To really make good use of ultraviolet visible spectrophotometer optical analysis instrument, also must start from the instrument theory, master the physical significance, technical indicators are used instrument test method and the error analysis of the impact of, to ensure that can choose instruments to oneself work requirements, ensure to choose appropriate instrument conditions performance from the technical index of the instrument are given, it can achieve error analysis of control need to. UV visible spectrophotometer in the pharmaceutical industry in the use of many countries, and the Pharmacopoeia are clear requirements many drug must use UV visible spectrophotometer to analyze test. China Pharmacopoeia of people with drug detection, relative test error can not be more than 1% of many drugs. So, how to choose the user ultraviolet instrument suitable for pharmacopoeial? This study theories of stray light theory, noise, spectral bandwidth from the instrument and the bill law to consider. Stray light hypothesis we used UV visible spectrophotometer is 0.5%, the absorbance of upper limit of measurement instrument can only be 0.55A. If 0.55A is greater than the drug absorbance detected, such as a 0.8A, then the measurement error can reach 1.42% (greater than 1%), it does not conform to the provisions of the relative error of Chinese Pharmacopoeia 1% requirements, namely, the instruments are not qualified. Therefore, we must stand in the height of instrument theory, pay attention to the instrument of stray light control and selection.
From the experiment, if the instrument of stray light is 0.0001%, in the measurement of very thick samples (absorbance limit is 3.4A), the measurement of stray light caused by the relative error is 0.032%, which has a far better indicator of national pharmacopoeia (1%). Even the stray light some UV visible spectrophotometer to reach 0.00008% (such as Cary500, Lambda900 etc.). Actually this kind of instrument in addition to display manufacturers of optical design and manufacturing level, is of no practical significance to the user. Because of. Because of stray light in the instrument reaches 0.00008%, the absorbance of 3.4A specimens were tested and analyzed, the measurement of stray light caused by the relative error is 0.0008%. In the actual analysis of the testing work, there can be no such samples. Therefore, from the user's actual conditions of view, great attention should be paid to the stray light of the instrument, and there is no need to reduce stray light instrument of the infinite. Practice has proved, in the analysis of stray light, ultraviolet visible spectrophotometer should be better than 0.05%, general instrument of stray light in around 0.01% yuan a full two foot requirements.