Effect of instrumentation

VanLandingham, M.R., The effect of instrumental uncertainties on AFM indentation measurements. Microsc. Today, 97, 12-15 (1997). 

The effect of instrumental broadening can be eliminated by deconvolution (see p. 38) of the instrumental profile from the measured spectrum. If deconvolution shall be avoided one can make assumptions on the type19 of both the instrumental profile and of the remnant line profile. In this case the deconvolution can be carried out analytically, and the result is an algebraic relation between the integral breadths of instrumental and ideal peak profile. From such a relation a linearizing plot can be found (e.g., measured peak breadths vs. peak position ) in which the instrumental breadth effect can be eliminated (Sect. 8.2.5.8). 

After H0bs has properly been extracted (cf. Sect. 2.2.2), the effect of instrumental broadening can be eliminated by numerical deconvolution (see p. 38). If the peaks shall be modeled by analytical functions (Sects. 8.2.5.7-8.2.5.8), the consideration... 

Lorentzians, Gaussians, and combinations of both like pseudo-Voigt functions 38Frequently the effect of instrumental broadening is tacitly considered as already eliminated. 

Studying the effects of instrumental performance should be the province of the manufacturers. Unfortunately, the perception is that it is to their benefit to release such results only if they turn out to be good , and there is little incentive for them to perform studies whose only purpose is to increase scientific knowledge. Thus it is up to academia to pick up this particular ball, if there is any interest in it at all. 

Getting back to the current state of the columns, this column is one more in the set [2-9] dealing with the rigorous derivation of the expressions relating the effect of instrument (and other) noise to their effects to the spectra we observe. The impetus for this was the realization that the previously existing theory was deficient in that the derivations extant ignored the effect of noise in the reference reading, which turns out to have appreciable effects on the nature of the derived noise behavior. 

This chapter is a continuation of a series of chapters starting with Chapter 40 up to 49 [1-10] dealing with the rigorous derivation of the expressions relating the effect of instrument (and other) noise to their effects to the spectra we observe. 

Taylor and Zeitlin [43] described an X-ray fluorescence procedure for the determination of total sulfur in seawater. They studied the matrix effects of sodium chloride, sodium tetraborate, and lithium chloride and show that the X-ray fluorescence of sulfur in seawater experiences an enhancement by chloride and a suppression by sodium that fortuitously almost cancel out. The use of soft scattered radiation as an internal standard is ineffective in compensating for matrix effects but does diminish the effects of instrument variations and sample inhomogeneity. 

Snyder JL, Grob RL, McNally ME, OostdykTS.The effect of instrumental parameters and soil matrix on the recovery of organochlorine and organophosphate pesticides from soils using supercritical fluid extraction. J. Chromatogr. Sci. 1993 31 183-191. 

The tracer-subtraction procedure adds negligible uncertainty to the measured CaJ Ca ratios. However, it is in fact essentially impossible to entirely eliminate the effects of instrumental mass discrimination for the measurements of either the Ca- Ca mixed tracer or for the standard Ca isotope ratios. Hence, it is necessary to have a standard material with an agreed-upon value of 5 Ca. At the time of writing of this article there is no such standard. 

This chapter deals with the properties of high-pressure liquid chromatography columns. It is divided into two sections column physics and column chemistry. In the section on column physics, we discuss the properties that influence column performance, such as particle size, column length and column diameter, together with the effect of instrumentation on the quality of a separation. In the section on column chemistry, we examine in depth the surfaces of modern packings, as well as the newer developments such as zirconia-hased packings, hybrid packings or monoliths. We have also included a short section on... 

Table III. Effect of instrumental bandwidth on column efficiency...

Apart from the problem of nonlinearity, the calibration curve approach has another pitfall measured ion abundance ratios can change with time, leading to the possibility of significant errors since the calibration and sample measurements cannot be simultaneous (Schoeller, 1980). In order to minimize the effect of instrumental drift and to optimize precision, the National Bureau of Standards (NBS) proposed a bracketing protocol for the development of definitive (i.e., essentially bias-free and precise) IDMS methods (Cohen et al., 1980 White et al., 1982 Yap et al., 1983). It involves the measurement of each sample between measurements of calibration standards whose ion abundances most closely surround the ion abundance ratio of the sample. Measurements are made according to a strict protocol, used with samples prepared under restrictive conditions ... 

VCD spectra are measured by collecting blocks of AC and DC scans. Typically, we collect 12288 AC scans and 1536 DC scans in 48 blocks of 256 AC scans preceded and followed by 32 DC scans. Each block of Fourier transformed AC scans is divided by the average of the Fourier transformed 32 block DC scans that were collected just before and just after the AC block. This minimizes the effect of instrumental drift in taking this ratio since the entire spectral collection process requires approximately 2.5 hours to complete. For most of our measurements with neat liquids, we employ 4 cm l resolution, although resolution as high as 1 cm l has been used. 

Grant, D.W. Clarke, A. A study of the effects of instrument variables on accuracy and precision in gas chromatography. II. Errors associated with the injection of liquid samples by microlitre syringes. J. Chromatogr. 1974, 97, 115. 

Hancock, B.C. York, P. Rowe, R.C. Characterization of wet masses using a mixer torque rheometer 1 effect of instrument geometry. Int. J. Pharm. 1991, 76, 239-245. 

The effectiveness of instrument design and setup to reduce cell-accumulation wall interactions was demonstrated, first, by the recovery of cells in the corresponding elution peak (>70%). Second, it was shown by conservation of cell viability, which was, after SdFFF elution, similar to that of the control population. Finally, reduction of interactions was partially demonstrated by a very low cell release peak, which was observed at the end of the fractogram when channel rotation was stopped and the mean gravity was equal to zero (external field applied =lg Fig. 4) such procedure is not possible in GFFF. This residual signal corresponded to reversible cell sticking due to weak interactions between cells and the accumulation Cells or cellular materials can... 

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