What is Stray light and how it is monitored?

尽管是一个重要的规范，杂散光线is mostly overlooked in a correctly calibrated spectrophotometer. It happens because users don’t know what exactly it is and how it gets monitored. If you fall under this crowd, it is time that you learn more about the stay light.

In this article, we have included that you need to know about the stray light. So you won’t ignore it the next time while using the spectrophotometer.

What Is Stray Light?

A Spectrophotometric detector responds to the total light energy reaching it without discriminating between the individual wavelengths. Stray light is any light reaching the detector that lies outside the wavelength band width selected for analysis by the单色仪。It arises due to light scatter, diffraction by optical components or even by sample or on account of instrument malfunction.

在更简单的单词中，我们还可以说明杂散光是分光光度计分析不是必需的电磁辐射，并且只会干扰该过程。其中一些例子可以是：

• 这light coming from any gaps in the spectrophotometer’s fold.
• 这light reflections coming from mechanical mounting surfaces present inside the system.
• 系统表面上的任何缺陷，如灰尘，散射不必要的光等。

Stray light introduces an error in the measured absorption signal. The absorbance readings begin to drop due to increase in stray light and leads to a negative deviation from the Beer- Lambert’s law which is the basis for quantitative estimations in UV – VIS spectroscopy.

当杂散光分量变为这种浓度的总透射光的较大部分时，效果在较高的浓度下变得显着。换句话说，杂散光降低了仪器的响应的线性度。

杂散光可以在任何波长下姿势问题，但在仪器的能量吞吐量相对较低的UV范围内，杂散光的增加变得显着。

Types of Stray Light

这杂散光分光光度计is typically divided into two types: Ghosts and Flare. Let’s understand them in depth.

Ghost Stray Light:由于光源的多重反射，您是否曾因你的图像中有没有注意到你的图像中的不必要的眩光？这被称为鬼魂。它主要发生在成像表面之间发生反射时。我们也可以称之为第二个图像。

耀斑迷路光：Unlike the reflection in ghost light, here stray light is created due to scattering. This scattering of light can happen because of the presence of certain imperfections in the system, such as mechanical elements. These are also called the veiling glare.

所有分光光度计都有杂散光吗？

大多数人都担心是否杂散光分光光度计所有设备都是常见的，或者他们的工具有一些问题。嗯，他们的浮雕，所有分光光度计都有一些limit of stray light。

它通常由于衍射，散射或机器中的问题而导致。如果您想最大限度地减少分光光度计中的杂散灯，您将不得不选择高端型号。它们是以一种方式设计的，以便它们提供更准确的结果，干扰最小。

尽管如此，你还需要记住会有一些limit of stray light在您的工具中存在，无论您选择哪种型号。此外，此问题不会随着频谱范围的变化而消失。你会找到杂散光线in UV, VIS, and NIR. The stray light has to be checked every now and then because it gets worse with time.

现在您可以继续监控杂散光线in UV, NIR, or可见分光光度计范围。

杂散光线监测

通过使用切断过滤器来测量杂散光。这种滤光片在要进行测量的波长处吸收光的光，但是传输更高波长的波长。因此，在截止波长以下的任何光传输都是由于杂散光而导致的

ASTM Procedure

This procedure is adopted for measurement of stray light transmittance at three different wavelengths, namely, 220nm, 340 nm and 370 nm so as to observe stray light over a wider range of wavelengths. Cut-off standard sealed cuvettes containing following solutions are used:

10g / L碘化钠220nm

340nm和370nm的50g / l亚硝酸钠

这些溶液在UV区域中具有尖锐的截止，因此如果在这些截止值下方检测到任何光，则它是杂散光。

这些也可以在市场上发现作为液体杂散光校准过滤器。这些是专家们优先于几年。它们跌缩的唯一方法是由于它们有限的波长过滤。杂散光必须通过该波长，或者它不会被测试。

However, now there are also solid stray light calibration filters available. The significant benefit of these filters is that they can test the stray light at almost all possible wavelengths. Therefore, these options are more efficient for the purpose.

药典程序

欧洲药典建议测量of absorbance of a standard solution of 12 g/L solution of Potassium chloride at 198 nm and the absorbance reading should be 2A or higher.

It can be is seen that stray light is an important instrument specification for its ability to correctly reflect accuracy of spectrophotometric measurements at higher absorbance values.