Submitted by: Submitted by yybmw117
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Words: 743
Pages: 3
Category: Science and Technology
Date Submitted: 07/17/2011 11:01 PM
Experimental
Instrumentation
All atomic measurements were carried out by a mercury analyzer, Model QuickTrace M-7500 equipped with autosampler model ASX 510, 4-channel, 12-roller, peristaltic pump, and computer controller was used for all experiments. A microwave heating system, Model MARS-5 equipped with XP-1500 Plus vessels, EST-300 Plus temperature sensor, and ESP-1500 Plus pressure sensor was used to prepare decomposition solutions. The system has temperature feedback control and pressure monitoring that prevents pressure buildup in excess of vessel rating.
Reagents and standard solutions
Mercury standard solutions with Hg concentration of approximately 0, 0.05, 0.1, 0.2, 0.5, and 2 µg/L were prepared by placing 0, 0.5, 1, 2, 5, and 20 g portions of 5 µg/L Hg solution in tared tubes, weighing the portions, and diluting to 53.000 ± 0.001 g with diluent. Solutions containing known Hg concentrations in diluent were analyzed periodically during experiment. Diluent containing 10% v/v HNO3, 7% v/v HCl and 0.02% w/v NaCl was prepared by adding 200 mL HNO3, 140 mL HCl, and 0.4 g NaCl to approximately 1700 mL H2O. A separate argon stream containing 10% or 20% w/v SnCl2 ∙ 2H2O and 7% v/v HCl was prepared by mixing 35 mL HCl with 300 mL H2O and adding 50 or 100 g SnCl2 ∙ 2H2O. Argon used for Hg analyzer was high purity grade compressed gas. An organic mercury solution, methylmercury chloride solution 1000 mg/L, was used to determine recovery of organic Hg. NaCl solution used for decomposition was 1% w/v in H2O. Autosampler rinse solution containing 1% v/v HNO3 and 1% HCl was prepared by adding 20 mL portions of HNO3 and HCl to H2O.
Procedure
Fish sample were purchased at local retail stores. Inedible heads, tails, viscera, bones, and skin were removed and discarded. Samples were processed in a food processor until a visually homogeneous paste was obtained. Addition of reagent water less than 20% the weight of sample was necessary to adequately...