Hydride hấp thụ nguyên tử thế hệ hệ thống lấy mẫu để Một số giống chịu lạnh, hệ thống hơi thủy ngân. Các mẫu được phản ứng trong một mạch bên ngoài với một đại lý natri borohydride giảm, thường. Sản phẩm phản ứng khí này sau đó được Đuôi để lấy mẫu tế bào trong đường dẫn ánh sáng của quang phổ kế AA. Các thủy ngân unlikable kỹ thuật, các sản phẩm phản ứng không khí tự do chất phân tích nguyên tử hiđrua mục tiêu dễ bay hơi. Luận án phân tử loài không có khả năng. | 11 Hydride-Generation Atomic Absorption Technique PRINCIPLE Hydride-generation sampling systems for atomic absorption bear some resemblance to cold-vapor mercury systems. Samples are reacted in an external vessel with a reducing agent usually sodium borohydride. Gaseous reaction products are then carried to a sampling cell in the light path of the AA spectrometer. Unlike the mercury technique the gaseous reaction products are not free-analyte atoms but volatile hydrides. These molecular species are not capable of causing atomic absorption. To dissociate the hydride gas into free atoms the sample cell must be heated. In some hydride systems the absorption cell is mounted over the burner head of the AA spectrometer and the cell is heated by an air-acetylene flame. In other systems the cell is heated electrically. In either case the hydride gas is dissociated in the heated cell into free atoms and the atomic absorption rises and falls as the atoms are created and then escape from the absorption cell. The maximum absorption reading or peak height is taken as the analytical signal. Recommended wavelengths are nm for As and nm for Se. Advantage The advantage of the technique is the easily achievable detection limits below micrograms per liter. Disadvantage The disadvantage of the technique is that its results depend heavily on a variety of parameters including the valence state of the analyte reaction time gas pressures concentration and cell temperature. Therefore the success of the hydride generation technique will vary with the care taken by the operator in attending to the required detail. The formation of analyte hydrides is also suppressed by a number of common matrix components leaving the technique subject to chemical interference. application The method is applicable to the determination of arsenic As and selenium Se via conversion to their hydrides with sodium borohydride reagent and aspiration into an atomic absorption .
