Skip to main content
UploadLanguage (EN)Support
BusinessMobileSocial MediaMarketingTechnologyArt & PhotosCareerDesignEducationPresentations & Public SpeakingGovernment & NonprofitHealthcareInternetLawLeadership & ManagementAutomotiveEngineeringSoftwareRecruiting & HRRetailSalesServicesScienceSmall Business & EntrepreneurshipFoodEnvironmentEconomy & FinanceData & AnalyticsInvestor RelationsSportsSpiritualNews & PoliticsTravelSelf ImprovementReal EstateEntertainment & HumorHealth & MedicineDevices & HardwareLifestyle
SS
Uploaded bySamiksha Sawant
PPTX, PDF14,269 views

Attenuated total reflectance spectroscopy

This document discusses the attenuated total reflectance (ATR) infrared spectroscopy sampling technique. It begins by introducing ATR and explaining that it allows for little to no sample preparation and a very thin sampling pathlength. It then discusses factors that affect the ATR spectrum such as the refractive indices of the crystal and sample, angle of incidence, depth of penetration, and quality of sample contact. Common ATR crystal materials and their spectral ranges and depths of penetration are presented. Applications include identification of functional groups, contaminated pet food detection, and more. In conclusion, ATR provides high quality reproducible data for a variety of solid and liquid samples.

Technology◦
Downloaded 399 times
PRESENTED BY: SAMIKSHA SAWANT M.PHARM(IP), 1st SEM GUIDED BY : DR.SUPRIYA MAHAJAN1
INFRARED SAMPLING METHODS 2 Transmissio n Internal Reflecti on
WHY ATR? ATR generally allows little or no sample preparation, which greatly speeds sample analysis. It allows very thin sampling pathlength and depth of penetration of the IR beam into the sample. Useful for samples that are too thick to be analysed bt transmission and those that strongly absorb radiation 3
4 1 2 3 4
WHAT IS ATR? An evanescent wave is a penetrating electromagnetic field whose intensity quickly decays as it moves away from its source. An evanescent beams interacts with the sample, sample absorbs energy. Thus there is reduction in the intensity of the reflected wave reaching the detector. 5
MATERIALS ATR SPECTRAL RANGE (cm-1) REFRACTIVE INDEX DEPTH OF PENETRATION (microns) Germanium 5500-675 4 0.66 Silicon 8900-1500 & 360-120 3.4 0.85 AMTIR 11,000- 725 2.5 1.77 ZnSe 15000-650 2.4 2.01 Diamond 25000-100 2.4 2.01 MATERIALS USED FOR MAKING ATR CYRSTAL 6
FACTORS AFFECTING THE SPECTRUM Refractive indices of the ATR crystal and the sample Angle of incidence of the IR beam Critical angle Depth of penetration Wavelength of the IR beam Effective pathlength Number of reflections Quality of the sample contact with ATR crystal ATR crystal characteristic 7
1) REFRACTIVE INDEX OF CYRSTAL AND SAMPLE The refractive indices of the crystal and sample are important considerations in the ATR sampling technique by virtue of the following equation, 8
2) THE CRITICAL ANGLE 9 Total internal reflection critical angle - when the angle of refraction (r) becomes equal to 90 degrees and Snell's law reduces to:
3) THE DEPTH OF PENETRATION (DP) OF THE IR BEAM INTO THE SAMPLE 10 Further useful consideration for ATR analysis is the depth of penetration (dp) of the IR beam into the sample. The depth of penetration is given by:
4) EFFECTIVE PATH LENGTH: 11
5) QUALITY OF SAMPLE CONTACT WITH THE ATR CRYSTAL:  Intimate contact of the sample be made onto the surface of the ATR crystal.  For rigid, irregular shaped or porous samples, high pressure sufficient to deform the sample will increase the extent of sample contact and thereby increase sample absorbance. 12
SAMPLING 13 Analysing liquids Analysing solids
APPLICATIONS Identification of functional groups and drug substances Used in identification of paints, varnishes Useful for substances that are difficult to handle by conventional sampling technique- rubber, cured resins etc. Used in forensic and biomedical fields 14
CASE STUDY: Identification and Characterization of Toxicity of Contaminants in Pet Food Leading to an Outbreak of Renal Toxicity in Cats and Dogs HPLC and MS, which revealed presence of melamine and cyanuric acid Infrared spectroscopy on individual crystals from cat kidneys confirmed that they were melamine- cyanuric acid cocrystals. Pathological evaluation of cats and dogs that had died from the acute renal failure indicated the presence of crystals in kidney tubules. 15
These spectra were obtained using an infrared microscope equipped with a 20× ATR objective. The germanium ATR crystal has a contact area of approximately 100 μm. The reference compound was prepared by cocrystallization from solutions of melamine and cyanuric acid 16
CONCLUSION ATR is a powerful IR sampling technique that provides excellent quality data in conjunction with the best possible reproducibility It has revolutionized IR solid and liquid sampling through faster sampling Minimizes user to user variations Has versatality and is non destructive technique for variety of materials- soft solid materials, liquids, powders, gels, pastes, polymers etc. 17
REFERENCES  http://toxsci.oxfordjournals.org/content/106/1/251.full  http://old.vscht.cz/anl/vibspec/FTIR%20Reflection%20 Techniques.pdf  http://www.utsc.utoronto.ca/~traceslab/ATR_FTIR.pdf  http://www.piketech.com/files/pdfs/ATRAN611.pdf  Handbook of analytical instruments, R S Khandiur, 170- 173  Instrumental Methods of Analysis, Willard, Merritt, Dean and Settle, seventh edition, 311-315  Analytical Chemistry Handbook, John A. Dean, 6.16-6.20  Instrumental Methods of Analysis, Dr. Supriya S. Mahajan, 63-70 18
THANKYOU! 19