4. Name the sample preparation or sample introduction techniques with the following description (5 points). a. Magnetic stir bar with polydimethylsiloxane coating for pre-concentration of organic analytes b. Use of a sampling bottle allowing vapor from solid or liquid samples to be analyzed c. Cartridges packed with silica particles having different functional groups like C18 or phenyl phases d. GC accessory with a sparging needle and sorbent tube to aid in the analysis of volatile compounds in wastewaters e. Use of liquid nitrogen to allow the GC analysis of gases like methane, ethane, and ethylene