Secondary RMs

One approach to providing secondary RMs is the NIST Traceable Reference Material (NTRM) program for gas standards (Jenks et. al. 1998 NIST 1997). The NTRM program is to be extended to metals, trace elements and pure substances. It may be possible to extend this concept to other types of RM, but it is difficult to see how it can easily be applied to the production of complex matrix CRMs. 

On the other hand, when iodine monobromide in toluene at low temperature was employed to induce the cyclization of secondary rm-butyl homoallyl carbonates, very high 1,3-asymmetric induction was observed, leading mainly to the ris-isomer11, l2. 

One solution to the problem may be to reduce the demand for CRMs by making available secondary RMs, designed and produced according to the quality standards established and implemented today for CRM production and traceable to CRMs. Such materials might find a use in all kinds of day-to-day quality control procedures and similar measures. This solution may lower the cost of production however, this approach is not applicable to all situations (e.g. CRMs are still lacking in many instances and the traceability link of secondary RMs to CRMs is questionable). 

Sorensen TL, Sellebjerg F (2001) Distinct chemokine receptor and cytokine expression profile in secondary progressive MS. Neurology 57 1371-1376 Sorensen TL, Tani M, Jensen J, Pierce V, Lucchinetti C, Folcik VA, Qin S, Rottman J, Sellebjerg F, Strieter RM, Frederiksen JL, Ransohoff RM (1999) Expression of specific chemokines and chemokine receptors in the central nervous system of multiple sclerosis patients. J Clin Invest 103 807-815... 

A further distinction is made between pure solutions and matrix-based RMs. The former are available for many organic and inorganic analytes, with certified concentrations, but their role in quality control and assessment is limited. They may be used for the preparation of calibration solutions for a particular measurement but more usually these materials represent the base for traceability, through secondary... 

Much of the early work with certified reference materials was linked to the derivation of reference methods and there was a period in which primary or definitive (i.e. very accurate but usually very complex) and secondary (or usable) methods were reported e.g. steroid hormones (Siekmann 1979), creatinine (Siekmann 1985), urea (Welch et al. 1984) and nickel (Brown et al. 1981). Although there are some application areas, such as checking the concentrations of preparations listed in a pharmacopoeia, where a prescribed, defined method has to be used, in practice such work is limited. However, this approach to chemical analysis is no longer widely used and will not be further discussed. The emphasis now is placed on using RMs to demonstrate that a method in use meets analytical criteria or targets deemed to be appropriate for the application and to develop figures of merit (Delves 1984). 

In Tables 6.3 and 6.4 RMs of three major producers are mentioned, i.e. the World Health Organization (WHO, International Standards), BCR (European Union, CRMs) and the National Institute of Standards and Technology (NIST, USA, SRMs). Some important national producers of clinical reference materials are the Chemicals and Inspection Testing Institute (CITI, Japan), National Institute for Biological Standards and Control (NIBSC, UK), and Deutsche Gesellschaft fiir Klinische Chemie (DGKC). There are numerous commercial producers of secondary reference materials. 

The majority of these RMs are available from the issuing organizations several older materials may not be available from primary sources but may still be available in the secondary market (e.g. from existing stock in laboratories). 

Such errors include mis-reading certificate or report data supplied by the producers, using secondary information from catalogs and/or literature listings, and reporting incorrect data. For the correct use of a RM/CRM, it is essential to read the information that accompanies the product once an appropriate RM/CRM has been obtained. The only reliable source of information is the Certificate of Analysis or Report of Assigned Values issued with the RM/CRM, and it must be the most up to date version available. Failure to follow a producer s recommendation will invariably result in error. 

BRM-2 highlighted the distinction between primary (certified) and secondary (e.g. check samples for proficiency testing) RMs. 

A series of palmitoylethanolamine-derived inhibitors has been described in the literature as FAAH inhibitors [77, 78]. This study explored the effect of shortening the chain length and replacement of the ethanolamine head group with primary, secondary and tertiary amide alternatives. Of the compounds synthesised and tested, two compounds gave reasonable affinities for FAAH inhibition, palmitoyl-isopropylamide (63) (IC50 = 13/rM) and palmitoyl-allylamide (64) (IC50 = 3.4/rM). Both these compounds had little affinity for either CBi or CB2 receptors. 

Smith PE, Farquhar RM Hancock RG (1991) Direct radiometric age determination of carbonate diagenesis using U-Pb in secondary calcite. Earth Planet Sci Lett 105 474-491 Spalding RF, Mathews TD (1972) Submerged stalagmites from caves in the Bahamas Indicators of low sea level stand. Quat Res 2 470-472... 

There is also a major issue concerning secondary-side trace inductances, one that we will discuss a little later. Other than that, there are no issues, except of course the fact that because there is only one capacitor, the effective ESR won t be very good (nor the RMS ripple current-handing capability). 

The storage of a freeze dried product starts with the end of the secondary drying and its transfer into a suitable packing. In the drying plant a certain residual moisture content (RM) is achieved as a function of the product temperature and the drying time (Section 1.2.2). 

During secondary drying, a small RM should be reached, since Tg of the dry product increases with decreasing water content. Tg- of amorphous, freeze dried sucrose increases from 16 °C with 8.5 % RM to 63 °C or 64 °C between 1.0 and 0.7 % RM. It should be taken into account, that RM cannot be taken only at the end of drying, but a possible increase during storage by water desorbed from the stopper has to be considered (see Section 1.3.2 and Pikal et al. [3.7]). 

Levin RM, Yu HJ, Kim KB, Longhurst PA, Wein AJ, Damaser MS 1997 Etiology of bladder dysfunction secondary to partial outlet obstruction. Calcium dysregulation in bladder power generation and the ability to perform work. Scand J Urol Nephrol Suppl 184 43—50... 

Summarizing the results related to the barriers to rotation of a secondary alkyl group in the 9-position of a 1-substituted triptycene, we note that the maximum barrier is realized when the peri substituent is chlorine or bromine. Evidently the size of the substituent that gives the maximum barrier to rotation is shifted from that in the 9-rm-alkyl systems. This is considered to be a reflection of the strain in the ground state, which is usually larger in the tertiary alkyl systems than in the secondary, if the same substituent is present in the peri position. 

Hydrocyclones are 20-500 mm in diameter, with the smaller units giving a much better separation. Typical values of length to diameter ratios range from about 5 to 20. Because of the very high shearing stresses which are set up, floes will be broken down and the suspension in the secondary vortex will be completely deflocculated, irrespective of its condition on entry. Generally, hydrocylones are not effective in removing particles smaller than about 2-3 rm. 

Lewis et al. (entry 11 of Table 2) examined the temperature-dependence of isotope effects in the action of both the human enzyme and the soybean enzyme, by measuring the relative amounts of per-protio and per-deuterio-13-hydroperoxy-products by HLPC. The observed effects are, therefore, composed of primary, secondary, and perhaps remote isotope-effect contributions. Isotope effects on fecat/ M for both enzymes (determined by competition between labeled substrates) are increased by high total substrate concentration, an effect previously observed but stiU ill-understood. At 100 /rM substrate, the effects are roughly independent of temperature below about 15 °C, and are about 60 (H/D) for the human enzyme and 100 (H/D) for the soybean enzyme. Above 15 °C, the effects decline to about 50 for the human enzyme and about 60 for the soybean enzyme, perhaps because non-isotope-sensitive steps become more nearly rate-limiting (see Chart 4). 

The crystal structure of MPT synthase and the simultaneously determined NMR structure of the MoaD-related ThiS protein involved in thiamine biosynthesis [37] unambiguously demonstrated the evolutionary relationship between a subset of enzymes involved in the biosynthesis of S-containing cofactors (e.g. Moco, thiamine and certain EeS-clusters) and the process of ubiquitin activation. MoaD displays significant structural homology to human ubiquitin (Figure 3.3B and C), resulting in a superposition with a root mean square (rms) deviation of 3.6 A for 68 equivalent Ca atoms out of 76 residues in ubiquitin. The key secondary structure... 

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