Montmorillonite colloids and polystyrene colloids have similar UV absorption wavelengths. It is difficult to distinguish and quantify them by UV-Vis spectrophotometry. Is there a simple way to quantitate the two separately in a mixed system?
Two quick thoughts: Total Organic Carbon analysis is fast and accurate if you can find the apparatus. Thermogravimetric analysis (TGA) should work too. You heat the mixture until the polystyrene is burnt away and measure the change in weight very accurately.
Polystyrene being a thermoplastic polymer and flows @ temperature around 100 degree Celsius $ heat conductivity of 0.033w/m.k. you can measure the initial weight of the mixture and then heat it to about 100 degree Celsius. The polystyrene is burnt out, then measure the resultant component. Then subtract the initial value from the final measurement.
Thank you for your advices Alan Parker and Dare Owoyemi , but polystyrene colloids and montmorillonite colloids are in mixed solution systems.We are looking for simpler analytical methods, such as quantitative analysis using the fluorescence properties of polystyrene, or for UV-Vis absorption wavelengths that are sensitive to each.The methods are as follows:
- Step1: Scan polystyrene colloid solution and montmorillonite colloid solution with UV-VIS spectrophotometer in the wavelength range 200-800 nm with resolution of 1 nm respectively. Observe changes in absorbance and see if there is a wavelength of λ1 that is sensitive to polystyrene colloids but insensitive to clay minerals. If present, quantify polystyrene colloid in this wavelength range.
- Step2: The standard curve of polystyrene colloid and montmorillonite colloid was determined by selecting the wavelength of λ2 , which is sensitive to both polystyrene colloid and montmorillonite colloid.Taking the concentration of polystyrene colloid solution measured in step 1 into the standard curve equation of polystyrene colloid measured at wavelength λ2 , the absorbance of polystyrene colloid under wavelength λ2 is obtained. According to Lambert-Beer's law, the absorbance is additive. Subtracting the absorbance of polystyrene colloid solution at λ2 from the absorbance of the mixed solution is the absorbance of montmorillonite colloid, and then calculating the concentration of montmorillonite colloid solution according to the standard curve equation of montmorillonite at λ2.
- Note: It is also necessary to verify whether there is a large difference between the polystyrene colloidal standard curve and the polystyrene colloid-montmorillonite colloidal mixing standard curve under the wavelength λ1. If the two are substantially coincident, it indicates that the presence of montmorillonite does not affect the polystyrene colloid quantification under the condition of λ1, and this method is feasible.
The method of using fluorescence quantification is similar to the method mentioned above, except that polystyrene is quantified by fluorescence spectrophotometer.
The methods mentioned above still need to be verified by experiments, and we are preparing to carry out relevant research in the near future.
Oh, OK. Just don't forget that the signal from Montmorillonite is due to Mie scattering, not absorbance or fluorescence. So the parameters controlling it are going to be very different from those that matter in molecular spectroscopy. Scattering occurs for all wavelengths, so you can choose one to determine the clay where polystyrene is inactive.
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