1.1 杂散辐射功率（SRP）可能是分光光度测量中的一个重要误差源，由于通常不怀疑其存在，因此这种误差存在的危险性增加 ( 1- 4. ) . 2. 本试验方法提供了在远离通过吸收分光光度计单色器传输的标称带通波长处的相对辐射功率的估计值，即杂散辐射功率比（SRPR）。描述了用于紫外、可见光、近红外和中红外的常规商用分光光度计的测试滤光材料，其区分所需波长和对SRP贡献最大的波长- 红外范围。这些程序适用于常规设计的仪器，包括常规光源、探测器（包括阵列探测器）和光学布置。真空紫外和远红外提出了本文未讨论的特殊问题。 注1: 研究 ( 3. ) 已经表明，在测试使用中等窄带通SRP阻塞滤波器的光栅分光光度计时必须特别小心。测试此类仪器时，精确校准波长标度至关重要。参考实践 E275 . 1.2 这些程序既不全面也不可靠。 由于现成滤光材料的性质，除少数例外，该程序对紫外线中波长很短或红外中频率较低的SRP不敏感。锐截止长通滤波器可用于测试可见光和近红外中的较短波长SRP，锐截止短通滤波器可用于测试较长的可见光波长。这些程序不一定对“尖峰”SRP或“附近SRP”有效（这些术语的一般性讨论和定义见附件。）然而，它们在大多数情况下和典型应用中都是足够的。 它们确实涵盖了在单或双单色器中使用棱镜或光栅的仪器，以及单光束和双光束仪器。 注2: 带有阵列探测器的仪器固有地倾向于具有更高水平的SRP。有关使用滤波器降低SRP的信息，请参见附件。 1.3 设计良好的单色器在有利的光谱区域中遇到的SRP（即SRPR）的比例通常为0.1 % 透射率或更好，并且使用双单色仪时，透射率可以小于1×10 -6 ，即使使用宽带连续光源。在这些情况下，可能很难确定它是否低于某一水平。 由于SRP测试滤波器总是吸收一些SRP，并且如果指定的测量波长不是非常接近SRP滤波器的截止波长，则可能吸收相当多的SRP，因此该测试方法低估了真实的SRPR。然而，实际测量有时需要特殊的技术和仪器操作条件，这与使用过程中出现的情况不同。当使用连续光源进行吸收测量时，由于双单色仪中狭缝宽度对SRP的影响，这些测试程序可能在一定程度上抵消SRP滤波器的吸收影响； 也就是说，由于可能会使用比正常宽度更大的狭缝宽度来向单色器提供足够的能量，以允许评估SRP，因此指示的杂散比例可能会大于在使用中通常会遇到的杂散比例（但净效应更可能是低估了真实SRPR）。指示的SRPR是否等于或不同于正常使用值取决于SRP随更宽缝隙增加的程度，以及SRP滤波器吸收的SRP数量。必须接受的是，SRPR获得的数值是特定测试条件以及仪器正常使用性能的特征。 这表明在进行样品测试测定的分析波长附近，样品的高吸光度测量是否或多或少可能受到SRP的偏置。 1.4 测试程序不能完全代表正常操作的主要原因是，在高吸光度的样品测量中，SRP的影响被“放大”。为了充分评估SRP，可能有必要在测试期间以某种方式增加灵敏度。这可以通过增加狭缝宽度来实现，从而获得足够的能量，在单色能量被SRP滤波器去除后，允许对SRP进行有意义的测量。 然而，一些仪器通过增加光电倍增管探测器的倍增电压自动提高灵敏度。在紫外线和可见光范围内的高端双单色仪尤其如此。增加能量或灵敏度的另一个原因可能是许多仪器只有吸光度标度，这显然不会扩展到零透射率。即使SRP比例高达1 % 可能超出测量范围。 注3: 具有内置光学衰减器以平衡样品吸收的仪器可能会在10以下进行相对不准确的测量 % 透射率，因为衰减器线性较差。 应咨询分光光度计制造商，了解如何在如此低的透射率水平下校准衰减器的透射率。 1.5 SRP测量并不总是需要高精度；10或20以内的可靠测量值 % 可能足够了。然而，监管要求或特定分析的需要可能需要更高的准确性。艰苦的测量总是可取的。 1.6 以国际单位制表示的数值应视为标准值。本标准不包括其他计量单位。 1.7 本标准并非旨在解决与其使用相关的所有安全问题（如有）。 本标准的用户有责任在使用前制定适当的安全和健康实践，并确定监管限制的适用性。 ====意义和用途====== 5.1 杂散辐射功率可能是分光光度测量中的一个重要误差源。SRP通常随着时间的推移而增加；因此，应定期进行测试。此外，SRPR测试是分光光度计整体状况的良好指示器。常规执行的SRPR测试结果的控制图记录可以作为需要纠正措施的有用指标，或者至少是关键测量可靠性变化的有用指标。 5.2 本试验方法提供了一种确定光谱范围内选定波长处分光光度计杂散辐射功率比的方法，由所用SRP滤波器确定，从而揭示可能出现重大光度误差的波长区域。它不提供计算指示吸光度（或透射率）值校正的方法。使用测试方法时必须小心和理解，因为可能会出现错误的结果，尤其是对于一些包含中等窄带通SRP阻塞滤波器的现代光栅仪器。本试验方法不为比较不同分光光度计的性能提供依据。 注8: 凯 ( 3. ) 讨论测量透射率（吸光度）的校正方法，如果可以获得有关仪器特性和性能的足够信息，有时可以使用这些方法。另请参见 A1.2.5 . 5.3 本试验方法描述了分光光度计在所用特定试验参数方面的性能。当测量分析样品时，样品在分析波长处对标称带通之外的辐射的吸收可能会导致光度误差，低估透射率或高估吸光度，并相应低估SRPR。 5.4 使用SRP滤波器的该测试方法表明的SRPR几乎总是低估了真实值（参见 1.3 ). 制造商文献中引用的值表示完全按照制造商规范测试的新仪器的性能。这意味着，制造商规定的SRPR可以作为未来性能的基准，前提是用户执行制造商规定的测试。建议用户及时测试新仪器，从而根据自己的测试设施建立一个比较基准。 溶液过滤比法( 4.3 )是绘制SRPR控制图的一种方便方法。Mielenz等人。， ( 4. ) 表明其结果往往与指定波长方法的结果密切相关，但为了与制造商规范进行关键比较，必须使用制造商使用的方法。由于一些仪器通过合并随着波长范围的扫描而改变的中等窄带通SRP阻塞滤波器来降低SRP，如果SRP滤波器的截止波长太接近仪器SRP的吸收边缘，则SRPR测定可能会非常不准确- 还原过滤器 ( 3. ) .

1.1 Stray radiant power (SRP) can be a significant source of error in spectrophotometric measurements, and the danger that such error exists is enhanced because its presence often is not suspected ( 1- 4 ) . 2 This test method affords an estimate of the relative radiant power, that is, the Stray Radiant Power Ratio (SRPR), at wavelengths remote from those of the nominal bandpass transmitted through the monochromator of an absorption spectrophotometer. Test-filter materials are described that discriminate between the desired wavelengths and those that contribute most to SRP for conventional commercial spectrophotometers used in the ultraviolet, the visible, the near infrared, and the mid-infrared ranges. These procedures apply to instruments of conventional design, with usual sources, detectors, including array detectors, and optical arrangements. The vacuum ultraviolet and the far infrared present special problems that are not discussed herein. Note 1: Research ( 3 ) has shown that particular care must be exercised in testing grating spectrophotometers that use moderately narrow bandpass SRP-blocking filters. Accurate calibration of the wavelength scale is critical when testing such instruments. Refer to Practice E275 . 1.2 These procedures are neither all-inclusive nor infallible. Because of the nature of readily available filter materials, with a few exceptions, the procedures are insensitive to SRP of very short wavelengths in the ultraviolet, or of lower frequencies in the infrared. Sharp cutoff longpass filters are available for testing for shorter wavelength SRP in the visible and the near infrared, and sharp cutoff shortpass filters are available for testing at longer visible wavelengths. The procedures are not necessarily valid for “spike” SRP nor for “nearby SRP.” (See Annexes for general discussion and definitions of these terms.) However, they are adequate in most cases and for typical applications. They do cover instruments using prisms or gratings in either single or double monochromators, and with single and double beam instruments. Note 2: Instruments with array detectors are inherently prone to having higher levels of SRP. See Annexes for the use of filters to reduce SRP. 1.3 The proportion of SRP (that is, SRPR) encountered with a well-designed monochromator, used in a favorable spectral region, typically is 0.1 % transmittance or better, and with a double monochromator it can be less than 1×10 -6 , even with a broadband continuum source. Under these conditions, it may be difficult to do more than determine that it falls below a certain level. Because SRP test filters always absorb some of the SRP, and may absorb an appreciable amount if the specified measurement wavelength is not very close to the cutoff wavelength of the SRP filter, this test method underestimates the true SRPR. However, actual measurement sometimes requires special techniques and instrument operating conditions that are not typical of those occurring during use. When absorption measurements with continuum sources are being made, it can be that, owing to the effect of slit width on SRP in a double monochromator, these test procedures may offset in some degree the effect of absorption by the SRP filter; that is, because larger slit widths than normal might be used to admit enough energy to the monochromator to permit evaluation of the SRP, the stray proportion indicated could be greater than would normally be encountered in use (but the net effect is still more likely to be an underestimation of the true SRPR). Whether the indicated SRPR equals or differs from the normal-use value depends on how much the SRP is increased with the wider slits and on how much of the SRP is absorbed by the SRP filter. What must be accepted is that the numerical value obtained for the SRPR is a characteristic of the particular test conditions as well as of the performance of the instrument in normal use. It is an indication of whether high absorbance measurements of a sample are more or less likely to be biased by SRP in the neighborhood of the analytical wavelength where the sample test determination is made. 1.4 The principal reason for a test procedure that is not exactly representative of normal operation is that the effects of SRP are “magnified” in sample measurements at high absorbance. It might be necessary to increase sensitivity in some way during the test in order to evaluate the SRP adequately. This can be accomplished by increasing slit width and so obtaining sufficient energy to allow meaningful measurement of the SRP after the monochromatic energy has been removed by the SRP filter. However, some instruments automatically increase sensitivity by increasing dynode voltages of the photomultiplier detector. This is particularly true of high-end double monochromator instruments in their ultraviolet and visible ranges. A further reason for increasing energy or sensitivity can be that many instruments have only absorbance scales, which obviously do not extend to zero transmittance. Even a SRP-proportion as large as 1 % may fall outside the measurement range. Note 3: Instruments that have built-in optical attenuators to balance sample absorption may make relatively inaccurate measurements below 10 % transmittance, because of poor attenuator linearity. The spectrophotometer manufacturer should be consulted on how to calibrate transmittance of the attenuator at such lower level of transmittance. 1.5 High accuracy in SRP measurement is not always required; a measurement reliable within 10 or 20 % may be sufficient. However, regulatory requirements, or the needs of a particular analysis, may require much higher accuracy. Painstaking measurements are always desirable. 1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. ====== Significance And Use ====== 5.1 Stray radiant power can be a significant source of error in spectrophotometric measurements. SRP usually increases with the passage of time; therefore, testing should be performed periodically. Moreover, the SRPR test is an excellent indicator of the overall condition of a spectrophotometer. A control-chart record of the results of routinely performed SRPR tests can be a useful indicator of need for corrective action or, at least, of the changing reliability of critical measurements. 5.2 This test method provides a means of determining the stray radiant power ratio of a spectrophotometer at selected wavelengths in a spectral range, as determined by the SRP filter used, thereby revealing those wavelength regions where significant photometric errors might occur. It does not provide a means of calculating corrections to indicated absorbance (or transmittance) values. The test method must be used with care and understanding, as erroneous results can occur, especially with respect to some modern grating instruments that incorporate moderately narrow bandpass SRP-blocking filters. This test method does not provide a basis for comparing the performance of different spectrophotometers. Note 8: Kaye ( 3 ) discusses correction methods of measured transmittances (absorbances) that sometimes can be used if sufficient information on the properties and performance of the instrument can be acquired. See also A1.2.5 . 5.3 This test method describes the performance of a spectrophotometer in terms of the specific test parameters used. When an analytical sample is measured, absorption by the sample of radiation outside of the nominal bandpass at the analytical wavelength can cause a photometric error, underestimating the transmittance or overestimating the absorbance, and correspondingly underestimating the SRPR. 5.4 The SRPR indicated by this test method using SRP filters is almost always an underestimation of the true value (see 1.3 ). A value cited in a manufacturer’s literature represents the performance of a new instrument, tested exactly in accordance with the manufacturer’s specification. The implication is that the manufacturer’s stated SRPR can serve as a benchmark for future performance, provided that the user performs the manufacturer’s specified test. It is recommended that users test new instruments promptly, thereby establishing a comparative benchmark in terms of their own testing facilities. The solution filter ratio method ( 4.3 ) is a convenient method for control-charting SRPR. Mielenz, et al., ( 4 ) show that its results tend to correlate well with those of the specified wavelength method, but for critical comparison with the manufacturer’s specification, the method used by the manufacturer must be used. Because some instruments reduce SRP by incorporating moderately narrow bandpass SRP-blocking filters that are changed as the wavelength range is scanned, it is possible for SRPR determinations to be highly inaccurate if the cutoff wavelength of the SRP filter falls too close to the absorption edge of an instrument’s SRP-reducing filter ( 3 ) .