Length HPLC standard

HPLC reverse phase procedures were established to follow the continuous release rates of a variety of agents from the two resins. Also a USP standard release test procedure (8) was used. Because of its ease of detection at the higher ultraviolet wave lengths, bovine insulin was used as the model delivery agent... 

Another CE method was developed and employed for the separation of the components of FD C Red No. 3 (erythrosine). The separations were also carried out by RP-HPLC and the efficacy of the methods was compared. The chemical structures of the main components of the dye are shown in Fig. 3.167. The components of erythrosine were separated in a fused-silica capillary (43 cm effective length X 75 /xm i.d.). The running buffer was 50 mM sodium tetraborate, 25 mM SDS (pH 9.3). Analytes were detected at 516 nm. HPLC measurements were realized in an octylsilica column (150 X 4.6 mm i.d. particle size 5 /xm) at 35°C. Solvent A was 0.1 M aqueous ammonium acetate and solvent B consisted of methanol. The gradient programme was 0 min, 55 per cent A 20 min 35 per cent A 21 min, 100 per cent B, final hold, 4 min. The flow rate was 1 ml/min. The separations of the components of the standard mixture (left) and those of a real sample (right) by CE are shown in Fig. 3.168. The electropherograms clearly illustrate that the method allows the baseline separation of the dye components even in real commercial samples. The main... 

The overall analysis time is dependent on a few factors, one of which is column length. With a standard analytical column length of 250 mm, run times of 25 to 30 min can be expected. Shorter, 150-mm columns may be used to shorten the run time however, some resolution can be lost when using this approach. One must also account for preparation time for HPLC analysis. This includes steps such as sample preparation, instrument equilibration, and data analysis. This generally takes 1 hr per sample for instrumental and data analysis, plus -1 hr... 

The majority of published HPLC techniques used in fat-soluble vitamin assays have utilized 5- or 10-/zm particles of porous silica or derivatized silica packed into stainless steel tubes of typical length of 250 mm and standard internal diameter (ID) of 4.6 mm. Radially compressed... 

Instrumental methods in chemistry make it possible to characterize any chemical compound by a very large number of different kind of measurements. Such data can be called observables. Examples are provided by Spectroscopy (absorbtions in IR, NMR, UV, ESCA. ..) chromatography (retentions in TLC, HPLC, GLC. ..) thermodynamics (heat capacity, standard Gibbs energy of formation, heat of vaporization. ..) physical propery measures (refractive index, boiling point, dielectric constant, dipole moment, solubility. ..) chemical properties (protolytic constants, ionzation potential, lipophilicity (log P)...) structural data (bond lengths, bond angles, van der Waals radii...) empirical structural parameters (Es, [Pg.34]

Many of the HPLC dye applications require the analysis of trace levels of dyes. For example with the examination of fibre dyes, the casework sample is typically a single strand of fibre which is only 2 5 mm in length and the dye content is approximately 10 ng. Fortunately, because of the relatively high absorptivity of dyes, these detection levels can be achieved by using a visible wavelength detector and a column with an internal diameter of 3.2 mm. By employing a column of this diameter as opposed to the standard 4.6 mm, less dilution of the sample occurs and can effectively increase sensitivity by a factor of between two and three. Microbore columns, i.e. columns with diameters of smaller than 2 mm are not favoured for routine analyses beeause of diffieulties in maintaining their efficiency and reproducibility. 

Instrumental methods in chemistry have dramatically increased the availability of measurable properties. Any molecule can be characterized by many different kinds of data. Examples are provided by Physical measures, e.g. melting point, boiling point, dipole moment, refractive index structural data, e.g. bond lengths, bond angles, van der Waals radii thermodynamic data, e.g. heat of formation, heat of vaporization, ioniziation energy, standard entropy chemical properties, e.g. pK, lipophilicity (log P), proton affinity, relative rate measurements chromatographic data, e.g. retention in HPLC, GLC, TLC spectroscopic data, e.g. UV, IR, NMR, ESCA. 

AEO can be sensitively determined in the form of these corresponding UV-active phenylisocyanate derivatives by UV detection. In this case, the residue of the extraction of a water sample or a solid matrix is dissolved in dichloromethane or dichloroethane. This solution is mixed with phenylisocyanate as well as 1-octanol and/or 1-eicosanol as internal standards and heated to 55 to 60°C for 45 to 120 min. Then the AEO derivatives are separated either by reversed-phase HPLC with regard to different alkyl chain lengths or by normal phase HPLC with regard to different ethoxylate oligomers.The addition of the internal standard is imperative for quantitative determination because derivatization is not completed even after 2 h. ... 

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