Quantification standards

Environmental factors Often heterogenous with limited quantification Standardization essential... 

The NP-HPLC fractions were spiked with the internal quantification standards PCB 103 or TCN, and concentrated prior to HRGC analysis... 

In addition, the curve must be linear over the entire concentration range. The linearity is denoted by the R squared value (r the Pearson correlation coefficient) and should be ideally 1 or very close to 1 (but at least above 0.985). A linear standard curve also indicates that the efficiency of amplification of real-time PCR is consistent at varying template concentrations. The validity of the standard curve method is based on an assumption of equal amplification efficiencies between DNA samples used as quantification standards and unknown test samples under investigation. If the standard... 

Since our intent was to use the competitive A-B ELISA to quantify 3-Cys-A adducts formed in biological samples at unknown and perhaps variable levels of protein modification, experiments were conducted to determine the effect of adduct substitution level on quantification. Standards of known substitution level were prepared by derivatizing 9,000 g liver supernatant with various concentrations of [3H]NAPQI. After extensive dialysis to remove noncovalently bound materials, protein concentrations were determined and the substitution level of each standard was determined by scintillation counting. These synthetic standards, which ranged from 0.5 to 30 nmol 3-(cystein-S-yl)[3H]acetaminophen per mg protein, were analyzed in the competitive immunoassay. When the data were plotted with percent inhibition as a function of protein concentration, the results show an ordered family of inhibition curves where the most highly substituted proteins were the... 

Reducing sugar production was monitored with /7-hydroxybenzoic acid hydrazide (PHBAH) (41), First, 100 pL sample was mixed with 50 pL 1.5 % PHBAH in 0.5 M NaOH in a 96-well plate. After 10 min at 95 C, 50 pL H2O was added and 100 pL solution was read at 410 nm in another 96-well plate. D-Glucose served as quantification standard. Initial v was derived from five samplings taken during the first hour of hydrolysis. 

Separation, identification, and quantification Using GC-MS with internal quantification standards that are added as spikes at the extraction stage. If the subsequent GC-MS analyses reveal that accurate determination of PCDDs and PCDFs is not possible owing to the presence of interfering peaks then liquid chromatography separation may be employed. 

The most important goal for MALDI-MSI certainly is to develop quantification protocols for tissue analysis. While relative quantification within a tissue area is normally obtained, quantification between different tissue areas (e.g., between bone tissue and adjacent coimective tissue) requires quantification standards to be reproducibly added to the tissue sample. Nonetheless, a number of approaches to reach quantitative conditions in MALDI-MSI are currently being followed, which suggests that a common protocol might become available in the near future. 

In relation to quantification, standard addition methodology is usually used due to the presence of matrix effect [75]. For that, spiking samples with different amounts of standard compounds were prepared, in order to obtain a concentration range in agreement with the levels observed in assayed samples. Tentatively identified compounds (with no standard available) were quantified as equivalents of the most similar compound, taking into account their molecular weight [94]. In the other cases, triphenyl phosphate (TPP) was used as an internal standard for quantification purposes... 

Chromatographic peak areas are calculated automatically by the data system by reference to the response obtained from certain specified, compound-dependent ions. From the peak areas of the target compounds, quantification is achieved by comparison with the internal standards, which are present in known concentration. The laboratory responsible for the analysis must report the target compounds and all tentatively identified (nontarget) compounds. Standard EPA forms must be completed and submitted. A laboratory is said to be in compliance when it has satisfied all aspects of its CLP contract. 

To quantitate proteins from staining, a densitometer aided by computer software is used to evaluate band areas of samples compared to band areas of a standard curve. Amido black, Coomassie Brilliant Blue, and silver stains are all appHcable for use in quantification of proteins. 

To analyze pesticides from the sample, several GC techniques were used GC with FID and EC detectors and GC/MS with external standards. Pesticides are mostly analyzed using split/splitless technique where higher amount of injected solution exits the gas chromatograph without decomposing therefore by quantification of the several pesticides in the filter, we found out how harmful is exposing analysts to pesticide compounds during the GC analysis. 

The set of Glass Standard Reference Material NIST SRM 610 - 614 was used for quantification of amount up to 45 trace elements in the synthetic oxide single crystals and natural quartzites. 

IDENTIFICATION AND QUANTIFICATION.—Such plan provisions shall expressly identify and quantify the emissions, if any, of any such pollutant or pollutants which will be allowed, from the construction and operation of major new or modified stationary sources in each such area. The plan shall demonstrate to the satisfaction of the Administrator that the emissions quantified for this purpose will be consistent with the achievement of reasonable further progress and will not interfere with the attainment of the applicable national ambient air quality standard by the applicable attainment date. 

Nevertheless, quantification is possible, a good example being the evaluation of the composition of chromatographic separations adsorbed onto glass, alumina, polyethylene, or paper. When compared with known standards, the presence of only a few nanograms of a strong fluorophore may be quantified to better than 10%. 

The most common application of dynamic SIMS is depth profiling elemental dopants and contaminants in materials at trace levels in areas as small as 10 pm in diameter. SIMS provides little or no chemical or molecular information because of the violent sputtering process. SIMS provides a measurement of the elemental impurity as a function of depth with detection limits in the ppm—ppt range. Quantification requires the use of standards and is complicated by changes in the chemistry of the sample in surface and interface regions (matrix efiects). Therefore, SIMS is almost never used to quantitadvely analyze materials for which standards have not been carefiilly prepared. The depth resoludon of SIMS is typically between 20 A and 300 A, and depends upon the analytical conditions and the sample type. SIMS is also used to measure bulk impurities (no depth resoludon) in a variety of materials with detection limits in the ppb-ppt range. 

Ion implantation is often used to produce reliable standards for quantification of SIMS analyses. Ion implantation allows the introducdon of a known amount of an element into a solid sample. A sample with a major component composition similar to that of the unknown sample may be implanted to produce an accurate standard. The accuracy of quandfication using this implantation method can be as good as 2%. 

Previous studies of the interaction of energetic particles with suri ces have made it clear that under nearly all conditions the majority of atoms or molecules removed from a surface are neutral, rather than charged. This means that the chained component can have large relative fluctuations (orders of magnitude) depending on the local chemical matrix. Calibration with standards for surfaces is difficult and for interfaces is nearly impossible. Therefore, for quantification ease, the majority neutral component of the departing flux must be sampled, and this requires some type of ionization above the sample, often referred to as post-ionization. SALI uses effi-... 

NAA is a quantitative method. Quantification can be performed by comparison to standards or by computation from basic principles (parametric analysis). A certified reference material specifically for trace impurities in silicon is not currently available. Since neutron and y rays are penetrating radiations (free from absorption problems, such as those found in X-ray fluorescence), matrix matching between the sample and the comparator standard is not critical. Biological trace impurities standards (e.g., the National Institute of Standards and Technology Standard Rference Material, SRM 1572 Citrus Leaves) can be used as reference materials. For the parametric analysis many instrumental fiictors, such as the neutron flux density and the efficiency of the detector, must be well known. The activation equation can be used to determine concentrations ... 

A further critical point are the intensities correlated to spectra of the pure elements. Calculated and experimentally determined values can diverge considerably, and the best data sets for 7 measured on pure reference samples still show a scatter of up to 10%. The use of an internal standard or a simultaneously measured external standard seems to be the most successful way to reducing the inaccuracy below 10%. (Eor a more detailed discussion of background subtraction and quantification see, e.g., Seah [2.9].)... 

The accuracy achievable by the ratio method amounts to approximately 5-10 atom% when ionization edges of the same type are used, i. e. only K edges or only L edges, whereas the error in quantification increases to +15-20 atom% for the use of dissimilar edges. Improvement of the quantification accuracy up to approximately 1 atom% is possible if standards are used. 

Under Cs bombardment the matrix effect can be significantly reduced by using the MCs" ion signals for quantification of species M. The detection limit is increased, i.e. the detection power deteriorates, by two or more orders of magnitude, but sometimes even standard-free quantification has been reported [3.51]. MCs" ions have high masses this is a disadvantage because many mass interferences occur in this mass range. 

In Raman spectroscopy the intensity of scattered radiation depends not only on the polarizability and concentration of the analyte molecules, but also on the optical properties of the sample and the adjustment of the instrument. Absolute Raman intensities are not, therefore, inherently a very accurate measure of concentration. These intensities are, of course, useful for quantification under well-defined experimental conditions and for well characterized samples otherwise relative intensities should be used instead. Raman bands of the major component, the solvent, or another component of known concentration can be used as internal standards. For isotropic phases, intensity ratios of Raman bands of the analyte and the reference compound depend linearly on the concentration ratio over a wide concentration range and are, therefore, very well-suited for quantification. Changes of temperature and the refractive index of the sample can, however, influence Raman intensities, and the band positions can be shifted by different solvation at higher concentrations or... 

In an experiment in which a sample is subjected to controlled shock loading and preserved for post-shock analysis, the shock-recovery experiment, the quantification, and the credibility of the experiment rest directly upon the apparatus in which the experiments are carried out. Quantification must be established with two-dimensional numerical simulation and this can only be accomplished if the recovery fixtures are standardized. The standardized fixtures must be capable of precise assembly so that the conditions actually achieved in the experiment are those of the simulation. 

D. Hainzl, J. Burhenne and H. Pariar, HRGC-ECD and HRGC-NICI SIM quantification of toxaphene residues in selected marine organism by envir onmentally relevant chloroboT nanes as standard , Chemosphere 2S 237-243 (1994). 

Quantification External standard External and internal standard... 

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