D Sample Containers

Figure 3.32. An automated thermobalance, (a) Balance, furnace, and sample changer mechanism (ft) furnace and sample holder (50). ( ) A. gas flow-meter B. furnace C. sample-holder disk D. cooling fan E, Cahn Model rtl recording balance F. balance platform, (ft) A. gas inlet tube B, thermocouples C. furnace heater windings and insulation D. sample container E. sample-holder disk F. ceramic sample probe.

A sample contains a weak acid analyte, HA, and a weak acid interferent, HB. The acid dissociation constants and partition coefficients for the weak acids are as follows Ra.HA = 1.0 X 10 Ra HB = 1.0 X f0 , RpjHA D,HB 500. (a) Calculate the extraction efficiency for HA and HB when 50.0 mF of sampk buffered to a pH of 7.0, is extracted with 50.0 mF of the organic solvent, (b) Which phase is enriched in the analyte (c) What are the recoveries for the analyte and interferent in this phase (d) What is the separation factor (e) A quantitative analysis is conducted on the contents of the phase enriched in analyte. What is the expected relative erroi if the selectivity coefficient, Rha.hb> is 0.500 and the initial ratio ofHB/HA was lO.O ... 

Preferably, high pressure Hquid chromatography (hplc) is used to separate the active pre- and cis-isomers of vitamin D from other isomers and allows their analysis by comparison with the chromatograph of a sample of pure reference i j -vitainin D, which is equiUbrated to a mixture of pre- and cis-isomers (82,84,85). This method is more sensitive and provides information on isomer distribution as well as the active pre- and cis-isomer content of a vitamin D sample. It is appHcable to most forms of vitamin D, including the more dilute formulations, ie, multivitamin preparations containing at least 1 lU/g (AOAC Methods 979.24 980.26 981.17 982.29 985.27) (82). The practical problem of isolation of the vitamin material from interfering and extraneous components is the limiting factor in the assay of low level formulations. 

Fig. A. 1. A setup for replacing the air in the sample container with argon, using a balloon. At the connection D, a short piece of thick-walled silicon-rubber tubing is used.

A radioactive sample contains 3.25 X 1018 atoms of a nuclide that decays at a rate of 3.4 X 1013 disintegrations per 15 min. (a) What percentage of the nuclide will have decayed after 150 d (b) How many atoms of the nuclide will remain in the sample (c) What is the half-life of the nuclide ... 

If the signal decay is a single-exponential curve, equations 16 and 17 result in values for X that are in agreement with each other. Dissimilar values indicate multiexponential decay, which usually means that the sample contains more than one fluorophore. Multiexponential decay can be resolved by using a phase fluorometer with phase sensitive detection. A time-independent, direct-current signal is produced that is proportional to the cosine of the difference between the phase angle of the detector ( D) and the phase angle of the fluorescence ( ) ... 

The situation is somewhat more complex for virus sample amphfied or isolated directly from patient plasma, as these samples comprise a heterologous mix of related yet genetically distinct quasi-species. Often these samples contain mixtures of CCR5-tropic (R5), CXCR4-tropic (X4), and/or dual-tropic viruses these samples are classified in phenotypic ttopism assays as dual/mixed tropic (D/M) (Whitcomb etal. 2007). 

The precursor of ° Ru is ° Rh (tip, = 3 years). It is prepared by irradiating natural ruthenium metal with 20 MeV deuterons, " Ru (d, n) Rh. The target is then allowed to decay for several months to diminish the accompanying Rh activity. In a report on ° Ru Mossbauer spectroscopy [111], the authors reported on spectra of Ru metal, RuOa, and [Ru(NH3)4(HS03)2] at liquid helium temperature in standard transmission geometry using a Ge(Li) diode to detect the 127 keV y-rays. The absorber samples contained 1 g of ruthenium per cm. ... 

These catalysts were prepared by the same proprietary procedure and each contains 10% Pd except D which contains 9% Pd. Samples A , C and F were prepared nsing a stronger base for fixing of Pd onto the carbon support. 

Figure 8.4 Reproducibility of sliding spark emission spectra taken at different sites on the surface of an ABS sample containing Cd and Zn. A Zn I 213.86 nm B Cd II 214.44 nm C Cd II 226.50 nm D C III 229.68 nm E Cd I 228.80 nm. After Golloch and Siegmund [154]. Reproduced from A. Golloch and D. Siegmund, Fresenius Z. Anal. Chem., 358, 804-811 (1997), by permission of Springer-Verlag, Copyright (1997)...

A series of 2-chloro-l,3,2-oxazaphospholidine derivatives 131a-f were prepared by reaction of six enantio-pure alcohols 129a-f with phosphorus trichloride carried out in the presence of an organic base as HC1 scavenger (Scheme 38) [69], The 31P and II-NMR spectra of crude 131a, d, e containing a small amount of the HC1 salt produced during the synthesis of 131, as well as the distilled samples, indicated that the formed chloro derivatives were ca. 1 1 mixtures of the cis and trans isomers. 

Note that it is highly desirable that the identity of every sample is confirmed before analysis, and that samples are adequately pure for the measurement in question. In the pH-metric methods, the sensor is a pH electrode and cannot distinguish between analyte and impurity. In the methods that depend on UV absorbance, if a sample contains an impurity with stronger absorbance than the sample, then the calculation of results from experimental data is complicated. Combinatorial samples are by nature poorly characterized, and even in the chromatographic methods in which analyte and impurity will be separated, it may be difficult to assign the peaks unambiguously. It is therefore advisable to purify samples before they are submitted for analysis of log D and pKa. 

Fig. 5 A, diffuse reflectance IR spectra of SQ-33600 displaying the absorption band due to bound water of hydration after exposure to different relative humidity conditions of (a) initial sample containing 3.5% water, (b) 6%, (c) 15%, (d) 31%, (e) 43%, (f) 52%, (g) 70%, and (h) 84%. B, variable-temperature diffuse reflectance IR spectra of SQ-33600 initially containing 3.5% water.

Fig. 10. Absorption bands in Sb-doped in Si that had been passivated in (a) an H2 and (b) a D2 plasma. Samples containing P or As donors show virtually identical bands, which are assigned to bond-wagging modes of donor-H(D) complexes. The spectra were measured near liquid He temperature. [Reprinted with permission from The American Physical Society, Bergman, K., Stavola, M., Pearton, S.J., Lopata., J. (1988). Phys. Rev. B 37, 2770 ]...

Fig. 2. PTI spectrum of a p-type, ultra-pure Ge sample, obtained by Fourier transform spectroscopy. The sample contains the acceptors B, Al, and A(D,C) in a total concentrations of 6 x 1010 cm-3. The most narrow lines are 0.09 cm-1 ( = 11 peV) wide. 

D. The original sample contained some anhydrous copper(II) sulfate. 

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