Fourier Transform Infrared Instrument Research Articles

Determining aqueous deuterium detection limits via infrared spectroscopy to understand its capabilities for real-time monitoring of tritiated water

Tritiated water will be present in many demonstrator class fusion devices in a wide array of locations and concentrations. Accurate and fast measurement will be a key requirement to ensure suitable process monitoring, safety assurance and tritium tracking is in place. This work quantifies the deuterium detection limits achievable using a benchtop transmission Fourier transform infrared (FTIR) instrument and an industrialised attenuated total reflectance (ATR)-FTIR instrument to understand the capabilities of these techniques for real-time monitoring of aqueous tritium. Deuterium limits of detection of 4.62 × 10-5 mol mL-1 and 1.07 × 10-3 mol mL-1 were demonstrated with measurement times of 10s for the transmission FTIR and ATR-FTIR, respectively. These instruments are considered viable for the measurement of high concentration tritiated water and have many potential benefits associated with their deployment.

Evaluation of Bioactive Compounds, Release Profiles, and Toxicity Test from Microcapsules Containing R. tuberosa L. Extracts Utilizing Gum Arabic

This study is essential to analyze the toxicity and release of bioactive compounds in R. tuberosa L. extract microcapsules coated with gum Arabic and to provide information on the use of microcapsules as a drug delivery system with controlled release of active ingredients. Investigations focused on the effect of pH and timing on discharge kinetics, as well as toxicity evaluation. The release of active ingredients from microcapsules was carried out in medium variations, namely pH 2.2 and pH 7.4, with release durations of 30, 60-, 90-, 120-, and 150-min. Bioactive compounds were released by 59.23% at pH 2.2 and 58.21% at pH 7.4 within 150 min. The BSLT (brine shrimp lethal toxicity) assay was used using brine shrimp larvae (Artemia salina L.), resulting in a non-toxic classification as evidenced by an LC50 value of 5729 μg/mL. Microcapsules in optimum conditions were then characterized using FTIR (Fourier-Transform Infrared) and SEM (scanning electron microscopy) instruments. The FTIR analysis showed variations in functional groups in R. tuberosa L. extracts, gum Arabic, and microcapsules. Furthermore, the SEM examination highlighted the morphology of microcapsules that were mostly spherical.

Using a portable IR spectrometer for materials characterization and identification

This work is an assessment of contactless techniques for space hardware ground testing and characterization. It is based on Fourier Transform Infrared (FT-IR) spectroscopy, namely a commercially available portable FT-IR instrument operating in reflection and transmission measurements at a considerable distance from the measured surfaces. The two methodologies are evaluated namely related to 1) molecular contamination monitoring, and 2) materials identification. These techniques can provide important information in support of Manufacturing, Assembly, Integration and Testing activities as well as non-conformance investigations. Non-contact characterization techniques are particularly relevant when dealing with sensitive surfaces and/or surfaces with limited access such as optical components already integrated in the optical bench.

Rapid assessment of canola spoilage under sub-optimal storage condition using FTIR spectroscopy

The storage environment of grains and oilseeds influences their physico-chemical properties that determine shelf-life and nutritional quality. In case of oilseeds, and more specifically canola, analytical chemistry methods are commonly used to determine their quality which is characterized by fatty acid value (FAV) of samples. As wet chemistry methods are time consuming and require the use of chemicals, Fourier transform infrared (FTIR) spectroscopy combined with multivariate data analysis was investigated for rapid assessment of canola quality as affected by sub-optimal storage. Moreover, in order to conduct the analysis on-site outside of a laboratory setting, the feasibility of using a portable instrument was studied. An FTIR spectrum of canola seeds stored at sub-optimal storage condition (35°C and 84% relative humidity) was obtained weekly for a period of five weeks. The quality degradation over this storage period was measured in terms of reduction in germination and FAV content. Principal components analysis (PCA) was applied on FTIR spectral data for dimensionality reduction and the first two principal components could successfully separate canola samples of different qualities (based on their respective storage durations). Quantitative analysis for prediction of FAV using partial least squares (PLS) regression method was done and models were built utilizing the entire spectral data as well by grouping the spectral into three spectral bands. A root mean square error of prediction (RMSEP) of 4.4% and R2=0.96, was achieved with the model built using the entire mid-infrared region. The spectral bands of 1000–1500 cm-1 and 2500–3000 cm-1 were also able to provide comparable results. Various combinations of spectral pre-processing of data were also explored. The results establish that portable FTIR instruments provide an accurate and rapid alternative to chemical analysis for predicting spoilage and determining canola quality.

IDENTIFIKASI GUGUS FUNGSI DARI SENYAWA METABOLIT SEKUNDER EKSTRAK ETANOL DAUN KAYU JAWA Lannea coromandelica

Lannea Coromandelica is a plant that is widely used as a traditional medicinal plant. The Javanese wood plant Lannea Coromandelica is known to contain secondary metabolites in the form of alkaloids, flavonoids, saponins, and tannins. The aim of this study was to identify the functional groups of secondary metabolites of the Javanese wood leaf extract Lannea coromandelica. The method used is by extracting the Javanese leaves of Lannea coromandelica using 96% ethanol solvent and then identifying the functional groups of secondary metabolites using the FTIR (Fourier Transform Infrared) instrumentation. Identification results with FTIR showed absorption at wave number (cm-1) : 3424.39, 2919.45, 2850.72, 1626.59, 1561.39, 1441.97, 1377.81, 1232.30, 1100.41 there is an -O-H group, a C-O carbonyl group, an aromatic C=C ring, and a span of two. C-H and C-N groups which identify the presence of alkaloid compounds, saponins, flavonoids and tannins which are known as secondary metabolites from Javanese wood leaves Lannea coromandelica.

Monitoring Worker Exposure to Respirable Crystalline Silica: Application for Data-driven Predictive Modeling for End-of-Shift Exposure Assessment.

In the ever-expanding complexities of the modern-day mining workplace, the continual monitoring of a safe and healthy work environment is a growing challenge. One specific workplace exposure concern is the inhalation of dust containing respirable crystalline silica (RCS) which can lead to silicosis, a potentially fatal lung disease. This is a recognized and regulated health hazard, commonly found in mining. The current methodologies to monitor this type of exposure involve distributed sample collection followed by costly and relatively lengthy follow-up laboratory analysis. To address this concern, we have investigated a data-driven predictive modeling pipeline to predict the amount of silica deposition quickly and accurately on a filter within minutes of sample collection completion. This field-based silica monitoring technique involves the use of small, and easily deployable, Fourier transform infrared (FTIR) spectrometers used for data collection followed by multivariate regression methodologies including Principal Component Analysis (PCA) and Partial Least Squares (PLS). Given the complex nature of respirable dust mixtures, there is an increasing need to account for multiple variables quickly and efficiently during analysis. This analysis consists of several quality control steps including data normalization, PCA and PLS outlier detection, as well as applying correction factors based on the sampler and cassette used for sample collection. While outside the scope of this article to test, these quality control steps will allow for the acceptance of data from many different FTIR instruments and sampling types, thus increasing the overall useability of this method. Additionally, any sample analyzed through the model and validated using a secondary method can be incorporated into the training dataset creating an ever-growing, more robust predictive model. Multivariant predictive modeling has far-reaching implications given its speed, cost, and scalability compared to conventional approaches. This contribution presents the application of PCA and PLS as part of a computational pipeline approach to predict the amount of a deposited mineral of interest using FTIR data. For this specific application, we have developed the model to analyze RCS, although this process can be implemented in the analysis of any IR-active mineral, and this pipeline applied to any FTIR data.

Highly luminescent copper nanoclusters as temperature sensors and “turn off” detection of oxytetracycline

Polyethyleneimine (PEI), playing roles as a templating agent, has been successfully applied to prepare blue-green-emitting copper nanoclusters (Cu NCs@PEI) on the basis of a rapid chemical reduction synthesis method. Some characterization methods, such as fluorescence spectrophotometer, UV spectrophotometer, Fourier transform infrared instrument (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM) and fluorescence lifetime, were used for the analysis of physical, chemical and optical properties of Cu NCs@PEI. The Cu NCs@PEI displayed a blue-green emission wavelength at 485 nm and the corresponding quantum yield (QY) was 2.24%. Subsequently, the as-synthesized Cu NCs@PEI were applied for the trace analysis of oxytetracycline on the basis of the inner filter effect (IFE) and static quenching, which caused the fluorescence to be effectively quenched. Additionally, this proposed platform based on the Cu NCs@PEI for oxytetracycline sensing possessed an excellent linear range from 0.5 to 300 μM with a lower detection limit of 0.032 μM (S/N = 3) and correlation coefficient R2 of 0.9972. Surprisingly, as the temperature increased, the fluorescence intensities of Cu NCs@PEI decreased gradually. Thence, the Cu NCs@PEI could be applied for the sensing of temperature. Finally, the practicability of the detection method have been successfully verified by analyzing oxytetracycline in real samples, enlarging its applicable fields for oxytetracycline sensing.

Crystallization mechanism of micro flake Cu particle-filled poly(ethylene glycol) composites

Poly(ethylene glycol) (PEG) is used as phase change materials while the low thermal conductivity restricted the thermal storage efficiency. Incorporation of the metal particles (MPs) into PEG could enhance the thermal conductivity while the crystallization kinetic mechanism of the MP-filled PEG composites is altered. Flake MPs are characterized with layer structure and a large aspect ratio, while there are few research works related to the effect of flake MPs on the crystallization kinetic mechanism of flake MP-filled polymer composites. In this work, different micro flake copper (Cu) particles contents were introduced into the PEG matrix via the physical blending method. The Fourier transform infrared instrument (FT-IR) was used to characterize the chemical compatibility of the PEG/Cu composites. The differential scanning calorimetry (DSC) method was to characterize the crystalline kinetic mechanism of the micro flake Cu particle-filled polymer composites by using the isothermal model and non-isothermal model. It was found that the COC conformation of the confined PEG in the composites was altered, and more helical conformations were transferred from the zigzag conformations. The addition of the Cu particles in the PEG matrix enhanced the heterogeneous nucleation meantime hindered the diffusion of the PEG molecular chains. As a result, the crystallization rate of the PEG/Cu composites was optimized only when there was a middle Cu content in the PEG matrix (14.89 wt% in this work). Additionally, the PEG/Cu composites had 3D PEG crystal growth geometry in the isothermal crystallization process while the stronger dependence of the PEG crystal growth geometry on the temperature was found in the non-isothermal crystallization especially when the Cu amount was higher than 14.89 wt%.

Performance Comparison of Four Portable FTIR Instruments for Direct-on-Filter Measurement of Respirable Crystalline Silica.

Exposure to dusts containing respirable crystalline silica is a recognized hazard affecting various occupational groups such as miners. Inhalation of respirable crystalline silica can lead to silicosis, which is a potentially fatal lung disease. Currently, miners' exposure to respirable crystalline silica is assessed by collecting filter samples that are sent for laboratory analysis. A more timely field-based silica monitoring method using direct-on-filter (DoF) analysis is being developed by researchers at the National Institute for Occupational Safety and Health (NIOSH) to provide mine operators with the option to evaluate miners' exposure at the mine. This field-based silica monitoring technique involves the use of portable Fourier transform infrared (FTIR) instruments. As a step in the development of this new analytical technique, four commercially available portable FTIR instruments were evaluated for their ability to provide reproducible measurements from filter samples containing respirable crystalline silica. Reported testing indicates that measurements varied within ±4.1% between instruments for filter samples that contained high-purity respirable crystalline silica. Measurements varied within ±3.0% between instruments for filter samples that contained varying mineral composition. Filter samples were repeatedly analyzed by the same instrument over short and extended periods of time, and mean coefficients of variation did not exceed ±1.6 and ±2.4%, respectively. Mixed model analysis revealed that there was no statistically significant (P < 0.05) change in average measurements made over an extended period of time for all instruments. Results suggest that each of the four FTIR instruments evaluated in this study were able to generate precise and reproducible DoF analysis results of respirable dust samples.

Sensitivity-Enhanced Fourier Transform Mid-Infrared Spectroscopy Using a Supercontinuum Laser Source.

Fourier transform infrared (FT-IR) spectrometers have been the dominant technology in the field of mid-infrared (mid-IR) spectroscopy for decades. Supercontinuum laser sources operating in the mid-IR spectral region now offer the potential to enrich the field of FT-IR spectroscopy due to their distinctive properties, such as high-brightness, broadband spectral coverage and enhanced stability. In our contribution, we introduce this advanced light source as a replacement for conventional thermal emitters. Furthermore, an approach to efficient coupling of pulsed mid-IR supercontinuum sources to FT-IR spectrometers is proposed and considered in detail. The experimental part is devoted to pulse-to-pulse energy fluctuations of the applied supercontinuum laser, performance of the system, as well as the noise and long-term stability. Comparative measurements performed with a conventional FT-IR instrument equipped with a thermal emitter illustrate that similar noise levels can be achieved with the supercontinuum-based system. The analytical performance of the supercontinuum-based FT-IR spectrometer was tested for a concentration series of aqueous formaldehyde solutions in a liquid flow cell (500 µm path length) and compared with the conventional FT-IR (130 µm path length). The results show a four-times-enhanced detection limit due to the extended path length enabled by the high brightness of the laser. In conclusion, FT-IR spectrometers equipped with novel broadband mid-IR supercontinuum lasers could outperform traditional systems providing superior performance, e.g., interaction path lengths formerly unattainable, while maintaining low noise levels known from highly stable thermal emitters.

The application of rapid handheld FTIR petroleum hydrocarbon-contaminant measurement with transport models for site assessment: A case study

Conventional contaminated site assessment requires sophisticated sampling and laboratory analyses, which are costly and time consuming. There is a trend for soil analyses to shift from complex laboratory procedures to rapid, simple and non-destructive spectroscopic methods that can be used in the field. Handheld Fourier Transform Infrared (FTIR) spectroscopy has the advantage of providing information for rapid in situ site characterisation. To apply the infrared (IR) spectral application for petroleum hydrocarbon (PH) contamination site investigation, the coherent bands at locations from 3000 to 2800 cm−1 represent carbon (C) – hydrogen (H) bonding for long-chain alkanes due to –C–H stretching vibrations. The areas of the coherent bands at these locations can be used to quantify the total petroleum hydrocarbon (TPH) concentrations in soils. With additional spectral data from IR spectroscopy there is potential for predicting soil texture and water content, which are the basic inputs for modelling the migration of PH at contaminated sites. This study demonstrates the innovative coupling of spectral analytical models and a handheld FTIR instrument, with a soil erosion model, the Revised Universal Soil Loss Equation (RUSLE), and the Hydrus hydrological model. The integration of these models were used to investigate the potential downstream water and groundwater contamination risks from the migration of PH at a PH-contaminated site.

Highly UV and Corrosion - Resistant Poly(vinylidene fluoride)‐Co‐Hexafluoropropylene - Carbon Nanotubes Superhydrophobic Nanocomposite Coating for C-Steel

A robust superhydrophobic nanocomposite coating (PVDFHFP-CNTs) of poly(vinylidene fluoride)‐co‐hexafluoropropylene (PVDFHFP) and carbon nanotubes (CNTs) was fabricated on carbon steel using a two-step process: electrospinning and spray coating. The wettability properties of the prepared coating were inspected by measuring the water contact angle (WCA). Before the addition of CNTs, the WCA and the sliding angle (SA) of the PVDFHFP were 150°±3 and 2°±3, respectively while after the addition of CNTs, their values increased to 155°±2 and 3°±2, respectively. The wettability of the as-prepared coatings was also inspected after exposure to UV radiation with a light power of 0.89 W m-2 for 41 cycles according to ASTM standard D4587 – 11 (general metal coatings Standard) whereas each cycle includes 8 h exposure to UV illumination at 60 °C, and condensation for 4 h at 50 °C. It was found that the measured WCA and water contact water angle hysteresis (WCAH) for PVDFHFP-CNTs nanocomposite 152° ± 2 and 6° ± 2 compared to 147° ± 2 and 17° ± 3 of pure PVDFHFP, respectively. The morphology of the superhydrophobic coating was explored. It shows a beaded-like fiber structure. Spectra elements of the prepared coatings were obtained using the Fourier transform infrared instrument (FTIR). The surface roughness of the fabricated super water-repellent coatings were measured using atomic force microscope (AFM). The electrochemical behavior of superhydrophobic coating was evaluated by electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl before and after exposure to UV radiation. The outcomes showed the high corrosion resistance of PVDFHFP-CNTs compared to the neat PVDFHFP coating in presence and absence of UV.

Multicolor Discrete Frequency Infrared Spectroscopic Imaging.

Advancement of discrete frequency infrared (DFIR) spectroscopic microscopes in image quality and data throughput are critical to their use for analytical measurements. Here, we report the development and characterization of a point scanning instrument with minimal aberrations and capable of diffraction-limited performance across all fingerprint region wavelengths over arbitrarily large samples. The performance of this system is compared to commercial state of the art Fourier transform infrared (FT-IR) imaging systems. We show that for large samples or smaller set of discrete frequencies, point scanning far exceeds (∼10-100 fold) comparable data acquired with FT-IR instruments. Further we show improvements in image quality using refractive lenses that show significantly improved contrast across the spatial frequency bandwidth. Finally, we introduce the ability to image two tunable frequencies simultaneously using a single detector by means of demodulation to further speed up data acquisition and reduce the impact of scattering. Together, the advancements provide significantly better spectral quality and spatial fidelity than current state of the art imaging systems while promising to make spectral scanning even faster.

Long-Term Strategy for Assessing Carbonaceous Particulate Matter Concentrations from Multiple Fourier Transform Infrared (FT-IR) Instruments: Influence of Spectral Dissimilarities on Multivariate Calibration Performance.

Matching the spectral response between multiple spectrometers is a mandatory procedure when developing robust calibrations whose prediction is independent of instrument-related signal variations. A viable alternative to complex calibration transfer methods consists of matching the instrument spectral response by controlling a set of key instrumental and environmental parameters. This paper discusses the applicability of such an approach to three Fourier transform infrared (FT-IR) spectrometers used for the routine assessment of carbonaceous particulate matter concentrations in the Interagency Monitoring of PROtected Visual Environments (IMPROVE) speciation network. The effectiveness of the proposed matching procedure is evaluated by comparing the spectral response for each individual instrument in order to characterize the extent, and nature, of the remaining inter-instrument spectral dissimilarities. Instrument-related contributions to the signal were determined to be small compared with the spectral variability induced by the filter type used for sample collection. The impact of spectral differences on prediction was addressed through the comparison of model performance derived from multiple calibration scenarios. A hybrid model yielding accurate and homogeneous prediction regardless of the instrument was proposed for organic carbon (OC) and elemental carbon (EC), two major constituents of atmospheric particulate matter. Coefficients of determination of 0.98 (OC) and 0.90 (EC) with median biases not exceeding 0.20 µg (OC) and 0.07 µg (EC) are reported. The long-term stability, assessed from weekly measurements of reference samples, shows a deviation in predicted concentrations of less than ±5% over a 2.5-year period for most of the data collected. Extending OC and EC hybrid models to the prediction of ambient samples collected during the two subsequent years provides satisfactory performance. The proposed instrument matching procedure coupled with the relative simplicity of the hybrid model is an alternative to computationally advanced calibration transfer methodologies for the characterization of carbonaceous particulate matter using multiple FT-IR instruments.

Synthesis and characterization of 2‐hydroxyethylmethacrylate/2‐(3‐indol‐yl)ethylmethacrylamide‐based novel hydrogels as drug carrier with in vitro antibacterial properties

ABSTRACTIn this study, a new cationic monomer 2‐(3‐indol‐yl)ethylmethacrylamide (IEMA) derived from tryptamine was synthesized in a single step and characterized by Fourier transform infrared (FTIR), 1H‐NMR, and 13C‐NMR. Then, one‐step preparation of novel poly[2‐hydroxyethylmethacrylate‐c‐2‐(3‐indol‐yl)ethylmethacrylamide], or p(HEMA‐c‐IEMA), copolymeric hydrogels has been performed successfully with IEMA and 2‐hydroxyethylmethacrylate (HEMA) as monomers using free radical aqueous polymerization. The hydrogels were characterized with scanning electron microscopy, FTIR, elemental analysis, thermogravimetric analysis, and texture profile analysis instruments. p(HEMA‐c‐IEMA) hydrogels were used for swelling, diffusion, drug release, and antibacterial activity studies. The drug‐release behavior of the hydrogels was determined as a function of time at 37 °C in pH 1.2 and 7.2. The swelling and drug‐release studies showed that an increased IEMA amount caused a higher increase in swelling and drug‐release values. Additionally, zero‐order, first‐order, and Higuchi equation kinetic models were applied to the drug‐release data, and the data fit well in the Higuchi model, and the Peppas power‐law model was applied to the release mechanism. Finally, the antibacterial activities of the hydrogels were screened against Gram‐positive bacteria (Bacillus cereus and Staphylococcus aureus) and Gram‐negative bacteria (Escherichia coli and Salmonella typhimurium). © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45550.

Rapid and automatic chemical identification of the medicinal flower buds of Lonicera plants by the benchtop and hand-held Fourier transform infrared spectroscopy

With the utilization of the hand-held equipment, Fourier transform infrared (FT-IR) spectroscopy is a promising analytical technique to minimize the time cost for the chemical identification of herbal materials. This research examines the feasibility of the hand-held FT-IR spectrometer for the on-site testing of herbal materials, using Lonicerae Japonicae Flos (LJF) and Lonicerae Flos (LF) as examples. Correlation-based linear discriminant models for LJF and LF are established based on the benchtop and hand-held FT-IR instruments. The benchtop FT-IR models can exactly recognize all articles of LJF and LF. Although a few LF articles are misjudged at the sub-class level, the hand-held FT-IR models are able to exactly discriminate LJF and LF. As a direct and label-free analytical technique, FT-IR spectroscopy has great potential in the rapid and automatic chemical identification of herbal materials either in laboratories or in fields. This is helpful to prevent the spread and use of adulterated herbal materials in time.

Preparation and electric property of PA/PVDF blend for energy storage material

This paper selected typical polar polymers which are polyvinylidene fluoride (PVDF) and polyamide (PA) to prepare PA/PVDF blend for energy storage material. Three kinds of PA (PA6, PA66 and PA11) with representative characters were chosen as the main research polymers for blending with PVDF. The electrical properties of three kinds of all-polymeric blends were tested and the microstructure was characterized by X-ray diffractometer (XRD), Fourier transform infrared instrument (FTIR), Scanning electron microscope (SEM) and Differential scanning calorimetry (DSC). Our finding suggests that the created high-e polymeric blends represent a novel type of material that is easy to process. In addition, the dielectric constant and breakdown strength of PA/PVDFs are relatively high so that it can be applied to electronic components.

Spatio-Temporal Variability of Water Vapor in the Free Troposphere Investigated by Dial and Ftir Vertical Soundings

We report on the free tropospheric spatio-temporal variability of water vapor investigated by the analysis of a five-year period of water vapor vertical soundings above Mt. Zugspitze (2962 m a.s.l., Germany). Our results are obtained from a combination of measurements of vertically integrated water vapor (IWV), recorded with a solar Fourier Transform InfraRed (FTIR) spectrometer and of water vapor profiles recorded with the nearby differential absorption lidar (DIAL). The special geometrical arrangement of one zenith-viewing and one sun-pointing instrument and the temporal resolution of both optical instruments allow for an investigation of the spatiotemporal variability of IWV on a spatial scale of less than one kilometer and on a time scale of less than one hour. We investigated the short-term variability of both IWV and water vapor profiles from statistical analyses. The latter was also examined by case studies with a clear assignment to certain atmospheric processes as local convection or long-range transport. This study is described in great detail in our recent publication [1]. 1. INSTRUMENTATION AND GEOGRAPHICAL ARRANGEMENT The Zugspitze (47:42 ◦ N, 10:98 ◦ E, 2962 m a.s.l.) is by far the highest mountain on the northern rim of the Alps. The free troposphere above this site is representative of Central Europe. The mountain is above the moist boundary layer for most of the year. Due to reduced absorption losses this site is ideal for sensitive spectroscopic measurements of water vapor throughout the free troposphere. While the FTIR instrument is located on the summit of Mt. Zugspitze the DIAL instrument is located at the Schneefernerhaus research station (UFS) on the steep southern slope of Mt. Zugspitze at an altitude of 2675 m a.s.l., 680 m southwest of the FTIR instrument (Fig. 1). The solar FTIR instrument uses direct radiation from the sun in the mid-infrared as light source (Table). The instrument provides water vapor columns integrated along its slanted viewline towards the sun with a precision better than 0.05 mm. It is based on a Bruker IFS125HR interferometer and is described in detail by [2].

Retrieval of ammonia from ground-based FTIR solar spectra

Abstract. We present a retrieval method for ammonia (NH3) total columns from ground-based Fourier transform infrared (FTIR) observations. Observations from Bremen (53.10° N, 8.85° E), Lauder (45.04° S, 169.68° E), Réunion (20.9° S, 55.50° E) and Jungfraujoch (46.55° N, 7.98° E) were used to illustrate the capabilities of the method. NH3 mean total columns ranging 3 orders of magnitude were obtained, with higher values at Bremen (mean of 13.47 × 1015 molecules cm−2) and lower values at Jungfraujoch (mean of 0.18 × 1015 molecules cm−2). In conditions with high surface concentrations of ammonia, as in Bremen, it is possible to retrieve information on the vertical gradient, as two layers can be distinguished. The retrieval there is most sensitive to ammonia in the planetary boundary layer, where the trace gas concentration is highest. For conditions with low concentrations, only the total column can be retrieved. Combining the systematic and random errors we have a mean total error of 26 % for all spectra measured at Bremen (number of spectra (N) = 554), 30 % for all spectra from Lauder (N = 2412), 25 % for spectra from Réunion (N = 1262) and 34 % for spectra measured at Jungfraujoch (N = 2702). The error is dominated by the systematic uncertainties in the spectroscopy parameters. Station-specific seasonal cycles were found to be consistent with known seasonal cycles of the dominant ammonia sources in the station surroundings. The developed retrieval methodology from FTIR instruments provides a new way of obtaining highly time-resolved measurements of ammonia burdens. FTIR-NH3 observations will be useful for understanding the dynamics of ammonia concentrations in the atmosphere and for satellite and model validation. It will also provide additional information to constrain the global ammonia budget.

The Establishment of Performance Verification Procedures for Fourier Transform Infrared Spectrometers

An integral part of any laboratory Quality Management System (QMS) is the ability to verify an analytical instrument0s performance prior to analyzing ocial samples. Performance verification procedures provide the instrument user the means to assess whether a system is functioning properly. They are a routine predetermined set of tests and acceptance criteria that can be provided by the instrument manufacturer and/or established by the laboratory itself. Performance verification procedures that have been established for a Fourier transform infrared (FT-IR) microscope system outfitted with a macro sampling accessory allow the user to determine the daily and/or annual functionality of the instrument. Specifications were established for the IR microscope operating in transmission, reflection/absorption (R/A) and attenuated total reflection (ATR) sampling modes. The specifications for the macro sampling accessory were established for transmission and ATR sampling modes only. The acceptance criterion for each performance verification specification was calculated from a series of measurements made using each accessory and sampling mode. The performance verification procedures, as well as their associated specification and acceptance criteria described in this study, are general enough that they can be applied to FT-IR instruments from dierent manufacturers.