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FT『N』IR與FTIR的差異與了解FTNIR的效益

FTNIR屬於吸收光譜的一種,根據光源與樣品之間的關係可以分為穿透與漫反射兩種,前者適用於液體樣品,後者則適用於粉末與顆粒樣品。

FTNIR與FTIR的差異

『N』代表Near,NIR就是近紅外波段光譜的意思,波長範圍從900至2500奈米(nm)之間,換算成波數(cm-1)之後範圍在4000cm-1至10000cm-1之間。與FTIR相比,一般稱為FTIR光譜,實際上屬於Middle-IR,也就是中紅外光譜,波數範圍在400cm-1到4000cm-1之間。

兩者從振動光譜(Vibrational Spectroscopy)的原理來定義時,FTIR屬於基頻(Fundamental Frequency),而FTNIR屬於基頻的合頻(Combination)或倍頻(Overtone),可以從下圖來了解。

FTNIR雖然屬於紅外光譜,但是可以克服FTIR對於含水率較高的樣品無法分析的問題,此外FTNIR也可以透過玻璃罐或者包裝袋等,直接對內容物進行分析。

FTNIR的光譜訊號來源主要是FTIR的基頻經過合頻或是倍頻之後的結果,因此只有C-H、N-H及O-H等官能基的能量足以達到近紅外光譜的範圍內。

FTNIR主要觀察的官能基

由官能基的分布,我們可以初步的對NIR光譜進行分類,依據官能基的屬性,我們可以大概知道樣品中的水分(O-H)、蛋白質(N-H)及油脂(C-H)等含量。

當我們進一步將NIR導入至產業中,從光譜訊號中得知,NIR可以做為水份及其他相對應的有機物質分析方法。

下面舉例幾個石化產業標準方法,其中有許多NIR光譜可以協助加快分析穩定生產效能的測試項目,例如水分、酸鹼、鹼價、黏度、密度,針對燃料的RON、MON,以及針對聚合物的末端官能基檢測的項目。

標準方法編號   方法名稱 分析目標
ASTM E1655   Standard Practices for Infrared Multivariate Quantitative Analysis NIR方法開發
ASTM D6122   Standard Practice for Validation of the Performance of Multivariate Online, At-Line, and Laboratory Infrared Spectrophotometer Based Analyzer Systems NIR方法驗證
ASTM D6299   Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance NIR儀器驗證
ASTM D6342   Standard Practice for Polyurethane Raw Materials: Determining Hydroxyl Number of Polyols by Near Infrared (NIR) Spectroscopy

Hydroxyl number

ASTM D4274   Standard Test Methods for Testing Polyurethane Raw Materials: Determination of Hydroxyl Numbers of Polyols

Hydroxyl number

UOP326-17   Diene Value by Maleic Anhydride Addition Reaction Diene value
ASTM D2699   Standard Test Method for Research Octane Number of Spark-Ignition Engine Fuel RON
ASTM D2700   Test Method for Motor Octane Number of Spark-Ignition Engine Fuel MON
ASTM D5769   Standard Test Method for Determination of Benzene, Toluene, and Total Aromatics in Finished Gasolines by Gas Chromatography/Mass Spectrometry Aromatic content
ASTM D664   Standard Test Method for Acid Number of Petroleum Products by Potentiometric Titration

Acid value

ASTM D2896   Standard Test Method for Base Number of Petroleum Products by Potentiometric Perchloric Acid Titration

Base number

ASTM D445   Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity) Viscosity
ASTM D6304   Standard Test Method for Determination of Water in Petroleum Products, Lubricating Oils, and Additives by Coulometric Karl Fischer Titration Moisture
ASTM D2270   Standard Practice for Calculating Viscosity Index from Kinematic Viscosity at 40 °C and 100 °C Viscosity
ASTM D789   Standard Test Method for Determination of Relative Viscosity of Concentrated Polyamide (PA) Solutions Viscosity
ASTM D6979   Standard Test Method for Polyurethane Raw Materials: Determination of Basicity in Polyols, Expressed as Percent Nitrogen amine value
ASTM D7409   Standard Test Method for Carboxyl End Group Content of Polyethylene Terephthalate (PET) Yarns CEG
ASTM 6869   Standard Test Method for Coulometric and Volumetric Determination of Moisture in Plastics Using the Karl Fischer Reaction (the Reaction of Iodine with Water) Moisture
ASTM D7252   Standard Test Method for Polyurethane Raw Materials: Determination of Monomer and Isomers in Isocyanates

NCO content

 

FTNIR的潛力與效益

這些品管依據的傳統分析方法,大多採濕式化學的方式,因此樣品都需要前處理,分析過程會消耗化學溶劑,分析完之後的樣品也屬於化學廢液,除了有機溶劑與酸鹼溶液的危害之外,還有相關的處理與時間成本。重點是部分的方法無法轉變成線上分析方法,這對於需要即時取得產線狀態的工廠,無疑是非常大的限制,反觀FTNIR可以透過光纖探頭,深入到產線中的每一個角落,提供24/7的數據,藉由觀察大量的數據變化,也許可以找出產能優化的關鍵。

立即與利泓聯繫,請填寫以下資訊,我們將請專員與您聯繫。