Monitoring the drying process of peppermint leaves using near-infrared spectroscopy

Kudo, M., Moffat, A.C. and Watt, R.A. (2001) Monitoring the drying process of peppermint leaves using near-infrared spectroscopy. AAPS Pharmaceutical Sciences, 3 (Supplement 631).

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Abstract

Purpose. To determine how near-infrared spectroscopy (NIRS) can be used as a novel technique to control the drying process of pharmaceutically important natural products. Methods. Leaves of peppermint were used as an example in this study. A sample of fresh leaves was coarsely chopped and placed in a 10cm glass dish. Percentage water was determined by an MM710 NIR backscatter gauge (NDC Infrared Engineering) pre-calibrated using SpeedCal, by Karl Fischer titration, and by weight loss of a sample in an oven at 35ºC. The leaves were sampled in this way every 20 minutes until readings indicated that they had reached below the moisture percentage specified by the British Pharmacopoeia (11%). Results. Percentages obtained using loss on drying were significantly higher than those measured using the NIR gauge and Karl Fischer. This could indicate that loss on drying is not a reliable method for the analysis of water content alone, as other materials which may be present in the leaves (e.g. volatile oils, sugars) can account for the higher values. However, there was a good correlation between NIR gauge readings and Karl Fischer results. Responses were linear across the range, with the resulting R2 value of 0.995. Differences between the two methods were as small as 0.32%. Conclusions. NIRS can be used as a reliable method to control the drying process of peppermint leaves, and in general, of natural products of pharmaceutical interest. It appears just as accurate as using Karl Fischer titrations, with the added advantage of being rapid and non-destructive.

Item Type:Article
Departments, units and centres:Department of Pharmaceutical and Biological Chemistry > Centre for Cancer Medicine
ID Code:284
Journal or Publication Title:AAPS Pharmaceutical Sciences
Deposited By:Library Staff
Deposited On:19 Oct 2006
Last Modified:19 Sep 2007 11:13

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