Sample mass

The first problem to be faced is what amount of adsorbent should be used for the adsoiption experiment. This of course depends inter alia on the sensitivity of the measuring equipment and the texture and surface properties of the adsorbent. 

With most modem equipment, the most reliable measurements are generally obtained with total areas ranging from 20 to SO m2 in the adsorption bulb. For materials with specific surface areas under 1 m2 g 1 a mass of 10 g or more may be found necessary, but the improvement in sensitivity is counterbalanced by the unavoidable pressure and temperature gradients within the sample. 

At the other extreme, with materials of specific surface area above 500 m2 g 1 one must be careful not to reduce the mass of sample by too much it must remain representative of the batch of adsorbent and it must be weighed with an accuracy consistent with the accuracy provided by the adsorption measurement. For these two reasons, it is usually unwise to use a sample mass under, say, 50 mg. If the full adsorption-desorption isotherm is to be determined, one can be limited by the capacity of adsorptive reservoir or dosing volume or by the automatic control range of the electronic microbalance (typically, between 50 and 100 mg with sensitivity 1 pg). It therefore often happens that the measurement of one isotherm cannot provide the best determination of the specific surface area and at the same time the best determination of the full adsorption-desorption isotherm. 

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Element mass = njMQ i(%)i +n2M(j 2( )2 The total mass of the sample is Sample mass = njMQ j -i-njMQ 2... 

The liquid was applied and dried on cellulose filter (diameter 25 mm). In the present work as an analytical signal we took the relative intensity of analytical lines. This approach reduces non-homogeneity and inequality of a probe. Influence of filter type and sample mass on features of the procedure was studied. The dependence of analytical lines intensity from probe mass was linear for most of above listed elements except Ca presented in most types of filter paper. The relative intensities (reduced to one of the analysis element) was constant or dependent from mass was weak in determined limits. This fact allows to exclude mass control in sample pretreatment. For Ca this dependence was non-linear, therefore, it is necessary to correct analytical signal. Analysis of thin layer is characterized by minimal influence of elements hence, the relative intensity explicitly determines the relative concentration. As reference sample we used solid synthetic samples with unlimited lifetime. 

The analysis was performed by SRXRF at the XRF beam-line of VEPP-3, Institute of Nuclear Physics, Novosibirsk, Russia. For the accuracy control the different types of the International Certified Reference Materials were used. There were obtained all metrological characteristics, namely precision, accuracy and lower limits of detections. This is the SRXRF method, that allow to analyze the sample mass of 0.5 mg directly without the destruction. The puncture from patient may be picked out more than once. 

Maintain integrity of particulate sample (mass, size, chemical composition)... 

To demonstrate the effect in more detail a series of experiments was carried out similar to that of volume overload, but in this case, the sample mass was increased in small increments. The retention distance of the front and the back of each peak was measured at the nominal points of inflection (0.6065 of the peak height) and the curves relating the retention data produced to the mass of sample added are shown in Figure 7. In Figure 7 the change in retention time with sample load is more obvious the maximum effect was to reduce the retention time of anthracene and the minimum effect was to the overloaded solute itself, benzene. Despite the reduction in retention time, the band width of anthracene is still little effected by the overloaded benzene. There is, however, a significant increase in the width of the naphthalene peak which... 

The mass of naphthalene injected was progressively increased from 1.1 mg to 19.1 mg. The results obtained are shown in Figure 8, as curves relating the retention distance of the front and rear of each peak against sample mass. 

The technique of column overloading is only feasible if more than adequate resolution is possible between the solute of interest and its nearest neighbor. Many samples require a column to be constructed that will only just separate the solutes of interest and under these circumstances the loading capacity must be increased without overloading the column. It has been shown in earlier chapters that the maximum sample (mass or volume) that can be placed on a column is proportional to the plate volume of the column and the square root of its efficiency. Thus, the maximum sample mass (M) will be given by... 

It is also clear from equation (2) that the sample mass can also be extended by increasing the capacity ratio (k ) of the eluted solutes (i.e, by careful phase selection). In this case the maximum load will increase linearly with the value of (k ) but so will... 

Mg = sample mass used in a DIERS test or equivalent test, g dP/dt = pressure rise in test, psi/see T = maximum temperature in test, K... 

Column i.d. x L (mm) Flow rate (ml/min) Injection voiume (fil) Sample mass (mg)... 

X 0.75 cm) Ve i = 28 ml = 50 ml eluent 0.05 M NaCI flow rate 0.80 ml/min detection Optilab 903 interferometric differential refractometer applied sample mass/volume 200 /tl of 2-mg/ml aqueous solutions sum of individual chromatograms (theory —) and (theory/experimental) ratio (—) plotted for quantification of deviations in separation performance between narrow distributed samples and broad distributed samples. 

E. Sample Mass Spectrum TBDMS Derivatized Amino Acids... 

B. Sample Mass Spectrum of an Aliphatic Halogenated Compound... 

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