Santosh Mishra

Graduate Student

Santosh.Mishra@mavs.uta.edu

 


Research Profile

The objective of my graduate study research is to develop an automated system to determine metals in aerosols by capillary ion chromatography technique so as to sensitively measure these atmospheric trace constituents in a near real time manner. In order to achieve this objective, the sample has to be collected in a continuous manner, pretreated (digested) to as to isolate it from the complex matrix, separate the mixture of metals and detect it using suitable sensitive detector. Optical detection will be used for the detection of metal ions. In analytical chemistry, UV-Visible absorption measurement is by far the most common detection technique. These measurements have been extended to optically transparent analytes in presence of absorbing background. Capillary scale absorbance and fluorescence detectors were originally used in context to capillary electrophoresis and now are used in micro-fluidic devices. Capillary scale detectors will unequivocally play decisive role as the miniaturization advances. The augmentation in detection sensitivity is of paramount importance for capillary scale detection.

Capillary scale absorbance detector

Dasgupta research group has been involved in maximizing the detection sensitivity of the absorbance detectors for more than two decades. The fabrication of light emitting diode (LED) based capillary scale multi-reflection absorbance detector is the latest acquirement towards the enhancement of detection sensitivity. The external surface of the capillary is silver coated to augment the optical pathlength. We have studied different geometries (different light incidence angles and different silver coated length) and have optimized the geometry of the capillary scale absorbance detector. A multi-reflection cell based on 180 m bore capillary with a ~2 cm long illuminated volume shows over a 50-fold gain in S/N compared to a single-pass on-tube configuration with the same capillary. The photograph of the capillary scale LED based absorbance detector is as shown below.



Following figure on the left hand side shows the signal-to-noise ratio results for 110 nM injected bromothymol blue (BTB) dye with several geometries like round and square capillaries with different angles of light incidences and various lengths of externally silvered capillary with 45 degrees of light incidence. The limit of detection (LOD) of the capillary scale absorbance detector (circular cross-section, 20 mm silver length, 45 degrees light incidence) is 4.4 fmol (2.6 pg, 1 ml of 22.0 nM injected dye) BTB under pulseless (pneumatic) flow conditions and the resultant absorbance peak is shown (on the right hand side) below.



     


    We have also confirmed that the reflective geometry is less susceptible to artifacts actuated by refractive index changes and the results are compared with that of single-pass capillary scale absorbance detector. The following figure shows the immunity of multireflection cell to the refractive index effects where first signal corresponds to 10 M alkaline BTB dye while the second one corresponds to the same analyte in a matrix of 100 NaCl. The heavy and the light traces correspond to the signal from multireflection cell and single pass cell respectively. More details can be found in our recent publication listed below. 


Capillary scale fluorescence detector

We have also successfully fabricated capillary scale fluorescence detectors in our lab. Liquid-core-waveguide (LCW) principle is utilized to enhance the performance of the capillary scale fluorescence detector. The following figure shows the schematic design of capillary scale LCW fluorescence detector made with Teflon AF coated 100 m bore silica capillary, 365 nm LED and light-to-voltage sensor (TSL250R). The figure on the right hand side shows the performance of this detector wherein the limit of detection (LOD) of 46 pg Al3+ could be achieved. More details can be found in our recent publication listed below.


 

Capillary scale post-column reagent mixer

Metal ions (present in ambient air in trace amounts), often colorless and difficult to detect by optical method, will have to be converted to chromophoric/fluorophoric complex by postcolumn reagent addition technique. 4-(2-pyridylazo)resorcinol, PAR (which forms intensely colored metal complexes with various transition metals) was selected as the reagent to be introduced in capillary scale flow-injection-analysis system. Progress has been done in converting the metal ions (in carrier stream) into deeply colored PAR-transition metal complex. This involved the development of capillary scale postcolumn reactor which could electrodialytically generate and introduce negatively charged PAR ions into the flowing stream containing metal ions. We have worked on the fabrication of capillary scale post-column mixer so as develop a capillary chromatography system. We have tried different designs of capillary scale post-column reagent mixers like bent-T, monolith, open tubular membrane, concentric capillary and electrodialytic generator. Subsequently, we will study the separation and detection of trace levels of transition metals using this capillary scale ion chromatography system. The schematic of the desired set up is as shown as below.


 

Education 

  • M.S. (Chemistry) Florida Institute of Technology, Melbourne, Florida, 2005

  • B. Tech. (Chemical Technology-Textiles) University Institute of Chemical Technology (UICT)-University of Mumbai, India, 2002

  • B.Sc. (Chemistry) S.I.E.S. College of Arts, Science and Commerce, University of Mumbai, India, 1998

 

Awards

  • UTA College of Science Research Day 2008 Poster Competition: Second Prize

  • International Ion Chromatography Symposium (IICS) 2008: Student Travel Grant Award

  • Younger Chemists Committee (YCC) Leadership Award - American Chemical Society (SWRM-2004)

  • Sri. J. R. D. Tata Trust Scholarship (merit based scholarship), Mumbai 2001, 2002

  • Sri. Ratan Tata Trust Scholarship (merit based scholarship), Mumbai 1999, 2000

  • Prof. A.N.Kothare Scholarship (merit based scholarship), Mumbai 1998

 

Publications

  • Capillary scale liquid core waveguide based fluorescence detectors for liquid chromatography and flow analysis. Song, G. Q.; Villanueva-Fierro, I.; Ohira, S. I.; Mishra, S., Bailiff, H.; Savage, C. R.; Dasgupta, P. K. Talanta (2008), 77 (2), 901-908. DOI: 10.1016/j.talanta.2008.07.047 

  • Capillary scale light emitting diode based mulit-reflection absorbance detector. Mishra, Santosh K.; Dasgupta, Purnendu K. Analytica Chimica Acta (2007), 605 (2), 166-174. DOI: 10.1016/j.aca.2007.10.030 

  • Oxidation of Sulfonamide Antimicrobials by Ferrate(VI) [FeVIO42-]. Sharma, Virender K.; Mishra, Santosh K.; Nesnas, Nasri. Environmental Science & Technology (2006), 40(23), 7222-7227. DOI: 10.1021/es060351z

  • Ferrate(VI) oxidation of ibuprofen: a kinetic study. Sharma, Virender K.; Mishra, Santosh K. Environmental Chemistry Letters (2006),  3(4),  182-185. LINK: http://springer.metapress.com/content/f7157q04015h1867/ 

  • Kinetic assessment of the potassium ferrate(VI) oxidation of antibacterial drug sulfamethoxazole. Sharma, Virender K.; Mishra, Santosh K.; Ray, Ajay K. Chemosphere (2006), 62(1), 128-134. DOI:10.1016/j.chemosphere.2005.03.095  

  • Novel trends in textile preparatory processes: Part 2. Mishra, Santosh Kumar; Rashinkar, Shilpa; Sayed, Usha. Colourage  (2002),  49(2),  21-22,24-26.

  • Novel trends in textile preparatory processes: Part 1. Mishra, Santosh Kumar; Rashinkar, Shilpa; Sayed, Usha. Colourage  (2001),  48(12),  15-18.

 

Presentations

Oral Presentations

  • LED based multi-reflection absorbance detector and exploration of capillary scale post-column reaction detection. International Ion Chromatography Symposium (IICS) 2008, Sep. 21-24, 2008. Portland, OR, USA. 

  • Versatile and affordable miniature detector for environmental and biological microanalysis. UTA Annual Celebration of Excellence by Students (ACES) 2008, Mar. 28, 2008. UTA, Arlington, TX, USA.

  • Eco-friendly Finishing of Textiles: Challenges before Chemical Engineering in the New Millennium. Proceedings of International Symposium & 54th Annual Session of IIChE (CHEMCON-2001), Dec. 19-22, 2001. Chennai, India.

Poster Presentation

  • Simple & versatile, capillary scale absorbance and fluorescence detectors. UTA College of Science Research Day 2008, Oct. 3, 2008, UTA, Arlington, TX, USA.

 

 


 

 

 

 

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