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Environmental Sampling and Analysis for Metals - Chapter 9

Một quang phổ hấp thụ nguyên tử với một lò than chì Được trang bị hoàng kim năm phun nước nóng bằng điện, thay vì của một đầu ghi tiêu chuẩn, cung cấp độ nhạy cảm tốt hơn và giới hạn phát hiện thấp hơn nhiều so với phương pháp ngọn lửa (xem Chương 8). Độ nhạy của AAS AAS điện nhiệt hoặc lò than chì (Graas) Làm cho nó lý tưởng cho việc phân tích dấu vết kim loại. Việc xác định NHẤT Graas Nhạy cảm nguyên tố kim loại và giới hạn phát hiện IS 20-1000 lần tốt. | 9 Graphite Furnace Atomic Absorption Spectrometry 9.1 GENERAL DISCUSSION 9.1.1 Application An atomic absorption spectrophotometer equipped with a graphite furnace or an electrically heated atomizer instead of a standard burner head offers better sensitivity and a much lower detection limit compared to the flame method see Chapter 8 . The sensitivity of electrothermal AAS or graphite furnace AAS GrAAS makes it ideal for trace metals analysis. The GrAAS determination of most metallic element sensitivities and detection limits is 20 to 1000 times better than that of conventional flame techniques. Many elements can be determined at concentrations as low as 1.0 pg l. The GrAAS technique is subject to more interference than the FAA procedure and requires more analysis time. However extensive studies of the furnace technique combined with the development of improved instrumentation have changed the GrAAS into a highly reliable routine technique for trace metals analysis. It is also much more automated than the other techniques in this field. The entire process is automated once the sample has been introduced and the furnace program initiated. With the use of automatic samplers a completely unattended operation is possible. An additional benefit of the GrAA technique is the use of microliter sample sizes. Routine determination at the microgram-per-liter ppb level for most elements makes it ideal for environmental applications but it is also suitable for biological and geological samples and many clinical analyses. The graphite furnace method can determine most elements measured by atomic absorption in a wide variety of matrices. 9.1.2 Principle Electrothermal atomic absorption spectroscopy GrAAS is based on the same principle as direct-flame atomic absorption spectroscopy FLAAS . In the GrAAS technique a tube of graphite is located in the sample compartment of the AAS with the light path passing through it. A small volume of sample solution is quantitatively placed into .