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
RF
Uploaded byRENATT FRANCIS
PPTX, PDF7,234 views

Atr new

Attenuated total reflectance (ATR) spectroscopy is a sampling technique used in infrared spectroscopy that allows samples to be examined directly in the solid or liquid state without preparation. It works by using an infrared beam that undergoes total internal reflection within an ATR crystal, producing an evanescent wave that extends into the sample in contact with the crystal. This evanescent wave causes absorption bands within the sample that are detected to produce its infrared spectrum. ATR offers advantages like speed and little sample preparation, but disadvantages include some crystal absorption and the need for good contact between the sample and crystal.

Education◦
Submitted by, Renatt. c. Francis 1st year M.Pharm, Pharmacy Practice Attenuated total Reflectance (ATR)
•Attenuated total reflectance (ATR) is a sampling technique used in conjunction with infrared spectroscopy which enables samples to be examined directly in the solid or liquid state without further preparation What is ATR
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. 3
Evanescent Waves •The infrared radiation interacts with the sample through a series of standing waves, called evanescent waves •An evanescent wave is a penetrating electromagnetic field whose intensity quickly decays as it moves away from its source
Principle of ATR • ATR spectroscopy utilizes the phenomenon of total internal reflection • A beam of radiation entering a crystal will undergo total internal reflection when the angle of incidence at the interface between the sample and crystal is greater than critical angle • In this way, an evanescent wave penetrates into the sample in contact with the crystal, producing a spectrum of the sample
Conditions  sample must direct contact with ATR crystal  The refractive index of the crystal must be greater than that of sample
How it works??? 7
• The depth of penetration in ATR spectroscopy is a function of the wavelength, λ, the refractive index of the crystal, n2, & the angle of incident radiation , Ө. • The depth of penetration , dp, for a non-absorbing medium is given by the following: where n1is the refractive index of the sample.
Crystal Composition • Crystal used in ATR cells are made from materials that have low solubility in water & a very high refractive index. Crystals are typically made of: • Zinc Selenide (ZnSe) • Germanium (Ge) • Diamond • Zinc Sulfide (ZnS) • Silicon (Si)
Advantage •ATR sampling is fast and easy because little or no sample preparation is required •Other techniques, such as infrared transmission, often require the sample to be heated, pressed or ground in order to collect the spectrum
Disadvantages • The ATR crystal absorbs energy at lower energy levels • If the sample does not have good contact with the crystal, the data will not be accurate • Most ATR crystals have pH limitations
References • Organic spectroscopy by William kemp, page no92-94 • 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
THANK YOU…