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Title Udvikling og automatisering af fluoroscensspektrofotometrisk bestemmelse af calcium på ppb niveau med begrænset interferens påvirkning i grundvand
Author Holst, Casper Torben (Analytikergruppen, Institut for Kemi, Danmarks Tekniske Universitet, DTU, DK-2800 Kgs. Lyngby, Denmark)
Institution Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark
Thesis level Master's thesis
Year 2009
Abstract Calcium exists throughout the human body, and is essential to a long range of functions, including heart muscle regulation. Calcium is also abundant in nature, and calcium determination is routinely carried out in industry, the medical domain and environmental monitoring. An on-line system capable of determining calcium concentration in water have been developed in this project. The system has a detection limit of 0.6 g/L, and reliable measurements have been documented within the range 0.1 - 50 mg/L. The system is able to perform on-line analysis with a time delay from injection to detection of 60 seconds, or batch analysis with a sample rate of 15 samples per hour. A Labview program has been developed to handle data sampling and instrument control, as well as a database resulting in easy and timesaving data processing The database ensures that the process time per sample remains constant even during large sample series, that can generate more than 100.000 data lines. The developed system uses uorescence detection at 515 nm on a calceincalcium complex exited at 330 nm. The uorescent system exhibits a sigmoid calibration curve covering one decade, with the linear section being half a decade. Adjustment of reagent concentrations enables moving the measurement window to such an extent that the method's dynamic measurement range can be expanded to 0.1 - 50 mg/L calcium. Focusing on industrial use and treatment of groundwater, Cu(II), Zn(II), Fe(III), Al(III), Mn(II), Sr(II) and Ba(II) as well as Mg(II) have been selected to investigate possible interferences. Among these elements, especially Cu(II) has proven problematic. Fluorescence intensity from a sample containing 1 mg/L calcium begins to decline with a Cu(II) concentration as low as 0,1 mg/L, decreasing linearly to only half intensity with a Cu(II) concentration of 2 mg/L. The method has been used to determine calcium concentration in 10 water samples taken from various locations on Zealand. The results have been compared against total water hardness measured by hardness sticks, as well as the declared concentration. The developed system has been validated against a certied reference material (BCR-616), by measurement on 60 real replicates over the course of three days. The system exibits a high precision with a pooled standard error of 0.9%. Recovery compared to the certified reference was 122.70,5%.
Imprint Technical University of Denmark (DTU) : Kgs. Lyngby, Denmark
Pages 80
Admin Creation date: 2011-01-06    Update date: 2011-01-06    Source: dtu    ID: 272310    Original MXD