urgent, thank you in advance and have a nice day

QUESTION 1 (16 marks) a) Analysis of pesticide and herbicide residues in canned foods, fruits and vegetables was done using supercritical fluid chromatography (SFC) with carbon dioxide as the mobile phase, isobaric condition at 360 bar, isothermal condition at 100 C (373.15K) and mass spectrometry detector (MSD). i) It was found some of the polar pesticides and herbicides were not detected. Explain the possible reason for this observation. Suggest an approach to rectify the problem. (4 marks) ii) Poor separation was observed whereby some of the earlier eluted analytes were not separated well, while others took a very long time to be eluted. Explain the possible reasons for the observation and suggest an approach to resolve the problem. (6 marks) b) Hydrocarbon mixture containing compound with carbon chain less than 10 carbons were analysed by SFC. Suggest an appropriate stationary phase, modifier fluid (if necessary), and a compatible detector to be used if carbon dioxide is utilized as the mobile phase. Explain your answer. (6 marks)