Chemistry: analytical and immunological testing – Geochemical – geological – or geothermal exploration – For metallic ores
Reexamination Certificate
1994-08-10
2001-06-05
Bhat, Nina (Department: 1761)
Chemistry: analytical and immunological testing
Geochemical, geological, or geothermal exploration
For metallic ores
C436S028000, C436S171000, C436S178000, C422S067000, C210S263000, C210S638000
Reexamination Certificate
active
06242261
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to techniques for the measurement of available ions in various media such as water, soil and sediments or for the measurement of free ions in disrupted cells. The techniques are based on the immobilization of ions on the surface of ion-exchange material. Particularly, the invention relates to techniques useful for on-site assessment of either nutrient availability in soils or sediments or free inorganic ions in plant material.
BACKGROUND OF THE INVENTION
A good soil test is one which is simple, rapid and can remove all or a representative portion of the available nutrient pool in a wide variety of soil types. Few existing tests excel in both these requirements. Methodology which provides the best estimate of nutrient availability is often too complicated and cumbersome for routine labs making fertilizer recommendations to producers. Furthermore, many existing P, N, S and K tests do not take into account all factors affecting nutrient availability in soil. Some tests are specific to a region or soil type, performing poorly when transposed to other environments. For example, P and K tests which are based on chemical removal of specific P and K fractions are usually limited in geographic scope since the importance of a fraction may vary depending on the physical and chemical environment of the soil.
Anion-exchange resins are considered one of the better indices of plant available P. Cation-exchange resins have also been used for extraction of available K in soils. However, conventional resins in bead form are generally difficult to separate from soil and are not well-suited for routine analysis. Still, there are numerous prior art references teaching the use of ion-exchange resin beads to evaluate nutrient availability in soil samples.
In Brazilian Patent 8605998, nutrients are extracted from soil samples for analysis using capsules with at least two opposite fabric walls containing standard amounts of ion-exchange resins which are placed in a beaker with a sealed cover. Measured amounts of dry soil and a fixed amount of water are added in the beaker, placed on a special tray and agitated in a specially built machine by free tumbling. Beakers are taken to a washer-separator and washed with deionized water to remove soil and other particles. The capsules are then transferred to a clean beaker containing a solution of NaCl and HCl. The resulting solution contains the substances to be analyzed and the resin is regenerated by washing with successive solutions to remove cations and anions and restore its exchange capacity.
A technique of this type has at least two major drawbacks. Firstly, there is the necessity of bringing a soil sample to the laboratory and to dry such soil sample, a step which can require up to three days. Secondly, the use of resin beads is extremely impractical as it is very difficult to wash from the beads the soil that could have accumulated during agitation of the capsules containing the resin beads in the soil suspension. Also the bags are susceptible to fraying and rupture due to abrasion by the soil during shaking.
U.S. Pat. No. 4,816,161 relates to an ion extractor comprising a tube filled with cation or anion-exchange resin beads. It is used for extracting ions from streams, lakes and marine sediments. The resin beads are retained in a dialysis tube by support tubes which each have a screen of an appropriately-sized mesh attached to the interior ends by means of a suitable adhesive. Hence, when it is used, the extractor is placed in an aqueous suspension of the soil sample to be analyzed. Once the resin has been contacted with the soil suspension, it is eluted with acid in order to leach the exchange ion from the exchange sites and to return the resin to a homoionically saturated exchange state for subsequent reuse. The sample leachate is collected in tubes and analyzed to determine the concentrations of constituents of interest. Again, in this type of system, it is required to produce a soil suspension as direct contact between the soil and the ion-exchange resin beads is avoided.
U.S. Pat. No. 4,775,513 and re-issue 33,487 relate to a device for water treatment that uses a water-tight container of flexible material containing ion-exchange material. The ion-exchange material can be selected from silicates, clays and synthetic resin beads. The invention uses colorimetry to determine the exhaustion of the ion-exchange capacity of the resin beads. The container is filled with water and shaken to allow contact between the beads and the ions.
It is suggested to use the device described in U.S. Pat. No. 4,775,513 as a soil-testing device. However, the device is impractical as the chemicals to be tested for must first be extracted from the soil and it is necessary to filter the soil extract prior to submitting it to chemical analysis.
In Sibbesen (1977, Plant in Soil, 46:665-669), a method is described, whereby ion-exchange resin beads are sewn in nylon-netting bags which are used to extract available phosphate from a soil-water suspension.
Similarly, in Skogley et al. (1990, Communications in Soil Sciences and Plant Analysis, 21:1229-1243), the use of ion-exchange beads sewn-up in bags is reported as a test for P, K and S availability. In this procedure, soil samples are brought to the lab, water is added and a saturated paste is prepared by addition of water to the soil until it is completely saturated. As the authors note, saturated pastes are difficult to prepare uniformly and reproducibly. As well, the authors note that the test was only successful for K and S, amounts extracted were very small and difficult to measure and the extraction time required is 2 days or more. Added to the fact that the method is cumbersome and requires considerable amount of time, a special vacuum extractor instrument is required in the elution step.
In Yang et al. (1991, Soil Sci. Soc. Am. Journal, 55:1358-1365), the authors provide theoretical considerations of the testing approach outlined by Skogley et al. However, nothing is suggested to modify or improve the Skogley et al. technology.
In Saggar et al. (1990, Fertilizer Research, 24:173-180), the authors describe a simplified procedure for determining the amount of phosphate extracted from soils by using ion-exchange resin membranes in soil suspensions. Again, the procedure presents some of the drawbacks described previously.
In a paper entitled “Universal bioavailability of environment soil test” (International Symposium on Soil Testing and Plant Analysis, Aug. 22-27, 1991, Orlando, Fla.), E. O. Skogley describes research work in which anion and cation-exchange resins contained in nylon or polyester bags were buried in the face of soil pits for 6 months to study nutrient movement after an intense forest burn. As mentioned previously, there are problems in desorbing or stripping the nutrient ions of the resin beads contained in the bags. Furthermore, the bags do not work efficiently in the field as muddy soil debris often penetrate through the netting. Once inside the netting, the soil is very difficult to wash out. The washing step is extremely important as if the beads are not washed properly, the acid that is used in the elution will dissolve all of the P, S and N in the soil, not just the plant available ions on the resin, giving erroneous results. Another drawback of this type of method is the fact that soil debris are often found in the final eluent which interferes with the final analysis. Also, one of the reasons why very few papers have been published on the actual burial of resin beads in soil stems from the fact that the time period required to extract measurable amounts of nutrients from soil using beads ranges from at least 1 to 5 days and amounts to unrealistic values.
The potential of anion and cation-exchange membranes has been evaluated for routine soil-testing in laboratory environments. Essentially, the method consists of immersing the ion-exchange membrane in a water-soil suspension, washing the immersed membrane with water and diluting the membrane in an aci
Huang Weize
Schoenau Jeffrey John
Bhat Nina
Ratner & Prestia
University of Saskatchewan
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