Migration of trace elements and radioisotopes to various fractions of solid wastes generated as a result of the sewage sludge incineration process.

The research was aimed at providing new knowledge in the field of chemical characteristics of solid waste generated in the process of combustion of sewage sludge in fluidized bed furnaces. The research material consisted of disposed fluidized beds (DFB), sewage sludge ash (SSA) and air pollution control residues (APC) from three Polish installations for the thermal treatment of sewage sludge. Natural radionuclides as well as anthropogenic isotope 137Cs were determined in the tested materials and the migration of a wide spectrum of trace elements to various waste fractions generated in the process of sewage sludge combustion was examined. It was observed that both radioisotopes and most of the trace elements determined accumulate in SSA and DFB, while the APC fraction contains a much smaller amount of them. The exceptions are mercury and selenium, whose volatile compounds migrate to the exhaust gas dedusting system and accumulate in the APC fraction (up to 40 mg/kg and 13 mg/kg, respectively). A potential threat from the 226Ra isotope in SSA is identified in the context of the management of this waste in the production of building materials because the typical activity of 226Ra in SSA collected from areas with very low Ra content in natural environment exceeds 1.5-6 times the activity of this isotope in conventional cement mixtures. When managing SSA and DFB, special attention should be paid to the content of metalloids such as As, B and Se, due to the high content of mobile forms of these elements in the mentioned materials.

Combination of isotope dilution with liquid chromatography-inductively coupled plasma mass spectrometry for the simultaneous monitoring and evaluation of cadmium and inorganic arsenic in polished rice.

A new monitoring and evaluation technique for cadmium (Cd) and inorganic arsenic (i-As) in rice was developed, where the isotope dilution (ID) method was applied in combination with high performance liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS), following heat-assisted extraction. Cadmium and i-As in a rice sample were extracted using the HNO3-H2O2 extractant, and an appropriate amount of enriched 111Cd was spiked into it. Cadmium and As species were measured simultaneously by LC-ICP-MS. The cadmium concentration was calculated from the isotope dilution analysis, and i-As was determined by the comparison (1 point calibration) method using additional 111Cd as an internal standard. The proposed method provides accurate and precise determination of Cd based on the isotope dilution analysis. Moreover, it can be applied to a rapid screening test to find contaminated rice samples, by means of monitoring the intensity ratios of natural 111Cd and i-As to the additional 111Cd. The developed technique was applied to analyzing multiple rice reference materials, and the measurement results of Cd and i-As agreed with the certified values within the uncertainty range. It is noted that the grain size of rice samples does not affect the extraction data, when the rice sample is crushed into powder less than 850 µm. The proposed method was very useful for the monitoring and evaluation of Cd and i-As in rice as a precise analytical method as well as a screening method.

Elimination of spectral interference of 87Rb with 87Sr during ICP-MS measurements using a chromatographic technique.

A new chromatographic separation technique was developed for the measurement of the strontium (Sr) isotope abundance ratio using inductively coupled plasma mass spectrometry (ICP-MS). This technique, LC-ICP-MS, utilizes the addition of 18-crown-the eluent and an ODS column. The technique completely eliminates the spectral interference of 87Rb (an isobar of 87Sr) with 87Sr during the ICP-MS measurement. 18-Crown-6 selectively forms a clathrate compound with some metals. When the Sr isotope abundances are measured using LC-ICP-MS with an ODS column, the addition of a specific amount of 18-crown-6 to the HNO3/0.1% methanol eluent elongates the retention time of Rb. Therefore, Rb can be completely separated from Sr using LC because Rb is captured into the 18-crown-6 molecule and forms a clathrate compound. The technique enables the measurement of Sr isotope abundance ratios easily, even in the presence of a large amount of Rb. The proposed technique was applied to the measurement of Sr isotope abundance ratios in rice samples. To validate the LC-ICP-MS technique, a fraction containing Sr was collected, and the 87Sr/86Sr isotope ratio was precisely measured using ICP-MS.

An online internal standard technique for high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS).

An online internal standard correction technique for high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) was designed using an autosampler system equipped with HPLC to improve the analytical precision. The autosampler was programed to operate in the following sequence: it first takes up a portion of sample solution, rinses the nozzle, sucks air as a spacer, takes an internal standard solution and finally injects all of them into a sampling loop through an injection valve. The repeatability of the sampling (amount 20 µL) was improved from 2.5 to 1.2% using the online internal standard technique. This technique was applied to As speciation in food samples, since food safety monitoring requires high precision and high sample throughput. Rhenium was very suitable as an internal standard element due to its retention time, peak shape and water solubility. This technique effectively improved the analytical precision of the As speciation and got rid of the operation of adding an internal standard solution into samples.

Speciation analysis of Gadolinium-based contrast agents using aqueous eluent-hydrophilic interaction liquid chromatography hyphenated with inductively coupled plasma-mass spectrometry.

Gadolinium chelates are widely used as contrast agents for magnetic resonance imaging (MRI). In recent decades, the amount of Gd in river water has been increasing owing to the input of Gd-based contrast agents. To identify and quantify the Gd-based contrast agents in river water, the novel technique of hydrophilic interaction liquid chromatography (HILIC) hyphenated with inductively coupled plasma-mass spectrometry (ICP-MS) was developed. To avoid deposition of carbon on the ICP-MS interface, a mobile phase consisting of an ammonium acetate buffer diluted with pure water was applied to separate Gd-based contrast agents. Despite the absence of an organic solvent in the mobile phase, six Gd-based contrast agents, Gd-DTPA, Gd-EOB-DTPA, Gd-DOTA, Gd-DTPA-BMA, Gd-BT-DO3A, and Gd-HP-DO3A, were successfully separated. This technique was applied for river water samples. As a result, Gd-DOTA, Gd-BT-DO3A, and Gd-HP-DO3A were observed from the sample near the outfall of a wastewater treatment plant (WWTP), indicating that at least some of the Gd-based contrast agents are passed through treatment in a WWTP. In addition to Gd-based contrast agents, unidentified Gd compounds were found to be present in river water. These results infer that transformation and/or dissociation of Gd chelates may be caused during the treatment procedure in a WWTP.

Isotopic analysis of tungsten using multiple collector-inductively coupled plasma-mass spectrometer coupled with electrothermal vaporization technique.

We have developed a micro-electrothermal vaporization (µETV) device for the multiple collector-ICP-mass spectrometry (µETV-MC-ICPMS) to improve analytical precision in the (182)W/(183)W and (184)W/(183)W ratio measurements from nanogram quantities of W. The W solution was loaded onto the Re-filament, and the gradual evaporation of W was achieved by controlling the incident current onto the Re filament and D-Glucose. With the W evaporation under the Ar atmosphere, the measured W isotope ratios became erroneous mainly due to the contribution of signal spikes Ala-Arg-Gly-Phy-Tyr. In strike contrast, signal intensity profile became smooth when the He ambient/carrier gas was employed, and this resulted in better precision in the isotope ratio measurements. The measured UV-vis isotope ratio data obtained with present µETV technique were significantly deviated from the ratio data obtained with solution nebulization technique, mainly due to the contribution of the isotope fractionation effect through the evaporation process. Rigorous testing for the correction of the isotope fractionation processes pH-activity curve revealed that the Rayleigh fractionation law, rather than the conventional exponential law, provided the most reliable ratio data (1.851720±0.000018 for (182)W/(183)W and 2.141248±0.000028 for (184)W/(183)W ratios), which agreed well with the ratio data obtained through the conventional solution nebulization technique (1.851718±0.000039 for (182)W/(183)W and 2.141248±0.000022 for (184)W/(183)W). Moreover, mass dependency for the mass fractionation law suggested that W was evaporated as oxides (WO3), rather than the metallic form (W), from the Re filament, and therefore, information concerning the chemical form of the analytes could also be derived by the ETV technique developed in this study. The data presented here demonstrate clearly that the ETV sample introduction technique has a potential to become a sensitive tool for the precise isotope analysis for the MC-ICPMS technique.