Reference elemental concentrations

Sample Solutions. The urine sample solutions all originated from one composite urine sample. The latter was made by combining 150-mL aliquots of the entire first-morning voids of 16, presumably healthy, male subjects. Aliquots of the composite were used to prepare three sets of sample solutions as indicated in Table IV. The solutions in each set were "spiked with internal reference elements and with appropriate volumes of multielement stock solution to make a (multiple) standard addition series (12). The final gallium and yttrium internal reference-element concentrations were 1.0 and 0.1 mg/L, respectively, for both the reference and standard addition solutions. The added analyte concentrations for both the reference and standard addition solutions were 0, 2, 4, 10, and 20 times the approximate "normal analyte concentrations for urine, as listed in Table II. 

Fig. 7-23. Scatter diagrams for iron, titanium, magnesium, calcium, vanadium, and chromium in the atmospheric aerosol versus aluminum as reference element. Concentrations are given in units of ng/ m3. Symbols indicate the type of sampling site O marine, A marine-influenced, 9 remote continental, Antarctic. The range of X/Al ratios in crustal rock is shown by the solid lines and X/Al ratios in soil by the dashed lines. [Adapted from Rahn (1975b).]...

Conveniently, a matrix element is chosen as the reference element (index ref) (el) indicates the element to be quantified. By use of a standard sample with known concentrations Cel and Cief, RSF is adjusted to the specific matrix. Relative precision up to 1% is possible by use of standards. 

Because of the complex nature of the discharge conditions, GD-OES is a comparative analytical method and standard reference materials must be used to establish a unique relationship between the measured line intensities and the elemental concentration. In quantitative bulk analysis, which has been developed to very high standards, calibration is performed with a set of calibration samples of composition similar to the unknown samples. Normally, a major element is used as reference and the internal standard method is applied. This approach is not generally applicable in depth-profile analysis, because the different layers encountered in a depth profile of ten comprise widely different types of material which means that a common reference element is not available. 

If relative sensitivity factors are used, reference measurement of standard samples is not necessary. The ratio of two different elemental concentrations in one sample is given by ... 

A common approach for identifying the enriched elements in a material is to calculate the enrichment factor (EF). The EF of an element, M, is obtained by comparing its concentration with that of a reference element, R, such as cerium or... 

Gladney ES (1980) Elemental concentrations in NBS biological materials and environmental standard reference materials. Anal Chim Acta 118 385-396. 

Gladney ES, O Malley BT, Roeiandts I, and Gills TE (1987,1993 update) Standard Reference Materials Compilation of Elemental Concentration Data for NBS Chemical, Biological Geological and Environmental SRMs. NBS Spec Pub 260-111, NIST, Gaithersburg, MD. 

Gladney ES, Perrin DR, Owens JW, and Knab D (1979) Elemental concentrations in the United States Geological Survey s geochemical exploration reference samples - a review. Anal Chem 51 1557-1569. 

Within collaborative work on element concentrations in a number of biological reference materials using solid sampling and other analytical methods, calibration of Cd, Cu, Pb and Zn in BCR CRM 185 Bovine liver with solid CRMs was performed for each element with a reference material of the same matrix, NIST SRM 1577... 

Schauenburg H, Weigert P (1991) Determination of element concentrations in biological reference materials by solid samphng and other analytical methods. Fresenius Anal Chem 342 950-956. 

Speciated Components Little information is available for RMs with respect to the chemical forms or species in which elements occur. In the first approximation, bioavaila-ble, extractable, or leachable levels of elements are of interest. Secondly, at a higher degree of sophistication, data on the levels of the actual species or inorganic moieties such as nitrate, ammonium, phosphate, bromide, bromate, iodide, iodate, and molecular species of which the elements are constituents would be of relevance to those conducting mechanistic and speciation research. Reference materials that are certified for extractable elemental concentrations are not available to monitor the usual procedures in soil science based on extraction. 

Chase and Long (1997) propose that this conundrum can be eliminated by the use of Zero Reference Materials (ZRMs) in analytical methods development to fully evaluate the method. A ZRM is a product matrix that lacks those nutrient components that are to be assayed, i.e. a blank matrix. The use of a ZRM in method development can and will give a true indication as to how the method will perform as the spiked nutrient levels approach zero. For example, two products. Corn Starch (NIST RM 8432) and Microcrystalline Cellulose (NIST RM 8416), contain very low elemental concentrations and could conceivably serve as real sample blanks or ZRMs in some analytical procedures. 

Elements Concentration factor Eluent Detection limit (Mfifl) Reference... 

Table 2. Chemical Paste Compositional Reference Units Mean Elemental Concentrations.

Figure 2. Development of elemental concentration-distance profiles as a function of time for a mass-transport-limiting situation, (a) Diffusion to a large (r0 > <5) organism, (b) Diffusion to a small (ro

In addition to the emission due to the test element, radiation is also emitted by the flame itself. This background emission, together with turbulence in the flame, results in fluctuations of the signal and prevents the use of very sensitive detectors. The problem may be appreciably reduced by the introduction into the sample of a constant amount of a reference element and the use of a dual-channel flame photometer, which is capable of recording both the test and reference readings simultaneously. The ratio of the intensity of emission of the test element to that of the reference element should be unaffected by flame fluctuations and a calibration line using this ratio for different concentrations of the test element is the basis of the quantitative method. Lithium salts are frequently used as the reference element in the analysis of biological samples. 

Empirical Analysis uses reference standards to establish an empirical calibration line (Piorek Rhodes 1988) and can be useful for samples where all major elements present cannot be analyzed. The standards should be matrix-matched and contain a range of element concentrations bracketing the desired level of quantification. 

TTFA. The TTFA steps will be Illustrated for the first two clusters In Figure 1. These correspond to clusters one and two In Table II. As evident In Figure 1, these two clusters are quite similar. Based on the relative elemental concentrations In Table II, we refer to these as the silicon and alblte clusters. 

Ondov JM, Zoller WH, Olmez I, et al. 1975. Elemental concentrations in the National Bureau of Standards environmental coal and fly ash standard reference materials. Anal Chem 47 1102-1109. 

Iron was chosen as the reference element because its major source is likely to be soil and it is measured with good accuracy and precision by FIXE. Crustal abundances were taken from Mason (21). Enrichment factors greater than 1 indicate an enrichment of that element relative to crustal abundances values less than 1 indicate a depletion. The results of this calculation are shown in Table 4. For this calculation it was assumed that ammonium and nitrate accounted for all aerosol nitrogen. It is seen that Si and Ca are near their crustal abundance, indicating a probable soil dust source. The low EF for Al is probably due to a systematic error in the Al measurement rather than a true depletion. Potassium, although present in small concentrations, is slightly enriched relative to crust. The other fine aerosol species, C, N, S, and Pb are enriched by factors of thousands over their natural crustal abundance, indicating that they are not due to wind-blown dust. 

Certified reference materials (CRMs) are mainly applied to validate the analytical procedure developed for routine analysis in order to determine the accuracy of analytical data, the recovery for selected elements, the uncertainty of trace element determination and the detection limits. Otherwise, in solid-state mass spectrometric techniques, such as SSMS, LA-ICP-MS, GDMS, SNMS or SIMS, one point calibration using CRMs has been established as an important calibration strategy to obtain reliable analytical data. The one point calibration is performed using the experimentally determined relative sensitivity coefficients (RSCs) on a suitable CRM with a similar trace/matrix composition. An RSC of a chemical element is defined as the ratio of the measured element concentration (experimentally determined) divided by the certified element concentration (accepted or recommended value of element concentration) in a given matrix. 

An interesting approach is the application of multiple ion collector mass spectrometry (MC-TIMS and MC-ICP-MS) for the determination of Cd and T1 in high purity zinc metal after trace matrix separation by the certification of reference materials from the Bureau Communie de Reference (BCR).29 Accurate and precise element concentrations in high purity zinc metal have been obtained with both mass spectrometric techniques via precise isotope ratio measurements using the isotope dilution strategy the analytical data. 

In addition, there exist a multitude of different applications in water analysis by ICP-MS for environmental control. For example, Lawrence et cdP determined rare earth element concentrations in natural waters (these are river, lake, sea or groundwater) by quadrupole ICP-MS using external calibration and employed river water reference material SLRS-4 to validate the analytical data. The speciation of yttrium and lanthanides in water samples by SEC-ICP-MS was studied by Haraguchi et a/.18 whereby the detection of La, Ce and Pr corresponded to the occurrence of large organic molecules. 

For a trace element concentration to be certified by NBS, it must be determined by at least two independent methods, the results of which must agree within a small experimental error range of 1% to 10%, depending on the nature of the sample and the concentration level of the element. Such accuracy in determining some trace elements for certification of coal SRM is achieved most easily by NAA with radiochemical separation. Scientists at NBS have extensively tested a neutron activation method that involves a combustion separation procedure on coal as well as on several other matrices to be certified as standard reference materials. The procedures they have thus developed to determine mercury (12), selenium (13), and arsenic, zinc, and cadmium (14) are outlined in a following section on methods for determining specific elements in coal. 

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