Several options exist for determining the composition, concentration, and purity of a laboratory sample. Among the most commonly used techniques are Ultraviolet/Visible (UV/Vis), Infrared (IR), and Atomic Absorption Spectrometry. Each technique is capable of providing some or all of these pieces of information you need. In addition, each of these instruments is capable of interrogated different types of samples, including air, industrial chemicals, biological fluids and foods. Therefore, selection of an appropriate technique for analysis of your sample is essential in obtaining the desired data.
UV/VIS光谱仪
Several types of UV/Vis spectrophotometers exist, however they all operate on the same basic principle. In short, discrete bandwidths of light are passed through a sample. “Visible” light energy can be seen by humans, while its close neighbor, ultraviolet, cannot. In the entire electromagnetic spectrum ranging from high-frequency, nano-width gamma rays to low-frequency, “long wavelengths” with no definitive size, light (colors) visible to humans makes up a very small percent.
Lambda 465 UV/Vis光谱仪，Perkin Elmer
Pi electrons, depending on their bonding and degree of conjugation, absorb light differentially and at different wavelengths. The initial intensity of the light given off is compared to the intensity of the light that is transmitted through the sample to a detection system. Using Beer’s law, one can easily determine the concentration of the sample. Additionally, because compounds absorb light at unique wavelengths, it is possible to interrogate the composition of the sample.
UV/Vis spectrometers work well for investigating samples that contain transition metals, colored compounds (dyes or pigments), and organic compounds. Biological materials are especially well-suited to analysis by UV/Vis. This type of investigation will reveal wavelengths where the samples absorb light well, thus, if a full spectrum is read, one can determine not only concentration, but also the purity of a given sample. A drawback? UV/Vis does not indicate the exact wavelength being absorbed.
这种类型的分析的好处是仪器的相对经济定价。明显的限制是，样品必须在可见或紫外带宽中表现出来，这不是许多有机化合物的现实。
Infrared Spectrometers
IR spectroscopy examines samples using the infrared region of the electromagnetic spectrum, the group of frequencies making up visible light’s other close neighbor. In IR spectroscopy, infrared light is transmitted onto a sample. Different elemental bonding will vibrate at differing harmonic frequencies. The absorption of light at these frequencies is then detected and plotted across the IR spectrum. Based on the unique absorbance patterns, researchers are able to identify the particular bonds that occur in a sample. With this information, they can determine the molecules that are present.
光谱两种IR分光光度计通过Perkin Elmer
红外光谱法在鉴定有机和无机化学的化合物方面特别有用。红外光谱的原理也已用于制造科学设备。例如，IR传感器用于测量CO2生物孵化器的水平。
红外光谱可以几乎以任何形式研究样品，这是一个值得注意的优势。因此，如果一个人有兴趣研究未知化合物的组成，那么红外光谱可能是一种非常强大的技术。该方法的一个缺点是它无法识别频谱是单个化合物还是多种化合物的结果。
原子吸收光谱仪
Atomic absorption spectroscopy is capable of determining 70 different elements in a sample. In AAS, the sample is first placed in an atomizer. Atomizers convert the sample into its elemental composition in a gaseous state. A source of radiation is then passed through the sample and measurements are taken. Based on the absorption of this radiation by each component, investigators are able to determine the composition of the sample, as each individual element will have a different (known) absorption rate.
德国耶拿分析仪器公司ScanDrop Nano-Volume光谱仪
There are numerous uses for AAS. In clinical laboratories, it detects the presence of metals in biological fluids or tissue samples. In the pharmaceutical industry, AAS may be used to determine if any catalyst remains from synthesis reactions in a manufactured compound. In environmental sciences, it can analyze the metal content in soil or water samples. The obvious benefit of AAS is its ability to determine elemental compositions. Drawbacks of AAS include the cost of the instrumentation and the limited number of compounds identified.
因此，很明显，UV/VIS，IR和AA光谱仪都是可以检查有机和无机样品中独特性能的强大仪器。为实验室选择适当的工具将取决于上面列出的特征，优势和缺点。最后，人们可以考虑在协同方面使用这些技术进行非常有力的调查系列。
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