Variation in the Transmission Near-Infrared Signal with Depth in Turbid Media

Transmission near-infrared (NIR) measurements of a 1 mm thick aspirin disk were made at different positions as it was moved through a stack of eight 0.5 mm thick disks of microcrystalline cellulose (Avicel). The magnitude of the first derivative of absorbance for the aspirin interlayer at 8934 cm−1...

Full description

Saved in:
Bibliographic Details
Published in:Applied spectroscopy 2014-03, Vol.68 (3), p.383-387
Main Authors: Kellichan, Nicola, Nordon, Alison, Matousek, Pavel, Littlejohn, David, McGeorge, Gary
Format: Article
Language:English
Subjects:
Absorption
Aspirin
Cellulose
Cellulose - chemistry
Disks
Dosage Forms
Interlayers
Models, Chemical
Photons
Spectrometry
Spectroscopy
Spectroscopy, Near-Infrared - methods
Stacks
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Transmission near-infrared (NIR) measurements of a 1 mm thick aspirin disk were made at different positions as it was moved through a stack of eight 0.5 mm thick disks of microcrystalline cellulose (Avicel). The magnitude of the first derivative of absorbance for the aspirin interlayer at 8934 cm−1 was lower when the disk was placed at the top or bottom of the stack of Avicel disks, with the largest signal observed when the aspirin was positioned at the central positions. The variation in signal with depth is consistent with that observed previously for transmission Raman spectrometry. In both cases, the trend observed can be attributed to lower photon density at the air-sample interface, relative to the center of the sample, owing to loss of photons to the air. This results in a reduction in the number of photons absorbed or Raman photons generated and subsequently detected when the interlayer occupies a near-surface position.
ISSN:0003-7028
1943-3530
DOI:10.1366/13-07002