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Mifsud DV, Herczku P, Rácz R, Rahul KK, Kovács STS, Juhász Z, Sulik B, Biri S, McCullough RW, Kaňuchová Z, Ioppolo S, Hailey PA, Mason NJ. Energetic electron irradiations of amorphous and crystalline sulphur-bearing astrochemical ices. Front Chem 2022; 10:1003163. [PMID: 36226122 PMCID: PMC9549411 DOI: 10.3389/fchem.2022.1003163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Accepted: 08/30/2022] [Indexed: 11/13/2022] Open
Abstract
Laboratory experiments have confirmed that the radiolytic decay rate of astrochemical ice analogues is dependent upon the solid phase of the target ice, with some crystalline molecular ices being more radio-resistant than their amorphous counterparts. The degree of radio-resistance exhibited by crystalline ice phases is dependent upon the nature, strength, and extent of the intermolecular interactions that characterise their solid structure. For example, it has been shown that crystalline CH3OH decays at a significantly slower rate when irradiated by 2 keV electrons at 20 K than does the amorphous phase due to the stabilising effect imparted by the presence of an extensive array of strong hydrogen bonds. These results have important consequences for the astrochemistry of interstellar ices and outer Solar System bodies, as they imply that the chemical products arising from the irradiation of amorphous ices (which may include prebiotic molecules relevant to biology) should be more abundant than those arising from similar irradiations of crystalline phases. In this present study, we have extended our work on this subject by performing comparative energetic electron irradiations of the amorphous and crystalline phases of the sulphur-bearing molecules H2S and SO2 at 20 K. We have found evidence for phase-dependent chemistry in both these species, with the radiation-induced exponential decay of amorphous H2S being more rapid than that of the crystalline phase, similar to the effect that has been previously observed for CH3OH. For SO2, two fluence regimes are apparent: a low-fluence regime in which the crystalline ice exhibits a rapid exponential decay while the amorphous ice possibly resists decay, and a high-fluence regime in which both phases undergo slow exponential-like decays. We have discussed our results in the contexts of interstellar and Solar System ice astrochemistry and the formation of sulphur allotropes and residues in these settings.
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Affiliation(s)
- Duncan V. Mifsud
- Centre for Astrophysics and Planetary Science, School of Physical Sciences, University of Kent, Canterbury, United Kingdom
- Institute for Nuclear Research (Atomki), Debrecen, Hungary
- *Correspondence: Duncan V. Mifsud, ; Péter Herczku, ; Nigel J. Mason,
| | - Péter Herczku
- Institute for Nuclear Research (Atomki), Debrecen, Hungary
- *Correspondence: Duncan V. Mifsud, ; Péter Herczku, ; Nigel J. Mason,
| | - Richárd Rácz
- Institute for Nuclear Research (Atomki), Debrecen, Hungary
| | - K. K. Rahul
- Institute for Nuclear Research (Atomki), Debrecen, Hungary
| | | | - Zoltán Juhász
- Institute for Nuclear Research (Atomki), Debrecen, Hungary
| | - Béla Sulik
- Institute for Nuclear Research (Atomki), Debrecen, Hungary
| | - Sándor Biri
- Institute for Nuclear Research (Atomki), Debrecen, Hungary
| | - Robert W. McCullough
- Department of Physics and Astronomy, School of Mathematics and Physics, Queen’s University Belfast, Belfast, United Kingdom
| | - Zuzana Kaňuchová
- Astronomical Institute, Slovak Academy of Sciences, Tatranská Lomnica, Slovakia
| | - Sergio Ioppolo
- School of Electronic Engineering and Computer Science, Queen Mary University of London, London, United Kingdom
| | - Perry A. Hailey
- Centre for Astrophysics and Planetary Science, School of Physical Sciences, University of Kent, Canterbury, United Kingdom
| | - Nigel J. Mason
- Centre for Astrophysics and Planetary Science, School of Physical Sciences, University of Kent, Canterbury, United Kingdom
- Institute for Nuclear Research (Atomki), Debrecen, Hungary
- *Correspondence: Duncan V. Mifsud, ; Péter Herczku, ; Nigel J. Mason,
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Mifsud DV, Kaňuchová Z, Ioppolo S, Herczku P, Traspas Muiña A, Sulik B, Rahul KK, Kovács STS, Hailey PA, McCullough RW, Mason NJ, Juhász Z. Ozone production in electron irradiated CO 2:O 2 ices. Phys Chem Chem Phys 2022; 24:18169-18178. [PMID: 35861183 DOI: 10.1039/d2cp01535h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The detection of ozone (O3) in the surface ices of Ganymede, Jupiter's largest moon, and of the Saturnian moons Rhea and Dione, has motivated several studies on the route of formation of this species. Previous studies have successfully quantified trends in the production of O3 as a result of the irradiation of pure molecular ices using ultraviolet photons and charged particles (i.e., ions and electrons), such as the abundances of O3 formed after irradiation at different temperatures or using different charged particles. In this study, we extend such results by quantifying the abundance of O3 as a result of the 1 keV electron irradiation of a series of 14 stoichiometrically distinct CO2:O2 astrophysical ice analogues at 20 K. By using mid-infrared spectroscopy as our primary analytical tool, we have also been able to perform a spectral analysis of the asymmetric stretching mode of solid O3 and the variation in its observed shape and profile among the investigated ice mixtures. Our results are important in the context of better understanding the surface composition and chemistry of icy outer Solar System objects, and may thus be of use to future interplanetary space missions such as the ESA Jupiter Icy Moons Explorer and the NASA Europa Clipper missions, as well as the recently launched NASA James Webb Space Telescope.
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Affiliation(s)
- Duncan V Mifsud
- Centre for Astrophysics and Planetary Science, School of Physical Sciences, University of Kent, Canterbury CT2 7NH, UK. .,Institute for Nuclear Research (Atomki), Debrecen H-4026, Hungary.
| | - Zuzana Kaňuchová
- Astronomical Institute, Slovak Academy of Sciences, Tatranská Lomnica SK-059 60, Slovakia.
| | - Sergio Ioppolo
- School of Electronic Engineering and Computer Science, Queen Mary University of London, London E1 4NS, UK.
| | - Péter Herczku
- Institute for Nuclear Research (Atomki), Debrecen H-4026, Hungary.
| | - Alejandra Traspas Muiña
- School of Electronic Engineering and Computer Science, Queen Mary University of London, London E1 4NS, UK.
| | - Béla Sulik
- Institute for Nuclear Research (Atomki), Debrecen H-4026, Hungary.
| | - K K Rahul
- Institute for Nuclear Research (Atomki), Debrecen H-4026, Hungary.
| | | | - Perry A Hailey
- Centre for Astrophysics and Planetary Science, School of Physical Sciences, University of Kent, Canterbury CT2 7NH, UK.
| | - Robert W McCullough
- Department of Physics and Astronomy, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, UK
| | - Nigel J Mason
- Centre for Astrophysics and Planetary Science, School of Physical Sciences, University of Kent, Canterbury CT2 7NH, UK.
| | - Zoltán Juhász
- Institute for Nuclear Research (Atomki), Debrecen H-4026, Hungary.
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Mifsud DV, Hailey PA, Herczku P, Sulik B, Juhász Z, Kovács STS, Kaňuchová Z, Ioppolo S, McCullough RW, Paripás B, Mason NJ. Comparative electron irradiations of amorphous and crystalline astrophysical ice analogues. Phys Chem Chem Phys 2022; 24:10974-10984. [PMID: 35466978 DOI: 10.1039/d2cp00886f] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Laboratory studies of the radiation chemistry occurring in astrophysical ices have demonstrated the dependence of this chemistry on a number of experimental parameters. One experimental parameter which has received significantly less attention is that of the phase of the solid ice under investigation. In this present study, we have performed systematic 2 keV electron irradiations of the amorphous and crystalline phases of pure CH3OH and N2O astrophysical ice analogues. Radiation-induced decay of these ices and the concomitant formation of products were monitored in situ using FT-IR spectroscopy. A direct comparison between the irradiated amorphous and crystalline CH3OH ices revealed a more rapid decay of the former compared to the latter. Interestingly, a significantly lesser difference was observed when comparing the decay rates of the amorphous and crystalline N2O ices. These observations have been rationalised in terms of the strength and extent of the intermolecular forces present in each ice. The strong and extensive hydrogen-bonding network that exists in crystalline CH3OH (but not in the amorphous phase) is suggested to significantly stabilise this phase against radiation-induced decay. Conversely, although alignment of the dipole moment of N2O is anticipated to be more extensive in the crystalline structure, its weak attractive potential does not significantly stabilise the crystalline phase against radiation-induced decay, hence explaining the smaller difference in decay rates between the amorphous and crystalline phases of N2O compared to those of CH3OH. Our results are relevant to the astrochemistry of interstellar ices and icy Solar System objects, which may experience phase changes due to thermally-induced crystallisation or space radiation-induced amorphisation.
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Affiliation(s)
- Duncan V Mifsud
- Centre for Astrophysics and Planetary Science, School of Physical Sciences, University of Kent, Canterbury CT2 7NH, UK. .,Atomic and Molecular Physics Laboratory, Institute for Nuclear Research (Atomki), Debrecen H-4026, Hungary
| | - Perry A Hailey
- Centre for Astrophysics and Planetary Science, School of Physical Sciences, University of Kent, Canterbury CT2 7NH, UK.
| | - Péter Herczku
- Atomic and Molecular Physics Laboratory, Institute for Nuclear Research (Atomki), Debrecen H-4026, Hungary
| | - Béla Sulik
- Atomic and Molecular Physics Laboratory, Institute for Nuclear Research (Atomki), Debrecen H-4026, Hungary
| | - Zoltán Juhász
- Atomic and Molecular Physics Laboratory, Institute for Nuclear Research (Atomki), Debrecen H-4026, Hungary
| | - Sándor T S Kovács
- Atomic and Molecular Physics Laboratory, Institute for Nuclear Research (Atomki), Debrecen H-4026, Hungary
| | - Zuzana Kaňuchová
- Astronomical Institute, Slovak Academy of Sciences, Tatranska Lomnicá, SK-059 60, Slovakia
| | - Sergio Ioppolo
- School of Electronic Engineering and Computer Science, Queen Mary University of London, London E1 4NS, UK
| | - Robert W McCullough
- Department of Physics and Astronomy, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, UK
| | - Béla Paripás
- Department of Physics, Faculty of Mechanical Engineering and Informatics, University of Miskolc, Miskolc H-3515, Hungary
| | - Nigel J Mason
- Centre for Astrophysics and Planetary Science, School of Physical Sciences, University of Kent, Canterbury CT2 7NH, UK.
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Herczku P, Mifsud DV, Ioppolo S, Juhász Z, Kaňuchová Z, Kovács STS, Traspas Muiña A, Hailey PA, Rajta I, Vajda I, Mason NJ, McCullough RW, Paripás B, Sulik B. The Ice Chamber for Astrophysics-Astrochemistry (ICA): A new experimental facility for ion impact studies of astrophysical ice analogs. Rev Sci Instrum 2021; 92:084501. [PMID: 34470410 DOI: 10.1063/5.0050930] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Accepted: 07/27/2021] [Indexed: 06/13/2023]
Abstract
The Ice Chamber for Astrophysics-Astrochemistry (ICA) is a new laboratory end station located at the Institute for Nuclear Research (Atomki) in Debrecen, Hungary. The ICA has been specifically designed for the study of the physico-chemical properties of astrophysical ice analogs and their chemical evolution when subjected to ionizing radiation and thermal processing. The ICA is an ultra-high-vacuum compatible chamber containing a series of IR-transparent substrates mounted on a copper holder connected to a closed-cycle cryostat capable of being cooled down to 20 K, itself mounted on a 360° rotation stage and a z-linear manipulator. Ices are deposited onto the substrates via background deposition of dosed gases. The ice structure and chemical composition are monitored by means of FTIR absorbance spectroscopy in transmission mode, although the use of reflectance mode is possible by using metallic substrates. Pre-prepared ices may be processed in a variety of ways. A 2 MV Tandetron accelerator is capable of delivering a wide variety of high-energy ions into the ICA, which simulates ice processing by cosmic rays, solar wind, or magnetospheric ions. The ICA is also equipped with an electron gun that may be used for electron impact radiolysis of ices. Thermal processing of both deposited and processed ices may be monitored by means of both FTIR spectroscopy and quadrupole mass spectrometry. In this paper, we provide a detailed description of the ICA setup as well as an overview of the preliminary results obtained and future plans.
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Affiliation(s)
- Péter Herczku
- Institute for Nuclear Research (Atomki), PO Box 51, Debrecen H-4026, Hungary
| | - Duncan V Mifsud
- Institute for Nuclear Research (Atomki), PO Box 51, Debrecen H-4026, Hungary
| | - Sergio Ioppolo
- School of Electronic Engineering and Computer Science, Queen Mary University of London, London E1 4NS, United Kingdom
| | - Zoltán Juhász
- Institute for Nuclear Research (Atomki), PO Box 51, Debrecen H-4026, Hungary
| | - Zuzana Kaňuchová
- Astronomical Institute, Slovak Academy of Sciences, Tatranská Lomnica SK-059 60, Slovakia
| | - Sándor T S Kovács
- Institute for Nuclear Research (Atomki), PO Box 51, Debrecen H-4026, Hungary
| | - Alejandra Traspas Muiña
- School of Electronic Engineering and Computer Science, Queen Mary University of London, London E1 4NS, United Kingdom
| | - Perry A Hailey
- Centre for Astrophysics and Planetary Science, School of Physical Sciences, University of Kent, Canterbury CT2 7NH, United Kingdom
| | - István Rajta
- Institute for Nuclear Research (Atomki), PO Box 51, Debrecen H-4026, Hungary
| | - István Vajda
- Institute for Nuclear Research (Atomki), PO Box 51, Debrecen H-4026, Hungary
| | - Nigel J Mason
- Centre for Astrophysics and Planetary Science, School of Physical Sciences, University of Kent, Canterbury CT2 7NH, United Kingdom
| | - Robert W McCullough
- Department of Physics and Astronomy, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, United Kingdom
| | - Béla Paripás
- Department of Physics, Faculty of Mechanical Engineering and Informatics, University of Miskolc, Miskolc H-3515, Hungary
| | - Béla Sulik
- Institute for Nuclear Research (Atomki), PO Box 51, Debrecen H-4026, Hungary
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Sz�cs R, Caron I, Taylor KA, Gee SP, Ferguson PD, Kelly MA, Beaman JV, Lipczynski AM, Hailey PA. Generic approach to chiral separations: Chiral capillary electrophoresis with ternary cyclodextrin mixtures. ACTA ACUST UNITED AC 2001. [DOI: 10.1002/1520-667x(2000)12:11<568::aid-mcs20>3.0.co;2-t] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Marziano I, Sharp DCA, Dunn PJ, Hailey PA. On-Line Mid-IR Spectroscopy as a Real-Time Approach in Monitoring Hydrogenation Reactions. Org Process Res Dev 2000. [DOI: 10.1021/op000030m] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ivan Marziano
- Pfizer Central Research, Ramsgate Road, Sandwich CT13 9NJ, United Kingdom
| | - David C. A. Sharp
- Pfizer Central Research, Ramsgate Road, Sandwich CT13 9NJ, United Kingdom
| | - Peter J. Dunn
- Pfizer Central Research, Ramsgate Road, Sandwich CT13 9NJ, United Kingdom
| | - Perry A. Hailey
- Pfizer Central Research, Ramsgate Road, Sandwich CT13 9NJ, United Kingdom
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Candolfi A, De Maesschalck R, Jouan-Rimbaud D, Hailey PA, Massart DL. The influence of data pre-processing in the pattern recognition of excipients near-infrared spectra. J Pharm Biomed Anal 1999; 21:115-32. [PMID: 10701919 DOI: 10.1016/s0731-7085(99)00125-9] [Citation(s) in RCA: 165] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The effect of data pre-processing (no pre-processing, offset correction, de-trending, standard normal variate transformation (SNV), SNV + de-trending, multiplicative scatter correction, first and second derivative transformation after smoothing) on the identification of ten pharmaceutical excipients is investigated. Four pattern recognition methods are tested in the study, namely the Mahalanobis distance method, the SIMCA residual variance method, the wavelength distance method and a method based on triangular potential functions. The performance of the 32 method combinations is evaluated on the basis of two NIR data sets. The first one, measured in 1994, is used to build the classification models, the second, measured from 1994-1997, is used to assess the quality of the models. The best approach for the given data sets is the wavelength distance method combined with de-trending, a simple baseline correction method. More general recommendations for pre-processing excipient NIR data and for choosing an appropriate classification method are given.
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Affiliation(s)
- A Candolfi
- ChemoAC, Vrije Universiteit Brussel, Belgium
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Abstract
Soft independent modelling of class analogy (SIMCA) is applied to identify near-infrared (NIR) spectra of ten excipients used in the pharmaceutical industry. For each class at least 15 excipient samples were collected for the data base, considering different batches and occasionally various suppliers. Therefore the data of the classes are not always homogeneous. The performance of the original SIMCA method, which is usually described in the literature and also applied by the users, carried out at two confidence levels, 95 and 99%, on original data, SNV (standard normal variate transformation) and second derivative pre-processed data, is discussed. Reasons for the rejection rates are given. No objects were assigned to a wrong class using SIMCA.
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Affiliation(s)
- A Candolfi
- ChemoAC, Vrije Universiteit Brussel, Belgium
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Sekulic SS, Wakeman J, Doherty P, Hailey PA. Automated system for the on-line monitoring of powder blending processes using near-infrared spectroscopy. Part II. Qualitative approaches to blend evaluation. J Pharm Biomed Anal 1998; 17:1285-309. [PMID: 9800649 DOI: 10.1016/s0731-7085(98)00025-9] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Near Infrared (NIR) spectroscopy is seen as a very powerful tool in a variety of applications involving powder characterisation. Here we deal with a typical pharmaceutical application of powder blend monitoring. A D-optimal experimental design is used to cover the 85-115% range of the target formulation which is comprised of the active component at 3.5% w/w, Microcrystalline Cellulose (Avicel PH102) at 62%, Dibasic Calcium Phosphate Anhydrous at 31.5%, Sodium Starch Glycolate (Explotab) at 2%, and 1% Magnesium Stearate. A miniature Flobin blender has been modified to enable the use of a fibre optic probe for on-line NIR spectral data collection. The experiments were successful in detecting spectral changes which eventually converged to constant variance. While the NIR spectrum of a powdered sample is rich in information which is representative of both the physical and chemical characteristics of the sample, it is at times difficult to select the appropriate mathematical treatments in order to extract the desired information. This article investigates several possible pre-treatments (including detrending (DT), standard normal variates (SNV), second derivatives, and the combination of SNV and DT) together with several ways in establishing blend homogeneity, which includes the running block standard deviation, dissimilarity calculations and principal components analysis (PCA). The focus of this work is to investigate qualitative tools of analysis for blend homogeneity determinations, while future work will focus on quantitative data interpretation.
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Affiliation(s)
- S S Sekulic
- Pfizer Central Research, Groton, CT 06340, USA
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DeBraekeleer K, Cuesta Sánchez F, Hailey PA, Sharp DC, Pettman AJ, Massart DL. Influence and correction of temperature perturbations on NIR spectra during the monitoring of a polymorph conversion process prior to self-modelling mixture analysis. J Pharm Biomed Anal 1998; 17:141-52. [PMID: 9608436 DOI: 10.1016/s0731-7085(97)00177-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The influence of temperature variations on the rank of a NIR dataset, has been investigated by comparing the results of principal component analysis (PCA) and evolving factor analysis (EFA), applied to two datasets measured at constant temperature and varying temperature. After temperature correction, the concentration profiles and spectra were obtained with PCA, SIMPLISMA and the orthogonal projection approach (OPA). The same resolution methods were used on the dataset measured at constant temperature.
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Hailey PA, Doherty P, Tapsell P, Oliver T, Aldridge PK. Automated system for the on-line monitoring of powder blending processes using near-infrared spectroscopy. Part I. System development and control. J Pharm Biomed Anal 1996; 14:551-9. [PMID: 8738184 DOI: 10.1016/0731-7085(95)01674-0] [Citation(s) in RCA: 117] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
An automated system for the on-line monitoring of powder blending processes is described. The system employs near-infrared (NIR) spectroscopy using fibre-optics and a graphical user interface (GUI) developed in the LabVIEW environment. The complete supervisory control and data analysis (SCADA) software controls blender and spectrophotometer operation and performs statistical spectral data analysis in real time. A data analysis routine using standard deviation is described to demonstrate an approach to the real-time determination of blend homogeneity.
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Affiliation(s)
- P A Hailey
- Engineering Department, Pfizer Central Research, Sandwich, Kent, UK
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Sekulic SS, Ward HW, Brannegan DR, Stanley ED, Evans CL, Sciavolino ST, Hailey PA, Aldridge PK. On-Line Monitoring of Powder Blend Homogeneity by Near-Infrared Spectroscopy. Anal Chem 1996; 68:509-13. [DOI: 10.1021/ac950964m] [Citation(s) in RCA: 199] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- S. Sonja Sekulic
- Pfizer Central Research, Eastern Point Road, Groton, Connecticut, 06340 and Pfizer Central Research, Ramsgate Road, Sandwich, Kent, CT13 9NJ, UK
| | - Howard W. Ward
- Pfizer Central Research, Eastern Point Road, Groton, Connecticut, 06340 and Pfizer Central Research, Ramsgate Road, Sandwich, Kent, CT13 9NJ, UK
| | - Daniel R. Brannegan
- Pfizer Central Research, Eastern Point Road, Groton, Connecticut, 06340 and Pfizer Central Research, Ramsgate Road, Sandwich, Kent, CT13 9NJ, UK
| | - Elizabeth D. Stanley
- Pfizer Central Research, Eastern Point Road, Groton, Connecticut, 06340 and Pfizer Central Research, Ramsgate Road, Sandwich, Kent, CT13 9NJ, UK
| | - Christine L. Evans
- Pfizer Central Research, Eastern Point Road, Groton, Connecticut, 06340 and Pfizer Central Research, Ramsgate Road, Sandwich, Kent, CT13 9NJ, UK
| | - Steven T. Sciavolino
- Pfizer Central Research, Eastern Point Road, Groton, Connecticut, 06340 and Pfizer Central Research, Ramsgate Road, Sandwich, Kent, CT13 9NJ, UK
| | - Perry A. Hailey
- Pfizer Central Research, Eastern Point Road, Groton, Connecticut, 06340 and Pfizer Central Research, Ramsgate Road, Sandwich, Kent, CT13 9NJ, UK
| | - Paul K. Aldridge
- Pfizer Central Research, Eastern Point Road, Groton, Connecticut, 06340 and Pfizer Central Research, Ramsgate Road, Sandwich, Kent, CT13 9NJ, UK
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