SUMMARY OF ASL TEST METHODS

Transcription

1 SUMMARY OF ASL TEST METHODS 1. Determination of Macro and Micro Elements in Plant Tissue by Dual View Inductively Coupled Plasma Optical Emission Spectrometer This method describes multi-elemental determinations by ICP-OES using simultaneous optical systems and axial or radial viewing of the plasma. The instrument measures characteristic emission spectra by optical spectrometry. The sample is predigested and the mineral elements in the sample digest are efficiently ionized by the plasma formed with argon gas ionized in an applied radio frequency field. Each element has characteristic emission spectra when ionized. The spectra are dispersed by a grating spectrometer, and the intensities of the emission lines are monitored by photosensitive devices. Photo currents from the photosensitive devices are processed and controlled by a computer system allowing effective multi-element determination. The following analytes have been determined by this method: Al, Ca, Cu, Fe, Mg, Mn. Mo. P. K. Na. S, Zn. (For details, refer to QM-AD002-AP01 - Determination of Macro and Micro Elements in Plant Tissue by Dual View Inductively Coupled Plasma Optical Emission Spectrometer. ASL Quality Management System. IRRI-GQNC.) 2. Total Kjeldahl Nitrogen Determination This method determines the total Kjeldahl Nitrogen (TKN) in plants or soils by digesting the sample in an acid and catalyst mixture at high temperature (about 380 C) to decompose and convert the various organic nitrogen forms to ammonium ion (NH 4 + ). The ammonium formed is then determined colorimetrically in a Technicon AutoAnalyzer II (TAA) via the Berthelot reaction which converts the ammonia to an emerald green complex whose intensity is measured at 660 nm. The TKN content of the sample is reported as %N with two decimal places. (For details, refer to QM-AD002-AP04 - Total Kjeldahl Nitrogen Determination. ASL Quality Management System. IRRI-GQNC.) 3. Crude Silica Determination by Gravimetric Method The plant material sample is digested with 1:10 HClO 4 :HNO 3 acid mixture to decompose the organic matter. The remaining residue after digestion is then filtered and collected in an ashless filter paper. The filter paper is placed in a beaker and ignited in a furnace at 490 C for 4-5 hours. The ash is weighed as crude silica. (For details, refer to QM-AD002-AP05 - Crude Silica Determination by Gravimetric Method. ASL Quality Management System. IRRI-GQNC.) 1

2 4. Determination of Plant Boron by Inductively Coupled Plasma Optical Emission Spectrometry A weighed plant material sample (250 mg) is first converted to ash and then extracted with 10 ml of 0.5N HCl solution by shaking for 30 minutes. It is then filtrated thru #40 filter paper. The filtrate is transferred into test tubes for ICP-OES analysis. (For details, refer to QM-AD002-AP06 - Determination of Plant Boron by Inductively Coupled Plasma Optical Emission Spectrometry. ASL Quality Management System. IRRI- GQNC.) 5. Determination of Cadmium in Rice Grain and Straw by Graphite Furnace Atomic Absorption Spectrometry The weighed rice sample (~0.5g) is digested with concentrated nitric acid and analysis of Cd is done by Graphite Furnace Atomic Absorption Spectrometry (GF- AAS). The low level Cd concentration in rice grain or straw requires the use of the more sensitive GF-AAS. (For details, refer to QM-AD002-AP032 - Determination of Cadmium in Rice Grain and Straw by Graphite Furnace Atomic Absorption Spectrometry (GF-AAS). ASL Quality Management System. IRRI-GQNC.) 6. Total Nitrogen and Total Carbon Analysis by Combustion Method This analytical method quantitatively determines the total amount of nitrogen and carbon present in all forms in soil, botanical and miscellaneous materials using a dynamic combustion system coupled with a gas chromatograph equipped with a thermal conductivity detector (GC-TCD). The test method is based on the instantaneous oxidation of the sample by flash combustion and subsequent reduction of oxides of nitrogen which convert all organic and inorganic substances into N 2 and CO 2 which are then analyzed by GC-TCD. The Analyzer System is fully controlled through a dedicated computer system. The method is applicable for the determination of total Nitrogen (TN) and total Carbon (TC) which are reported as percentage (%) with two decimal places. (For details, refer to QM-AD002-AP07 - Total Nitrogen and Total Carbon Analysis by Combustion Method. ASL Quality Management System. IRRI-GQNC.) 7. N-15 and C-13 Analysis by Flash Combustion and Gas Chromatography- Isotope Ratio Mass Spectrometry This analytical method quantitatively determines the stable isotopes N-15 and C-13 in plant and soil samples. The technique involves the coupling of flash combustion with a gas chromatograph and isotope ratio mass spectrometer (GC-C-IRMS). Sample materials are subjected to flash combustion oxidation and reduction system which 2

3 converts all organic and inorganic substances into N 2 and CO 2 which are then analyzed by GC-IRMS where the gas stream passes into a gas chromatograph where components of interest are separated and fed into a mass spectrometer. In the mass spectrometer, the sample gas molecules are ionized, passed through an ion-mass deflecting system and finally detected according to ion-mass ratio. The following analytes have been determined by this method: Total Nitrogen (%), Total Carbon (%), 15 N Atom%, and 13 C Delta per mill. (For details, refer to QM-AD002-AP08 - N-15 and C-13 Analysis by Flash Combustion and Gas Chromatography-Isotope Ratio Mass Spectrometry. ASL Quality Management System. IRRI-GQNC.) 8. Soil ph Measurement by the Electrometric Method This method is designed primarily for the determination of soil ph, but it applies equally well for the ph determination of any aqueous solutions or waters. Soil ph is a measure of the relative acidity or alkalinity of the soil solution that is in equilibrium with the solid particles. Soil ph is measured electrometrically in a saturated paste or a supernatant liquid that is in equilibrium with a soil suspension of a certain ratio of soil-to-liquid mixture. ASL s default method is to use a 1:1 ratio and deionized water as the suspending liquid unless requested otherwise to use an electrolyte (1 M KCl or 0.01 M CaCl 2 ) by the customer. The electrometric measurement of ph is done using a glass electrode-calomel electrode system and is based on measuring the difference in electrical potential between solution and electrode. ph value is reported with one decimal place. (For details, refer to QM-AD002-AP09 - Soil ph Measurement by the Electrometric Method. ASL Quality Management System. IRRI- GQNC.) 9. Soil Particle Size Analysis (Hydrometer Method) Settling rates of primary particles are based on the principle of sedimentation as described by Stokes Law and measured using a hydrometer. The use of the ASTM 152H-Type hydrometer is based on a standard temperature of 20 C and a particle density of 2.65 g/cm 3 and units are expressed as grams of soil per liter. Corrections for temperature and for solution viscosity are made by taking a hydrometer reading of a blank solution. Generally this method is of lower precision than the pipette or sedimentation methods and is used to determine soil texture. The method has a detection limit of 2.0% sand, silt and clay (dry basis) and is generally reproducible to within ± 8%. (For details, refer to QM-AD002-AP010 - Soil Particle size Analysis (Hydrometer Method). ASL Quality Management System. IRRI- GQNC.) 10. Soil Particle Size Analysis (Pipette Method) 3

4 This method quantitatively determines the physical proportions of three sizes of primary soil particles as determined by their settling rates in an aqueous solution using a pipette. Proportions are represented by stated class sizes: sand ranging from um; silt ranging from um and clay < 2.0 um and those stated by the USDA Soil Survey and Canadian Soil Survey Committee. Generally this method is more precise than the hydrometer method. The method has a detection limit of 0.2% sand, silt and clay (dry basis) and is generally reproducible to within ± 5%. (For details, refer to QM-AD002-AP011 - Soil Particle size Analysis (Pipette Method). ASL Quality Management System. IRRI- GQNC.) 11. Available P Analysis (Olsen Method) This method estimates the relative bioavailability of ortho-phosphate (PO 4 -P) in soils by extraction using alkaline sodium bicarbonate (ph 8.5) solution and determining the P concentration in the extract spectrophotometrically using a Technicon AutoAnalyzer II.. Results are reported as parts per million (ppm) phosphorus (P) in the soil. It is applicable to soils that are mildly acidic to alkaline ph and is based on the method developed by Olsen et al., (1954) to correlate crop response to fertilizer on calcareous soils. (For details, refer to QM-AD002-AP12- Available P Analysis (Olsen Method). ASL Quality Management System. IRRI-GQNC.) 12. Determination of Available Phosphorus (Bray P-2) in Soil The soil phosphorus measured is that which is extracted by a solution consisting of 0.1 N HCl and 0.03 N NH 4 F, referred to as Bray P-2 extractant. The amount of phosphorus extracted is determined colorimetrically (630 nm) as phosphomolybdenum blue with ascorbic acid as the reducing agent and Sb added to give a stable Mo- P-Sb compound (Murphy and Riley 1962). In the original Bray and Kurtz method, SnCl 2 was used as a reductant. The Bray P method is used for acidic soils (ph< 6.8), in contrast to the Olsen P method which is used for alkaline soils. (For details, refer to QM-AD002-AP13 - Determination of Available Phosphorus (Bray P-2) in Soil. ASL Quality Management System IRRI-GQNC.) 13. Estimation of Soluble Salts in Soils by Electrical Conductivity Measurement This SOP describes the estimation of soluble salts in soil extracts by electrical conductivity measurement. The term soluble salts, as applied to soils, refers to major dissolved inorganic solutes. Of the soluble anions, sulfates and chlorides predominate, while the cations involved are usually calcium, magnesium, potassium 4

5 and sodium. The extract is obtained by centrifuging the 1:1 soil:water mixture (weight to volume) after shaking it in an automatic shaker for 30 minute. The electrical conductivity of the supernatant is measured using Horiba conductivity meter ES - 12 which is equipped with temperature compensation. The result is reported as microsiemens per centimeter (µs/cm) at 25 C. If needed, cations and anions are also determined. (For details, refer to QM-AD002-AP 14 - Estimation of Soluble Salts in Soils by Electrical Conductivity Measurement. ASL Quality Management System, IRRI-GQNC.) 14. Available Potassium (K) in Soil by Ammonium Acetate Extraction and Flame Emission Spectrometry This procedure describes the determination of available K in soil samples by extraction with a neutral 1N ammonium acetate solution and analytical determination by flame emission spectrometry. The procedure is a measure of soil solution K +, most of the exchangeable K, and small, but varying, proportions of fixed or structural K. The measurement of extractable K from a soil treated in this manner can be expected to serve only as an index to plant available K. (For details, refer to QM-AD002-AP 15 - Available Potassium (K) in Soil by Ammonium Acetate Extraction and Flame Emission Spectrometry. ASL Quality Management System. IRRI-GQNC.) 15. Organic Carbon Determination (Walkley and Black Method) This method quantifies the amount of oxidizable soil carbon as determined by reaction with K 2 Cr 2 O 7 and H 2 SO 4. On the completion of the reaction, the organic carbon may be determined by directly measuring spectrophotometrically the amount of green chromium sulfate produced during the reaction. The dilution heat of the concentrated sulfuric acid is the sole source of heat. Since there is no external heat applied, the method provides only an estimate of readily oxidizable organic carbon. (For details, refer to QM-AD002-AP16 - Organic Carbon Determination (Walkley and Black Method). ASL Quality Management System IRRI-GQNC.) 16. Determination of Active Iron and Manganese by Inductively Coupled Plasma Optical Emission Spectrometry This procedure applies to the determination of active or free oxide forms of iron and manganese in soil sample through soil extraction with sodium dithionite to reduce and remove Fe and Mn in the soil. Adding EDTA forms complexes with Fe and Mn in soil. After letting it stand in a water bath for 20 min, the mixture is filtered into a 250 5

6 ml volumetric flask using fluted filter paper. The extract is transferred to a 15 ml test tube for the analysis of Fe and/or Mn by ICP-OES. The results are reported in %. This method is an adaptation of the method of Asami and Kumada (1959) for use with ICP-OES. (For details, refer to QM-AD002-AP 17 - Determination of Active Iron and Manganese by Inductively Coupled Plasma Optical Emission Spectrometry. ASL Quality Management System. IRRI-GQNC.) 17. Determination of Available Copper and Zinc in Soil by Flame Atomic Absorption Spectrometry (FAAS) This SOP describes the procedure for the determination of available copper and zinc in soil sample by extraction with hydrochloric acid and FAAS analysis. The extraction method using 0.05 M HCl is based on the study correlating available copper and zinc with copper and zinc deficiency in wetland rice made by Ponnamperuma, et al., (1981). Available Copper Cu) and Zinc (Zn) in soils are determined by treating a 10 gram fine air dried soil with 20 g of 0.05 N hydrochloric acid. After shaking for 30 minutes, the soil is filtered using Whatman No. 42 and the extract analyzed by atomic absorption spectrometry. (For details, refer to QM- AD002-AP 18 - Determination of Available Copper and Zinc in Soil by Flame Atomic Absorption Spectrometry (FAAS). ASL Quality Management System. IRRI- GQNC.) 18. Determination of Exchangeable Bases in Soil (Ammonium Acetate Extraction) by Flame Atomic Absorption and Flame Emission Spectrometry This method describes the determination of exchangeable bases such as calcium, magnesium, sodium and potassium extracted from soil by leaching with ammonium acetate solution and analyzing the individual cation in the leachate by flame atomic absorption (FAAS) and flame emission spectrometry (FES). The exchangeable bases determination is used for the assessment of soil fertility and is part of the determination of the cation exchange capacity. (For details, refer to QM-AD002-AP 19 - Determination of Exchangeable Bases in Soil (Ammonium Acetate Extraction) by Flame Atomic Absorption and Flame Emission Spectrometry. ASL Quality Management System IRRI-GQNC.) 6

7 19. Determination of Cation Exchange Capacity (CEC) of Soils This method determines the cation exchange capacity (CEC) of the soil by leaching a test portion of the soil sample with a neutral 1 M ammonium acetate solution of ph=7. The ammonium acetate leachate contains the exchangeable cations Ca, Mg, K, and Na which are determined by ICP-AES or AAS thru a separate method (see QM- AD002-AP19). The total amount of ammonium retained by the soil is regarded as an estimate of the cation exchange capacity. The adsorbed ammonium is released by leaching with an acidified potassium chloride solution and analyzed spectrophotometrically using a Technicon AutoAnalyzer II. (For details, refer to QM- AD002-AP 20 - Determination of Cation Exchange Capacity (CEC) of Soils. ASL Quality Management System. IRRI-GQNC.). 20. Determination of NH 4 - and NO 3 -Nitrogen in Water, Wastewater, Soil Extracts and other Aqueous Samples This procedure is designed to determine simultaneously ammonium-n and nitrate N in aqueous samples such as water, wastewater, soil extracts by colorimetric method in an automatic auto-analyzer equipped with separate colorimeters. The sample is fed into two separate channels where one channel converts NH 4 -N into a colored bluegreen complex via the Berthelot reaction and analyzed at 660 nm, while the other channel converts NO 3 -N into a pink colored compound and analyzed at 520 nm. (For details, refer to QM-AD002-AP 23 - Determination of NH and NO 3 -Nitrogen in Water, Wastewater, Soil Extracts and other Aqueous Samples. ASL Quality Management System. IRRI-GQNC.) 21. Determination of Exchangeable Aluminum (Al 3+ ) and Acidity (H + ) (Titration Method) A 10.0 g of 2mm air-dried soil sample is extracted with 1 N KCl solution using a Spectra mesh vacuum manifold. The extract is then titrated with a standard 0.1 N NaOH to determine the exchangeable acidity with phenolphthalein as indicator. NaF is added in the first end point to release the hydroxyl-al and titrated with standard 0.1 N HCl to a second end point for the exchangeable aluminum. (For details, refer to QM-AD002-AP 21 - Determination of Exchangeable Aluminum (Al 3+ ) and Acidity (H + ) (Titration Method). ASL Quality Management System. IRRI-GQNC.) 7

8 22. Determination of Trace elements in water by Inductively Coupled Plasma Optical Emission Spectrometry Samples can be directly analyzed without any digestion if it is in aqueous form. Filtration could be done if suspended particles are present. This method describes multi-elemental determinations by ICP-OES using simultaneous optical systems and axial or radial viewing of the plasma. The instrument measures characteristic emission spectra by optical spectrometry. Samples and standards are nebulized and the resulting aerosol is transported by Argon carrier gas to the plasma torch. Element specific emission spectra are produced by radio frequency inductively coupled plasma. The spectra are dispersed by a grating spectrometer, and the intensities of the emission lines are monitored by photosensitive devices. Photo currents from the photosensitive device are processed and controlled by a computer system. (For details, refer to QM-AD002-AP 22 - Determination of Trace elements in water by ICP-OES). ASL Quality Management System. IRRI- GQNC.) 23. Determination of Water-soluble Boron in Soils by Inductively Coupled Plasma Optical Emission Spectrometry Hot water-soluble boron is extracted from the soil by heating in the microwave oven. The boron in the filtered extract is determined using inductively coupled argon plasma-atomic emission spectroscopy. (For details, refer to QM-AD002-AP 25 - Determination of Trace elements in water by ICP-OES). ASL Quality Management System. IRRI-GQNC.) 24. Determination of Total N in Aqueous Samples The organic and inorganic nitrogen in aqueous sample is mixed with the oxidant K 2 S 2 O 8 and is reacted in the presence of ultra violet radiation to convert it to nitrate. The nitrate (NO 3 - ) is reduced to nitrite (NO 2 - ) by reaction with hydrazinsulfate and copper sulfate in an alkaline solution. The NO 2 - ions are detected by reaction with sulfanilamide and N-(1-Naphtyl) ethylendiamine hydrochloride in acidic solution to form a violet diazo dye. The absorbance of this dye is then measured in a flow cell at a wavelength of 540 nm. (For details, refer to QM-AD002-AP 27 - Determination of Total N in Aqueous Samples. ASL Quality Management System. IRRI-GQNC.) 8