Internal reference standards

Specifications for hGH products are defined by the governmental licensing authorities, eg, the U.S. Pood and Dmg Administration. Draft monographs for hGH have been prepared by both the EnitedStates Pharmacopia and the European Pharmacopeia commissions and should be formally adopted by 1995. These specifications are suitable for biosynthetic hGH. The much less purified pituitary-derived hGH has virtually disappeared from commercial production. An international reference standard for pituitary-derived hGH (lot 80/505) has been used for caUbration, particularly for bioassay purposes. A highly purified biosynthetic hGH standard (lot 88/624) has been prepared and should be formally adopted by 1995, or before. 

The analysis was performed by XRF method with SR. SRXRF is an instrumental, multielemental, non-destructive analytical method using synchrotron radiation as primary excitation source. The fluorescence radiation was measured on the XRF beam-line of VEPP-3 (E=2 GeV, 1=100 mA), Institute of Nuclear Physics, Novosibirsk, Russia. For quality control were used international reference standards. 

Fig. 3.16 Schematic drawing of the MIMOS II Mossbauer spectrometer. The position of the loudspeaker type velocity transducer to which both the reference and main Co/Rh sources are attached is shown. The room temperature transmission spectrum for a prototype internal reference standard shows the peaks corresponding to hematite (a-Fe203), a-Fe, and magnetite (Fe304). The internal reference standards for MIMOS II flight units are hematite, magnetite, and metallic iron. The backscatter spectrum for magnetite (from the external CCT (Compositional Calibration Target) on the rover) is also shown...

Relative sensitivity factors (RSFs) may be more readily applied if the intensities are not referred to an internal reference standard, when the concentration is given by... 

Indeed, there are potentially several different levels to approach standardization of IHC For the greatest scientific rigor, it is required to perform serial experiments based upon the hypothesis mentioned above to investigate and validate, if possible, standardization of IHC based on the AR technique (Chapter 5 in detail). Another approach, that may be combined with AR, is the systematic development of Quantifiable Internal Reference Standards (QIRS) that will allow assessment of the degree of protein degradation... 

Two different and possibly complementary approaches have been explored. One utilizes a panel of quantifiable internal reference standards (QIRS), which are common proteins present widely in tissues in relatively consistent amounts.11,22 In this instance because the reference proteins are intrinsic to the tissue they are necessarily subjected to identical fixation and processing, and incur no additional handling or cost, other than synchronous performance of a second IHC assay (stain), such that the intensity of reaction for the QIRS and the test analyte can be compared by IA, allowing calculation of the amount of test analyte (protein) present on a formulaic standard curve basis. The other approach seeks to identify external reference materials and to introduce these into each step of tissue preparation for cases where IHC studies are anticipated in this instance the logistical issues of production, distribution, and inclusion of the reference standard into all phases of tissue processing also must be considered, along with attendant costs. 

Taylor CR. Quantifiable internal reference standards for immunohistochemistry the measurement of quantity by weight. Appl. Immunohistochem. Mol. Morphol. 2006 14 253-259. 

The International Reference Standard for neomycin is defined as containing 680 units of activity per mg or alternatively 1 unit of activity is contained in 0.00147mg of standard material. 

Good quality control procedures are crucial to allowing the results of this project to integrated year upon year. More than 10% of all samples analyzed are for quality control. About half of these are duplicates the others are blanks, certified or internal reference standards and spiked samples. 

SACHEM Inc. of Cleburne, Texas, manufactures various concentrations of tetramethylammo-nium hydroxide (TMAH) solutions to meet customer specifications. To ensure consistent performance, electronic industry requires very narrow concentration specifications for the solutions. In SACHEM s quality control laboratory, standardized acids such as HC1 or H2S04 are used as titrants for the TMAH solutions to check their concentrations. The performance of the assay titration is controlled by daily analysis of internal reference standards (IRSs). If the IRS results are within controlled limits, then the assay results of a product can be reported. If not, the results cannot be reported until the root cause is uncovered and eliminated. Safety glasses and gloves are worn while performing this work in the laboratory. 

As the commonly used international reference standard PDB has been exhausted for several decades, there is a need for introducing new standards. Even though several different standards are in use today, the international standard the 5-values are referred to remains to be the PDB-standard (Table 2.2). 

EF-1 was analyzed by spectrophotometer IH and 13C NMR (Bmker AC 200, 200MHz) using as solvent chloroform (CDCI3) and methanol (CD3OD) deuterated at a ratio of 9 1 to tetrame-thylsilane (TMS) as internal reference standard. An aliquot of EF-1 (5 mg) was methylated with diazomethane and subjected to mass spectrometry (MS Agilent Technologies). The spectral data obtained were compared with the literature [Oliveira et al, 2006]. 

Can all calibrations performed in-house or by subcontractors be traced to a national or international reference standard ... 

The Codex Alimentarius is a code of food standards for all nations. All members of CAC and interested international organizations are invited to comment on proposed standards, including possible implications for their economic interests. Members are encouraged to consult with interested and affected parties in their countries. Codex standards are recognized by the World Trade Organization as the international reference standards for food safety. 

In order to quantify compound X (with mass Mx) in a mixture, a quantity p mg of reference compound R (with mass MR) is added to P mg of the sample containing compound X. The internal reference standard R is chosen so that the signal it generates does not interfere with the signal used to quantify compound X (Fig. 9.25). 

Other, more limited approaches may also be employed. (2) When side reactions are unimportant and the products are stable, a pair of nucleophiles may be allowed to compete for a deficiency of alkylating agent. The relative amount of alkylated products, R, is determined when all the alkylating agent is consumed R is [MeHet,]/[MeHet2], the molar ratio of methylated products. The rate-constant ratio then is calculated with the aid of Eq. (18).62,148 This special approach allows a rate-constant ratio to be calculated using a product ratio instead of concentrations of individual products. It is conveniently applied when, say, it is hard to find an internal reference standard in NMR methods of analysis, thereby making the determination of concentrations difficult. 

The collected microbubble-surfactant monolayer material was subsequently lyophilized and redissolved in CD3OD. As with the preceding NMR measurements (see Section 7.1), H-NMR spectra at 270 MHz were obtained with the same Bruker Hx-270 NMR spectrometer. In this case, approximately 0.5% solutions (w/v in CD3OD) of the microbubble-surfactant monolayer material were employed in the measurements (all taken at 26°C). Tetra-methylsilane was used as an internal reference standard (ref. 394). 

Carbon-13 chemical-shifts are defined relative to the carbon signal of internal tetramethylsilane (Me4Si) hence, when measuring spectra in organic solvents, Me4Si should be added to the sample solution as the internal reference-standard.23 However, any homo- or hetero-nu-clear signal of the solvent, or of an added reference compound, may be used to calculate the 13C-chemical shifts, provided that its shift rela-... 

Reference Standard. If an international reference standard (WHO, NIBSC) or compendial reference standard (USP) is used, the applicant should submit the citation for the standard and a certificate of analysis. If an inhouse working reference standard is used, a description of the preparation, characterization, specifications, and testing and results should he provided. 

By specifically and selectively reconstructing the total ion peak observed after a loop flow injection to display only the m/z values of interest, the area count for that ion can be extracted from the composite total ion peak. The measured area count can then be used to estimate the quantity of specific alkaloid by comparison to a calibration curve. Thus, component compounds in a mixture are separated by mass, as opposed to chromatography, for quantitation. To normalize the variability of the API response, an internal reference standard is added to the sample prior to loop injection. Alkaloids for which standards are not available are reported as equivalents of a closely related and available standard used to generate the calibration curve, for example, deltaline and methyllycaconitine have been used as calibration standards to represent the non-MSAL and MSAL types of alkaloids, respectively, in the plant material. Calibration curves for these two compounds were linear (r > 0.990) and there appears to be no selective suppression of lower-level alkaloids (figure 13.21). Multiple analyses of Delphinium barbeyi samples returned a level ofprecision that was less than 10 % (relative standard deviation) for all components [56]. 

Because of the difficulties associated with the Delphinium classification, the diterpene alkaloid content was assessed as an aid to determining the chemical taxonomic diversity of the toxic larkspur species [59]. Plant samples were collected from 18 different locations in five western states in the US. The crude methanolic extracts were analyzed for diterpene alkaloids using FI-ESI-MS. The data from the individual ESI mass spectra were statistically analyzed using canonical discriminant analysis and analysis of variance. In brief, the sample (100 mg) was extracted by mechanical shaking at room temperature with methanol (5mL) for 16h. Reserpine (500 p.g) was added as an internal reference standard and the sample mixed for 5 min and then centrifuged. An aliquot (30 jxL) of the supernatant was then diluted with of 1 1 methanol/1 % acetic acid (1.0 mL) and an aliquot (20 jjlL)... 

---