Rice straw

Potential resources of xylans are by-products produced in forestry and the pulp and paper industries (forest chips, wood meal and shavings), where GX and AGX comprise 25-35% of the biomass as well as annual crops (straw, stalks, husk, hulls, bran, etc.), which consist of 25-50% AX, AGX, GAX, and CHX [4]. New results were reported for xylans isolated from flax fiber [16,68], abaca fiber [69], wheat straw [70,71], sugar beet pulp [21,72], sugarcane bagasse [73], rice straw [74], wheat bran [35,75], and jute bast fiber [18]. Recently, about 39% hemicelluloses were extracted from vetiver grasses [76]. 

Homogenizing and milling for brown rice and rice straw samples must be carried out while freezing with dry-ice. During evaporation of organic solvents, the temperature of the water-bath should be kept at 40 °C or lower. 

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. 

To the flasks for the crop and soil samples (Section 6.1), add 2mL of 0.01 M Tris-HCl buffer solution (pH 7.7) and 50 and 100 qL of 1M Tris-HCl buffer solution for wheat grain, bariey grain and rice straw, and for soil, respectively. Adjust the pH to about 7.7 (confirm the pH with a pH test paper using the sample of untreated area). Homogenize the residue with ultrasonication and transfer the homogenate to the top of an ion-exchange column. Wash the flask twice with 2mL of 0.01 M Tris-HCl buffer solution and transfer the washings to the column. Elute the column with 40 mL of the same buffer solution. Discard this eluate. 

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. 

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. 

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. ... 

Brown rice, wheat and bean. Several analytical procedures have been developed for rice grain. In the case of rice straw, finely cut samples are added to water and allowed to stand for 2 h, then extracted with acetone. Unpolished rice grain samples are milled with an ultracentrifuge mill and sieved through a 42-mesh screen prior to extraction. 

With a fortification level of 5.00mgkg the average recovery of flutolanil and the metabolites from untreated rice straw is 80%. 

Rice (rice grain, rice straw), leek, lettuce, sugar beet (root), sugar beet (leaf), kidney beans, string beans and soil Gas-chromatographic determination... 

Mepronil in plant materials is extracted with aqueous acetone. Rice straw sample is extracted with aqueous methanol. Soil samples are refluxed with alkaline methanol. After filtration, the solvent is removed by evaporation under reduced pressure and... 

Weigh 10 g of the sample into a 500-mL Erlenmeyer flask and add 120 mL of water-acetone (1 9, v/v). Sonicate the mixture for 30 min. Carry out the subsequent procedures in a same manner as for 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. 

Citrus, cotton, melon, watermelon, banana, tomato, eggplant, onion, cabbage, carrot, chicory, leek, maize, hazelnut, potato, rice (straw, grain), air, sweet corn, soybean, French bean, sugar beet, flowers and ornamentals, sunflower, tobacco, soil and water... 

Weigh 50 g of the ground hulled rice, citrus flesh, or tomato sample (20 g citrus peel or rice straw) into a 500-mL Erlenmeyer flask and extract with 250 mL of acetone (or methanol for rice straw) by shaking for 1 h. Filter by suction and collect the extract in a 500-mL round-bottom flask. Wash the cake with 100 mL of acetone (or methanol for rice straw) and filter off. Combine the filtrates and concentrate to around 2 mL at 40 °C with a rotary evaporator. 

With a fortification level of l-2mgkg recoveries of buprofezin from untreated hulled rice, rice straw, tomato, citrus flesh and citrus peel samples are 85, 97, 93, 87 and 75%, respectively. 

The limits of detection of buprofezin and /t-OH-buprofezin are 0.005 mg kg for hulled rice, tomato and citrus flesh and 0.01 mg kg for rice straw and citrus peel. 

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