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 Spectrometers
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 Spectrometer by 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光谱仪可很好地研究包含过渡金属，彩色化合物（染料或色素）和有机化合物的样品。生物材料特别适合通过紫外线/VIS分析。这种类型的研究将揭示出样品充分吸收光线的波长，因此，如果读取了全光谱，则不仅可以确定浓度，还可以确定给定样品的纯度。缺点？紫外线/vis并不表示被吸收的精确波长。
One benefit to this type of analysis is the relatively economical pricing of the instrumentation. The obvious limitation is that the sample must show itself in either the visible or UV bandwidths, which is not the reality for many organic compounds.
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。
IR spectroscopy can investigate samples in nearly any form, which is a noteworthy advantage. Therefore, if one is interested in investigating the composition of an unknown compound, IR spectroscopy can be a very powerful technique. One drawback of this method is that it cannot identify whether the spectrum is a result of single or multiple compounds.
Atomic Absorption Spectrometers
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
AAS有很多用途。在临床实验室中，它检测到生物液或组织样品中金属的存在。在制药行业中，可以使用AAS来确定生产化合物中合成反应是否存在任何催化剂。在环境科学中，它可以分析土壤或水样中的金属含量。AAS的明显好处是它确定元素组成的能力。AAS的缺点包括仪器的成本和确定的化合物数量有限。
Thus, it is clear that UV/Vis, IR, and AA spectrometers are all powerful instruments that can examine unique properties within organic and inorganic samples. Selecting the appropriate instrument for your laboratory will depend on the characteristics, advantages, and drawbacks listed above. Lastly, one may consider using these techniques in concert for an extremely powerful line of investigation.
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