Linearity of response

Figure 9. Linearity of response and reproducibility. The error flags indicate the root mean square error for five measurements at each value. The average relative error is about 10%.

The FT-Raman spectra of a range of drugs (theophylline, indomethacin, diclofenac, and promethazine) in several polymers (sodium alginate, hydroxy-propylmethylcellulose, and polyethylene glycol) have been obtained [56,57]. In these studies, the linearity of response of Raman scattering to species concentration was exploited to analyze diclofenac at concentrations of 0.01-6.0% w/w... 

Table 8.7). Thus, intensity and concentration are directly proportional. However, the intensity of a spectral line is very sensitive to changes in flame temperature because such changes can have a pronounced effect on the small proportion of atoms occupying excited levels compared to those in the ground state (p. 274). Quantitative measurements are made by reference to a previously prepared calibration curve or by the method of standard addition. In either case, the conditions for measurement must be carefully optimized with reference to the choice of emission line, flame temperature, concentration range of samples and linearity of response. Relative precision is of the order of 1-4%. Flame emission measurements are susceptible to interferences from numerous sources which may enhance or depress line intensities. 

Flame ionization detectors are capable of detecting virtually all organic compounds and show a lower limit of detection of approximately 1 X 10-9 mol. They also show good linearity of response and the fact that they do not respond to oxides of carbon or nitrogen or to water makes them particularly convenient for aqueous samples. They have the disadvantage, however, that samples are destroyed unless a stream-splitting device is incorporated. 

In some cases, sample preparation for CZE requires only the dilution of the sample, mostly to accommodate detection (for signal and linearity of response). However, as was previously mentioned, sample characteristics such as viscosity, buffer composition (pH and excipients), and salt content can especially affect electrophoretic injection and performance. 

The parameters that require qualification for a UV absorbance detector are wavelength accuracy, linearity of response, detector noise, and drift. These determine the accuracy of the results over a range of sample concentrations and the detection limits of the analysis. 

The linearity of response of the bioassay depends on the linearity of the luminometer used. To determine the linearity of response, a concentration range of luciferase was prepared and the aetivity measured. A good linear correlation between the detected amount of light and the luciferase eoneentration was found T = 0.9997). 

Linearity of Response and Reaction Products. The response vs. concentration curves obtained for CO, NO and NO2 gas sensor cells are depicted in Figures 5, 6 and 7 respectively. In all instances good linearity over the range studied was observed between current and partial pressure of each of the above gases (as depicted by equation (k)). The proportionality constants, K, with standard de-... 

Pump flow rate accuracy and gradient accuracy Detector linearity of response, noise, drift, and wavelength accuracy Injector precision, linearity, and carryover Column heater temperature accuracy... 

Detector linearity of response, noise, drift, and wavelength accuracy... 

An advantage of the atomic emission method is its linearity of response over a large range of concentrations, which permits treatment of complex matrices with a minimum of preparation. A single solution often allows the determination of many elements, from very high to trace concentrations, without the need for successive dilutions. 

Linearity of response versus absolute amount injected must be confirmed for each different sample type and for each different set of chromatographic operating conditions. This linearity cannot be assumed. Nonlinearity may result from column overload, detector overload, or adsorption problems. 

The carrier should be chosen with a TC either larger than most of the samples to be run, nitrogen with organic samples, for instance, or smaller, such as argon with some fixed gas analyses. Temperature dependence and linearity of response should be investigated carefully for all compounds to be analyzed. It should be remembered that a much lower current is necessary to reach the same filament temperature in low-conductivity gases. Mixtures of carrier gas, particularly where one of the constituents is also a sample compound, lead to further complexities. 

A simple cleanup procedure based on acidic protein precipitation and LLE with ethyl acetate was used for the determination of OXA, CLO, and DICL in bovine muscle. The detection was accomplished with particle-beam MS with negative-ion chemical ionization, which was found more sensitive than electron-impact mode. Deviation from the linearity of response was observed, which could be caused by the phenomenon of coeluting carrying analyte particles through the particle beam (60). 

The variation of neutron count rate with charge weight by thermal neutron transmission is shown in Fig 17 for a brass cylinder (5cm long x 1.3cm diam x 0.8mm thick wall) with RDX as the charge (fill capacity, lOg). Each point represents a 10-sec count. Non-linearity of response at the top and bottom of the cylinder is due to... 

It should be noted that the flame photometric detector is more sensitive to thiophenes than it is to benzothiophenes (22). Studies in our laboratory have shown that the flame photometric detector response to thiophene is approximately 25% greater than that for the corresponding quantity of benzothiophene. Hence a consequence of this non-linearity of response is that the thiophenes are not as quantitatively dominant as suggested by some of the FPD pyrograms. 

The ideal on-line detector has versatility, high sensitivity, the capacity for continuous monitoring of the column effluents, low noise level, wide linearity of response, stable baseline, insensitivity to flow rate and temperature changes, and response to all types of compounds. It is rugged, not too expensive, and is able to measure accurately a small peak volume without increasing its volume appreciably. The terms noise, sensitivity, and linearity are typically used in describing detector performance, as discussed below. 

The critical properties of detectors are sensitivity, selectivity and linearity of response, reproducibility, and reliability of operation. Spectrometric detectors, MS and Fourier transform infrared (FUR), are described in more detail in other sections. The following detectors are useful for the detection of CWC-related chemicals. 

Giachetti et al. [60] compared the performance of mass selective detector (MSD), electron capture detector (ECD) and nitrogen-phosphorus detector (NPD) of gas chromatography systems in the assay of six nonsteroidal antiinflammatory drugs in the plasma samples. As a practical test, six NSAIDs (mefenamic, flufenamic, meclofenamic and niflumic acids, diclofenac and clonixin) added to plasma samples were detected and quantified. The analyses were carried out after solvent extraction from an acidic medium and subsequent methylation. The linearity of response was tested for all the detection systems in the range of 1-25 ng/mL. Precision and accuracy were detected at 1, 5 and 10 ng/mL. The minimum quantifiable level for the six drugs was about 1 ng/mL with each of the three detection systems. 

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