Raman Spectroscopy

Bugay, David E.; Brittain, Harry G.

doi:10.1201/9780849361333.ch9

Cited by 4 publications

(3 citation statements)

References 61 publications

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“…A list of stretching frequencies and complete spectra are provided in Table S1 and Figure S2 (Supporting Information). Raman measurements are also recorded for characterization, with the added advantage that this technique does not require any sample preparation (such as KBr pellet), and hence unintended phase transitions are avoided . Similar to IR, the N–H Raman shift for TMP molecule was observed at 3471.7 cm –1 , 3315.8 cm –1 in Form 1, and 3467.2 cm –1 , 3329.2 cm –1 in Form 2, and 3467.2 cm –1 , 3328.1 cm –1 in Form 3, and 3467.2 cm –1 , 3315.8 cm –1 in Form 4 (Figure b).…”

Section: Results and Discussionmentioning

confidence: 96%

“…Spectroscopic methods such as IR and Raman are able to identify and distinguish between polymorphs, molecular conformations, and hydrogen bonding interactions by probing the vibrational frequencies of atoms . The sensitivity of these techniques to subtle changes in the crystal structure has led to their application in a wide variety of investigations of polymorphic studies, and in confirming results obtained from PXRD analysis.…”

Section: Results and Discussionmentioning

confidence: 99%

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Tetramorphs of the Antibiotic Drug Trimethoprim: Characterization and Stability

Maddileti

Swapna

Nangia

2015

Crystal Growth & Design

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Trimethoprim (TMP) is a well-known antifolate drug and one of the most widely used broad-spectrum antibiotics. TMP was first approved by the United States FDA in combination with sulfamethoxazole (SMZ) in 1973, and three polymorphs of TMP (named Form I, II, and III) and a hydrate form were reported in 1978. However, a complete characterization and molecular level analysis of polymorphic structures are not available. We report herein four polymorphs (Forms 1−4) of TMP and a hemihydrate form with complete structural and thermal characterization. The polymorphs were isolated in the pure state by different techniques such as antisolvent method, freeze-drying, and spray drying. Polymorphs 1 and 2 of our study match with Forms I and II reported, and polymorphs 3 and 4 are novel. The X-ray crystal structure of a novel TMP Form 2 is now reported nearly four decades after the first crystal structure of Form 1 was determined by neutron diffraction (J. Am. Chem. Soc. 1976Soc. , 98, 2074Soc. −2078. The crystal structure of Form 1 has two types of R 2 2 (8) motifs, and Form 2 has a third type R 2 2 (8) and R 3 2 (8) motif of N−H•••N arom hydrogen bonds. The polymorphs were characterized by FT-IR and Raman spectroscopy, differential scanning calorimetry (DSC), 15 N ss-NMR, field emission scanning electron microscopy, powder X-ray diffraction, and also dynamic vapor sorption. Thermodynamic stability, phase transformations, and Hirshfeld surfaces are also discussed. The polymorphs were tested under accelerated International Conference on Harmonization (ICH) conditions of 40 °C and 75% RH for stability, and found that all the solid forms were stable for three months except TMP Form 3, which converted to Form 2. Slurry grinding and thermal experiments suggest that TMP Form 1 is the most stable modification among TMP crystal forms.

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Section: Results and Discussionmentioning

confidence: 96%

Section: Results and Discussionmentioning

confidence: 99%

Tetramorphs of the Antibiotic Drug Trimethoprim: Characterization and Stability

Maddileti

Swapna

Nangia

2015

Crystal Growth & Design

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“…Near-infrared (NIR) and Raman spectroscopy are both sensitive to, and capable of accurately predicting, these phenomena. 1,2 As NIR spectroscopy is based on optical absorption and Raman spectroscopy on the measurement of inelastic scattering, comparison of the parallel performance of these 2 classes of instrumentation is indirect. More often than not, the instrument eventually deployed is selected based on limited criteria that do not consider all aspects of performance.…”

Section: Introductionmentioning

confidence: 99%

Determination of figures of merit for near-infrared and raman spectrometry by net analyte signal analysis for a 4-component solid dosage system

2007

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Process analytical technology has elevated the role of sensors in pharmaceutical manufacturing. Often the ideal technology must be selected from many suitable candidates based on limited data. Net analyte signal (NAS) theory provides an effective platform for method characterization based on multivariate figures of merit (FOM). The objective of this work was to demonstrate that these tools can be used to characterize the performance of 2 dissimilar analyzers based on different underlying spectroscopic principles for the analysis of pharmaceutical compacts. A fully balanced, 4-constituent mixture design composed of anhydrous theophylline, lactose monohydrate, microcrystalline cellulose, and starch was generated; it consisted of 29 design points. Six 13-mm tablets were produced from each mixture at 5 compaction levels and were analyzed by near-infrared and Raman spectroscopy. Partial least squares regression and NAS analyses were performed for each component, which allowed for the computation of FOM. Based on the calibration error statistics, both instruments were capable of accurately modeling all constituents. The results of this work indicate that these statistical tools are a suitable platform for comparing dissimilar analyzers and illustrate the complexity of technology selection.

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