Sampling containers

Liquid chromatography, having a resolving power generally less than that of gas phase chromatography, is often employed when the latter cannot be used, as in the case of samples containing heat-sensitive or low vapor-pressure compounds. 

The heart of an NMR spectrometer is the probe, which is essentially a tuned resonant circuit with the sample contained within the main inductance (the NMR coil) of that circuit. Usually a parallel tuned circuit is used with a resonant frequency of coq = The resonant frequency is obviously the most important probe... 

Values of COT) can be derived from a constant volume calorimeter by measuring AU for small values of Tj - TO and evaluating AU/(T2 - T ) as a fiinction of temperature. The energy change AU can be derived from a knowledge of tlie amount of electrical energy required to change the temperature of the sample + container... 

Diagonal lines connecting the two axes show combinations of sample size and concentration of analyte containing the same absolute amount of analyte. As shown in Figure 3.6, for example, a 1-g sample containing 1% analyte has the same amount of analyte (0.010 g) as a 100-mg sample containing 10% analyte or a 10-mg sample containing 100% analyte. 

Effect of Constant Positive Determinate Error on Analysis of Sample Containing 50% Analyte (%w/w)... 

Ketkar and co-workers developed a new analytical method for measuring trace levels of atmospheric gases.The analysis of a sample containing 40.0 parts per thousand (ppt) 2-chloroethylsulfide yielded the following results... 

Using X-ray diffraction, Karstang and Kvalhein reported a new method for determining the weight percent of kalonite in complex clay minerals To test the method, nine samples containing known amounts of kalonite were prepared and analyzed. The results (as %w/w kalonite) are shown. 

A standard solution containing a known amount of analyte, prepared separately from samples containing the analyte. 

Illustration showing an alternative form of the method of standard additions. In this case a sample containing the analyte is spiked with a known volume of a standard solution of analyte without further diluting either the sample or the spiked sample. 

Three replicate determinations are made of the signal for a sample containing an unknown concentration of analyte, yielding values of 29.32, 29.16, and 29.51. Using the regression line from Examples 5.10 and 5.11, determine the analyte s concentration, Ca, and its 95% confidence interval. 

As a starting point, let s assume that our target population consists of two types of particles. Particles of type A contain analyte at a fixed concentration, and type B particles contain no analyte. If the two types of particles are randomly distributed, then a sample drawn from the population will follow the binomial distribution. If we collect a sample containing n particles, the expected number of particles containing analyte, ti, is... 

An analysis to determine the concentration of Cu in an industrial plating bath uses a procedure for which Zn is an interferent. When a sample containing 128.6 ppm Cu is carried through a separation to remove Zn, the concentration of Cu remaining is 127.2 ppm. When a 134.9-ppm solution of Zn is carried through the separation, a concentration of 4.3 ppm remains. Calculate the recoveries for Cu and Zn and the separation factor. 

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 ... 

Why does the procedure call for a sample containing no more than 60 mg of Mg + ... 

A sample containing 60 mg of Mg + will generate approximately 600 mg, or 0.6 g, of MgNH4P04 6H2O. This is a substantial amount of precipitate to work with during the filtration step. Large quantities of precipitate may be difficult to filter and difficult to adequately rinse free of impurities. 

As discussed earlier, the simultaneous analysis of samples containing two analytes requires the isolation of two precipitates. As shown in Example 8.2, conservation of mass can be used to write separate stoichiometric equations for each precipitate. These equations can then be solved simultaneously for both analytes. 

Many samples containing silicon also contain aluminum and iron. After dehydration, these metals are present as AI2O3 and Fe203. These oxides are potential interferents since they also are capable of forming volatile fluorides. 

The determination of silicon is commonly encountered in metallurgical and mining laboratories responsible for the analysis of ores, slags, and alloys. The volatilization gravimetric method, which is appropriate for samples containing high concentrations of silicon, was described earlier in Method 8.2. 

In this procedure the difference in the residue s mass before and after volatilizing SiE4 gives the mass of Si02 in the sample. Thus the sample contained... 

In volatilization gravimetry, thermal or chemical energy is used to decompose the sample containing the analyte. The mass of residue remaining after decomposition, the mass of volatile products collected with a suitable trap, or a change in mass due to the loss of volatile material are all gravimetric measurements. 

Samples containing a known amount of Mo were taken through the procedure while varying the temperature, the amount of precipitant added, and the pH of the solution. 

The procedure calls for placing a 100-pL aqueous sample containing the thiourea in a 60-mL separatory funnel along with 10 mL of a pH 7 buffer and 10 mL of a 12 pM solution of... 

Another important example of a redox titration for inorganic analytes, which is important in industrial labs, is the determination of water in nonaqueous solvents. The titrant for this analysis is known as the Karl Fischer reagent and consists of a mixture of iodine, sulfur dioxide, pyridine, and methanol. The concentration of pyridine is sufficiently large so that b and SO2 are complexed with the pyridine (py) as py b and py SO2. When added to a sample containing water, b is reduced to U, and SO2 is oxidized to SO3. 

Since the sample contains just KCl and NaBr, we know that g NaBr = 0.3172 g - g KCl... 

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