KBIN - OD NATUUR - ECOCHEM
Abstract Bachelor Project 1 FBT 2019-2020: Optimization and validation of pH determination in seawater with a continuous flow analyzer
As a result of the increased CO2 emission into the atmosphere, more and more CO2 is being absorbed by the seas and oceans. The pH is one of the parameters that can be used as an indicator to demonstrate the acidification of the seas and oceans, as the result of this extra CO2 absorption. Currently, the pH is measured directly from the sea, using a pH electrode. During the period of this internship, a more accurate method than an electrochemical measurement was optimized and validated.
The optimization was based on a protocol obtained by Skalar, the supplier of the continuous flow analyser used to generate results. First, the concentration of the colour reagent was optimized by preparing colour reagent of different concentrations and tested by analysing standards. The work continues with the chosen colour reagent to adjust the wash and sample times so that a nice separation between the peaks is achieved. Subsequently, the assembly of buffer solutions with different concentrations, to establish the correct range for the standard series (pH 7,5-8,5), was optimized.
For the optimization of the colour reagent, solutions of 10, 15, 20, 25 and 30 ml of m-cresol were prepared and analysed. This showed that the solution with 10 ml of m-cresol is ideal. For an ideal separation between the samples, a sample-time of 30 s, a wash-time of 250 s and an air-time of 0 s gave the best results . After checking the linearity of the regression, a stable calibration was obtained with a correlation coefficient (R²) of 0,9996. Linearity was checked against the residual deviation for random distribution. The repeatability was determined by measuring several samples repeatedly on the same day. A repeatability of 0,0468 % was obtained, much less than 2 % that was set as a target on beforehand. Reproducibility was determined by measuring several samples repeatedly for multiple days. During this research/examination the samples were tested for three days, showing a reproducibility of 0,4624 %. This value is substantially less than 5 %.
Abstract Bachelor Project 2 FBT 2019-2020: Optimization of the analysis of organotin compounds in water with gas chromatography and mass spectrometry (QqQ)
It is commonly known that marine pollution is a big problem. There is more to it than the big particles like plastic or fishing nets. Chemical pollution, such as organic compounds may be an even bigger issue. This bachelor’s thesis will have a more in-depth look at organotin compounds, a commonly used organic compound. The usage of tributyltin based antifouling paint on ships from the early 70’s onward to their total ban in 2008 made it possible for these compounds to pollute the sea in high concentrations.
Organotin compounds can cause many negative effects on the aquatic environment and several marine animals. Upon examination of several gastropods it was discovered that a lot of the female organisms had developed an imposex which made them infertile. Although the use of these organotin compounds has been banned or restricted since more than twenty years, the concentrations at sea are still too high, therefore it is important to monitor these concentrations and their changes over time.
The aim of this research is to optimize a method for the examination of organotin compounds in water so it can be validated and used in the future. For the optimization an automated method with four different cartridges and a manual method are tested and compared. Purification of the samples was done by gel permeation chromatography. For sample analysis, gas chromatography combined with mass spectrometry is used.
The recovery was mainly used for selecting the best method. Based on these data, the manual method could be selected as the best method, as the results were the most stable and showed the lowest spreading. When the pros and cons were taken into account, the manual method once again seemed the best option to be validated in the near future.