Capillary assay

Eriksson H J, Somsen G W, Hinrichs W L, et al. (2001). Characterization of human placental alkaline phosphatase by activity and protein assays, capillary electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. /. Chromatog. B. 755 311-319. 

The application of molecular electronic spectroscopy as a detector for separations is expected to continue to grow. Optical techniques are a primary detection approach for the hybrid technique of capillary electrochromatography which combines aspects of CE and HPLC, especially capillary LC. To increase throughput of sample handling, arrays of capillaries have been built with optical detection via CCD cameras. Using CE-LIF approaches, hundreds of capillaries can operate simultaneously on samples with simultaneous detection. Further advances are expected in the areas of remote sensing, immunochemical assays, capillary arrays, and detector sensitivity. 

The most widely appHed colorimetric assay for amino acids rehes upon ninhydrin-mediated color formation (129). Fluorescamine [38183-12-9] and (9-phthalaldehyde [643-79-8] are popular as fluorescence reagents. The latter reagent, ia conjunction with 2-mercaptoethanol, is most often used ia post-column detection of amino acids separated by conventional automated amino acid analysis. More recently, determiaation by capillary 2one electrophoresis has been developed and it is possible to determine attomole quantities of amino acids (130). 

L-pyrenyldiazomethane to form stable, highly fluorescent L-pyrenyhnethyl monoesters (87). These esters have been analy2ed in human blood by ce combined with lif detection. To mimini e solute adsorption to the capillary wall, they were coated with polyacrjiamide, and hydroxypropyl methylceUulose and dimethylfoTTnamide were used as buffer additives to achieve reflable separations. Separation was performed in tris-citrate buffer, pH 6.4, under reversed polarity conditions. The assay was linear for semm MMA concentrations in the range of 0.1—200 p.mol/L. 

The assay of ethyleneamines is usually done by gas chromatography. Compared to packed columns, in which severe tailing is often encountered due to the high polarity of the ethyleneamines, capillary columns provide better component separation and quantification. Typically, amines can be analyzed using fused siUca capillary columns with dimethyl silicones, substituted dimethyl silicones or PEG Compound 20 M as the stationary phase (150). 

The major problems in assay of protein by CE are the low efficiency and reproducibility by presents of protein adsorption on the inner surface of a capillary, and poor concentration sensitivity UV-detection. 

The developed assay was successfully applied for the arsenite and arsenate determination in contaminated waters of the gold recovery plant and in snow covers of the industrial anthropogenic sources vicinities as well. The data produced are in a good agreement with the results of independent methods atomic absorptioin and atomic emission spectrometry and capillary electrophoresis. 

B. 3-Hydroxycinchoninic acid. A 3-1., four-necked flask (Note 1) is equipped with a sealed mechanical stirrer, gas inlet tube, gas outlet consisting of a 1-mm. capillary (Note 7), and thermometer. The flask is charged with a freshly prepared solution containing 448 g. (8 moles) of reagent grade (85% minimum assay) potassium hydroxide and 900 ml. of water. The solution (hot from dissolution of potassium hydroxide) is stirred and 147 g. (1 mole) of isatin (Note 8) is introduced. The solid quickly dissolves to give an orange-yellow solution. 

Purification of the radioactive tracer was modified to include a fractional sublimation before a single extraction—recrystallization cycle to conserve the tracer material. Microgram samples were prepared in melting point capillaries for assay by mass spectroscopic analysis (Table III), made by direct probe injection of the sample into the ion source (18). The probe was heated rapidly to 200°C, and mass spectra were obtained during vaporization of the sample. Tri-, tetra-, and pentachlorodibenzo-p-dioxins vaporized simultaneously with no observed fractionation. 

In figure 7 a procedure was described for aspirating a sample from a capillary tube and simultaneously adding zinc sulfate and barium hydroxide solutions in order to produce a Somogyi filtrate. Aliquots of the supernatant are suitable for assay for glucose and urea by various procedures. The reason for this is the fact that zinc hydroxide precipitates uric acid, creatinine and other substances, such as low molecular polypeptides, along with the proteins, so that there results a solution which is clear with relatively few components. 

Enzyme-Linked Immunoadsorbent Assay (NRL) Multiplexed Sandwich Fluoroimmunoassay (LLNL) Capillary Electrophoresis (LLNL)... 

Assays. Nitrogen assays to determine 1-amidoethylene unit content were done by Kjeldahl method. Limiting viscosity numbers were determined from 4 or more viscosity measurements made on a Cannon-Fenske capillary viscometer at 30°C. Data was extrapolated to 0 g/dL polymer concentration using the Huggins equation(44) for nonionic polymers and the Fuoss equation(45) for polyelectrolytes. Equipment. Viscosities were measured using Cannon-Fenske capillary viscometers and a Brookfield LV Microvis, cone and plate viscometer with a CP-40, 0.8° cone. Capillary viscometers received 10 mL of a sample for testing while the cone and plate viscometer received 0.50 mL. 

In a different approach a super-high-throughput ee-assay was developed on the basis of chirally modified capillary array electrophoresis (CAE).90 CAE was used in the Human Genome Project, and commercially available instruments have been developed which comprise a high number of capillaries in parallel, for example the 96-capillary unit MegaBACE consisting of 6 bundles of 16 capillaries.91 The system can address a 96-well microtiter plate. It was adapted to perform ee-determinations of chiral amines, which are potentially accessible by catalytic reductive amination of ketones, transition metal catalyzed Markovnikov addition of ammonia, or enzymatic hydrolysis of acetamides (Scheme 14).90... 

Some, uPLC systems are equipped with UV absorbance detection, and other systems allow for both UV absorbance and fluorescence detection. Fluorescence detection increases the sensitivity and selectivity of certain applications and is the method of choice in many separation-based assays. The liquid (mobile phase + sample) leaving the individual flow cells designated for UV detection is transferred through capillaries to a bank of 24 flow cells designated for fluorescence detection. 

Introduces microparallel liquid chromatography (LC), ADME/PK high-throughput assay, MS-based proteomics, and the advances of capillary and nano-HPLC technology... 

Another method which uses capillary electrophoresis with laser-induced fluorescence detection can also be employed to detect zearalenone (Maragos and Appell 2007). In order to analyse trace amounts of zearalenone in plants, a sensitive, quick and accurate method, the enzyme-linked immunosorbent assay (ELISA) was developed by Chen et al. 1989. 

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