污水，土壤中元素检测方案(ICP-AES)

ICP ATOMIC EMISSION SPECTROSCOPYAPPLICATION NOTE 35 Waste Water and Soil Samples HORIBA Scientific Agnes Cosnier Longjumeau， France Keywords： environment 1 Introduction This Application Note examines the analysis offive different wastewater and soil samples，which are listed below. Sample 1： Distilled water Sample 2： Wastewater after treatment in waste-water plant (exit) Sample 3： Wastewater before treatment in thewaste plant Sample 4： Industrial wastewater Sample 5： Dried soil from agriculture waste， digested with HNO3 and HCIOa Samples 1-4 contained dilute HNO3. The 5 samples were initially analyzed using asemi-quantitative method to identify the ele-ments and their concentration ranges in eachsample. Profiles of each element of interestwere taken for all the samples， which were usedto show the peaks and the relative backgroundlevels. Then， quantitative analyses were per-formed using calibration curves at the appropri-ate concentration ranges. Finally， the StandardAddition Method was used to obtain results forSample 5， as this sample may have a muchmore significant matrix effect. The elemental analysis of these samples wasundertaken by Inductively Coupled PlasmaAtomic Emission Spectrometry (ICP-AES). Thesample is nebulized then transferred to anargon plasma. It is decomposed， atomized andionized whereby the atoms and ions are excited.We measure the intensity of the light emittedwhen the atoms or ions return to lower levels ofenergy. Each element emits light at characteris-tic wavelengths and these lines can be used forquantitative analysis after a calibration. 3 Instrument specification The work was done on a ULTIMA 2.The specifi-cations of this instrument are listed in Tables 1and 2. Table 1： Specification of spectrometer Parameters Specifications Mounting Czerny Turner Focal length 1m Nitrogen purge Yes Variable resolution Yes Grating number of grooves 2400 gr/mm 2nd order Table 2： Specification of RF Generator Parameters Specifications Type of generator Solid state Observation Radial Frequency 40.68 MHz Control of gas flowrate by computer Control of pump flow by computer Cooling air 4 Semi-quantitative analysis The analytical approach used in this ApplicationNote was to initially undertake a semi-quantita-tive analysis to detect the presence of elementsand estimate their concentration range， andthen perform a quantitative analysis to obtainaccurate and precise results. A semi-quantitative method is integrated intothe Analyst software for the ICP. It allows forrapid identification of elements in the samplefrom a qualitative and quantitative point ofview. Currently， the method contains 34 elements.Wavelengths have been chosen in order to cover awide variety of sample types： sensitive lines formost of the elements， except for Ca， Mg；includingappropriate background correction positions. Abackground correction point is placed on bothsides of the Pb and Al peaks， in case of high con-centration of Al or Ca， respectively. Calibration isperformed with 2 points (0 and 5 mg/L in deionizedwater) and both calibration and analyses aremeasured with 1 "replicate". The acquisition timeis 0.1 s per data point with 7 data points measuredto fit a gaussian curve. With these conditions， a semi-quantitative analysisis undertaken in about 3-4 minutes for the 34 ele-ments and allows the identification of differentkinds of samples. Note： the matrix for the calibration standards maybe adjusted (NaCI 100 g/L，20 %H2SO4…..) accord-ing to the samples that need to be analyzed， thusgiving more accurate results. The following plasma conditions were applied.Note that the power is slightly increased to 1200 Wfrom the 1000 W that would be typically used forclean water. This is to minimize matrix effects thatmay have an influence on signal quantity， as thestandards are in deionized water and the samplesare waste water/soil and acids. Table 3： Operating conditions Parameter Condition RF Generator power 1200 W Plasma gas flowrate 12 L/min Auxiliary gas flowrate 0 L/min Sheath gas flowrate 0.17 L/min Nebulizer gas flowrate 0.76 L/min Nebulizer flowrate 2.75 bars Sample uptake 1 mL/min Type of nebulizer Cross Flow Type of spray chamber Scott Argon humidifier No Injector tube diameter 3.0 mm Slits 20/15 um Note： a Meinhard nebulizer (K3 or C1 type) andcyclonic spray chamber can be used to gain sensi-tivity if required. The results can be printed and/orexported from the ICP software. To validate theresults， a certified sample was analyzed beforemeasuring the samples. Table 4： Results for sample"Reference 1643-d" n.c. means non-certified 5 Quantitative analysis Using the results obtained from the semi-quantita-tive method， several standards were prepared inthe appropriate concentration range for each ele-ment： Table 6： Standard concentration Element Standards (mg/L) 0 1 2 3 4 5 6 7 Al 0 0.02 0.05 0.1 1 10 37.3 150 As 0 0.02 0.05 0.1 1 10 B 0 0.02 0.05 0.1 1 10 Cd 0 0.02 0.05 0.1 1 10 Cr 0 0.02 0.05 0.1 1 10 Cu 0 0.02 0.05 0.1 1 10 Fe 0 0.02 0.05 0.1 1 10 37.3 150 Mn 0 0.02 0.05 0.1 1 10 Ni 0 0.02 0.05 0.1 1 10 Pb 0 0.02 0.05 0.1 1 10 Se 0 0.02 0.05 0.1 1 10 Zn 0 0.02 0.05 0.1 1 10 The plasma parameters are shown in Table 7. Table 7： Operating conditions Parameter Condition RF Generator power 1100 W Plasma gas flowrate 12 L/min Auxiliary gas flowrate 0 L/min Sheath gas flowrate 0.17 L/min Nebulizer gas flowrate 0.63 L/min Nebulizer flowrate 2.84 bars Sample uptake 1 mL/min Type of nebulizer Meihnard C1 Type of spray chamber Cyclonic Argon humidifier No Injector tube diameter 3.0 mm Slits 20/15 um The combination of a Meinhard C1 nebulizer andcyclonic Spray Chamber for sample introductionwas used for optimum sensitivity and detectionlimits. Note： sample number 5 was analyzed using theStandard Addition Method， as there may be amore significant matrix effect in this sample， com-pared to the first four， due to the major elements(650 mg/l of Ca and acids). Profiles of several samples for Cd are shownbelow in Figure 1. This demonstrates that thematrix is different because the spectral Iback-ground is raised in sample 5. + H20 2Cppb Sarple Sample 2 Gaimle 3 Figure 1： Cd spectrum in sample 5 From this calibration， other samples with similarmatrix can be analyzed. The methodology of the Standard AdditionMethod (S.A.M.) is as follows： ·Estimate the approximate concentration for eachelement of interest (using a rapid semi-quantita-tive method) · Prepare a stock solution with all the elements ofinterest and with appropriate concentrations (2-5times each element concentration). .Prepare at least 3 standards： spike the samplewith increasing concentrations； then we have theunknown sample which is declared as our blank(standard 0) and 3 standards in the same matrix.Four standards at least in total are recommended. ·Prepare the method in the software， using back-ground correction for baseline correction. Whencreating the method， it can be set up as a StandardAddition Method · Run the calibration： the results will be givenunder the Standard Addition Tab after running thecalibration. Alternatively， if the method was notset up as a Standard Addition， the intercept (orBEC) of each curve corresponds to the concentra-tion of the element in the sample The global report of the quantitative analyses isshown below in Tables 8-13. The following abbre-viations are used： Conc.： from quantitative method； Conc. (S.Q.)： from semi-quantitative method；Conc. SAM：from standard addition method. Table 8： Results for Sample 1 Line Net Intensity Conc SD Unit RSD(%) Conc.(S.Q.) AI 396.152 19 691.33 0.263 0.00459 mg/L 1.74 0.271 As 189.042 52.58

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