Labeling concentrations

The official permission to use a synthetic colorant in food is determined by its quality and safety. Detailed and accurate analysis became compulsory in order to verify purity and quantify the labeled concentrations of colorants in food. For the analysis of synthetic colorants added to food products, (1) simple and rapid methods are used to determine their presence, (2) accurate and precise methods evaluate then-concentrations, or (3) certain methods evaluate their degradations to unstable and unsafe forms. This chapter is dedicated to these three methods used to identify and quantify synthetic colorants as pure or mixed pigments in foodstuffs. 

Formulated halcinonide, at a concentration of 0.1% in either a cream base or polyethylene glycol-water lotion, after storage at approximately 23° for 3 years, showed no loss on halcinonide content, using high pressure liquid chromatography. 6 The contents remained unchanged within 2% of labeled concentration. 

Note If calculations were made on the basis of the anhydrous form (equivalent weight of CaCl2 = 115/5 = 55.5), an error would have been made, unless the labelled concentration was also in terms of the anhydrous form. 

The thermal and photochemical stability of both organic dyes and nanocrystals are influenced by an extremely broad variety of conditions that need to be considered excitation wavelength and intensity, matrix or microenvironment, label concentration, and, in the case of nanoparticles, surface chemistry. Therefore, the individual study of the stability of a chromophore under the conditions required can usually not be avoided. 

To demonstrate the ability to evaluate intersample variations, an over-the-counter (OTC) pain relief medication from two different manufacturers was compared. The samples contain three APIs each acetaminophen, aspirin and caffeine. Pure acetaminophen, aspirin and caffeine samples are obtained in either tablet form or powder compact and included within the same FOV as the tablets to provide simultaneous reference materials for the tablet samples. The tablets and pure components were arranged as shown in Plate 8.1a. Measurements on all samples were collected simultaneously. Tablet A samples from one manufacturer have a reported label concentration of 37%, 37%, and 10%, for the three API components, respectively. Tablet B samples from the second manufacturer contain the same three APIs, at label concentrations of 39%, 39%, and 10 %, respectively. In addition to these samples, tablet C samples are included in the array of tablets. These samples contain only acetaminophen as the API with a reported label concentration of 79%, and are made by the manufacturer who produces tablet A. The remaining mass of all three tablet types represents the excipient (binder, disintegrant, and lubricant) materials. 

Qualitatively, acetaminophen and aspirin appear to be more abundant than caffeine, which concurs with the label concentration values. Caffeine shows very distinctive areas of localized high concentration domains while aspirin is relatively evenly disnibuted on the spatial scale of the image. Acetaminophen appears to be somewhat in the middle, showing up as large domains that blend into one another. 

Accuracy is a measure for the difference between the average value found in the analyses and the theoretical value. Accuracy studies should be performed at a level of active ingredient equal to 100% of the established label concentration of the product tested. 

Devaux and McConnell9 took advantage of the fact that in fluid membranes such as egg phosphatidylcholine, the resonance spectra of spin labels such as V and VI depend strongly and monotonically on the label concentration c when c 3= 5 mole %. The normalized paramagnetic resonance spectra S0(H, c) of a series of samples, all of uniform concentration c, were determined experimentally.9 The observed time-dependent spectra are then obtained from the equation... 

Fig. 4. Schematic representation of transient method employed by Devaux and McConnell9 to measure the rates of lateral diffusion of phospholipids in model membranes. The upper diagram represents a concentrated patch of labels at the beginning of the experiment, time f = 0. At later times f>0, the molecules diffuse laterally, as shown in the lower two drawings. The paramagnetic resonance spectra depend on the spin-label concentration in the plane of the membrane, and an analysis of the time dependence of these spectra yielded the diffusion constant. [Reprinted with permission from P. Devaux and H. M. McConnell, J. Am. Chem. Soc., 94, 4475 (1972). Copyright by American Chemical Society.]...

Antigen labelled concentration this has to be in limiting amount to saturate the antibodies immobilised on the solid phase. 

TS produces an evanescent blue color in the water layer that upon agitation and standing passes into the ether layer. Assay Not less than the labeled concentration or within the range stated on the label. 

Assay Not less than 95.0% and not more than 105.0% of the labeled concentration of C3H603. 

For a DICE analysis, two different fluorescence dyes, CyDye minimal dyes and CyDye saturation dyes, are available. CyDye minimal dyes react with an NHS-ester bond of lysine e-amino residues and enable coelectrophoresis of up to three different samples in one approach. Eor special applications, e.g., samples from microdissection, the CyDye saturation dyes allow complete 2-D analysis and quantification of protein abundance changes in scarce sample amounts. The dyes react via a maleimide group with all available cysteine residues in the protein sample, giving a high labeling concentration. 

The problem is illustrated by reports that labeled concentrations of active ingredients often significantly overestimate the content in the dosage form. In one report, nearly one-third of the brands tested did not contain what their manufacturers claimed. It is a serous problem that undermines the nutraceutical market, encourages skeptics who criticize the value and role of nutraceuticals, and (most importantly) is potentially harmful to the public. 

Ideally, the expected masses are obtained by an alternative physical methodology that is highly accurate and precise. In the case of using a commercial standard, the vendor should provide statistics on the accuracy and precision of the method used to obtain/measure the stated label concentration. When using a previously released lot, the expected masses will be based on the certificate of analysis concentration for the lot of Analyte B used in this validation. In the latter case, the measurement of accuracy is relative to the historical certificate of analysis value. The validation protocol needs to state that the accuracy measurement is relative to the historical value rather than to an independently obtained measurement. 

To distinguish the two types of excimers clearly a solution of 1% of PEG (both chain ends labeled by chromophores) and 99% of PEG (unlabeled) was also prepared, fixing the total polymer concentration to be 1x10 M. Under this condition, only intramolecular excimer is formed because the excimer to monomer Intensity ratio, I /I, was observed to be constant regardless of small variation of PEG (labeled) concentration in the mixture with unlabeled PEG. We assumed that this allowed the behavior of an individual PEG chain to be examined as discussed in the following section. Furthermore, fully labeled PEG chains in 1x10 M... 

Lipid analysis is typically performed either by incorporating a nonexchangeable radiolabel marker, such as (14C) or (3H) cholesteryl hexadecyl ether (CHE), into the vesicle membrane, or by analyzing the phosphate content and extrapolating the result according to the original composition of the vesicles. Both approaches assume that the label concentration and vesicle composition do not change on vesicle preparation or subsequent manipulation. The phosphate assay is carried out as follows ... 

The first term of the spin Hamiltonian predominates strongly in the low spin label concentration regime. For nitroxide spin labels, the tensor,... 

Label concentrations in the heart and submaxillary salivary glands were similar to those for l-[ N]glutamate (35). 

Fig 3.5. Experimentally measured label concentration in a mycelium of Arthrobotrus superba growing out from a piece of wood into soil. The top diagram shows the distribution of labelled non-metabolizable glucose analogue added to the wood in trace amounts. The bottom diagram shows the distribution of added to the wood in trace amounts. 

This method requires low sample concentration in order to avoid interparticle interference effects. However, if an equimolar mixture of unlabelled and bilabelled particles (A + D) and an equimolar mixture of the two singly labelled particles (B -I- C) are measured, subtraction of the two scattering curves permits 7,2 to be measured at high concentration since the interparticle effects are eliminated [52], This is important for the triangulation of subunits in large systems such as the ribosome, since otherwise the label concentration becomes extremely low. 

Index No International Chemical Identification EC No CAS No Classification Labelling Concentration limits Notes... 

Table 16.4a shows the quantitative recovery of the rat plasma preparation for the UPLC trace in Figure 16.7. Injected plasma supernatant was quantified with 87.6% of the concentration, 35.9 fmol per milliliter plasma (pA/), of the initial plasma concentration 41 pM, while the precipitated protein pellet contained 13.4% of the original label concentration with 5.5 pM plasma equivalent concentration, showing 100% process retention prior to LC separation. The column recovery of this hydrophobic compound was only 85 6%,... 

Here, 0/ and a are respectively the steady-state concentrations of surface species and the relative label concentrations (isotope fractions) in them rf is the rate of a chemical reaction step y is the number of label atoms transferring from one substance to another in elementary reaction step (an analog of stoichiometric coefficient), P is a dimensionless coefficient equal to LW/VNa, where V is the gas-phase volume (crn ), L is the number of active sites per gram of catalyst (mol/g), W is the catalyst weight (g), Na is the number of gas molecules per unit volume (mol/cm ), and 0 Cf(x.j) is the operator depending on the mass transfer regime in the reactor ... 

Affinity labeling normally takes place in two steps the first is the reversible formation of a Michaelis-Menten complex, and the second, the irreversible reaction linking the labeling reagent covalently to the protein. Therefore, a plot of the rate constant for inactivation against affinity label concentration will reach a plateau. Demonstration of saturation kinetics constitutes the fourth criterion. 

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