In vivo identification of early-stage cartilage degradation could positively impact disease progression in osteoarthritis, but to date remains a challenge. The primary goal of this study was to develop an infrared fiber-optic probe (IFOP) chemometric method using partial least squares (PLS1) to objectively determine the degree of cartilage degradation. Arthritic human tibial plateaus (N = 61) were obtained during knee replacement surgery and analyzed by IFOP. IFOP data were collected from multiple regions of each specimen and the cartilage graded according to the Collins Visual Grading Scale of 0, 1, 2, or 3. These grades correspond to cartilage morphology that displayed normal, swelling or softening, superficially slight fibrillation, and deeper fibrillation or serious fibrillation, respectively. The model focused on detecting early cartilage degradation and therefore utilized data from grades 0, 1, and 2. The best PLS1 calibration utilized the spectral range 1733-984 cm(-1), and independent validation of the model utilizing 206 spectra to create a model and 105 independent test spectra resulted in a correlation between the predicted and actual Collins grade of R2 = 0.8228 with a standard error of prediction of 0.258 with a PLS1 rank of 15 PLS factors. A preliminary PLS1 calibration that utilized a cross-validation technique to investigate the possibility of correlation with histological tissue grade (33 spectra from 18 tissues) resulted in R2 = 0.8408 using only eight PLS factors, a very encouraging outcome. Thus, the groundwork for use of IFOP-based chemometric determination of early cartilage degradation has been established.
Grazing-angle Fourier transform infrared reflection−absorption spectrometry (IRRAS) using a fiber-optic accessory has
been investigated as a potential in situ technique for the
detection and quantification of contamination by active pharmaceutical agents on glass and metal surfaces. Two methods
were used for contamination preparation: one based on
smearing a known amount of sample, in solution, onto the
substrate and the other by spraying the substrate with an
aerosol of the analyte in a volatile solvent. Chemometric
calibrations using partial least-squares (PLS) regression are
presented and evaluated for acetaminophen on aluminum and
glass, and ibuprofen on aluminum and stainless steel. The
results indicate that surface loadings of 0.05 μg/cm2 is a readily
achievable limit of detection for the IRRAS technique.
The binuclear title complex [Pt2Me2(p-H) ( p -d ~p m ) ~] [PF,], dppm = Ph2PCH2PPh2, has been prepared and characterized by l H and n.m.r. spectroscopy and by an X-ray structure determination. Crystals are monoclinic, with space group P2,/c, a = 10.640(3), b = 20.341 (3), c = 23.201 (3) A, (3 = 91.88(2)', and Z = 4.The structure has been solved by the heavy-atom method and refined to R = 0.053 for 5 374 reflections with / 2 30(/). The cation has the ' A-frame ' structure with a Pt-Pt separation of 2.932(1) A; a closed threecentre two-electron Pt2 (p-H) bonding system is proposed. The complex undergoes slow reductive elimination of methane induced by added PMe,Ph and is photochemically decomposed, but it has high thermal stability.
Fourier transform infrared reflection-absorption spectroscopy has been used with a fiber-optic grazing-angle reflectance probe as a rapid, in situ method for trace surface analysis of acetaminophen and aspirin at loadings of approximately 0-2 microg cm(-2) on glass. Partial least-squares multivariate regression permits the loadings to be quantified, simultaneously, with root-mean-squared errors of prediction of RMSEP approximately 0.1 microg cm(-2) for both compounds. The detection limits are estimated to be LD approximately 0.2 microg cm(-2).
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