Detection And In-Line Monitoring Designing Of The Content Of Salicylic Acid In Aspirin And Its Preparation By AOTF-NIR Spectroscopy

Aspirin is also known as acetylsalicylic acid. Nowadays, as the most useful antipyretic, analgesic, anti-inflammatory and anti-rheumatic drug in the world, a low-dose is commonly used drugs to prevent cardiovascular and cerebrovascular diseases. In recent years, aspirin has many new uses and new breakthroughs in clinical, so that the production of aspirin has been expanded incessantly at home and abroad. However, the salicylic acid causes serious side effect to restrict the clinical application. However, the colorimetric examination method for free salicylic acid limits according to Chinese Pharmacopoeia is semi-quantitative, tedious and prone to errors. HPLC method also has some problems, which including hydrolysis caused by solvent. At the same time, it is time and labor consuming. AOTF near-infrared spectroscopy, as the most quickly developing analysis technology in the world, has advantages of bring rapid and non-destructive, does not need to deal with chemical reagents and samples. We used this technology to detect contents of salicylic acid in aspirin raw material and preparations . It can avoid the hydrolysis of the drug, With the fast and non-destructive analytical means, we can determinate the content of salicylic acid on-line.This paper is divided into four parts. Firstly, aspirin market conditions and conventional analysis methods for salicylic acid are reviewed. And then, the basic principles, analytical characteristics and chemo metrics methods of NIR are discussed. The third experiment part is very important. In the experimental conditions, we collected the representative samples and validate calibrations with different content of salicylic acid. Using Luminar 5030 AOTF near-infrared spectrometer, setting the parameters for the experiment: the wavelength range: 1100nm～2300nm; incremental wavelength: 2.0nm; scanning frequency: 300. Employing the exclusive spectral software SNAP! 2.03 of the BRIMROSE to scan the sample spectrum and getting the original spectrum. We pretreatment the spectrum into the absorbed spectrum, then the spectrum was proceed smoothly by savitzky-golay. Making the pre-spectral data and the sample' s content data to relevance by partial least squares and cross-validation, and then input The Unscrambler data to analytical software to built models. We got the ideal models by optimizing the wavelength and rejecting the normal data. And then we tested the sample to predict models. We got the accuracy of the models. Experiments proved that the corrected model of salicylic acid in different samples had been got after a wavelength optimization and the abnormal data removed. At the same time, experiments verified that the range of 0.01% -0.2% content of salicylic acid in aspirin and it' s preparation is successfully detected by such models. Factors that influence the stability of the model by examination of sample model with different concentrations of salicylic acid are also summed. Finally, we design on-line monitoring project in key positions on production line of aspirin preparation according to the experiment results, such as aspirin' s acetylating reaction and recrystallizating in temperature and time.From experiment results, it can be concluded that AOTF near-infrared spectroscopy technology could detect content of salicylic acid in aspirin and its preparation. The method is feasible, accurate and able to meet the requirements of in-line measurement in industry.The issued problems are to enrich the representative samples and to maintain the stability of the model; the designed program on-line is to be tested by practical production.