Lecture 3
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26 questions
| 🇬🇧 | 🇬🇧 |
| W'hy do we need multiple analytical techniques? | To cover the large, rich structural diversity in compounds |
| How much of OM can be analysed? What is contained in the other portion? | 5-10%, the other 90+% contains kerogen which remains behind as it forms the insoluble part of OM |
| To analyse the molecules we are interested in we first need to .... them from the .... matrix | Extract - inorganic |
| How do we extract these molecules? | Dissolve using solvent |
| The extraction of organic matter is done using .... solvents such as .... or .... . Because .... compounds prefer to dissolve in these. | Organic - n-hexane - dichloromethane - organic |
| How do we seperate the different fractions of the different organic components we have extracted? | They may be seperated using gas chromatography |
| What principle does gas chromatography rely on | GC relies on passing a mixture dissolved in a mobile phase through a stationary phase. The basic principle of gas chromatography is that each component in the sample absorbs into the stationary phase by a different amount. This leads to different retention times for different components, separating the analyte. |
| Difference between liquid and gas chromatography? | The mobile phase is liquid for LC and gas for GC |
| If the mobile phase of a column chromatography is very polar ... | The polar molecules will move out first, while apolar will not move or only move very slowly |
| Column chromatography is used to | Seperate the different fractions (such as apolar/polar/neutral) and ma be used in advance to LC/GC |
| What is the analytical window for GC? | Large compounds have a longer retention time, and anything with over C40-C45 can't be heated high enough by the gas chromatograph |
| Wht principle does mass spectrometry rely on? | Separates ionized particles such as atoms, molecules, and clusters by using differences in the ratios of their charges to their respective masses (mass/charge; m/z) |
| How does magnetic sector mass spectrometry work? | Ionized particles flow through a vaccumed tube at 90degree angle with a magnetic field that bend the molecules through the corner. This seperates and arranges the particles based on their mass/charge ratio at the detector. |
| What does time of flight mass spec. do different , and what is its advantage over normal mass spec.? | It relies on the fact that smaller molecules travel faster than larger ones, stop clock every 30us, Faster than mass spec. |
| A new type of mass spec is Fourier transform - ion cyclotron resonance, how does it work and what is its advantage? | Molecules spin due to radiofrequency, small change in spin is equivalent to its mass. We need fourier transform to convert spin to mass. It has a very high mass resolution, we can assign exact elemental formulas. |
| How does quadrupole mass spec work and what is its advantage? | Molecules are ioneized and split into framgents in very perdictable ways, it runs trhough 4 rods which act as quadrupoles, when the ions run through this only the resonant ions make it to the detector. It is the cheapest and easiest MS, but has low resolution. |
| Which mass spec has the highest resolution? What is its disadvantage | Fourier transform - very expensive |
| What is the cheapest MS, but has low resolution? | Quadrupole MS |
| Which mass spec is the fastest? | Time-of-flight |
| Which mass spec has the ionized particles run through a 90degree vaccum, magnitized tube? | Magnetic sector MS |
| Which particles go unnoticed in Mass spec.? | Those fragments wihtout a charge and unstable ions that fall apart before reaching detector |
| Why can mass spectra be used as a sort of barcode? | Because (as long as conditions are the same, ionized at same voltage) the way a molecule fragments is always the same and the spectra will look the same as well |
| What is the advantage of LC of GC? | Can be used for bigger molecules, onl requirement is that it needs to dissolve |
| He total organic carbon content can be determined useing an ... and may for example help us determine ... | Elemntal analyser - Redfield Ratio (C:N:P) in phytoplankton |
| Fragmentation is devined by... | The structure of the molecule |