Path-length Cell Research Articles

Trace detection and photothermal spectral characterization by a tuneable thermal lens spectrometer with white-light excitation

In the thermal lens experimental set-up we replaced the commonly employed pump laser by a halogen lamp, combined with an interference filter, providing a tuneable, nearly monochromatic pump source over the range of wavelengths 430–710 nm. Counter-propagating pump and probe beams are used and a 1 mm path-length sample cell together with the interference filter makes an optical cavity, providing amplification of the thermal lens signal, which leads to enhancement of the measurement sensitivity, and enables detection of absorbances on the order of 5 × 10−6. Amplified thermal lens signal allows us to replace the typical lock-in amplifier and digital oscilloscope with a silicon photodetector, Arduino, and a personal computer, offering the possibility for a compact, robust and portable device, useful for in-field absorption measurements in low concentration or weakly absorbing species. The use of a white light source for optical pumping, an interference filter for wavelength selection and direct diagnostic of the thermal lens signal increase the versatility of the instrument and simplifies substantially the experimental setup. Determination of Fe(II) concentrations at parts per billion levels was performed by the described white-light thermal lens spectrophotometer and the absorption spectrum for 50 μgL–1 Fe(II)-1,10-phenanthroline was well reproduced with an average measurement precision of 4%. The obtained limits of detection and quantitation of Fe(II) determination at 510 nm are 3 µgL−1 and 11 µgL−1, respectively. The calibration curve was linear in the concentration range of LOQ-500 µgL−1 with reproducibility between 2% and 6%, confirming that this instrument provides good spectrometric capabilities such as high sensitivity, tuneability and good reproducibility. In addition, the versatility of the instrument was demonstrated by recording the photothermal spectrum of gold nanostructured material and determination of excitation wavelength with most efficient optical to thermal energy conversion, which differs considerably (cca 100 nm) from the absorption maximum of the investigated sample.

Definition and dynamic control of a continuous chromatography process independent of cell culture titer and impurities

Advances in cell culture technology have enabled the production of antibody titers upwards of 30g/L. These highly productive cell culture systems can potentially lead to productivity bottlenecks in downstream purification due to lower column loadings, especially in the primary capture chromatography step. Alternative chromatography solutions to help remedy this bottleneck include the utilization of continuous processing systems such as periodic counter-current chromatography (PCC).Recent studies have provided methods to optimize and improve the design of PCC for cell culture titers up to about 3g/L. This paper defines a continuous loading strategy for PCC that is independent of cell culture background and encompasses cell culture titers up to about 31g/L. Initial experimentation showed a challenge with determining a difference in change in UV280nm signal (ie. ΔUV) between cell culture feed and monoclonal antibody (mAb) concentration. Further investigation revealed UV280nm absorbance of the cell culture feedstock without antibody was outside of the linear range of detection for a given cell pathlength. Additional experimentation showed the difference in ΔUV for various cell culture feeds can be either theoretically predicted by Beer’s Law given a known absorbance of the media background and impurities or experimentally determined using various UV280nm cell pathlengths. Based on these results, a 0.35mm pathlength at UV280nm was chosen for dynamic control to overcome the background signal. The pore diffusion model showed good agreement with the experimental frontal analysis data, which resulted in definition of a ΔUV setpoint range between 20 and 70% for 3C-PCC experiments. Product quality of the elution pools was acceptable between various cell culture feeds and titers up to about 41g/L. Results indicated the following ΔUV setpoints to achieve robust dynamic control and maintain 3C-PCC yield: ∼20-45% for titers greater than 10g/L depending on UV absorbance of the HCCF and ∼45-70% for titers of up to 10g/L independent of UV absorbance of the HCCF. The strategy and results presented in this paper show column loading in a continuous chromatography step can be dynamically controlled independent of the cell culture feedstock and titer, and allow for enhanced process control built into the downstream continuous operations.

Thermal Breakdown Kinetics of 1-Ethyl-3-Methylimidazolium Ethylsulfate Measured Using Quantitative Infrared Spectroscopy.

In this work, the thermal stability of the room temperature ionic liquid (RTIL) 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][EtSO4]) is investigated using infrared (IR) spectroscopy. Quantitative IR absorption spectral data are measured for heated [EMIM][EtSO4]. Spectra have been collected between 25 ℃ and 100 ℃ using a heated optical cell. Multiple samples and cell pathlengths are used to determine quantitative values for the molar absorptivity of [EMIM][EtSO4]. These results are compared to previous computational models of the ion pair. These quantitative spectra are used to measure the rate of thermal decomposition of [EMIM][EtSO4] at elevated temperatures. The spectroscopic measurements of the rate of decomposition show that thermogravimetric methods overestimate the thermal stability of [EMIM][EtSO4].

A small-volume PVTX system for broadband spectroscopic calibration of downhole optical sensors.

An instrument is presented that is capable of measuring the optical spectrum (long-wave ultraviolet through short-wave mid-infrared) of fluids under a range of temperature and pressure conditions from ambient pressure up to 138 MPa (20 000 psi) and 422 K (300 °F) using ∼5 ml of fluid. Temperature, pressure, and density are measured in situ in real-time, and composition is varied by adding volatile and nonvolatile components. The stability and accuracy of the conditions are reported for pure ethane, and the effects of temperature and pressure on characteristic regions of the optical spectrum of ethane are illustrated after correction for temperature and pressure effects on the optical cell path length, as well as normalization to the measured density. Molar absorption coefficients and integrated molar absorption coefficients for several vibrational combination bands are presented.

Development and validation of new FTIR method for quantitative analysis of gliclazide in bulk and pharmaceutical dosage forms

A Fourier transform infrared (FTIR) spectrophotometric method was developed for quantitiative analysis of gliclazide in pharmaceutical formulations. The method involves extraction of gliclazide from tablets with chloroform by sonication and the direct measurement of the absorbance in liquid phase using a reduced path length cell. In general the IR spectrum was measured in transmission mode, for quantitation of gliclazide the spectra were measured in absorbance mode. The infrared spectrum of gliclazide shows peaks at 1650 cm -1 , 3400cm -1 , 3000 cm -1 corresponding to the carbonyl group, N-H group, and C-H group respectively. Among which N-H group showed intense, clear peak which is selected for quantitative estimation of gliclazide. The method was validated as per ICH guidelines. The results obtained were compared statistically with the existing HPLC method by t-test which indicated there is no significant difference between the methods at the probability value 0.05. The results demonstrated that the proposed method is accurate, precise while being simple and rapid tool for the determination of gliclazide in bulk and tablet dosage forms.

Fully Automated System for 99Tc Monitoring in Hospital and Urban Residues: A Simple Approach to Waste Management.

99Tc is an artificial beta emitter widely used in nuclear medicine for diagnostic tests. A fully automated and rapid system for 99Tc monitoring is introduced with the aim to improve hospital residues management. This system can also be helpful for controlling urban wastewater. Figures of merit similar to those obtained with liquid scintillation counting were achieved by exploiting a simple, economic, and portable system with spectrophotometric detection. The combination of flow analysis techniques, i.e., lab-on-valve (LOV) and multisyringe flow injection analysis (MSFIA), with a selective resin ((weak base extraction chromatographic (WBEC) resin) enables the analysis to be performed in a short time, achieving high selectivity and sensitivity levels. After elution with NH4OH (3 mol·L-1), 99Tc is derivatized with 1,5-diphenylcarbohydrazide (DPC) and finally detected by a miniaturized fiber optic CCD spectrophotometer at 520 nm, exploiting a long path-length liquid waveguide capillary cell (LWCC) of 100 cm path length. The proposed method was optimized by experimental design, achieving a limit of detection (LOD) of 4 ng of 99Tc (2.5 Bq), a reproducibility of 6%, and a resin durability of 78 injections. The microcolumn allows one to preconcentrate up to 100 mL of sample without deterioration of the analytical signal. The automated system was successfully applied to hospital residues and urban wastewater, and the attained recoveries were between 90% and 110%.

Infrared Optical Measurements of Thermal Breakdown in Battery Electrolytes

Electrolyte thermal stability is critical for both battery safety and extending battery life. Battery fires are often the result of thermal breakdown of the liquid electrolyte leading to a flammable mixture of volatile products. Even in the absence of fire, electrolyte decomposition leads to battery swelling, harmful precipitates, reduced ion conductivities, and undesirable battery chemistry. Current methods of determining electrolyte stability using ex-situ techniques, such as thermal gravimetric analysis or differential scanning calorimetry, can over predict thermal stability, do not address materials compatibility within batteries, and cannot identify chemical decomposition mechanisms. Infrared optical detection of thermal stability offers an in-situ approach providing: speciation, identification of chemical bonds involved in decomposition, real-time detection, and chemical kinetics. In this work, the thermal stability of the room temperature ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][EtSO4]) is investigated using infrared (IR) spectroscopy. Quantitative IR absorption spectral data are measured for the heated ionic liquid. Spectra have been collected between 25°C and 100°C using a heated optical cell. Multiple samples and cell path lengths were used to determine quantitative values of the absorption coefficient. These results were compared to previous computational models of the ion pair to identify each absorption band with corresponding chemical bonds. The quantitative spectra were then used to measure the rate of thermal decomposition at elevated temperatures revealing the onset of breakdown above 75°C.

Sensitive measurements of trace gas of formaldehyde using a mid-infrared laser spectrometer with a compact multi-pass cell

A compact multi-pass cell with a pair of cylindrical mirrors for sensitive detection of trace gases in emission from combustion was constructed. The cell path-length was 9.8m and its volume was 0.13L. Each mirror shape was a square with a side length of 25.4mm and the mirrors were placed 100mm apart. The cell was applied to detection of formaldehyde (HCHO), which is formed during fuel combustion and is harmful to the environment. The direct absorption spectrum in the range 2979.06–2981.2cm−1 was recorded with a mid-infrared distributed feedback (DFB) interband cascade laser. The recorded spectrum of HCHO was in good agreement with a spectrum simulated using the HITRAN 2012 database. An absorption line at 2979.663cm−1 (4.26×10−21cm2molecule−1cm−1, ν5, 1184–1073), which showed the strongest absorption in the emission frequency range of the DFB interband cascade laser, was selected for HCHO detection. We also confirmed that there were no interferences of absorption peaks of major combustion products in the selected HCHO absorption peaks. At a signal-to-noise ratio of two and 3kPa using 2f wavelength modulation spectroscopy at less than 1MHz bandwidth, the limit of detection for HCHO was 73ppb by volume.

Fluorophore Absorption Size Exclusion Chromatography (FA-SEC): An Alternative Method for High-Throughput Detergent Screening of Membrane Proteins.

Membrane proteins play key roles in many fundamental functions in cells including ATP synthesis, ion and molecule transporter, cell signalling and enzymatic reactions, accounting for ~30% genes of whole genomes. However, the hydrophobic nature of membrane proteins frequently hampers the progress of structure determination. Detergent screening is the critical step in obtaining stable detergent-solubilized membrane proteins and well-diffracting protein crystals. Fluorescence Detection Size Exclusion Chromatography (FSEC) has been developed to monitor the extraction efficiency and monodispersity of membrane proteins in detergent micelles. By tracing the FSEC profiles of GFP-fused membrane proteins, this method significantly enhances the throughput of detergent screening. However, current methods to acquire FSEC profiles require either an in-line fluorescence detector with the SEC equipment or an off-line spectrofluorometer microplate reader. Here, we introduce an alternative method detecting the absorption of GFP (FA-SEC) at 485 nm, thus making this methodology possible on conventional SEC equipment through the in-line absorbance spectrometer. The results demonstrate that absorption is in great correlation with fluorescence of GFP. The comparably weaker absorption signal can be improved by using a longer path-length flow cell. The FA-SEC profiles were congruent with the ones plotted by FSEC, suggesting FA-SEC could be a comparable and economical setup for detergent screening of membrane proteins.

New and improved infrared absorption cross sections for chlorodifluoromethane (HCFC-22)

Abstract. The most widely used hydrochlorofluorocarbon (HCFC) commercially since the 1930s has been chloro-difluoromethane, or HCFC-22, which has the undesirable effect of depleting stratospheric ozone. As this molecule is currently being phased out under the Montreal Protocol, monitoring its concentration profiles using infrared sounders crucially requires accurate laboratory spectroscopic data. This work describes new high-resolution infrared absorption cross sections of chlorodifluoromethane over the spectral range 730–1380 cm−1, determined from spectra recorded using a high-resolution Fourier transform spectrometer (Bruker IFS 125HR) and a 26 cm pathlength cell. Spectra of chlorodifluoromethane/dry synthetic air mixtures were recorded at resolutions between 0.01 and 0.03 cm−1 (calculated as 0.9/MOPD; MOPD denotes the maximum optical path difference) over a range of temperatures and pressures (7.5–762 Torr and 191–295 K) appropriate for atmospheric conditions. This new cross-section dataset improves upon the one currently available in the HITRAN (HIgh-resolution TRANsmission) and GEISA (Gestion et Etude des Informations Spectroscopiques Atmosphériques) databases; in particular it provides coverage over a wider range of pressures and temperatures, has more accurate wavenumber scales, more consistent integrated band intensities, improved signal-to-noise, is free of channel fringing, and additionally covers the ν2 and ν7 bands.

Characterisation of Conformational and Ligand Binding Properties of Membrane Proteins Using Synchrotron Radiation Circular Dichroism (SRCD).

Membrane proteins are notoriously difficult to crystallise for use in X-ray crystallographic structural determination, or too complex for NMR structural studies. Circular dichroism (CD) is a fast and relatively easy spectroscopic technique to study protein conformational behaviour in solution. The advantage of synchrotron radiation circular dichroism (SRCD) measured with synchrotron beamlines compared to the CD from benchtop instruments is the extended spectral far-UV region that increases the accuracy of secondary structure estimations, in particular under high ionic strength conditions. Membrane proteins are often available in small quantities, and for this SRCD measured at the Diamond B23 beamline has successfully facilitated molecular recognition studies. This was done by probing the local tertiary structure of aromatic amino acid residues upon addition of chiral or non-chiral ligands using long pathlength cells (1–5 cm) of small volume capacity (70 μl–350 μl). In this chapter we describe the use of SRCD to qualitatively and quantitatively screen ligand binding interactions (exemplified by Sbma, Ace1 and FsrC proteins); to distinguish between functionally similar drugs that exhibit different mechanisms of action towards membrane proteins (exemplified by FsrC); and to identify suitable detergent conditions to observe membrane protein-ligand interactions using stabilised proteins (exemplified by inositol transporters) as well as the stability of membrane proteins (exemplified by GalP, Ace1). The importance of the in solution characterisation of the conformational behaviour and ligand binding properties of proteins in both far- andnear-UV regions and the use of high-throughput CD (HT-CD) using 96- and 384-well multiplates to study the folding effects in various protein crystallisation buffers are also discussed.

New and improved infrared absorption cross sections for dichlorodifluoromethane (CFC-12)

Abstract. Despite its widespread commercial use throughout the twentieth century, primarily in the refrigeration industry, dichlorodifluoromethane (CFC-12) is now known to have the undesirable effect of depleting stratospheric ozone. As this long-lived molecule slowly degrades in the atmosphere, monitoring its vertical concentration profile using infrared sounders on satellite platforms crucially requires accurate laboratory spectroscopic data. This work describes new high-resolution infrared absorption cross sections of dichlorodifluoromethane over the spectral range 800–1270 cm−1, determined from spectra recorded using a high-resolution Fourier transform spectrometer (Bruker IFS 125HR) and a 26 cm pathlength cell. Spectra of dichlorodifluoromethane/dry synthetic air mixtures were recorded at resolutions between 0.01 and 0.03 cm−1 (calculated as 0.9/MOPD; MOPD = maximum optical path difference) over a range of temperatures and pressures (7.5–761 Torr and 190–294 K) appropriate for atmospheric conditions. This new cross-section dataset improves upon the one currently available in the HITRAN and GEISA databases.

Compact Solid-State 213 nm Laser Enables Standoff Deep Ultraviolet Raman Spectrometer: Measurements of Nitrate Photochemistry.

We describe a new compact acousto-optically Q-switched diode-pumped solid-state (DPSS) intracavity frequency-tripled neodymium-doped yttrium vanadate laser capable of producing ~100 mW of 213 nm power quasi-continuous wave as 15 ns pulses at a 30 kHz repetition rate. We use this new laser in a prototype of a deep ultraviolet (UV) Raman standoff spectrometer. We use a novel high-throughput, high-resolution Echelle Raman spectrograph. We measure the deep UV resonance Raman (UVRR) spectra of solid and solution sodium nitrate (NaNO3) and ammonium nitrate (NH4NO3) at a standoff distance of ~2.2 m. For this 2.2 m standoff distance and a 1 min spectral accumulation time, where we only monitor the symmetric stretching band, we find a solid state NaNO3 detection limit of ~100 μg/cm(2). We easily detect ~20 μM nitrate water solutions in 1 cm path length cells. As expected, the aqueous solutions UVRR spectra of NaNO3 and NH4NO3 are similar, showing selective resonance enhancement of the nitrate (NO3(-)) vibrations. The aqueous solution photochemistry is also similar, showing facile conversion of NO3(-) to nitrite (NO2(-)). In contrast, the observed UVRR spectra of NaNO3 and NH4NO3 powders significantly differ, because their solid-state photochemistries differ. Whereas solid NaNO3 photoconverts with a very low quantum yield to NaNO2, the NH4NO3 degrades with an apparent quantum yield of ~0.2 to gaseous species.

FTIR spectroscopy for estimation of efavirenz in raw material and tablet dosage form

A Fourier transform infrared (FTIR) spectrophotometric method was developed for rapid and direct measurement of efavirenz in pharmaceutical formulations. The method involves extraction of efavirenz from tablets with chloroform by sonication and the direct measurement of the absorbance in liquid phase using a reduced path length cell. In general, the spectrum was measured in transmission mode. The equipment was configured to collect a spectrum at 8 cm-1 resolution and 45 scans per sec .The spectra were collected between 4000 cm-1 and 450cm-1, the band obtained at 1750cm-1 (carbonyl group) showed intense, clear peak in the liquid phase for quantitation. The method was validated as per ICH guidelines. The method fulfilled most validation requirements in the linearity range 200-1000µg/mL. The coefficient of determination, limit of detection and quantification was found to be 0.993, 49.12?g/mL and 148.84?g/mL respectively. Results of developed FTIR method were compared with the results obtained with the existing UV method statistically by using t-test, which indicated that there is no significant difference between the methods at P=0.05. The proposed FTIR method reduces the solvent consumption and also eliminates the use of reagents. Thus the developed method offers a good alternative for the quantitative estimation of efavirenz in bulk and pharmaceutical dosage forms and also to quantify efavirenz when combined with other API in the same dosage form.International Current Pharmaceutical Journal, May 2015, 4(6): 390-395

High resolution investigation of the v3 band of trifluoromethyliodide (CF3I)

The high-resolution absorption spectrum of trifluoromethyliodide (CF3I), an alternative gas to chlorofluorocarbons but with potential greenhouse effects, has been recorded at 0.001cm−1 resolution in the 200–350cm−1 region with the Bruker IFS125HR Fourier transform spectrometer at synchrotron SOLEIL. Due to the spectral congestion and the presence of numerous hot bands, the spectra have been recorded at the AILES Beamline facility at SOLEIL either at room temperature using a 150m optical path length cell or at 163K using the new LISA-SOLEIL cryogenic cell and at the Australian synchrotron using a flow cooling cell. This enables a detailed analysis of the v3 band at 286.29712(3)cm−1 of CF3I. The results of previous microwave measurements in the v3=1 and v6=1 vibrational states (Walters and Whiffen, 1983; Wahi, 1987) were combined with those of the present infrared analysis of the v3 band to obtain an improved set of parameters for the v3=1 (C–I stretching) and v6=1 (I–C–F bending) interacting vibrational states accounting for the Coriolis resonance coupling the v3=1 energy levels with those of the dark v6=1 state (located at ∼261.5 or at ∼267.6cm−1). Finally, a first investigation of the 2v3−v3 hot band is also performed.

Time-resolved visible and infrared difference spectroscopy for the study of photosystem I with different quinones incorporated into the A1 binding site

Room (298K) and low (77K) temperature time-resolved visible and infrared difference spectroscopy has been used to study photosystem I particles with phylloquinone (2-methyl-3-phytyl-1,4-naphthoquinone), menadione (2-methyl-1,4-naphthoquinone) and plastoquinone 9 (2,3-dimethyl-5-prenyl-l,4-benzoquinone), incorporated into the A1 binding site. Concentrated samples in short path-length (~5μm) sample cells are typically used in FTIR experiments. Measurements were undertaken using standard “dilute” samples at 298K, and concentrated (~5×) samples at both 298 and 77K. No concentration induced alterations in the flash-induced absorption changes were observed. Concentrated samples in short path-length cells form a transparent film at 77K, and could therefore be studied spectroscopically at 77K without addition of a cryoprotectant. At 298K, for photosystem I with plastoquinone 9/menadione/phylloquinone incorporated, P700+FA/B− radical pair recombination is characterized by a time constant of 3/14/80ms, and forward electron transfer from A1A− to Fx by a time constant of 211/3.1/0.309μs, respectively. At 77K, for concentrated photosystem I with menadione/phylloquinone incorporated, P700+A1− radical pair recombination is characterized by a time constant of 240/340μs, with this process occurring in 58/39% of the PSI particles, respectively. The origin of these differences is discussed. Marcus electron transfer theory in combination with kinetic modeling is used to simulate the observed electron transfer time constants at 298K. This simulation allows an estimate of the redox potential for the different quinones in the A1 binding site.

Uranium monitoring tool for rapid analysis of environmental samples based on automated liquid-liquid microextraction

A fully automated in-syringe (IS) magnetic stirring assisted (MSA) liquid-liquid microextraction (LLME) method for uranium(VI) determination was developed, exploiting a long path-length liquid waveguide capillary cell (LWCC) with spectrophotometric detection. On-line extraction of uranium was performed within a glass syringe containing a magnetic stirrer for homogenization of the sample and the successive reagents: cyanex-272 in dodecane as extractant, EDTA as interference eliminator, hydrochloric acid to make the back-extraction of U(VI) and arsenazo-III as chromogenic reagent to accomplish the spectrophotometric detection at 655nm. Magnetic stirring assistance was performed by a specially designed driving device placed around the syringe body creating a rotating magnetic field in the syringe, and forcing the rotation of the stirring bar located inside the syringe.The detection limit (LOD) of the developed method is 3.2µgL−1. Its good interday precision (Relative Standard Deviation, RSD 3.3%), and its high extraction frequency (up to 6h−1) makes of this method an inexpensive and fast screening tool for monitoring uranium(VI) in environmental samples. It was successfully applied to different environmental matrices: channel sediment certified reference material (BCR-320R), soil and phosphogypsum reference materials, and natural water samples, with recoveries close to 100%.

Quantitative infrared absorption cross sections of isoprene for atmospheric measurements

Abstract. Isoprene (C5H8, 2-methyl-1,3-butadiene) is a volatile organic compound (VOC) and is one of the primary contributors to annual global VOC emissions. Isoprene is produced primarily by vegetation as well as anthropogenic sources, and its OH- and O3-initiated oxidations are a major source of atmospheric oxygenated organics. Few quantitative infrared studies have been reported for isoprene, limiting the ability to quantify isoprene emissions via remote or in situ infrared detection. We thus report absorption cross sections and integrated band intensities for isoprene in the 600–6500 cm−1 region. The pressure-broadened (1 atmosphere N2) spectra were recorded at 278, 298, and 323 K in a 19.94 cm path-length cell at 0.112 cm−1 resolution, using a Bruker IFS 66v/S Fourier transform infrared (FTIR) spectrometer. Composite spectra are derived from a minimum of seven isoprene sample pressures, each at one of three temperatures, and the number densities are normalized to 296 K and 1 atm.

In-Line Measurement of Color and Total Phenolics during Red Wine Fermentations Using a Light-Emitting Diode Sensor

An in-line color and total phenolic sensor is described to track the color and total phenol evolution during red wine fermentations. The sensor uses multiple light-emitting diodes (LEDs) spanning the ultraviolet and visible spectrum, in particular 280 and 525 nm. The performance of phenolic sensor was evaluated by analyzing fermentation samples collected from multiple red wine fermentations performed during the 2012 season. The study confirmed that the LED phenolic sensor measurements strongly correlate with measurements performed with a reference UV-vis spectrophotometer and that in-line measurements can be made in a practical manner after removal of yeast and pulp with a 2.0 μm filter. The use of a 100 μm path-length flow cell avoids the need for dilution, making in-line measurements possible. The sensor provides in-line measurement on the evolution of the total phenolic content and color extraction patterns during red wine fermentations.

Transmission FTIR derivative spectroscopy for estimation of furosemide in raw material and tablet dosage form

A Fourier transform infrared derivative spectroscopy (FTIR-DS) method has been developed for determining furosemide (FUR) in pharmaceutical solid dosage form. The method involves the extraction of FUR from tablets with N,N-dimethylformamide by sonication and direct measurement in liquid phase mode using a reduced path length cell. In general, the spectra were measured in transmission mode and the equipment was configured to collect a spectrum at 4cm−1 resolution and a 13s collection time (10 scans co-added). The spectra were collected between 1400cm−1 and 450cm−1. Derivative spectroscopy was used for data processing and quantitative measurement using the peak area of the second order spectrum of the major spectral band found at 1165cm−1 (SO2 stretching of FUR) with baseline correction. The method fulfilled most validation requirements in the 2mg/mL and 20mg/mL range, with a 0.9998 coefficient of determination obtained by simple calibration model, and a general coefficient of variation <2%. The mean recovery for the proposed assay method resulted within the (100±3)% over the 80%–120% range of the target concentration. The results agree with a pharmacopoeial method and, therefore, could be considered interchangeable.