Semiquantitative assays

Glutathione semiquantitative assay in small volume of samples 157... 

For a semiquantitative assay, cut each dot and put it into separate test tubes. Perform the enzymatic reaction with TMB substrate, stop with sulfuric acid and read O.D. at 450 nm. (This procedure is similar to an EIA on microtiter plates.)... 

The diagnosis of G6PD deficiency is made by quantitative or semiquantitative assay. The methods used are based on the normal function of the G6PD enzyme in catalyzing the initial step in the pentose phosphate pathway (PPP). Screening tests depend on the inability of cells from deficient subjects to convert an oxidized substrate to a reduced state. The substrates... 

When drugs of abuse or other banned substances are determined, a two-step procedure is often used. In the first step, specimens are tested by a semiquantitative assay specimens determined positive in this step are examined by a confirmatory, quantitative assay in a second step. The second method is generally based on a... 

A number of semiquantitative assays for screening for increased UAE are available. These test strips, most of which are optimized to read positive at a predetermined albumin concentration, have been recommended for screening programs. In view of the wide variability in UAE, it must be borne in mind that a "normal value does not rule out renal disease. Because these assays measure albumin concentration, dilute urine may yield a false-negative test result. Refrigerated urine samples should be allowed to reach at least 10 °C before analysis. Albu Screen and Albu Sure (Cambridge Life Sci-... 

Quantitative (or at least semiquantitative) assays for the intermediates and product are useful for following the impact of reactions and operations throughout the processing. Often in-process assays can be used. 

Whatman No. 1 lilter papers (150 mm diameter) were treated with 1 mL of either a standard sample of PBO or the same PBO containing the Tinuvin 292. One set of control and treated papers were subjeeted to UV light for 20 hours and another set to alternating sunlight and UV. Semiquantitative assays were performed by solvent extraction of the papers and analysis of the extracts by... 

There are various ways to derive a calibration curve. Multi-point calibration curves, for example, include a minimum of three different concentrations of the analyte. For semiquantitative assays, a single-point calibration is common. The single point is usually the threshold concentration used to determine whether a specimen is positive or negative for the analyte of interest. Depending on the validation process and performance characteristics of the assay, a single-point calibration curve may also be used in quantitative applications over a limited range of linearity. A historical (pre-established) multi-point calibration curve may also be used, but only if the stability of the analytical method over time has been well established (Goldberger et al., 1997). 

The capacitance measurement technique applied to the antibody-coated sensor in our model system yielded a sensitivity to atrazine concentrations over the ppb to sub-ppb range. The immunoassay standard curve showed that the sensor is capable of the resolution needed for a semiquantitative assay [39]. Scatter in the data is sufficiently small to allow for a positive or negative result within... 

It is important to note that antimicrobial and biofilm resistance are two different characteristics though some materials show both properties at the same time. Antimicrobial materials do not automatically prevent biofilm formation and vice versa. Antimicrobial surfaces could kill bacteria on contact but if dead bacteria cell debris blocks the active biocidal surface, biofilm formation could eventually occur. For example, quaternary anunonium polymers can effectively kill bacteria but when the surface is fouled with dead bacteria debris, biofilm formation is inevitable [188]. Materials with antibiofilm properties will repel the bacterial adhesion very effectively but may not kill the bacteria when they do colonize the surface. PEG surfaces are well known to repel bacteria adhesion. However, PEG surfaces show little antimicrobial activity. Quantitative antibiofilm efficacy tests can be divided into two categories static (minimum biofilm eradication concentration assay, MBEC) and dynamic (flow cell assay). In addition, SEM is a semiquantitative assay, which is discussed in Section 2.5. 

Lang et al. (1992) stated that although TLC has value as an inexpensive qualitative and semiquantitative assay for vitamin E, HPLC or GC is more suitable for quantitative analysis. However, given proper sample preparation, TLC is suitable for all sample types and for separating tocopherol and tocotrienol homologs. Although one-dimensional systems are usually satisfactory, additional resolution can be achieved by developing in a second direction. Quantification can be done by in situ densitometry. TLC is also useful for sample cleanup prior to other quantitative procedures such as GC or HPLC. 

One modification of the guaiac test was the use of crystalline guaiaconic acid, prepared from the resin. Von Euler and Bolin (136) made the oxidation of this acid the basis of a semiquantitative assay, but their method does not give accurate data. 

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