Calibration species-specific

Inorganic mass spectrometry requires the development of suitable reference materials, such as matrix matched standard reference materials for trace, surface (including depth profiling and microlocal) analysis and/or the creation of matrix independent calibration procedures. The development of species specific standards will be intensified for speciation studies in the future. 

To study the abiotic formation of Me-Hg from Hg2+ as well as demethylation of Me-Hg to Hg2+ in biological tissues during treatment with TMAH, enriched isotope standards from Me198Hg and 201Hg2+ were added to the samples to monitor species transformation and to apply species-specific isotope dilution (SSID) calibration. The HPLC instrumental set-up with a C18 column and an aqueous phase eluent was directly coupled to ICP-MS [31]. 

Factors other than temperature and dissolution also appear to influence Mg/Ca in planktonic shells. Based on culturing, there is clear evidence for differences in uptake between species (Lea et al., 1999), with as much as a factor of two variations. For this reason, species-specific calibrations are necessary, although it is difficult to do this by any means other than culturing because of the complication of habitat depth. Salinity appears to exert a small effect on shell Mg/Ca, with an observed increase of between 6 4% for O. universa (Lea et al., 1999) and 8 3% for G. sacculifer (Niimberg et al., 1996a) per salinity unit (SU) increase. (Note this and all other... 

The stable carbon isotope ratios of dissolved inorganic carbon (DIC) and benthic foraminiferal calcite generally are determined with isotope ratio gas mass spectrometers calibrated via NBS 19 international standard to the VPDB (Vienna Pee Dee Belemnite) scale. All values are given in 8-notation versus VPDB with an overall precision of measurements including sample preparation usually better than +0.06 and +0.1%o for calcite and DIC carbon isotopes, respectively. Except one single-specimen based dataset (Hill et al. 2004), all stable isotope data from papers referred to in this overview are from species-specific multi-specimens analyses. The number of specimens used for a single analysis depended on size and weight of species but usually varied between 2 and 25. 

Intra-assay precision Run samples (S5 replicates) in a single run. Samples used for precision testing may include commercial QC samples, but precision testing should also include species-specific samples of the relevant matrix (e.g., serum, plasma, urine) for the intended study samples Test S3 samples at low, medium, and high concentrations across the calibration curve range Calculate mean, SD, and CV% CV 20%, CV<25% at LLOQ... 

Later, Busto et al. used synthesized Fe-labeled transferrin to determine individual transferrin isoforms in human serum samples for the species-specific mode. The stability of the prepared proteins was tested for 1 week and no iron exchange had occurred. They concluded that the results are in good agreement with other calibration methods, e.g. the species-unspecific method however, the species-spedfic mode can offer better precision. Hoppler et al. also synthesized and characterized Fe-labeled Phaseolus vulgaris ferritin for isotope dilution analysis. " ... 

Yang, L., Mester, Z., and Sturgeon, R. E. (2002) Species-specific isotope dilution-based calibration for trace element speciation and its combined uncertainty evaluation determination of tributyltin in sediment by HPLC-ICP-MS. Anal. Chem., 74,2968-76. 

Snell, J. R, Stewart, I. L, Sturgeon, R. E., and Freeh, W. (2000) Species specific isotope dilution calibration for determination of mercury species by gas chromatography coupled to inductively coupled plasma or furnace atomisation plasma ionisation-mass spectrometry. J. Aruil. At. Spectrom., 15,1540-5. 

ICS A 1 nterference check solution A Checks for freedom from interference at blank level in the presence of interfering species After initial calibration No specific requirements <3 X contract required quantitation limit value (CRQL)... 

Hundreds of chemical species are present in urban atmospheres. The gaseous air pollutants most commonly monitored are CO, O3, NO2, SO2, and nonmethane volatile organic compounds (NMVOCs), Measurement of specific hydrocarbon compounds is becoming routine in the United States for two reasons (1) their potential role as air toxics and (2) the need for detailed hydrocarbon data for control of urban ozone concentrations. Hydrochloric acid (HCl), ammonia (NH3), and hydrogen fluoride (HF) are occasionally measured. Calibration standards and procedures are available for all of these analytic techniques, ensuring the quality of the analytical results... 

Definition and Uses of Standards. In the context of this paper, the term "standard" denotes a well-characterized material for which a physical parameter or concentration of chemical constituent has been determined with a known precision and accuracy. These standards can be used to check or determine (a) instrumental parameters such as wavelength accuracy, detection-system spectral responsivity, and stability (b) the instrument response to specific fluorescent species and (c) the accuracy of measurements made by specific Instruments or measurement procedures (assess whether the analytical measurement process is in statistical control and whether it exhibits bias). Once the luminescence instrumentation has been calibrated, it can be used to measure the luminescence characteristics of chemical systems, including corrected excitation and emission spectra, quantum yields, decay times, emission anisotropies, energy transfer, and, with appropriate standards, the concentrations of chemical constituents in complex S2unples. 

The approach to standardization used by Haaijman (53) and others (66,67), in which the fluorophor is incorporated within or bound to the surface of a plastic sphere, is more versatile than the use of inorganic ion>doped spheres, since the standard can be tailored exactly to the specifications required by the analyte species. However, this approach increases the uncertainty of the measurement because the photobleaching characteristics of both the standard and the sample must be considered. The ideal approach is to employ both types of standards. The glass microspheres can be used to calibrate instruments and set instrument operating parameters on a day-to-day basis, and the fluorophor-doped polymer materials can be used to determine the concentration-instrument response function. 

This example assumes that RIA was chosen. The principle behind RIA is the competition between the analyte A and a radioactively tagged control C (e.g., a /-marked ester of the species in question) for the binding site of an antibody specifically induced and harvested for this purpose. The calibration function takes on the shape of a logistic curve that extends over about three orders of magnitude. (Cf. Fig. 4.38a.) The limit of detection is near the B/Bo = 1 point (arrow ) in the upper left corner, where the antibody s binding sites are fully sequestered by C the nearly linear center portion is preferrably used for quantitation. 

Application to solid polymer/additive formulations is restricted, for obvious reasons. SS-ETV-ICP-MS (cup-in-tube) has been used for the simultaneous determination of four elements (Co, Mn, P and Ti) with very different furnace characteristics in mg-size PET samples [413]. The results were compared to ICP-AES (after sample dissolution) and XRF. Table 8.66 shows the very good agreement between the various analytical approaches. The advantage of directly introducing the solid sample in an ETV device is also clearly shown by the fact that the detection limit is even better than that reported for ICP-HRMS. The technique also enables speciation of Sb in PET, and the determination of various sulfur species in aramide fibres. ETV offers some advantages over the well-established specific sulfur analysers very low sample consumption the possibility of using an aqueous standard for calibration and the flexibility to carry out the determination of other analytes. The method cannot be considered as very economic. 

In analytical chemistry, we do not have a standard mole. Therefore, solutions made up to a well-defined concentration using very pure chemicals are used as a basis from which we can compare other solutions or an instrument scale. This process is calibration . For some analyses, the chemical used may be a Certified Reference Material which has a well documented specification, e.g. in terms of the concentration of a particular species and the uncertainty of the specified value. However, it is not sufficient just to calibrate the apparatus/equipment used, it is important that the complete method of analysis is validated from extraction of the analyte from the sample to the final measurement. 

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