Influence of interfering co-appearing container peaks on the accuracy of direct quantitative Raman measurement of a sample in a plastic container.

The axially perpendicular offset (APO) scheme was previously demonstrated as a versatile scheme able to minimize or eliminate the glass background in the direct and non-sampling Raman measurement of an ethanol sample housed in a glass bottle. Alternatively, when directly analyzing a sample housed in a plastic container, another typical container yielding strong Raman peaks itself, the Raman peaks of both the container and the housed sample are unavoidably present together in a collected spectrum. Therefore, a crucial issue to investigate under this situation is how the magnitude of the co-appearing container peaks influences the accuracy for quantitative analysis of the housed sample.

Incorporating Non-NIR Absorbing Agent into Packed Powder Samples in Diffuse Reflectance NIR Measurement to Improve Representation of Sample Composition and Accuracy of Concentration Determination.

A strategy to improve accuracy of near-infrared (NIR) quantitative analysis of powder samples by alleviating the subsampling problem is demonstrated. The approach is to increase spectroscopic sampling volume for more accurate representation of its composition by filling the void space in a packed sample with liquid to reduce differences in refractive index between particle and unoccupied space. By this way, NIR radiation can propagate deeper into the packed powder due to decreased degree of reflection at the interfaces, leading to greater sampling volume.

Fast and non-destructive Raman spectroscopic determination of multi-walled carbon nanotube (MWCNT) contents in MWCNT/polydimethylsiloxane composites.

A versatile Raman spectroscopic method to determine the contents of carbon nanotubes (CNTs) in CNT/polydimethylsiloxane (PDMS) composites is demonstrated, and important issues directly related to the accuracy of the measurement have been investigated. Initially, Raman microscopic mappings over an area of 6.0 × 6.

A mechanical pencil lead-supported carbon nanotube/Au nanodendrite structure as an electrochemical sensor for As(iii) detection.

A mechanical pencil lead (MPL), an easily obtainable carbon-based material with a consistent size, was used as a frame to construct an MPL-supported carbon nanotube/Au nanodendrite (MPL-CNT/AuND) sensor through simple electrodeposition of Au onto the MPL in the presence of CNTs. A nanodendrite structure was adopted to ensure large numbers of active electrochemical sites because of its hierarchical structure with well-aligned terraces; the CNTs were used to firmly adhere the fabricated Au nanodendrites to the MPL surface to ensure ruggedness. The MPL-CNT/AuND structure was used to measure As samples in a concentration range from 0.

Development of hydrophobic surface substrates enabling reproducible drop-and-dry spectroscopic measurements.

We investigated several spectroscopic substrates with hydrophobic surfaces that were able to form reproducible droplets of aqueous samples for reliable high throughput drop-and-dry measurements. An amine-coated substrate, a polytetrafluoroethylene (PTFE) disk, and a perfluorooctyltrichlorosilane (FTS) coated substrate were prepared and initially evaluated for use in the determination of fat concentrations in milks using near-infrared (NIR) spectroscopy. Since the dried milk spots were not compositionally uniform due to the localization of components during sample drying, NIR spectra were collected by fully covering each spot to ensure a correct compositional representation of the sample.

Acquisition of reproducible transmission near-infrared (NIR) spectra of solid samples with inconsistent shapes by irradiation with isotropically diffused radiation using polytetrafluoroethylene (PTFE) beads.

A bead-incorporated transmission scheme (BITS) has been demonstrated for collecting reproducible transmission near-infrared (NIR) spectra of samples with inconsistent shapes. Isotropically diffused NIR radiation was applied around a sample and the surrounding radiation was allowed to interact homogeneously with the sample for transmission measurement. Samples were packed in 1.

Development of a particle-settling tolerant transmission Raman scheme for analysis of suspension samples.

We have demonstrated a simple and effective strategy, the so-called axial illumination scheme, that is able to obtain representative Raman spectra of suspension samples with minimal influence from internal particle settling. In a partially settled suspension sample, since particle concentrations at given points throughout the sample differ, the acquisition of Raman spectra representative of the entire sample composition is critically important for accurate quantitative analysis. The proposed scheme used axially irradiated laser radiation in the same or opposite direction of settling, thus allowing laser photons to migrate through the settling-induced particle-density gradient formed in the suspension and to widely interact with particles regardless of their settled locations.

Diffuser-incorporated transmission NIR measurement for reliable analysis of packed granular samples.

A diffuser-incorporated transmission near-infrared (NIR) scheme that enables direct spectral collection of packed granular samples with reliable sample representation and reproducibility has been demonstrated. The analytical utility of this method has been evaluated for the determination of polyethylene (PE) pellet density and the discrimination of the geographical origin of rice samples. Based on the preliminary observation of transmission spectral features acquired from spherical polyoxymethylene (POM) packings composed of different particle sizes as well as packing thickness, a portion of the radiation was propagated through the void space in the packing without fully interacting with the POM pellets.