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Near-Infrared Spectroscopy

Near-Infrared Spectroscopy (NIR) is a method of determining molecular information about a substance by measuring vibrations. NIR uses a wavelength from 780 to 2500 nm, which allows for the non-intrusive analysis of materials [3]. NIR spectroscopy has been developed over the past 25 years to become a widely used and accepted method of sampling.

Near-Infrared Spectroscopy as a Tool for Sampling Pharmaceutical Products

NIR is most commonly used when one needs to analyze “multicomponent molecular vibrational” properties of a particular substance in the presence of another substance [6]. The pharmaceutical industry has a wide range of uses for NIR, particularly in manufacturing and quality control. This is useful when measuring the homogeneity of a blend of materials. NIR is similar, in theory, to UV-Visible Spectroscopy in the way that it measures samples. NIR spectroscopy, however, does not require extensive preparation of samples.

NIR for Pharmaceutical Manufacturing

Multiple industries use NIR technology, but one of the areas where it is most effective is in monitoring and sampling of powders and tablets in the pharmaceutical manufacturing process. The most important factor in the manufacturing of pharmaceuticals is that the blend of ingredients be correct. There must be the correct ratio of active ingredient to excipient for the drug to work correctly and safely. An understanding of the blending process and how various materials work together is crucial to understanding how to make pharmaceuticals [4]. It is essential that pharmaceutical manufacturers have tools that allow them to study both the blending process and the resulting tablets for a better comprehension of how the processes work. In the long-term, a better understanding and better system of producing drugs can lead to safer pharmaceuticals and less expensive health care costs.

Traditional sampling uses a thief-probe to sample a blend and then analyzes it using UV-Visible spectroscopy, an accepted standard in the field. NIR represents a non-intrusive alternative to this method as well as a way to help eliminate bias [4]. Biased samples are those that do not accurately represent the whole. Reducing the bias of samples leads to a better understanding of how the bending process works, which leads to robust drug manufacturing procedures. Non-intrusive sampling allows for less preparation of samples and less loss of time for sampling and analysis.

NIR can be used to measure the Active Pharmaceutical Ingredient (API) in a drug during the manufacturing process. Capable of determining both physical and chemical properties of substances, NIR has begun to replace other methods for testing pharmaceutical products. One key point to note, however, about NIR is that the process relies on one sample point as opposed to multiple sample points as with other methods [4]. This requires that the location of the sampling probe be representative of the entire blending process, if NIR is being used to monitor active blending [4]. Thus, when using NIR, one runs the risk of inaccurate data if the probe is placed in the wrong location.

Investigative uses of NIR

NIR is an especially useful tool because it is non-intrusive. An area where this characteristic can be valuable is in counterfeit drug investigations. A Belgian study showed that, when compared to other spectroscopic techniques, NIR performed on an equal or higher level than its peers [5]. In the study NIR was used alongside, FT-IR spectroscopy and Raman spectroscopy in an effort to determine which sampling technique was best able to separate counterfeit Viagra™ and Cialis™ from the authentic products. The study found that NIR functioned as one of the best and worked even better when combined with FT-IR spectroscopy [5]. These functions of NIR have led to an increase in interest in the technique in recent years [4]. The process proves useful in tracing problems with pharmaceutical products to their source and determining the quality of drugs from Internet based pharmacies [4].

The Future of NIR in Pharmaceuticals

The future of NIR is positive. Studies indicate that NIR is capable of providing a better understanding of the pharmaceutical production process and of being used as a monitoring and sampling tool for manufacturing operations, counterfeit drug investigations and quality control [2,3,4].

References

1. Abbate S, Castiglioni E, Gangemi F, Gangemi R, Longhi G. 2010. NIR-VCD, Vibrational Circular Dichroism in the Near-Infrared: Experiments, Theory and Calculations. Chirality 21(1E):E242-E252.
2. Blanco M, Bautista M, Alcala M. 2008. API Determination by NIR Spectroscopy Across Pharmaceutical Production Process. Aaps Pharmscitech 9(4):1130-1135.
3. Feng T, Wang F, Pinal R, Wassgren C, Carvajal MT. 2008. Investigation of the variability of NIR in-line monitoring of roller compaction process by using Fast Fourier Transform (FFT) analysis. Aaps Pharmscitech 9(2):419-424.
4. Ma H, Anderson CA. 2008. Characterization of pharmaceutical powder blends by NIR chemical imaging. Journal of Pharmaceutical Sciences 97(8):3305-3320.
5. Sacre PY, Deconinck E, De Beer T, Courselle P, Vancauwenberghe R, Chiap P, Crommen J, De Beer JO. 2010. Comparison and combination of spectroscopic techniques for the detection of counterfeit medicines. Journal of Pharmaceutical and Biomedical Analysis 53(3):445-453.
6. Workman, Jerome Jr. [internet]. [updated 2005 Sep 12]. Waltham, MA: An Introduction to Near Infrared Spectroscopy; [cited 2010 Oct 28]. Available from http://www.spectroscopynow.com/coi/cda/detail.cda?id=1881&type=EducationFeature&chId=2&page=1