Screening test kits

Obtain calibrated field instruments and screening test kits... 

Because of the less than satisfactory results obtained in the first study of the Agri-screen test kit when used with peanut products and corn, a second collaborative study was run. In this second study of the Neogen kit, twelve coded test samples of raw and roasted peanuts and corn, with blind replicates, were analyzed by fourteen laboratories. The determination was slightly modified in that tetramethylbenzidine was used instead of ABTS as substrate for color development, and the analysts were instructed to compare color intensity with standards of varying concentration when using visual estimation. The results of this study are shown In Table III (9). 

Screening test kits - enzyme linked immuno-sorbent assay (ELISA)... 

Two types of kits are discussed in this section, sample collection kits and field test kits. Sample collection kits will generally contain all sample containers, materials, supplies, and forms necessary to perform sample collection activities. Field test kits contain the equipment and supplies necessary to perform field safety screening and rapid field testing of the air, water, and/or soil. Sample collection kits will generally be less expensive to construct than field test kits. Sample collection kits can be pre-positioned throughout a system, while the more expensive field kits may be assigned to specific site characterization teams or personnel. 

A number of different testing kits based on immunoassay technology are available for rapid field determination of certain groups of compounds, such as benzene-toluene-ethylbenzene-xylene (EPA 4030) or polynuclear aromatic hydrocarbons (EPA 4035, Polycyclic Aromatic Hydrocarbons by Immunoassay). The immunoassay screening kits are self-contained portable field kits that include components for sample preparation, instrumentation to read assay results, and immunoassay reagents. 

Screening tests for PBG are based on its reaction with DMAB (modified Ehrlichs reaction ). We recommend the trace PBG test kit available from Thermo Electron (UK), which isolates PBG from urine by ion-exchange resin before the reaction with DMAB. Older screening methods, such as those of Schwartz or Hoesch, give false-positive results due to the reaction of DMAB with urea, which is abundant in urine. 

Polynuclear aromatic hydrocarbons (PAH) are aromatic compounds that contain two or more benzene rings fused together. These substances may be analyzed by HPLC, GC, GC/MS and enzyme immunoassay techniques. The latter is a rapid screening method that may be applied for a qualitative or semiquanti-tative determination Test kits are commercially available for such screening. U.S. EPA (1995) has specified a method (Draft Method 4035) that detects a range of PAHs to different degrees and measures the composite of individual responses to determine the total PAHs in the sample. 

PCBs in soils and wastewaters can be rapidly screened on site or in the laboratory by immunoassay technique (Chapter 1.13). Immunoassay test kits are now commercially available from many suppliers. The samples can be tested at the calibration levels of 1 to 50 ppm. The kit primarily contains antibody-coated test tubes or magnetic particles, assay diluent, PCB-enzyme conjugate, a color-forming substance, and a solution to quench the reaction. The method does not distinguish accurately one Aroclor from another. PCBs can be measured semiquantitatively by comparing the optical density of the color formed in the sample against a set of calibration standards using a spectrophotometer. 

The measurements of water quality parameters (oxidation-reduction potential, pH, temperature, conductivity, dissolved oxygen, and turbidity) and the collection of field screening data with field portable instruments and test kits constitute a substantial portion of field work. Field measurements, such as pH, stand on their own as definitive data used for the calculations of solubility of chemical species and chemical equilibrium in water, whereas others serve as indicators of well stabilization or guide our decision-making in the field. Table 3.8 shows the diversity of field measurement... 

In addition to test kits used in EPA-approved screening methods, a variety of other test kits are available from several manufacturers, for example, immunoassay test kits for BTEX in soil and water and for chlorinated solvents in water colorimetric kits for the detection of lead kits for a wide range of water quality parameter manufactured by Hach Company. 

Reybroeck, W., S. Ooghe, H.D. Brabander, et al. 2007. Validation of the tetrasensor honey test kit for the screening of tetracyclines in honey. J. Agric. Food Chem. 55 8359-8366. 

Note. In emergencies, especially involving young children, die serum sample may be aspirated directly into die flame to give an indication of intoxication. A screening test for ferrous and ferric iron is given on p. 5. Commercial kits for the assay of iron in serum are available (see Reagent Appendix). 

On occasion, iodinations are not performed by the user. The talc-resin-TCA test is a simple technique for validating the suitability of I-labeled hormones obtained commercially, which often are expensive. As only the equivalent of three assay tubes of iodohormone are required for this simple screening test, it is not unreasonable to check the quality of every batch of commercially labeled material before its use, including io-dohormones supplied with RIA kits. 

A third collaborative study (10) was conducted examining the Immuno Dot Screen Cup (Afla-20, IDS Cup), a test kit containing antibodies with considerable cross reactivity with aflatoxins B2 and G,. The manufacturer s procedure was also modified to increase the reliability of detection at 20 ng/g total aflatoxins, and to broaden the applicability to include peanut butter samples. 

Use HiTrap Ion Exchange and HiTrap HIC Test Kits for media screening and simple method optimisation. 

The intermediate purification step was developed by screening pre-packed hydrophobic interaction media (RESOURCE HIC Test Kit) to select the optimum medium for the separation (results not shown). RESOURCE ISO was selected on the basis of the resolution achieved. In this intermediatestep, shown in Figure 15, the maximum possible speed for separation was sacrificed in order to achieve higher resolution and allow significant reduction of remaining impurities. 

Hydrophobic properties are difficult to predict and it is always recommended to screen different media. A HiTrap HIC Test Kit (containing five 1 ml columns pre-packed with different media suitable for production scale) was used to screen for the most appropriate medium. Buffer pH was kept at pH 5.0 to further minimise the need for sample conditioning after capture. Results of the media screening are shown in Figure 20. 

To increase speed and efficiency in method development use small pre-packed columns for media scouting and method optimisation. HiTrap HIC Test Kit and RESOURCE HIC Test Kit are ideal for this work. Using pre-packed columns at any scale will ensure reproducible results and high performance. Figure 38 shows an example of media screening with HiTrap HIC Test Kit... 

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