Quantitative analysis reporting results

An analysis, particularly a quantitative analysis, is usually performed on several replicate samples. How do we report the result for such an experiment when results for the replicates are scattered around a central value To complicate matters further, the analysis of each replicate usually requires multiple measurements that, themselves, are scattered around a central value. 

Marecek and colleagues developed a new electrochemical method for the rapid quantitative analysis of the antibiotic monensin in the fermentation vats used during its production. The standard method for the analysis, which is based on a test for microbiological activity, is both difficult and time-consuming. As part of the study, samples taken at different times from a fermentation production vat were analyzed for the concentration of monensin using both the electrochemical and microbiological procedures. The results, in parts per thousand (ppt), are reported in the following table. 

TXRF is frequently used for contamination control and ultrasensitive chemical analysis, in particular in relation to materials used in semiconductor manufacturing [278,279], and metallic impurities on resin surfaces, as in PFA sheets [279,280], TXRF has been used by Simmross et al. [281] for the quantitative determination of cadmium in the four IRMM polyethylene reference materials (VDA-001 to 004). Microsamples (20-100 ig) from each reference material were transferred by hot pressing at 130 °C as 3 xm thin films straight on to quartz glass discs commonly used for TXRF analysis. The results obtained were quite satisfactory (Table 8.50). Other reports of the forensic application to plastic materials by TXRF have appeared [282], including a study of PE films by elemental analysis [283],... 

To show some examples of the many cases of lipid paint materials reported in the literature, Table 7.3 reports the results of characteristic parameters obtained in the quantitative analysis of FAs in a series of samples (<1 mg) from paintings on various supports. 

Second, if the results of a quantitative analysis are to be reported to three or more significant figures, then weight measurements that enter directly into the calculation of the results should be made on an analytical balance so that the results of the analysis can be correctly reported after the calculation is performed. 

When a weight measurement enters directly into the calculation of a quantitative analysis result that is to be reported to four significant figures, is an ordinary top-loading balance satisfactory for this measurement Explain. 

There is a recent trend towards simultaneous CE separations of several classes of food additives. This has so far been applied to soft drinks and preserved fruits, but could also be used for other food products. An MEKC method was published (Lin et al., 2000) for simultaneous separation of intense sweeteners (dulcin, aspartame, saccharin and acesulfame K) and some preservatives (sorbic and benzoic acids, sodium dehydroacetate, methyl-, ethyl-, propyl- and isopropyl- p-hydroxybenzoates) in preserved fruits. Ion pair extraction and SPE cleanup were used prior to CE analysis. The average recovery of these various additives was 90% with good within-laboratory reproducibility of results. Another procedure was described by Frazier et al. (2000b) for separation of intense sweeteners, preservatives and colours as well as caffeine and caramel in soft drinks. Using the MEKC mode, separation was obtained in 15 min. The aqueous phase was 20 mM carbonate buffer at pH 9.5 and the micellar phase was 62 mM sodium dodecyl sulphate. A diode array detector was used for quantification in the range 190-600 nm, and limits of quantification of 0.01 mg/1 per analyte were reported. The authors observed that their procedure requires further validation for quantitative analysis. 

The earliest applications for quantitative analysis of liquid samples and solid preparations entailed sample dissolution in an appropriate solvent. A number of moisture determinations in APIs and pharmaceutical preparations based on both reflectance and transmission measurements have been reported. Their results are comparable to those of the KF method. The high sensitivity provided by the NIR technique has fostered its use in the determination of moisture in freeze-dried pharmaceuticals. ° The noninvasive nature of NIR has been exploited in determination of moisture in sealed glass vials. " " ... 

Table I indicates good agreement between the molecular weight distribution statistics obtained by coupled GPC/Viscometer method and the nominal values for t BS 706. The discrepancy between the Mark-Houwink parameters obtained here and the reported values for polystyrene standard ( ) in THF at 25°C (i.e., a = 0,706 and k = 1.60 x 10 ) may in part be due to the uncertainty involved in the determination of the dead volume between DRI and viscometer detectors. Our simulation studies over a range of dead volume values (0 to 120u)l) showed that a and k are quite sensitive to the dead volume between the detectors. Larger dead volume results in smaller o and larger k values. This is a direct result of a clockwise rotation of log [q] vs. log M(v) curve (Figure 12) which occurs when the dead volume correction is applied in quantitative analysis. The effect on the molecular weight statistics, however, appeared to...

Many of the currently available studies of metal-metal bonding were completed before the multipole model and the topological analysis of the total density were fully developed. For this reason, the discussions reported below focus on the deformation density distributions, and their comparison with theoretical results, though a more quantitative analysis is now possible and would be of considerable interest. 

The widespread use of chromatography in quantitative analysis is mainly due to its reliability and to its use in standardised analyses. This type of analysis relies mainly on reproducibility of the separation and on the linear relationship that exists between the injected mass of the compound and the area of the peak in the chromatogram. The use of an integrating recorder or a microcomputer with the appropriate data treatment software allows automation of all the calculations associated with the analysis. Computer software can analyse the results and produce a computerised report. Trace and ultratrace analyses by chromatography are often the only recognised methods (EPA Methods for Environmental Analyses), although their costs are relatively high. The three most widely used methods are described below in their simplest formats. 

The phenomenon has been studied by Gao and Sonin [16] and it has been shown that the cross-sectional area and apparent contact angle of a printed bead is a function of the substrate temperature and the print-scan velocity. A quantitative analysis of jet-printed phase change materials was reported by Schiaffino and Sonin [17] for isothermal conditions. The results showed that the contact angles for the printed drops could be varied as a function of the substrate temperature. By adjusting the substrate temperature and the scanning speed, the feature size and print quality can be adjusted without having to modify the substrate surface energy. 

S NMR spectroscopy is potentially an adequate method for both qualitative and quantitative analysis of mixtures of organosulphur compounds. Kosugi62 has reported the 33S spectra of mixtures of 1- and 2-naphthalenesulphonates and of 1,5- and 2,6-naphthalene disulphonates at concentrations of approximately 0.15 M in D20. In both cases, (NH4)2S04 was used as an internal standard to determine chemical shifts and for quantitative analysis. At a magnetic field of 5.9 T, the 33S spectra of the two mixtures show two quite sharp and well-resolved resonances, and the results reported indicate that the quantitative analysis of these isomers is possible with a relative error of less than 10%. 

The results of formaldehyde and methyl glyoxal analysis in commercial foods are shown in Table VIII. Formaldehyde was identified in the levels of 3.7-17 ppm in coffee obtained from various commercial sources. It was found at higher levels in instant coffees than in brewed coffee. This suggests that formaldehyde may escape from coffee during brewing. Formaldehyde has been reported in coffee volatiles by several researchers (31). There are however, no reports on quantitative analysis of formaldehyde in coffee prior to the present study. 

The content and length of any given report will depend on the subject matter of the experiment and on the standards established by the instructor. It is om behef that at least in some cases the report should be quite complete and should include a quantitative analysis of the experimental uncertainties and a detailed discussion of the significance of the results (see the sample report given below). For many experiments a brief report with only a qualitative treatment of errors and a short discussion may be considered adequate. In either case, a clear presentation of the data, calculations, and results is essential to every report on experimental work. 

U.S. EPA (1991) derived a cancer inhalation unit risk for sulfur mustard based on the results of inhalation animal studies conducted by McNamara et al. (1975, see Section 3.7.2) however, it was emphasized in the EPA report that the studies of McNamara et al. (1975) contained deficiencies which made a quantitative analysis difficult. Conducted in 1970, the studies do not conform to the modem norms of acceptable experimental protocol, and it is likely that there was bias in the assignment of the animals to the test categories (U.S. EPA, 1991). In addition, many of the exposures were very brief, included only a few animals, and many of the animals were sacrificed (and some were replaced) before their capacity to develop late-appearing tumors was fully developed (U.S. EPA, 1991). Despite these shortcomings, it was noted by EPA that the McNamara et al. data are the best available for estimating the carcinogenic potency of sulfur mustard. The authors of the EPA report analyzed two sets of McNamara s data one from a toxicity study and one from a carcinogenicity study (see Section 3.7.2). 

---