28 Seeing Past Fluorescent Excipients


MIRA XTR DS demonstrates superior resolution in comparison with traditional handheld 785 nm and 1064 nm systems in Raman analysis of two common excipients found in food and drug products (Figure 4).


Excitation at 1064 nm shows some improvement over traditional 785 nm interrogation, but even at this wavelength, spectra for both excipients lack sufficient signal-to-noise and peak resolution for confident library matching. Gum Arabic and microcrystalline cellulose (MCC) are excellent examples of fluorescent excipients that could potentially obscure the signal of other target ingredients in a mixture.


Non-destructive Analysis


Strongly coloured materials, such as a black plastic cap and blue cardboard, traditionally pose a challenge for measurement with 785 nm Raman systems. High quality data is obtained with MIRA XTR DS, which is in stark contrast to interrogation using both 785 and 1064 nm lasers, as seen in Figure 5. The spectra of both materials at 785 nm showed the broad, characteristic emission of fluorescence. Excitation at 1064 nm resulted in immediate burning of both plastic and paper cardboard. It is well known that this can be an issue, and the manufacturer of the system used here offers a large spot adapter (LSA), designed to spread out incident laser light and reduce sample damage. However, high laser powers are notorious for causing burns.


Figure 6. The difference between real and imitation honey can be detected with MIRA XTR DS at sufficient sensitivity to perceive different mixtures of the two substances.


acetyl fentanyl are both ‘designer drug’ analogues of fentanyl [11] and reveal signature peaks of low intensity with 785 nm laser excitation that are difficult to resolve in spectra dominated by fluorescence interference.


Figure 5. Raman spectra for two coloured materials tested at different wavelengths and with MIRA XTR DS.


The power to authenticate materials


Food authentication is highly desirable when it comes to traditional, certified products like meat, cheese [8], olive oil, and honey. Because Raman has the sensitivity to distinguish between different sugars [9] and even grass-fed vs. grain-fed beef [10], it is posited as a method for instant, on-site interrogation of other food products.


A more illustrative application of fluorescence eXTRaction can be seen in Figure 6.


Fentanyl analysis with MIRA XTR DS


Capabilities of MIRA XTR DS for eXTRacting Raman spectra from background fluorescence can also be essential in the detection of narcotics and illicit drugs. Butyryl fentanyl and


Figure 7. MIRA XTR DS can distinguish very similar molecular analogues of fentanyl.


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