. Differences were statistically insignificant within 95% confidence interval. 相似文献
Journal of Thermal Analysis and Calorimetry - In the current study, huntite and hydromagnesite (HH) was used as flame-retardant additive in linear low-density polyethylene (LLDPE). The effect of HH... 相似文献
water proton T1 in blood from healthy volunteers and patients with acute leukaemia, lymphoma; iron deficiency anaemia, post hepatitic cirrhosis and tuberculosis, was measured by a FT-NMR spectrometer. Relaxation measurements were performed at 60MHz frequency and a temperature of (20 ± 0.5)C. The T1 measured for each disease correlates strongly with hemoglobin content. The spin-lattice relaxation time in each abnormal group was signaficantly (p < 0.001) elevated over normal group. There is little overlap between the healthy and abnormal groups. On the contrast, T1 ranges obtained for malignant groups and non-malignant diseases do overlap. 相似文献
In the study, fluorescent imaging of live cells was performed using fluorescent carbon quantum dots derived from edible mushrooms species; Agaricus bisporus, Pleurotus ostreatus, and Suillus luteus as a fluorophore agent. Carbon quantum dots were synthesized through a facile and low-cost method based on microwave irradiation of dried mushroom samples in hydrogen peroxide solution under optimized conditions (microwave energy, solution type, duration of microwave treatment, amount of mushroom). Upon purification with centrifugation, microfiltration, and dialysis, the lyophilized carbon quantum dots were identified through UV–visible, fluorescence and FT-IR, X-ray photoelectron spectroscopy, X-ray diffraction, high-resolution transmission electron microscopy, and quantum yield calculation. Cell viability assessment of the carbon quantum dots was evaluated against human epithelial cell line PNT1A using the Alamar Blue Assay. In vitro fluorescence cell imaging studies demonstrated that the carbon dots could dynamically penetrate the cell membrane and nuclear membrane and localize in both the cytoplasm and the nucleus.
The acid catalysed hydrolysis of some cyclic sulfamates, X-3-(p-tolylsulfonyl)-1,2,3-benzoxathiazole 2,2-dioxides ( 1a , X = Me; 1b , X = H; 1c , X = Cl; 1d , X = NO 2 ) have been studied in concentrated aqueous sulfuric and perchloric acid solutions. Analysis of the data by the Excess Acidity Method, activation parameters, substituent, solvent deuterium isotope effect and order of the catalytic effects of the acids are all in agreement with an A-1 mechanism in the studied range. 相似文献