Microlayer Research Lesson

Our research was split into two parts: sampling and extraction. Sampling consisted of going out to Corpus Christi Bay and collecting water samples to take back with us to the lab. Extraction was the process (conducted in the lab) of taking the samples and combining them with dichloromethane** and extracting purely the sample using proper lab equipment and following a precise list of steps.

**dichloromethane: a solution that cleans and takes away organic compounds.

Sampling Process (2 hours):

powder-free nitrile gloves                     glass plate                                 DI water                                         ethanol                                                          kim wipes                                  container of ice
clean vials & caps                                      funnels                                        rope
scraper

– Once we arrived to the sampling location we put on a pair of gloves. Then we put the rope through the hole at the top of the glass plate and tied multiple knots, making sure the rope was securely tied to the glass plate. We then cleaned the glass plate and scraper with DI water first and ethanol second; we made sure to use kim wipes to dry off them off after cleaning them. While this was being done, someone else was preparing the vial and funnel for sampling by removing the foil*** from the vial and funnel and placing the stem of the funnel into the opening of the of the vial.

– To begin the actual sampling process, one person held onto the rope and the glass plate and the second person held onto the funnel, vial, and scraper. The first person then took the rope and lowered the glass plate into the water, making sure the entire plate was under the water. They then “conditioned” the plate by bringing the plate almost entirely out of the water and then back down into the water; they did this a total of three times. After they had conditioned the plate three times, thy brought the plate completely out of the water (only holding onto the rope not the plate) and brought it over the vial that the second person was holding. The second person would maneuver the vial and funnel so that one of the bottom corners of the plate would fall into the funnel which allowed the Bay water to flow into the funnel. The second person would then use the scraper to scrape off the water from both sides of the plate, getting as much water into the vial as they could.

– Once the sample was taken we would screw a clean lid onto the vial, label the vial
appropriately using a sharpie, and place the vial into the container filled with ice. Each sample vial had to be marked with the correct date, location number, and sample number so we could keep track of them. Before we could take another sample, we would have to clean the glass plate and the scraper again with the DI water and ethanol.

*** the glassware (funnels and vials) we used in the lab were cleaned by being covered in foil and place in an over for four hours to remove any bacteria or organisms.

Extraction Process (1  1/2 hours):

powder-free nitrile gloves                              dichloromethane (DCM)
40 mL vial and lid                                               N-alkane composite standard
separation funnel                                               graduated cylinder
ring stand                                                              syringe

– First we put on a pair of gloves and removed the sample vials and standard from the refrigerator so that they could warm up to room temperature (about one hour). Making sure the stopcock on the funnel was closed, we then poured the sample into the separation funnel while also measuring the amount of sample and recording it. We then rinsed the vial out twice with DCM, added that to the funnel, and rinsed out the funnel with DCM to get rid of any residue. Using the syringe we then added the appropriate amount of the standard (based on concentration) to the funnel. Then we measured 5 mL of DCM in the graduated cylinder, added that to the funnel, attached a glass stopper to the funnel, and started to shake the funnel for two minutes.

– We “burped” the funnel by removing the stopper every 10-15 seconds to release any built-up pressure. Once the two minutes was up we placed the funnel back on the ring stand and allowed the layers of DCM and water to separate completely. The DCM settled at the bottom because it’s heavier than water. After about two minutes, we placed a vial underneath the funnel, making sure the bottom tip of the funnel led into the vial. 

– We then opened the stopcock and drained the DCM layer into the vial; we had to be careful with this step, because we only needed the layer of DCM and none of the water in this vial. Once that was done, we screwed a lid onto the vial, labeled it, and stored it in the refrigerator.