Can someone please help me with these chemistry questions

Question

1. What is the difference between gradient and isocratic elution systems in HPLC of opioids?
2. Why is the beer carbonated?
3. In order to detect pesticides or other hazardous contaminants with LC-MS, what must be run first?
4. Nerve agents inhibit the function of the enzyme _____________?

Answer 1

1. A gradient elution system uses more than one type of mobile phase that can gradually increase or decrease in polarity, while an isocratic elution uses only one mobile phase that does not change in polarity.
2. In fermentation, yeast converts sugars to carbon dioxide and ethanol. In the fermentation container, the carbon dioxide cannot escape so it is converted to its liquid form, carbonic acid. When the container is opened, the carbon dioxide is allowed to escape, forming bubbles.
3. A pure solution of the pesticide in question should be run so you have a standard to compare your sample runs to.
4. Acetylcholinesterase