Analytical methods metabolites

Analytical Methods for Determining Methyl Parathion and Metabolites in... 

The purpose of this chapter is to describe the analytical methods that are available for detecting, measuring, and/or monitoring methyl parathion, its metabolites, and other biomarkers of exposure and effect to methyl parathion. The intent is not to provide an exhaustive list of analytical methods. Rather, the intention is to identify well-established methods that are used as the standard methods of analysis. Many of the analytical methods used for environmental samples are the methods approved by federal agencies and organizations such as EPA and the National Institute for Occupational Safety and Health (NIOSH). Other methods presented in this chapter are those that are approved by groups such as the Association of Official Analytical Chemists (AOAC) and the American Public Health Association (APHA). Additionally, analytical methods are included that modify previously used methods to obtain lower detection limits and/or to improve accuracy and precision. 

Table 7-1 summarizes the analytical methods used to detect methyl parathion and its metabolites in biological tissues and fluids. 

Setting An established analytical method consisting of the extraction of a drag and its major metabolite from blood plasma and the subsequent HPLC quantitation was precisely described in a R D report, and was to be transferred to three new labs across international boundaries. (Cf. Section 4.32.) The originator supplied a small amount of drug standard and a number of vials containing frozen blood plasma with the two components in a fixed ratio, at concentrations termed lo, mid, and hi. The report provided for evaluations both in the untransformed (linear/linear depiction)... 

QSAR modeling. Therefore considerably larger and more consistent data sets for each enzyme will be required in future to increase the predictive scope of such models. The evaluation of any rule-based metabolite software with a diverse array of molecules will indicate that it is possible to generate many more metabolites than have been identified in the literature for the respective molecules to date, which could also reflect the sensitivity of analytical methods at the time of publishing the data. In such cases, efficient machine learning algorithms will be necessary to indicate which of the metabolites are relevant and will be likely to be observed under the given experimental conditions. 

Several methods are available for the analysis of trichloroethylene in biological media. The method of choice depends on the nature of the sample matrix cost of analysis required precision, accuracy, and detection limit and turnaround time of the method. The main analytical method used to analyze for the presence of trichloroethylene and its metabolites, trichloroethanol and TCA, in biological samples is separation by gas chromatography (GC) combined with detection by mass spectrometry (MS) or electron capture detection (ECD). Trichloroethylene and/or its metabolites have been detected in exhaled air, blood, urine, breast milk, and tissues. Details on sample preparation, analytical method, and sensitivity and accuracy of selected methods are provided in Table 6-1. 

Annex VI to Directive 91/414/EEC concerning the placing of plant protection products on the market. The section concerning residue analytical methods was not fully finalized when the Directive was first adopted. There were no provisions for methods to determine residues from a.i. and relevant metabolites in soil, water, and air. The criteria for foodstuffs partly proved to be not helpful for the practice of assessment (e.g., with regard to reproducibility, ISO 5725 requires validation in at least eight independent laboratories). 

For certain naturally occurring nontoxic a.i., an enforcement is not sensible (e.g., lecithin, rape seed oil). Analytical methods for residues in soil are not necessary if the DTgo values of the a.i. and relevant metabolites are less than 3 days (e.g., fosetyl), because in general, the results from residue analyses are not meaningful if the a.i. is rapidly degraded. 

Methods to determine the a.i., and/or relevant metabolites in air during or shortly after the application must be submitted unless it can be justified that exposure of operators, workers, or bystanders does not occur. In SANCO/825/00 it is stated that spray drift and particle-associated as well as gaseous substances have to be taken into consideration because both can cause relevant exposure of operators, workers, or bystanders. Therefore, an analytical method must also be submitted for relevant substances with a low vapor pressure (< 10-5 Pa). 

Analytical methods must be capable of determining the a.i. and/or relevant metabolites in the presence of the sample matrix. Where the sample contains more than one isomer, analog, etc., of an a.i. or relevant metabolite, the method should distinguish between individual isomers/analogues where this is necessary for carrying out risk assessment. 

January 1992, two working groups have been dealing with analytical methods for the determination of pesticide residues WG 3 Pesticides and PCBs in Fatty Foods and WG 4 Pesticides in Nonfatty Foods . So far analytical methods for 47 pesticides and their metabolites in fatty food and methods for more than 200 pesticides in nonfatty foods have been published in several standards (Table 6). 

Specificity is a measure of how selectively the analytical method measures the marker compound in the presence of other compounds. The descriptors used to establish specificity differ depending upon the guideline (see Table 3), but the purpose behind them is the same. In all cases, the method must be demonstrated to have no interference from several (at least five) confrol animals that represent variation in sex, age, and breed. Further, incurred residue samples or authentic metabolite standards must demonstrate no interference with the marker residue detection. The method must be tested with other approved dmgs for the target species to show that no interference exists if these compounds are also present. 

The official analytical method of the Ministry of Environment, Japan, recommends the use of a Cig cartridge to determine naproanilide. This method consists of the following procedure 5 mL of the 1N hydrochloric acid are added to the water sample and the solution is applied to a Cig cartridge, which is preconditioned with 5 mL each of acetonitrile and water, at a flow rate of 10-20 mL min. Naproanilide and its metabolite, 2-(2-naphthoxy)propionic acid, are eluted with 10 mL of acetonitrile. 

Thus, organic solvent extraction methods for the extraction of pesticides from water samples can be replaced by the SPE method using Ci8 and PS-2. Ethobenzanid, clomeprop, naproanilide and their acidic metabolites are determined by a multi-residue analytical method using Cig or PS-2 cartridge extraction after acidification of the water samples with hydrochloric acid or other acidic media, followed by HPLC or LC/MS detection. 

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... 

Analytical method for the determination of acetochior and its metabolites in plants and animals... 

This analytical method determines levels of major oxanilate and sulfonate soil metabolites of acetochlor, alachlor, and metolachlor in groundwater and surface water. The method consists of analysis of environmental samples by direct aqueous injection reversed-phase LC/MS/MS. 

Robert A. Bethem, ALTA Analytical Laboratory, developed the analytical method for the determination of acetanilide metabolites in water. The authors gratefully acknowledge Sharon J. Moran, Michael J. Miller, and David I. Gustafson of Monsanto Company for reading and reviewing this article, and Theresa M. Bix for editorial assistance. 

Analytical methods for fortified soils were developed for the simultaneous quantitation of the trifluralin metabolites, 2,6-dinitro-A-propyl-4-(trifluoromethyl)-benzenamine (1) and 2,4-dinitro-A,A-dipropyl-6-(trifluoromethyl)benzenamine (2) (Figure 2). The SFE method developed as described in Section 2.2.1 was extended to the determination of these metabolites. From soil fortified with 0.5-2.5 mg kg each of trifluralin, (1) and (2), the compounds were efficiently extracted by this procedure. Trifluralin and its metabolites (1) and (2) are characterized by absorbance bands in both the ultraviolet (UV) and visible ranges for HPLC however. 

At the present time, LC/MS/MS with triple-quadrupole instruments is the analytical method of choice for the determination of residues of sulfonylurea herbicides. We can expect to see improved triple-quadrupole instrumentation become more available and affordable as time passes, so that more analytical laboratories will have this capability. Time-of-flight (TOP) instrumentation may also play an increasingly important role in sulfonylurea analysis. Even though the metabolites are innocuous, stricter regulatory requirements may mandate that they be monitored, and LC/MS/MS is the method of choice for these compounds also. 

Analytical method for the metabolites of diphenyl ether herbicides in soil... 

The analytical method for carfentrazone-ethyl and its major metabolites in/on corn grain, grits, meal, flour, and starch (nonoil matrices) consists of extractions with acetone and deionized water, followed by a partition with hexane, which allowed the separation of the parent carfentrazone-ethyl from the acid metabolites. The hexane... 

The analytical method to determine carfentrazone-ethyl and the major animal metabolites (C-Cl-PAc and C-Pac) in bovine matrices is similar to the method for crop matrices. The hexane-aqueous partition to separate carfentrazone-ethyl from the acid metabolites can be replaced by a Cig SPE cartridge. After the SPE, use 12 mL of water-acetonitrile (7 3, v/v) to elute the metabolites and then use 12 mL of hexane-ethyl acetate (4 1, v/v) to elute carfentrazone-ethyl after drying the cartridge. Follow the rest of the respective analytical procedures for carfentrazone-ethyl and the acid metabolites described in Sections 6.3 and 6.4. However, no reflux under boiling is necessary for the analysis of acid metabolites based on a goat metabolism study, because no conjugated acid metabolites were detected. Also, since HM-C-Cl-Pac is not analyzed for in the bovine matrices, no acylation is needed in the method. Analyze the metabolites by GC/MS, and monitor the ions at m/z 362 for C-Cl-Pac and 303 for C-PAc. 

All of the compounds (pyraflufen-ethyl and its metabolites) are converted to E-2 and quantified as the total toxic residue of pyraflufen-ethyl. The conversion to E-2 is carried out by oxidative decomposition with concentrated sulfuric acid. The reaction mixture is extracted with a solvent and subjected to simple cleanup, followed by GC/NPD analysis. This method is rapid and simple compared with the Multi-residue analytical method , and has wide applicability to different varieties of the samples, such as plant materials, soils and water, with only minor adjustment of the analytical method. 

Organic solvent extraction. Two analytical methods for acetamiprid have been developed One method is for the parent only and the other determines the total residue of the parent and its metabolites (lM-1-2, lM-1-4 and lC-0). Air-dried soil (20-g equivalent dry soil) is weighed into a centrifuge tube and imidacloprid residue is extracted with 100 mL of methanol-0.1M ammonium chloride (4 1, v/v) using a mechanical shaker for about 30 min. After shaking, the tube is centrifuged at 8000 rpm for 2 min. The supernatant is filtered and the analysis of the soil residue is carried out in the same manner as described above for the parent compound. 

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