直读光谱仪分析准确性的探讨

A discussion on the accuracy of direct reading spectrometer analysis

大多数的直读光谱仪都应用在冶炼或铸造工艺的炉前分析方面，要想得到一个准确的分析结果，除了光谱仪本身性能好以外，正确使用、操作、维护和管理仪器，才能充分发挥它的作用，得到准确的分析结果。

Most of the direct reading spectrometer is applied to the analysis of the smelting or casting process before the furnace. In order to get an accurate analysis result, in addition to the good performance of the spectrometer itself, the correct use, operation, maintenance and management of the instrument can give full play to its function and obtain accurate analysis results.

分析过程中产生误差是难免的。误差来源很多，就光电光谱分析来讲，除了标准样品和分析样品的成分不均匀，组织状况不一致外，光谱的性能不稳定和样品表面处理不当，以及氩气纯度不够都会产生误差。所以对每一位分析者来讲，了解产生误差的原因以及进一步研究消除误差的方法是非常重要的。

It is unavoidable to produce errors in the process of analysis. There are many sources of error. In the light of photoelectric spectrum analysis, in addition to the uneven composition of the standard sample and the analytical sample and the inconsistency of the tissue, the instability of the spectral performance and the improper surface treatment of the sample, and the insufficient purity of the argon gas will produce errors. So for every analyst, it is very important to understand the cause of the error and further study the way to eliminate the error.

激发光源是光电光谱仪中一个极为重要的组成部分，它的作用是给分析试样提供蒸发、原子化或激发的能量。在光谱分析时试样的蒸发、原子化或激发之间没有明显界限，这些过程式几乎是同时进行。而这一系列过程均直接影响到分析结果。样品中组分析元素的蒸发、离解、激发、电离、谱线的发射以及光谱线的强度除了与试样成分的熔点、沸点、原子量、化学反应、化合物的离解能、元素的电离能、激发能、原子(离子)的能级物理和化学性质有关以外，还跟所使用的光源特性密切相关。不同的激发光源对各类样品、各种元素具有不同的蒸发行为和激发能量，因此要根据不同的分析对象，选择具有相应特性的激发光源。

The excitation light source is a very important part of the photoelectric spectrometer. Its function is to provide the energy of evaporation, atomization, or excitation for the analysis sample. There is no obvious boundary between evaporation, atomization, or excitation of the sample during the spectroscopic analysis. These processes are almost simultaneously carried out. And this series of processes directly affect the analysis results. In addition, the evaporation, dissociation, excitation, ionization, emission of spectral lines and the intensity of the spectral lines in the sample analysis are related to the melting points, boiling points, atomic quantities, chemical reactions, dissociation energy of compounds, ionization energy of the elements, excitation energy, energy levels of atoms (ions) and chemical properties of the elements. The characteristics of the light source are closely related. Different excitation sources have different evaporation behavior and excitation energy for all kinds of samples and various elements. Therefore, the excitation light source with corresponding characteristics should be selected according to the different analysis objects.

目前常用的光源有以下两种：一类是经典光源包括电弧及火花光源，其中以高压控波光源、低压火花高速光源和高能预火花光源在冶金分析中得到广泛应用，一类是等离子体光源居多，在不同领域中得到普遍采用。

There are two kinds of light sources commonly used at present. One is the classical light source including arc and spark source. The high voltage controlled wave light source, low voltage spark high speed light source and high energy pre spark source are widely used in metallurgical analysis. One kind is the majority of plasma sources, and is widely used in different domain.

光谱分析常用光源有以下几种放电方式：

There are several kinds of discharge modes commonly used in spectroscopic analysis.

1. 高能预火花放电最大电流可达150安和燃烧时间为150微秒，这样使试样中燃烧斑点内的组织结构更加均匀，由此来消除元素之间干扰及元素之间结合等效应。

The maximum current of 1. high energy pre spark discharge can reach 150 and 150 microseconds, which makes the microstructure more uniform in the combustion spots in the sample, thereby eliminating interference between elements and the binding between elements and so on.

2.火花型放电对大多数元素重现性好。

2. spark discharge has good reproducibility to most elements.

3. 电弧型放电重现性要比火花放电差2—3倍，但对痕量元素检出限要低得多。

The 3. arc discharge is 2 to 3 times more reproducible than the spark gap, but the detection limit for trace elements is much lower.

因此在选择光源时应尽量满足以下要求：

Therefore, we should try to meet the following requirements when choosing light sources.

1.高灵敏度，随着样品中元素浓度微小变化，其检出的信号有较大的变化；

1. high sensitivity, with the slight change of the element concentration in the sample, the detected signal has a great change.

2.低检出限，能对微量及痕量成分进行检验；

2. low detection limit, which can detect trace and trace components.

3.良好的稳定性，试样能稳定的蒸发、原子化和激发，使结果具有较高的精密度：

3. good stability, stable evaporation, atomization and excitation, resulting in high precision.

4.谱线强度与背景强度之比大(信噪比大)；

4. the ratio of spectral line intensity to background intensity is large (signal-to-noise ratio).

5. 分析速度快，预燃时间短；

5. the speed of analysis is fast and the time of pre combustion is short.

6.构造简单，容易操作，安全；

The 6. structure is simple, easy to operate and safe.

7.自吸收效应小，校准曲线的线性范围宽。

7. the self absorption effect is small, and the calibration curve has a wide linear range.

光源激发条件的选择，要根据分析对象经过试验来决定。 对于不同的试样在不同的光源下其预燃时间是不一样的，这主要取决于试样在火花放电时的蒸发过程，它不仅与光源的能量、放电气氛密切有关以外，还与试样组成、结构状态、夹杂物种类、大小等等密切有关。

The choice of light source excitation conditions depends on the object of the analysis. For different samples, the pre ignition time of different light sources is different, which mainly depends on the evaporation process of the sample in spark discharge. It is not only closely related to the energy and discharge atmosphere of the light source, but also closely related to the composition of the sample, the state of the structure, the type of inclusion and the size of the inclusions.

在氩气气氛中的火花放电一般可以分为两种极端状态：浓缩放电和扩散放电。当放电是在金属相上进行时称浓缩放电，当放电是在非金属相上进行时称扩散放电。在氩气中放电时，产生扩散放电的主要原因有以下三个方面：1.氩气的纯度；2.氩气的出入口管道或放电室的泄露是使放电过程中引入氧气的第二个来源：3. 样品本身是使放电过程中引入氧气的第三个来源(如夹杂物，气泡和裂纹等)；在氩气中放电时，氩气压力，氩气流量及冲洗时间也均影响光电光谱分析的结果。

Spark discharge in argon atmosphere can be divided into two extreme states: concentrated discharge and diffusion discharge. When the discharge is carried out on the metal phase, it is called concentrated discharge. When the discharge is carried out on the non-metallic phase, it is called diffusion discharge. The main reasons for the diffusion discharge in argon are the following three aspects: the purity of 1. argon; the leakage of the 2. argon inlet pipe or discharge chamber is the second source of oxygen in the discharge process: the 3. sample itself is the third source of oxygen in the discharge process (such as inclusions, bubbles and cracks). In argon discharge, argon pressure, argon flow rate and flushing time also affect the results of photoelectric spectroscopy.

基体效应又称共存元素、第三元素或伴随物效应，主要是指除了分析物以外存在于样品中所有其他成分的影响，是光谱分析中引起谱线强度变化，使分析结果产生误差的主要原因，这种效果应又称干扰效应，是光谱分析中最为复杂的问题。

The matrix effect, also known as the coexistence element, the third element or the adjoint effect, mainly refers to the influence of all other components in the sample except the analyte. It is the main cause of the variation of the spectral line intensity in the spectral analysis, which causes the error of the analysis results. This effect should also be called the interference effect, which is the most important in the spectral analysis. Complex problems.

在实际工作中，由于分析试样和标样的冶炼过程和物理状态的差异，常使校准曲线发生变化，通常标样多为锻造和轧制状态，而分析样品多为浇铸状态，为避免试样的冶金状态变化给分析带来的影响，常用一个与分析试样的冶金过程和物理状态一致的控制试样，用于控制试样的分析结果。

In actual work, due to the difference between the smelting process and the physical state of the sample and the standard sample, the calibration curve is often changed, usually the standard sample is mostly forging and rolling state, and the analysis sample is mostly casting state, in order to avoid the influence of the change of metallurgical state of the sample to the analysis. The control sample consistent with the gold process and physical state is used to control the analysis result of the sample.

在光谱分析中，取样方法及其对样品的处理是至关重要的，它直接影响分析的精度和准确度。在炉前分析时，对炉中铸态钢样采取快速红切，发现样品有裂纹、夹杂和气孔须重新取样。遇低碳钢将红料放入流水中急冷，促使样品组织结构形成马氏体和奥氏体，保证碳的分析结果的准确度。遇高碳样品切割后反要采取暖冷，以免产生裂缝。铸铁和球墨铸铁分析，必须使分析样品进行充分的白口化，要求取

In spectral analysis, sampling method and its treatment of samples are very important, which directly affects the accuracy and accuracy of the analysis. During the analysis of the furnace, fast red cutting of the cast steel sample in the furnace was carried out, and the samples were found to have cracks, inclusions and pores to be re sampled. Low carbon steel is used to cool the red material into the water, causing the martensite and austenite to form the microstructure of the sample, which ensures the accuracy of the carbon analysis results. When high carbon samples are cut, they should be warm and cold to avoid cracks. The analysis of cast iron and ductile iron must make the analysis sample fully whitening.