Maximum sample amount

With increasing solute amount values of the height equivalent to a theoretical plate increase and k values decrease if other parameters are fixed. Estimate of the maximum sample amount that can be charged to a column so as to avoid loss of column performance occurring due to overloading, can be made from the value of the adsorbent linear capacity, 0°. On this basis, it is found that the maximum sample size for porous silica is about 2 x 10-4 g of sample per gram of silica. 

In the previous section we considered the amount of sample needed to minimize the sampling variance. Another important consideration is the number of samples required to achieve a desired maximum sampling error. If samples drawn from the target population are normally distributed, then the following equation describes the confidence interval for the sampling error... 

A considerable amount of time is necessary to reach the point at which sample analyses can commence, and it is essential that the stability and reliability of the mass spectrometer be high to ensure maximum sample throughput during the limited time available between calibration checta. 

Recently, many experiments have been performed on the structure and dynamics of liquids in porous glasses [175-190]. These studies are difficult to interpret because of the inhomogeneity of the sample. Simulations of water in a cylindrical cavity inside a block of hydrophilic Vycor glass have recently been performed [24,191,192] to facilitate the analysis of experimental results. Water molecules interact with Vycor atoms, using an empirical potential model which consists of (12-6) Lennard-Jones and Coulomb interactions. All atoms in the Vycor block are immobile. For details see Ref. 191. We have simulated samples at room temperature, which are filled with water to between 19 and 96 percent of the maximum possible amount. Because of the hydrophilicity of the glass, water molecules cover the surface already in nearly empty pores no molecules are found in the pore center in this case, although the density distribution is rather wide. When the amount of water increases, the center of the pore fills. Only in the case of 96 percent filling, a continuous aqueous phase without a cavity in the center of the pore is observed. 

Storage stability studies for carfentrazone-ethyl compounds on crop matrices have shown a pattern of stability for at least 7-24 months, depending on the study program or the maximum sample storage interval for the study. Carfentrazone-ethyl was not stable in field corn starch, potato tuber and bovine kidney. The residue results indicated that a significant portion of carfentrazone-ethyl was converted to C-Cl-PAc in these matrices however, the total amount of carfentrazone-ethyl and C-Cl-PAc accounted for the original spiking level. Since both carfentrazone-ethyl and C-Cl-PAc were determined in these stability studies, the instability of carfentrazone-ethyl was not of any concern. 

Hassan et al. [39] used a sensitive color reaction method for the determination of primaquine in pharmaceutical preparation. Primaquine was treated with diazo-p-nitroaniline in acidic medium to give an orange-yellow product with an absorbance maximum at 478 nm. When the medium was made alkaline, bathochromic, and hypochromic shifts occurred the new maximum was located at 525 nm. The mean percentage recoveries for authentic samples amounted to 100 and 100.21 by the acid and alkaline procedures, respectively (P = 0.05). Both reactions could be used to determine primaquine salts in pharmaceutical preparations. The results obtained were in good agreement with those of the official methods. Recoveries were quantitative by both methods. 

Optimum conditions for electrophoresis The voltage of 150 V is applied for 30 minutes initially to obtain maximum sample entry, and increased gradually until it reaches 3500 V. The optimum time for application depends on the following factors (a) type of sample, (b) amount of protein in the sample, (c) length of the IPG strips, (d) pH gradient. 

By assuming that a proportional increase in the amount of sample injected results in a proportional increase in the detector response for the solute band of interest, the detector response for chromatogram I in Figure 7 will increase 14 times when the maximum sample volume of 7 /xL is injected. However, for the 4.6-mm i.d. column, the detector response will increase 400 times when the maximum sample volume of 200 (lL is injected. By taking into account the relative detector responses for the 0.5-/xL injection, at the maximum sample injection volumes, the 4.6-mm i.d. column with the 20-/liL detector flow cell will produce approximately five times the detector response of the 1-mm i.d. column with the 5-/zL flow cell. In most cases, studies can be designed to provide excess sample because aqueous environmental samples are seldom limited with respect to volume. 

By using data from the small-scale extractions of dichlorophenol as an example, the maximum theoretical amount that can be collected at —76 °C can be calculated to be 77. Actual experimental values show recovery to be about 62 for the three small-scale supercritical fluid carbon dioxide extractions of dichlorophenol. These data support the suggestion that the vapor pressure of the compound being trapped is an extremely critical physical constant when large volumes of C02 relative to the aqueous sample volume are being used for the extraction process. 

For example, a typical UMB (enzyme only) has an 80 pA response to a sample of 5 mM glucose. The same sensor has a response of 900 pA to 0.44 mM uric acid, 180 pA response to 0.21 mM acetaminophen, and 140 pAto 0.11 mM ascorbic acid (these are maximum clinical amounts of each of the three major interferences that could be found in human serum). The total response due to interferences is more than fifteen times that of the response due to an average clinical amount of glucose. 

Once the maximum injection volume is decided, the maximum sample load should be determined. In this example, the amount of the mono- and dicarboxylic acids was increased from 10 to 100 mg (of each acid) per injection in 1 mL of mobile phase. At first glance, the overlap between peaks suggested that the electronics of the refractive index detector were saturated... 

Liquid nebulization as a means of obtaining aerosols is commonly used for activities such as drug administration, hair spraying or perfume application [1,2]. Direct nebulization of a liquid phase containing the target analytes has been widely used in analytical chemistry for sample insertion into some detection systems (particularly atomic spectrometers). The main purpose of analytical nebulizers is to insert the maximum possible amount of sample, and hence of analyte, in the form of aerosol consisting of very small droplets, into the detection system. 

Pealc-maximum Peak injection with systematic overload Peak maximum equal to retention time Single component Small sample amounts Less sensitive to low efficiency columns than ECP/ FACP For special cases no detector calibration necessary... 

Estimating Maximum Sample Volume. The maximum amount of sample volume which may be introduced into the column at any one time is readily defined for size exclusion supports. Since these supports exhibit no adsorption, their capacity for a solute may range from 0 (totally excluded solute) to e V I... 

The percentage of oil hydrolysis (POH) was determined by titration of the released fatty acids and defined as the percentage weight of free fatty acids in the sample, in comparison with the maximum theoretical amount of free fatty acids that could be produced if all the oil in the sample was hydrolyzed ... 

The diameter of the droplets produced by a pneumatic nebulizer varies from < 5 ixm to about 25 xm. The spray chamber allows droplets to reach the burner which can be vaporized and atomized in the flame. If the spray chamber prevents small droplets (diameter of about 10 tm or less) from entering the flame, sensitivity will be decreased. On the other hand, if large droplets (>10/x-m) reach the flame, the flame noise will increase and the temperature will decrease. From the total mass of the sample nebulized, the maximum useful amount of droplets is about 10%, which gives the limit for the maximum attainable efficiency of the nebulizer. However, the nebuliza-tion efficiency can be improved in various ways by altering the droplet size distribution. A bead or bar placed close to the orifice of the nebulizer, or a counter flow nebulizer can be used for this purpose (Figure 37). 

In SPE-LC method development, several parameters have to be optimized. Most effort is directed toward the optimization of the SPE step. Obviously, coupling with LC and experimental conditions for the correct chromatographic separation in the second (analytical) column have to be also optimized. The main parameters involved in the SPE process are type and amount of sorbent, the sample volume that can be applied without losses of analytes, the composition and volume of the washing solution, and the composition and volume of the elution (desorption) solution. A helpful parameter to characterize the usefulness of a given precolumn is the breakthrough volume, which represents the maximum sample volume that can be loaded into the precolumn with a theoretical 100% recovery (the ratio between the amount of analyte extracted and the amount applied). 

Carbon Sample Amount of Oxygen Present (g/IOOg) BET (Nj) Surface Area (mVg) Pore Volume Vh,o (cmVg) Maximum Adsorption Capacity (mg/g) Cr(lll) Cr(VI) ... 

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