Raman spectra and Vibrational Assignments of Calcium Oxalate Polyhydrates

BELLETTI, GUSTAVO D.; COLOMBO, ESTEFANIA; TIELENS, FREDERIK; QUAINO, PAOLA

Santa Fe

Conferencia; VI San Luis Conference; 2018

INTEC

FourierTransform (FT)-Raman and FT-Infrared spectroscopies constitutesignificant tools for bio-medical diagnoses.Raman spectroscopy is not routinely used at the hospital formicrocrystalline pathologies, mainly because it has somedisadvantages compare to IR spectroscopy (the laser used as the probecan modify the chemistry of the deposit and the tissue may display asignificant background signal). However, Raman shows major advantagescompare to IR spectroscopy. Compositional mapping of samples simplydeposited on supports used routinely at the hospital, i.e. glass, canbe easily obtained with a submicron resolution. Measurements thoughtglass cover slip for air sensitive samples are also possible. Inaddition, in Raman the 50 cm-1to 400 cm-1spectral range is accessible (10 cm-1with enhanced filtering of the laser line), providing precise(unambiguous) chemical signature of the sample under scrutiny.Theuse of Raman spectroscopy, together with IR, as diagnostic tools atthe hospital ideally presupposes a complete understanding of theorigin of the different bands of pathological deposits. This isachievable through computational calculation Raman spectra of thedifferent constituting compounds. Inthis work, the vibrational spectra of the calcium oxalatepolyhydrates are investigated using DFT-D3, and theoretical Ramanspectra are obtained following the method of Fonari and Stauffer.The most important calcium oxalate compounds present in more than 70%of the kidney stones are analyzed: whewellite (monohydrate: COM),weddellite (dihydrate: COD), and caoxite (trihydrate: COT).Thetheoretical Raman vibrational spectra of the polyhydrates of thecalcium oxalates were computed and completely resolved. Most bandswere assigned and the theoretical predictions were compared withexperimental data. Then, we provide data that can be used to quantifythe different polyhydrates in natural mixtures such as in biologicalcalcifications or kidney stones. Suchan approach allowed a more accurate analysis of vibrational spectrahelping in the completion of the assignments of the vibrational bandsof the three calcium oxalate polyhydrates. Particular attention hasbeen paid to the low Raman frequencies and the presence of oxalicacid in natural calcium oxalate polyhydrates. The obtained resultsare expected to be supportive in the detection of the differentpolyhydrates in natural samples.p { margin-bottom: 0cm; direction: ltr; color: rgb(0, 0, 0); text-align: justify; }p.western { font-family: "CMR10", "Times New Roman"; font-size: 11pt; }p.cjk { font-family: "SimSun", "宋体"; font-size: 11pt; }p.ctl { font-family: "CMR10", "Times New Roman"; font-size: 10pt; }a:link { color: rgb(5, 99, 193); }