Raman spectral analysis for quality determination of grignard reagent

Authors: JOSHI, RAHUL - Chungnam National University; JOSHI, RITU - Chungnam National University; MO, CHANGYEUN - Kangwon National University; FAQEEZADA, MOHAMMAD - Chungnam National University; AMANAH, HANIM - Chungnam National University; MASITHOH, RUDIATI - Gadjah Mada University; Kim, Moon; CHO, BYOUNG-KWAN - Chungnam National University

Submitted to: Applied Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2020
Publication Date: 5/20/2020
Citation: Joshi, R., Joshi, R., Mo, C., Faqeezada, M., Amanah, H., Masithoh, R., Kim, M.S., Cho, B. 2020. Raman spectral analysis for quality determination of grignard reagent. Applied Sciences. 10(10):3545. https://doi.org/10.3390/app10103545.
DOI: https://doi.org/10.3390/app10103545

Interpretive Summary: Grignard reagents are organomagensium compounds that are often used in the chemical processes for making pharmaceuticals. Toluene is a common adulterant that can lower the quality of Grignard reagents. This study investigated the use of Raman spectroscopy to detect and predict the concentration of toluene in Grignard reagent. Samples spanning a range of mixture concentrations for tolune and Grignard reagent were used for Raman spectral measurements. The measurements were analyzed with a partial least squares method to develop a prediction model for toluene concentration. The model produced predicted concentration values that were highly correlated to the prepared sample concentrations, showing that this method of Raman spectroscopy measurement and analysis may be a useful tool for rapidly and effectively evaluating the quality of Grignard reagent. The benefits to be gained from a method such as this include improved, higher quality pharmaceutical processes and yields, which can affect the safety and quality of pharmaceuticals and chemicals produced and used for the food, agriculture, and medical fields.

Technical Abstract: Grignard reagent is one of the most popular materials in chemical and pharmaceutical reaction processes, which requires high quality with minimal adulteration. In this study, Raman spectroscopic technique was investigated for rapid determination of toluene content which is one of the common adulterant in Grignard reagent. Raman spectroscopy is the most suitable spectroscopic method mitigating moisture and CO2 interference in the molecules of Grignard reagent. Raman spectra for the mixtures of toluene and Grignard reagent with different concentrations were analyzed with a partial least square regression (PLSR) method. The combination of spectral wavebands in the prediction model was optimized with a variables selection method of variable importance in projection (VIP). The results obtained from the VIP-based PLSR model showed reliable performance for predicting the toluene concentration present in Grignard reagent with a correlation coefficient value of 0.97 and a standard error of prediction (SEP) of 0.71%. The results showed that Raman spectroscopy combined with multivariate analysis could be an effective tool for rapid determination of the quality of Grignard reagent.