Common moiety methods

If the relevant residue cannot be properly determined using a routine multi-method, an alternative method must be proposed. In the case of residues consisting of a variety of structurally related compounds, a common moiety method may be acceptable in order to avoid the use of an excessive number of methods for individual substances. For example, the relevant residue of isoproturon in plant material is defined as the sum of isoproturon and all metabolites containing the 4-isopropylaniline group. Therefore, residues are determined following hydrolysis as 4-isopropylaniline and are expressed as 4-isopropylaniline equivalents. It is not necessary to validate the method individually for all possible metabolites which are covered by the residue definition (e.g., all metabolites which contain the 4-isopropylaniline group), provided that it is demonstrated that in the first step, the conversion to the common moiety is complete. However, common moiety methods often lack sufficient specificity, and should therefore be avoided if possible. If need be, their use must be justified. 

The use of common moiety methods acceptable in exceptional circumstances where there is no other practical means of determining the target analyte, and in these cases, full justification is required. This should include an explanation of why the compound cannot be determined by a specific analytical technique. For existing a.i., common moiety methods are also acceptable, in cases where the residue definition includes a common moiety. Moreover, validation data must be presented separately for all relevant components. 

In general, a nonspecific method is not acceptable because it is possible for the identity of the source of the analyte to be called into question. However, in cases where derivatization from a common species is the only method available (e.g., dithio-carbamate compounds), the use of a nonspecific common moiety method may be acceptable. 

A final special case may occur during the validation of common moiety methods. Based on the normal set of recovery experiments (two control samples, five samples fortified at the LOQ and five samples fortified at 10 times the LOQ), in total 12 samples have to be analyzed per matrix and analyte. A typical intention of common moiety methods is their suitability for the parallel determination of residues of the parent compound and a broad spectrum of metabolites. In the common moiety method discussed above for residues of spiroxamine, validation experiments were performed with four compounds. This results in at least 48 experiments per matrix. Assuming a normal... 

On the other hand, some sensible reduction may be acceptable. In the spiroxamine example, an appropriate reduced validation protocol may be as follows a full set of recovery experiments at both levels performed with the intact spiroxamine (which has the longest reaction pathway to the common moiety) and separately with one primary metabolite. Such two complete validations should be an acceptable test of the working range of the common moiety method. 

The best way to test the practicability of the multi-residue approach is to start with the GC determination step. Most often the inability to vaporize the intact compound means that it is not possible to include a new pesticide in the multi-residue scheme. In the case of common moiety methods, a decomposition step is needed to produce the common analyte. Often for that step, modification of the reaction conditions (such as pH and temperature) are necessary, which would lead to a significant deviation from standard multi-residue procedures. 

Electrophilic attack of the HN—C=X moiety in imidazolone derivatives at X (which has usually been sulfur) can result in 4//-imidazoles. This has been the most commonly used method for the preparation of these compounds. 

RP-HPLC The most commonly used methods for the analysis of SFs are reverse-phase liquid chromatography with UV-detection, which allow the separation of SFs with different sterol moieties. The number of components separated is naturally dependent on the type of column used, but most reverse-phase columns provide a full separation of at least five to six components of y-oryzanol. Cl 8-columns are most abundantly applied for the separation of SFs, but other reverse-phase... 

There are in general two ways to synthesize side chain polymers, polymerization of peptide-functional monomers or introduction of the peptide moiety afterwards, by grafting. The latter technique is based on the synthesis of polymers containing some form of functionality in the side chain, normally an activated ester moiety, which can further react with a peptide. The most commonly used method for the polymerization of monomers containing active esters is free radical polymerization. In particular many activated acrylate esters have been polymerized in this manner [12] (Table 1) for use in a wide variety of applications, from the preparation of polymer drug conjugates [13,14] to supports for solid phase peptide synthesis [15,16]. 

The same general methodology can also be applied to edit (for example) a decoupled NMR spectrum into four subspectra, for the CH, CH, CH and C moieties separately. A common variant method called DEPT... 

It is well known that the phenol groups (which are bonded to the aporphine ring) and the benzylic amine function are responsible for the antioxidant and free radical scavenging activities of boldine [60], In addition, the presence of hydroxyl moieties in the chemical skeleton of boldine is responsible for its lipid peroxidation inhibitory activity [61], The level of boldine in the bark of boldo is more than 6% [62], Paper electrophoresis, voltammetric method, thin-layer chromatography and gas chromatography are common analytical methods for boldine determination [63],... 

Alkaline methanolysis with anhydrous sodium methoxide is probably the most common depolymraization method [5, 7, 12, 14, 39, 40, 49-51, 59-66], which yields the aliphatic acid components in the form of methyl esters. Complete suberin methanolysis is normally achieved by treating it with refluxing methanol containing 3 per cent of NaOMe for about 3 h [7, 60]. However, under such conditions, epoxy moieties are, at least in part, cleaved, leading to the corresponding methoxyhydrins. 

Similar to the Paal-Knorr pyrrole synthesis, the Knorr pyrazole synthesis is the most common synthetic method for the preparation of pyrazoles. The Knorr pyrazole synthesis involves the cyclocondensation of an appropriate hydrazine, 1, which acts as a bidentate nucleophile, with the three carbon unit of a 1,3-dicarbonyl moiety, 2, featuring two electrophilic carbons. With unsymmetrical substrates having two electrophilic centers (Ra R4), mixtures of regioisomers 3a and 3b are often obtained in reactions with substituted hydrazines (Ri H). However, when Ri = H, the prototropic tautomerism of pyrazoles renders 3a equivalent to 3b. 

This cascade process has been recognized as an efficient and powerful method for selective activation and direct functionalization of inactive C(sp )-H bonds. It represents an intriguing sequential C(sp )-H activation/C-C, C-N or C-O bonds formation process and proves to be a versatile protocol to construct 5-, 6-, or 7-membered hetero/carbon spiro or fused cycles, such as tetrahydroquinolines [22], chromans [23-25], spiroethers [26-30], and tetrahydropyrans [31-36], which are common moieties in biologically important natural products and pharmaceuticals. 

Prins cyclization and its many variants are convenient methods to assemble tetrahydropyran rings that are common moieties in many natural products. Early... 

An enzymatic method (45), which is specific for the citrate moiety, can be used as a combined assay and identification test for citric acid and its common salts down to 20 ppm. 

Residues of alachlor and acetochlor are determined by similar methods involving extraction, hydrolysis to the common aniline moieties, and separation and quantitation by reversed-phase FIPLC with electrochemical detection. The analytical method for acetochlor is included as a representative method for residue determination of alachlor and acetochlor in plant and animal commodities. Propachlor and butachlor residues, both parent and metabolite, are determined by similar analytical methods involving extraction, hydrolysis to common aniline moieties, and separation and quantitation by capillary GC. The analytical method for propachlor is included as a representative method. The details of the analytical methods for acetochlor and propachlor are presented in Sections 4 and 5, respectively. Confirmation of the residue in a crop or... 

Particularly, some newly developed drags, which incorporate the N-acyl sulfonamide moiety [8-10], are synthesized from the parent sulfonamides, by their coupling with acid chlorides or carboxylic anhydrides in basic conditions [11-15]. Unfortunately all these methods lead to substantial waste products. Less common reports mentioning this transformation under acidic conditions (Bronsted or Lewis acids) do not systematically examine the purpose and limitations of the reaction [16]. 

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