Benchmarking techniques

TIMS has been used for many years as the benchmark technique especially for uranium isotope analysis. Instrumental improvements have enabled ICP-MS to approach the accuracy and precision obtained by TIMS in measuring data. In addition, due to time consuming sample preparation steps and the need for a large volume of urine, the method has been replaced by the more powerful ICP-MS in many laboratories. An interlaboratory analytical exercise on the determination of natural and depleted uranium in urine was carried out by different ICP-MS instruments, by thermal ionization mass spectrometry (TIMS) and instrumental neutron activation analysis. TIMS has also been employed to determine fg quantities of Pu and °Pu in bioassay samples (such as human urine and artificial urine), ° in an interlaboratory comparison for the analysis of the Pu and Pu/ °Pu atomic ratios in synthetic urine by TIMS and AMS as reported in reference. ... 

These features picked out by the judges particularly identify the need to compare CERs with others by employing benchmark techniques. 

Microscopy remains the benchmark technique against which most others are compared, especially for particle sizing. It is particularly useful for identifying interparticle interactions and associations, specifically for floe or aggregate characterization and determination of floe morphology, which are difficult using other techniques. Therefore, microscopic methods are discussed in more detail than other methods. 

The sensitivity, selectivity, and convenience of positive and negative-ion ESI LC-MS makes this the current benchmark technique for analyzing phospholipid mixtures. Additional structural information can be obtained by MS/MS. Where these advanced... 

Thermal ionization mass spectrometry (TIMS) has long been a benchmark technique for accurately determining inorganic elemental isotope ratios, especially with regard to the isotope ratios of higher mass elements such as uranium. In order to determine the accurate isotope ratio for uranium from a urine sample, scientists use various combinations of co-precipitation, digestion, chromatography, and evaporation to eliminate matrix from 10 to 2000 mL of urine. These techniques help to concentrate the uranium to a volume of a few microli-... 

The corabination of an inductively coupled plasma ion source and a magnetic sector-based mass spectrometer equipped with a multi-collector (MC) array [multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS)] offers precise and reliable isotope ratio data for many solid elements. In fact, MC-ICP-MS provides data, the trueness (accuracy) and precision of which is similar to, or, in some cases, even superior to, that achieved by thermal ionization mass spectrometry (TIMS), considered the benchmark technique for isotope ratio measurements of most solid elements [1], The basic strength of ICP-MS lies in the ion source, which achieves extremely high ionization efficiency for almost all elements [2, 3]. Consequently, MC-ICP-MS is likely to become the method of choice for many geochemists, because it is a versatile, user-friendly, and efficient method for the isotopic analysis of trace elements [4-8], The ICP ion source also accepts dry sample aerosols generated by laser ablation [9-16], The combination of laser ablation (LA) with ICP-MS is now widely accepted as a sensitive analytical tool for the elemental and isotopic analysis of solid samples. 

A benchmark study examined the difficulty in reproducing QRA resLilts. Several expert teams were given identical systems to analyze using common techniques and a common database. The analysts were initially given total latitude concerning necessary assumptions, events to consider, data, and so forth. Figure 15 illustrates the results of the... 

Much of the microscopic information that has been obtained about defect complexes that include hydrogen has come from IR absorption and Raman techniques. For example, simply assigning a vibrational feature for a hydrogen-shallow impurity complex shows directly that the passivation of the impurity is due to complex formation and not compensation alone, either by a level associated with a possibly isolated H atom or by lattice damage introduced by the hydrogenation process. The vibrational band provides a fingerprint for an H-related complex, which allows its chemical reactions or thermal stability to be studied. Further, the vibrational characteristics provide a benchmark for theory many groups now routinely calculate vibrational frequencies for the structures they have determined. 

Infrared, Raman, microwave, and double resonance techniques turn out to offer nicely complementary tools, which usually can and have to be complemented by quantum chemical calculations. In both experiment and theory, progress over the last 10 years has been enormous. The relationship between theory and experiment is symbiotic, as the elementary systems represent benchmarks for rigorous quantum treatments of clear-cut observables. Even the simplest cases such as methanol dimer still present challenges, which can only be met by high-level electron correlation and nuclear motion approaches in many dimensions. On the experimental side, infrared spectroscopy is most powerful for the O—H stretching dynamics, whereas double resonance techniques offer selectivity and Raman scattering profits from other selection rules. A few challenges for accurate theoretical treatments in this field are listed in Table I. 

For W1 theory, MAD is increased to 0.37 kcal/mol (old SCF extrapolation) or 0.40 kcal/mol (new SCF extrapolation), with the maximum error being 0.78 kcal/mol. This should be compared with MAD of 1.25 kcal/mol for G2 theory, 0.89 kcal/mol for G3 theory, 0.88 kcal/mol for CBS-Q, and 0.61 kcal/mol for CBS-QB3, and the much higher maximum errors of these methods of 4.90 kcal/mol (SO2), 3.80 kcal/mol (SO2), 3.10 kcal/mol (OCS), and 1.90 kcal/mol (C2H2), respectively. While we would prefer to use W2 theory for no-nonsense benchmarking if at all possible, W1 theory still seems to offer great advantages over the other techniques. 

Lennernas s group at Uppsala has performed extensive studies to confirm the validity of this in vivo experimental set-up at assessing the rate and the extent of drug absorption. Recovery of PEG 4000 (a non-absorbable marker) is more than 95%, which indicates that the absorption barrier is intact. In addition, maintenance of functional viability of the mucosa during perfusion has been demonstrated by the rapid transmucosal transport of D-glucose and L-leucine. Estimation of absorption half-lives from the measured Pefr agree well with half-lives derived from oral dose studies in humans (i.e. physiologically realistic half-lives). Human Peff estimates are well correlated with the fraction absorbed in humans, and served as the basis for BCS development, and hence the technique is ultimately the benchmark by which other in situ intestinal perfusion techniques are compared. The model has been extensively used to... 

When sampling in the enviromnent, it is often impossible to determine which chemical mixtures are causing a total petroleum hydrocarbons reading, which is one of the major weaknesses of the method. At minimum, before using contaminants data from diverse somces, efforts should be made to determine that field collection methods, detection limits, and quality control techniques were acceptable and comparable. This will help the analysts compare the analysis in the concentration range with the benchmark or regulatory criteria concentrations should be very precise and accmate. 

High-performance liquid chromatography (HPLC) is one of the most widespread analytical and preparative scale separation techniques used for both scientific investigations and industrial and biomedical analysis. Now in its second edition, this revised and updated version of the Handbook of HPLC examines the new advances made in this field since the publication of the benchmark first edition twelve years ago. It reports detailed information on fundamental and practical aspects of HPLC related to conventional format and sophisticated novel approaches that have been developed to address a variety of separation problems in different fields. 

Table 6.2 contains a survey of glycoalkaloid content in potatoes analyzed using the above HPLC NH2 column technique. None of the whole potatoes exceeded the 200 mg total glycoalkaloids per kg of potatoes (see A + B column). However, this was not the case for potato peel. Five of the eight samples exceeded this benchmark. The high content of peels should not be of concern, unless consumers ate large amounts of peel, as they sometimes do in some commercial products, such as potato skin appetizers. 

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