Rice grains

In 1975 Wacker-Chemie introduced silicones under the name of m-polymers. These are also room temperature curing liquid polymers which give rubbery materials on cross-linking and are available both as one- and two-component systems. Their particular feature is that they contain dispersions of copolymers such as those of styrene and n-butyl acrylate in the shape of rods or rice grains in the fluid silicone polymer. A small amount of the organic copolymer is also grafted onto the silicone backbone. 

Starch is the principal carbohydrate reservoir in plants and is the major component of rice, grains, com, and potatoes. The long chains are sparingly soluble in water, so they collect in cells as granules. Starch is digested by a... 

The classical Chinese method consists of inoculating steamed rice grains spread on big trays with a strain of Monascus anka and incubating in an aerated and temperature-controlled room for 20 days. In these types of cultures, moisture content, oxygen, and carbon dioxide levels in the gas environment, as well as cereal medium composition, are the most important parameters to conhol. 

A 0.5-2-kg crop sample is cut into small pieces and homogenized thoroughly using a food processor. Rice grain is milled with an ultracentrifuge mill and sieved through a 42-mesh screen. The typical size of an analytical sample is less than 50 g. To prevent the decomposition of the anilide residues, crop samples should be frozen soon after collection and maintained frozen until analyzed. 

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. 

In Japan, bifenox is the only registered diphenyl ether herbicide. The tolerance and/or maximum residue limits (MRLs) are established at 0.1 mg kg for cereals such as rice grain, barley and wheat, and 0.05mgkg for potatoes (Ministry of Health, Labour and Welfare, Japan). Ibe California Department of Food and Agriculture (CDFA) established the minimum detectable quantity of diphenyl ether herbicides at 0.1 mgkg for bifenox, nitrofen and oxyfluorfen. ... 

Materials to be Rice (grain, straw), soil, water... 

Weigh the samples [strawberry, rice grain, 25 g wheat grain, barley grain, 10 g rice straw, 5 g soil (dry weight basis), 30 g] in round-bottom flasks of appropriate volumes (500- or 300-mL). For soil samples add 40mL of IN sulfuric acid and 120mL of acetone to the flask, and for other samples add 20 mL of 1 N sulfuric acid and 60 mL... 

Transfer the concentrated crop sample extract (strawberries, rice grain, barley grain and rice straw) into a 50-mL separatory funnel with a small volume of water. Extract the solution three times with 10 mL of a chloroform-methanol (3 1, v/v). Dry the chloroform-methanol layer with a small amount (about 8 g) of anhydrous sodium sulfate on a glass funnel and transfer the dried solution to a 100-mL separatory funnel. 

Extract the chloroform-methanol layer from the strawberry, rice grain, barley grain and rice straw samples twice with 30 mL of 0.1 M phosphate buffer solution (pH 7.0). Since an emulsion is formed, the first extraction should be conducted with very gentle shaking. Centrifuge the extract at 2500 rpm for 10 min, when an emulsion is formed. Discard the chloroform-methanol layer. 

Transfer crop and soil samples from Section 6.1 (strawberry and rice grain) and Section 6.2 with 5 mL of methanol to 30-mL test-tubes and add to each test-tube 0.05 mL of concentrated sulfuric acid. Attach a condenser and reflux the solution at 75 °C for 60 min to esterify prohexadione to its corresponding methyl ester. Cool the reaction mixture to room temperature, add 20 mL of water and extract the reaction solution twice with 20 mL of dichloromethane. Dry the dichloromethane layer with a small amount of anhydrous sodium sulfate and collect the dried solution in a 100-mL round-bottom flask. Evaporate the solvent under reduced pressure. 

Sample storage stability Prohexadione-calcium in strawberry, rice grain, rice straw, wheat grain and barley grain is stable at -20 °C for 40, 140, 60, 80 and 100 days, respectively. Approximately 88% of the applied prohexadione-calcium remained in soil when stored at —20 °C after 80 days. 

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... 

Collect 1 kg of rice grains and grind with a mill. Collect about 1 kg of rice straw and grind with a grinder. Soil, collected from the top 10-cm surface layer, is homogenized and passed through a 5-mm sieve. 

Weigh 5 g of the sample into a 500-mL round-bottom flask and add 50 mL of distilled water to swell the sample for 2h. Add 150mL of acetone and reflux the sample at 80 °C for 1 h after attaching a condenser. Conduct the subsequent procedures in a similar manner as for rice grains and concentrate the filtrates to approximately 50 mL. 

Liquid-liquid partition (rice grain, rice straw and soil)... 

Cartridge column chromatography (rice grain and rice straw)... 

Connect a Sep-Pak Plus NH2 column with a Sep-Pak Plus Silica column (place the silica column on the elution side). Condition the connected column with 5 mL of n-hexane. Dissolve the residue of rice grains and rice straw (Section 6.3.2) in a small volume of n-hexane and transfer the solution to the column. Elute with 6mL of n-hexane-ethyl acetate (9 1, v/v) and discard the eluate. Remove the NH2 column. Elute the Sep-Pak Plus Silica column with 15 mL of n-hexane-ethyl acetate (4 1, v/v) and collect the eluate in a 50-mL pear-shaped flask. 

Inject an aliquot (Vi) of the solution prepared from Section 6.3.2 (Vend) for soil and Section 6.3.3 (Vsna) for rice (grain, straw) into the gas chromatograph. 

The recoveries from control samples fortified with pyriminobac-methyl (for individual isomers) at levels of 0.1 mgkg were 96-106% for rice grains, 80-90% for rice straw and 77-92% for soil. The limit of detection was 0.005 mg kg for rice grains, 0.01 mgkg for rice straw and 0.005 mg kg for soil. 

Reflux extraction with acetone has been used for the analysis of rice grain and rice straw including metabolites, and showed good recoveries. ... 

Instrumentation Gas-chromatographic determination for rice grain, water and soil... 

Milled rice grain is soaked with water and allowed to stand at room temperature for 2 h. The soaked sample is mixed with acetone. The extract is Altered, the acetone in the extract is evaporated and the aqueous residue is transferred into a Cig cartridge. 

Mill the unpolished rice grain with an ultracentrifuge mill in the presence of dry-ice and sieve through a 42-mesh screen. 

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