Plants sampling

The need for skill and experience on the part of sample designers and persoimel cannot be overemphasized in chemical plant sampling. Safety precautions are of the utmost importance. Necessary steps must be taken to document the hazards involved in an operation and to ensure that the staff are weU-trained, informed, protected, and capable. Except for bulk powder sampling, most chemical plant sampling is hazardous and difficult and must be designed with care. The following discussions are based on the assumptions that most of these decisions have been made and a satisfactory sampling procedure has been planned. 

Microwave extraction realized at 120 °C for 30 min with Hexane -Acetone (3 2 V/V) as the extraction solvent was identified as the most effective extraction procedure for isolation of TPH from biotic matrices. The aim of this research is to develop a silica gel and alumina fractionation procedure for plant sample extraction. Column chromatography with two solvents (chloroform and hexane dichloromethane) as a mobile phase were used for clean-up of extract. In this research the efficiency of recovery received from chloroform as a mobile phase. 

Comparison of Various FNAA Techniques for Assay of Synthetic Octol Samples Precision of Single-Axis Rotation FNAA for Assay of Octol Plant Samples Fast Neutron Activation Analysis for Nitrogen in Explosives by... 

It is the preferred method where speed is not essential — but when the number of samples to be analyzed is large, multiple sample irradiation on the lucite wheel. with single-axis rotation is used. The precision of this latter technique for six plant samples of Octol is shown in Table 2a. 

Precision of single-axis rotation FNAA for assay of Octol Plant samples... 

For smaller and lower pressure plants, sampling steam and condensate to obtain reliable information may be a problem. Careful inspection may reveal a point in a line where a live steam sample can be directly obtained. But this point may prove to be of little value unless there is a means of connecting a temporary sample cooler (such as a stainless steel coil in a bucket of cold water). 

Capriel P, Haisch A, Khan SU. 1986. Supercritical methanol An efficacious technique for the extraction of bound pesticide residues from soil and plant samples. J Agric Food Chem 34 70-73. 

Fig. 1. Elongation rate of stem intemode 12 (A), silks (A), leaf 8 ( ), and nodal roots (O) of maize at various water potentials. Elongation rates are the average per hour for 24 h of growth in a controlled environment chamber. Water potentials were measured in the growing region of each organ in the same plants. Samples were taken immediately after the growth period when the plants had been in the dark for the last 10 h. Each point is from a single plant. Modified from Westgate Boyer (1985a).

These results corroborated that alfalfa absorbed the Au(0) from the medium and translocated it through the vascular system. The EXAFS results (Figure 5, Table 3) showed that the Au atoms in plant samples had longer distances that the Au atoms in the tetrachloroaurate, but had equivalent distance to the Au atoms in the gold foil, which confirmed that the Au in plant samples was Au(0). 

Figure 4. XANES spectra of the tetrachloroaurate compound, the Au foil [Au(0)], and the Au in the agar and plant samples. (Reprinted from Ref. [28], 2002, with permission from American Chemical Society.)...

Houba V, Novozamsky I and Lee J van der (1995) Influence of Storage of Plant Samples on the Chemical Composition. Sci Total Environ 176 73-79. 

The collected plant samples are analyzed as soon as possible after harvest. When samples or their extracts need to be stored, appropriate storage conditions are imperative. The stability of metabolites should be monitored during the storage period. 

The definition of residues for selective anilides in plant samples is summarized... 

In the case of plant samples having high oil contents (for example, rice grain, bean, and corn), acetonitrile-n-hexane partitioning is used to remove the oily materials. The concentrated residue obtained in Section (a) above is dissolved in 30 mL of n-hexane and transferred into a separatory funnel, containing 30 mL of acetonitrile, and the mixture is shaken vigorously. The acetonitrile layer is collected and another 30 mL of acetonitrile are added and shaken with the n-hexane layer. The combined acetonitrile phase is carefully evaporated to dryness. 

For plant samples, the average recovery of flumioxazin from untreated confiol samples fortified within the range 0.1-0.01 mgkg ranged from 75 to 106%. The limit of quantitation (LOQ) is 0.01 mg kg and the limit of detection (LOD) is 0.005 mg kg. ... 

Weigh 20 g of the plant sample into an Erlenmeyer flask and add 40 mL of 1 N HCl and 160 mL of acetonitrile. Shake the flask for 30 min at 300 strokes min using a shaker. Filter the aqueous acetonitrile extract through a No. 4 Kiriyama funnel filter paper. Wash the residue on the filter with 100 mL of acetonitrile. Combine the filtrates and remove acetonitrile with a rotary evaporator. Transfer the residue with 20 mL of saturated aqueous sodium chloride solution into a separatory funnel, extract the solution with 3 x 30 mL of n-hexane-ethyl acetate (9 1, v/v), and collect the organic phase in a flask. Dry with anhydrous sodium sulfate and remove the combined organic phase with a rotary evaporator. Transfer the residue into the Eppendorf tube with a... 

Pyriminobac-methyl in plant samples (rice grains and rice straw) and soil is recovered by refluxing with aqueous acetone. After removing acetone from the extract, pyriminobac-methyl in the aqueous solution is transferred into n-hexane. The n-hexane layer is dried and evaporated under reduced pressure. The residue from soil... 

The plant sample in lane 6 is also positive for the transgene of interest. Because the band for the effect gene (middle band) is typically fainter than the band for the selectable marker gene (bottom band), it appears that for lane 6, the PCR product amplitication for the effect gene is below the assay detection threshold. Because the selectable marker is clearly present and the PCR amplitication worked, lane 6 can be interpreted as a positive result for the transgene of interest. 

The residues R) of famoxadone in all plant samples, expressed in mgkg are calculated using an external standard with one-point calibration according to the following equations ... 

Weigh 20 g (fresh weight) of chopped and homogenized plant samples into a 300-mL Erlenmeyer flask. Add 80 mL of acetone and shake the flask vigorously for 30 min with a shaker. In the case of brown rice and pea, add 20 mL of water to 10 g of sample and allow to stand for 2 h before adding 80 mL of acetone. Filter the extraction mixture by suction through a glass filter and re-extract the residue on the filter with 50 mL of acetone, then filter the mixture by suction. Concentrate the combined filtrate in the 300-mL of round-bottom flask to remove acetone at below 30 °C after addition of a 25% aqueous solution of potassium carbonate (0.2 mL). 

Plant samples are homogenized with sodium hydrogencarbonate aqueous solution to prevent decomposition of the analytes during homogenization. Imibenconazole and its primary metabolite, imibenconazole-debenzyl, are extracted from plan materials and soil with methanol. After evaporation of methanol from the extracts, the residues are extracted with dichloromethane from the residual aqueous solution. The dichloromethane phase is cleaned up on Florisil and Cig columns. Imibenconazole and imibenconazole-debenzyl are determined by gas chromatography/nitrogen-phosphorus detection (GC/NPD). 

Plant samples (1000 g) are homogenized using a blender with 10% aqueous sodium hydrogencarbonate solution (400 mL). The pH of the homogenates must be adjusted to 6-8 with saturated aqueous sodium hydrogencarbonate solution in this step. 

Plant samples except for rice grain and rice straw... 

Untreated control samples were fortified with mepronil. The fortification levels were 0.05-0.25 mg kg for plant materials and 0.005-0.05 mg kg for soil. The following recoveries were obtained 93-95% from rice grain 93-99% from rice straw 86-96% from grape 99-103% from leek 90-110% from lettuce 96-106% from sugar beet (root) 92-100% from sugar beet (leaf) 91-96% from kidney beans 96-100% from string beans and 86-98% from soil. The limit of detection is 0.005 mg kg for plant samples, except for rice straw and soil materials, and 0.01 mg kg for rice straw. 

Plant material should be added to a disk mill (grain or seed matrices) or a vertical batch processor (all other matrices). Add an equal portion of pelletized dry-ice to the sample (vertical processor only). Macerate the plant sample (or sample -I- dry-ice) until a homogeneous mixture is obtained. Soil samples should be well mixed or... 

The residue definition for plant samples is acetamiprid only. In soil, it includes acetamiprid and three of its... 

For plant materials. Weigh 50 g of the plant sample into a 500-mL Erlenmeyer flask, add 10 g of Celite and extract with 60 mL of the distilled water and 200 mL of acetone (the calculated acetone water ratio remains constant at 2 1, v/v). Filter the extract by suction through a Buchner funnel. 

A 50-g amount (in the case of powder tea, 25 g) of each minced and homogenized plant sample is weighed into a 500-mL flask with a ground stopper and 100 mL of water are added. After standing for 2 h, 150 mL of acetone are added and the flask is vigorously shaken with a shaker for 30 min. The mixture is Altered by suction through a Alter paper with a layer of diatomaceous earth 1-cm deep. The residue on the filter paper is returned to the flask and re-extracted with 100 mL of acetone by shaking for 10 min and the mixture is filtered. The combined filtrate in the round-bottom flask is concentrated to less than 100 mL under reduced pressure below 40 °C. 

The plant samples are prepared prior to analysis as follows. 

A 50-g homogenized plant sample is weighed into a centrifuge tube and blended at 7000 rpm with 100 mL of methanol-water (7 3, v/v) for 10 min. The resulting mixture is centrifuged at 5000 rpm for 5 min. The supernatant is collected in a 200-mL volumetric flask with suction. In the case of strawberry and peach, the supernatant is filtered through a glass filter (17G-3) previously packed with 10 g of Celite 545. The residue is re-extracted with 50 mL of the same aqueous methanol in the same manner as described above, and the supernatant is collected in a 200-mL volumetric flask. The volumetric flask is filled to the mark with the same aqueous methanol. 

The latter problems are of particular interest to chemists, who should devise appropriate methods for resolving the complexity of chemicals, properly identifying them and finally determining their exact composition and makeup. The participation of chemists is needed to verify the concept of allelopathy as a concentration-dependent phenomenon. They should help to reconstitute the chemical composition as it was found in the original and isolated plant samples. This systematic approach leads to verification of the concept as well as to proper assessment of the initial observation with crude extracts, and to final application to the field situation. Once the concept is proven, same simulation experiments need to be performed to maximize the allelopathic effect (toxin action). The concentration of the toxic chemicals is varied to where the threshold levels of chemicals prove to be involved in the exhibition of allelopathy under field conditions. 

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