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ADVANCED FOOD ANALYSIS 3 - Coggle Diagram

- - - - Verification and library matching--> standard comparisation: best practing to inject mixture of pure standards at the end of each analytical run. Database/Library Integration: Modern software compares the spectra obtained
        during the run against digital libraries of pure substances.
      - Advanced Process Analysis--> This dual-information approach (retention time + spectrum) makes the DAD a highly
        resolutive detector (guardare immagine a pag. 15)
        
        The Optical Slit and Resolution--> Narrow Slit (1 nm): Increases spectral resolution. It allows for the precise
        separation of wavelengths, resulting in sharp, distinct peaks in the "Peak. Spectrum." Wide Slit (4 nm): Increases light throughput but decreases resolution. The peaks in the spectrum become blurred. 16 nm (Very wide): Resolution is almost completely lost. What were three distinct
        peaks now appear as a single large, rounded hump.
        
        sensitivity and noise--> Signal-to-Noise Ratio (S/
        N): A narrow slit lets in less light, making the electronic "noise" more prominent relative to the signal. Limit of Detection (LOD): The minimum concentration where a substance can be
        reliably detected (S/N>3). Limit of Quantification (LOQ): The minimum concentration where a substance can be accurately measured (S/N>1
        
        bandwith--> digital
        setting that determines how many diodes on the array contribute to the signal for a
        specific wavelength
        
        Narrow Bandwidth (8 nm): As seen in the left panel, a narrower bandwidth
        provides high spectral resolution.
        
        Narrow Bandwidth (8 nm): As seen in the left panel, a narrower bandwidth
        provides high spectral resolution.
        
        The goal of adjusting bandwidth is to optimize the Limit of Detection (LOD) and Limit ofQuantitation (LOQ). High S/N: Allows you to detect trace amounts of substances that would otherwise be hidden by baseline noise. The Trade-off: An analyst must choose between the precision of the spectrum (identity) and the smoothness of the baseline (quantification).
        
        fluorescenze detection--> how much light is absorbed and energy emitted by an analyte-->
        
        mechanism of fluorescence--> jump to a higher level, fluorescence ceases
        immediately once the excitation source is turned off, whereas phosphorescence involves a delayed, gradual decay, allowing materials to glow in the dark for extended periods
        
        Excitation Wavelength (λex ): Usually selected based on the molecule's
        maximum absorption peak to ensure the highest energy input. Emission Wavelength (λem ): The specific wavelength of light the molecule
        releases as it relaxes. might be excited at 255 nmand show a maximum emission peak at 382 nm
        
        pratical applications--> aminoacids: perform poorly in fluorescence. Aromatic compounds--> molecules with double bonds or benzene rings are fluorescent. Targeted identification--> a matrix with dozens of
        interfering peaks, one can isolate a target by settingthe instrument to only record signals where λ280 →λ340
        
        Building a Comprehensive Profile
        By combining Retention Time, the Absorption Spectrum (from DAD), and the Emission
        Spectrum (from FLD), scientists create a "chemical fingerprint" that is nearly impossible
        to misidentify. DAD measures UV absorbance (at 265 nm in the example), while the fluorimeter measures the emitted light (at 540 nm)
        
        Refractive Index (RI) detector--> measures the deviation of a light beam as it passes throught a liquid--> must be used isocratic elution. Refractive Index (RI) detector. A major risk in RI detection is co-elution, where two different sugars exit the column at
        the same time and appear as a single peak: Long columns (up to 30 cm): These provide a high number of theoretical plates
        for better separation. Specific stationary phases: Tailored to the specific analytes (e.g., sugars) to
        prevent loss of data.
        
        Amperometric Detection Methods--> based on electrochemical oxidation reduction
        
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