Residue cleanup procedures

Kadoum AM. 1968. Cleanup procedure for water, soil, animal, and plant extracts for the use of electron-capture detector in the gas chromatographic analysis of organophosphorus insecticide residues. Bull Environ Contam Toxicol 3 247-253. 

Another complicating characteristic of materials from the environment is that the size and nature of the residue to be analyzed in the mass spectrometer will change from sample to sample. To determine if this might have an effect on the observed TCDD signal, we analyzed identical samples of TCDD with differing amounts of squalane, a saturated hydrocarbon selected as a model for residues obtained from standard extraction and cleanup procedures. As is indicated in Table I (Part A), there was... 

Plant material water contents range from high (>90%, e.g. vegetables) to low (< 10%, e.g. straw, herbs, tea, hops, etc.). Thus the ratio between the analytes (residues) and the organic matter potentially interfering with the analysis is very different for, e.g., cucumber and camomile tea. Other ingredients in plant materials such as acids, oil, sugars, starch or substances typically for the taste and effect of plant materials may have properties similar to those of the analytes and thus interfere in or influence the cleanup procedures. 

A homogenized sample of cereals, vegetables, fruits or potatoes (10-20 g) is extracted with an organic solvent such as acetone and methanol. After filtration, the extract is concentrated to about 20 mL by rotary evaporation below 40 °C. The residue is transferred with 5% sodium chloride (NaCl) aqueous solution and partitioned twice with n-hexane. The n-hexane extracts are dried with anhydrous sodium sulfate and subjected to a Florisil column chromatographic cleanup procedure. The eluate from the Horisil column is concentrated to dryness and the residue is dissolved in an appropriate amount of acetone for analysis by GC/NPD. ... 

The eluate from the Cig cartridge is concentrated by rotary evaporation and the residue is dissolved in n-hexane and then subjected to a cleanup procedure using a Florisil cartridge. The eluate is dried and analyzed by gas chromatography (GC) with nitrogen-phosphorus detection (NPD). 

One application using MAE is a method to determine imidazolinone herbicides and their respective metabolites in plant tissue." Current residue methodologies for determining imazethapyr (imidazolinone herbicide) and its metabolites in crops involve laborious, time-consuming cleanup procedures after an aqueous/organic extraction. 

Residue analytical methods for neonicotinoids in crops, soil and water samples have been developed. The basic principle of these methods consists of the following steps extraction of the crop and/or soil samples with acetone or the other organic solvent, cleanup by liquid-liquid partition or column chromatography, and quantitative analysis by high-performance liquid chromatography with ultraviolet detection (HPLC/UV). Simple column cleanup procedures are used to improve the accuracy and sensitivity of these methods. 

The sample is homogenized with acetonitrile. An aliquot of the extract is evaporated to dryness and the residual material is dissolved in ethyl acetate-toluene (3 1, v/v), and subjected to cleanup by gel permeation chromatography (GPC). After GPC, the sample is subjected to an alumina and Florisil SPE cleanup procedure. The concentrated eluate is analysed by gas chromatography/thermionic nitrogen-specific detection (GC/TSD). 

Soil sample is extracted with a mixture of methanol and 0.1 M ammonium chloride. Acetamiprid, IM-1-2 and IM-1-4 residues are extracted with dichloromethane under alkaline conditions. After adding diethylene glycol, dichloromethane in the extract is removed by rotary evaporation, and the residue is subjected to a cleanup procedure using Florisil PR column chromatography and then with a packed Extrelut 20 column. 

Cleanup procedures for acetamiprid, IM-1-2 and IM-1-4. Dilute the concentrate with 10 mL of distilled water and apply the solution to an Extrelut 20 column, equilibrate for 20 min at ambient temperature and pass 100 mL of dichloromethane through the column. Collect the eluate and add 0.5 mL of diethylene glycol and then concentrate the dichloromethane to about 0.5 mL by rotary evaporation. Prepare the HPLC-ready sample solution by dissolving the residue in 50% aqueous acetonitrile. 

Cleanup procedure for IC-0. Dissolve the residue with 10 mL of pH 5 phosphate buffer solution and apply the solution to the top the Sep-Pak Cig Env. column pretreated with 10 mL each of methanol and distilled water. Discard the passed solution and elute IC-0 with 15 mL of a second buffer solution. Add 35 mL of distilled water and adjust the pH of solution to 1.5 with hydrochloric acid. Extract the solution with three portions of 50 mL of diethyl ether. Combine the diethyl ether extracts and dry over anhydrous sodium sulfate. Concentrate to dryness on a water-bath at ca 40 °C... 

Buprofezin and its metabolites, p-OH-buprofezin and BF12, are hydrophobic under neutral conditions. Having the organic base part in their chemical structure, these compounds form water-soluble salts under strongly acidic conditions. The change in solubilities of these compounds influences the cleanup procedure. Four different residue analytical methods have been developed to measure buprofezin and its metabolites in plants (rice, citrus and tomato cucumber, pepper, tomato, squash and eggplant), soil and water ... 

Fenpyroximate and M-1 residues in the plant (apple, grape, etc.) and soil samples can be analyzed using the multi-residue method Method DFG 819 with some minor deviations. In this method, gel permeation chromatography (GPC) is effectively used as the cleanup procedure. Residues in the water sample can be analyzed by a simpler method. 

Yurawecz MP, Puma BJ. 1986. Gas chromatographic determination of electron capture sensitive volatile industrial chemical residues in foods, using AOAC pesticide multiresidue extraction and cleanup procedures. J Assoc Off Anal Chem 69 80-86. 

A number of methods have been described for determination of tetracycline (chlortetracycline, tetracycline, and oxytetracycline) residues in tissues of food-producing animals (53-62), fish (63), eggs (64), and honey (65,66). Most of these methods use reversed-phase HPLC for determination. However, one uses TLC with UV densitometry ( ) and one uses GLC ( ), and one uses a direct mass spectrometric method CAD MIKE spectrometry (collisionally activated decomposition mass-analyzed ion kinetic spectrometry) for oxytetracycline in milk and meat (62). Several use solid-phase extraction in the cleanup procedure using XAD-2 resin (56,58) or Cj g cartridges... 

If analysis is to be attempted with a detection system of only moderate selectivity, a substantial cleanup procedure may be required in order to enhance the concentration of the extracted trace residue while decreasing die concentration of possible interfering substances in the sample matrix. This is die case with most of the relatively nonspecific physicochemical detection systems used in residue analysis. Occasionally a sample may be suitable for direct physicochemical analysis after an extraction and concentration step. However, the majority of edible animal products need extensive cleanup to separate the compounds of interest from animal lipids and other natural organic substances prior to detection. For such detection systems, there has been a general rule dictating diat the cleaner sample, the better the result obtained. 

Apart from improving extractions, ion-pairing techniques can also improve liquid-liquid partition cleanup. Examples of effective ion-pairing cleanup procedures have been described in the analysis of tetracycline (60) and penicillin (68) residues in milk using tetrabutylammonium reagent, the resulting ion pairs turned out to be fairly lipophilic and readily extractable with organic solvents. 

All radioimmunoassays published thereafter, except those described by Hock and Liemann (38), Freebairn and Crosby (39), and Pohlschmidt et al. (40), were based on a similar procedure (Table 28.2). However, Hock and Liemann (38) applied a more simplified extraction/cleanup procedure for the analysis of chloramphenicol residues in animal tissues, milk, urine, and plasma. In this assay, competitive inhibition between chloramphenicol labeled with " C and antibody has been demonstrated. 

Using mentioned extraction/deproteinization procedures, the obtained aqueous or organic extracts often represent very dilute solutions of the analyte(s). These extracts may also contain coextractives that, if not efficiently separated prior to analysis of the final extract, will increase the background noise of the detector making it impossible to determine the analyte(s) at the trace residue levels likely to occur in the analyzed samples. Hence, to reduce potential interferences and concentrate the analyte(s), the primary sample extracts are often subjected to some kind of additional sample cleanup such as liquid-liquid partitioning, solid-phase extraction, or online trace enrichment and liquid chromatography. In many instances, more than one of these cleanup procedures may be applied in combination to allow higher purification of the analyte(s). 

To reduce coextractives in the primary sample extract and concentrate the analyte(s), various types of sample cleanup procedures can be applied. They include conventional liquid-liquid partitioning, solid-phase extraction, matrix solid-phase dispersion, and online dialysis and subsequent trace enrichment (Table 29.5). In many applications, more than one of these procedures is applied in combination to decrease the background noise of the detector, thus making it possible to quantify trace level residue concentrations. 

Ultrafiltration through a 30000 molecular mass cut-off cellulose membrane is another cleanup procedure that has been successfully applied in the analysis of luxabendazole residues in biological fluids (364). Although efficient, this technique was not used for treatment of urine samples since it would have implied working with low flow rates and a consequent increase in analysis time. 

Carbadox-related residues can also be monitored by conversion to quinoxa-line-2-carboxylic acid. This conversion as well as its liberation are accomplished by alkaline hydrolysis of tissue, followed by isolation of the analyte from indigenous hydrolysis products through extraction and cleanup procedures (419-422). Enzymatic digestion of swine tissues with subtilisin A, which liberates quinoxa-line-2-carboxylic acid from macromolecules, has also been reported (423). 

The cost, tedium, and instrumentation requirements of the conventional methods for determining drug residues have created pressures to lower analytical costs and increase sample throughput. The result is a trend toward simpler, miniaturized, and automated extraction and cleanup procedures. 

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