Đang chuẩn bị nút TẢI XUỐNG, xin hãy chờ
Tải xuống
Tóm tắt Khai thác các mẫu rắn và nửa rắn bằng cách sử dụng dung môi lỏng là một thực tế phổ biến trong phòng thí nghiệm gần như mọi phân tích. Năm thử nghiệm thực nghiệm có kết quả trong phương pháp chắc chắn và tái sản xuất cho một loạt các lớp học chất phân tích. Tuy nhiên, mối quan tâm gần đây về khối lượng của dung môi hữu cơ được sử dụng (với sự tiếp xúc của con người liên quan), cùng với mua tăng lên và chi phí xử lý, đã nhấn mạnh sự cần thiết. | Chapter 3 Accelerated Solvent Extraction Devanand Luthria3 Dutt Vinjamoori6 Kirk Noelc and John Ezzelld aUSDA ARS FCL Beltsville MD 20705 Monsanto St. Louis MO 63167 cMonsanto Ankeny IA 50021 rfDionex Corporation Salt Lake City Technical Center Salt Lake City UT 84119 Abstract Extraction of solid and semisolid samples using liquid solvents is a common practice in nearly every analytical laboratory. Years of empirical testing have resulted in rugged and reproducible methodologies for a wide range of analyte classes. However recent concerns regarding the volumes of organic solvents used with the associated human exposure along with increased purchase and disposal costs have emphasized the need for more efficient sample extraction methods. In response to these concerns accelerated solvent extraction ASE Dionex Corporation Salt Lake City UT was introduced. Since its introduction in 1995 ASE has grown rapidly as an accepted alternative to traditional extraction methods. Accelerated solvent extraction takes advantage of the enhanced solubilities that occur as the temperature of a liquid solvent is increased. Increasing the temperature of solvent results in a decrease in viscosity allowing better penetration of the sample matrix. In addition analyte diffusion from the sample matrix into the solvent and overall solvent capacity are increased. In traditional Soxhlet extraction the solvent that comes into contact with the sample has passed through a cooling condenser and is therefore close to room temperature at the point of contact. The time required to complete Soxhlet extractions ranges from 6 to 48 h. Semi-automated Soxhlet systems that immerse the sample into boiling solvent are available. This increase in the temperature of the contacting solvent shortens the required extraction time to 2 h. Using these systems a further increase in temperature beyond the boiling point of the solvent is not possible due to solvent loss because these systems operate at atmospheric .
