Sample preparation deproteinization

Sample preparation Deproteinize serum or CSF with MeCN, centrifuge, add the supernatant to dichloromethane, inject a 100 pL aliquot of the aqueous layer. 

Sample preparation Deproteinize with 12.5% trichloroacetic acid. 

Sample preparation Deproteinize plasma with HCl and extract with dichloromethane. Remove the organic layer and evaporate it to dryness, reconstitute the residue in 100 pL mobile phase, inject a 40 pL aliquot. 

Stewart et al. (S8) estimated magnesium in serum and urine. Of four different methods of sample preparation (i.e., wet-ashing, deproteiniza-tion, simple dilution with water, and dilution with hydrochloric acid), deproteinization with trichloroacetic acid was found to be most satisfactory. No interference was seen from sodium, potassium, or phosphate, but sulfate produced depression. With protein a 6% decrease in the apparent magnesium concentration was seen. Calcium and sulfate were added to standards and samples to control sulfate depression. 

Dialysis can also be used as an on-line sample preparation technique for the deproteinization of biological samples prior to HPLC. Selecting the appropriate semipermeable membrane for the dialyzer can prevent interference from large macromolecules. Samples are introduced into the feed (or donor) chamber, and solvent is pumped through the lower acceptor (or recipient) chamber. The smaller molecules diffuse through the membrane to the acceptor chamber and are directed to an HPLC valve for injection. In case of low concentrations of compounds of interest, a trace enrichment step may be required this is accomplished with a column placed downstream of the dialyzer that will retain the analyte until the concentration is sufficient for detection. After this step, the analyte can be backflushed into the HPLC system. The technique is useful for blood studies as sampling can be achieved continuously without blood withdrawal. A commercial on-line system, such as Asted from Gilson, used for both cleanup and enrichment by a combination of dialysis with SPE, is shown in Fig. 7. 

Reversed-phase HPLC with fluorescence detection, after derivatization of plasma thiols with ammonium 7-fluorobenzo-2-oxa-l,3-diazole-4-sulphonate (SBD-F), is the most widely used method to determine total plasma amino thiols (cysteine, cysteinylglycine, and homocysteine). The time required for sample preparation (thiolic reduction, deproteinization, and precolumn derivatization g with SBD-F) and for thiol derivatives separation is nearly 2 h per sample. =... 

To analyze free amino acids in plasma or tissue homogenates, it is necessary to remove proteins and peptides present in solution. The most widely used deproteinization method is precipitation with 5-sulfosalicylic acid followed by centrifugation for separating the precipitate. In comparison to other precipitation agents such as trichloroacetic acid, perchloric acid, picrinic acid, or acetonitrile, the best results with respect to completeness of precipitation are obtained with 5-sulfosalicylic acid [39]. Other deproteinization methods comprise ultrafiltration and ultracentrifugation [40], which have only recently been considered as sample preparation methods for amino acid analysis. 

The analysis of food contaminants, in particular any toxic or biologically active residue, is important for public health or quality control reasons.19 Examples are mycotoxins (aflatoxins) and pesticide and drug residues. Sample preparation is typically elaborate and might involve deproteinization, solvent extraction, and clean-up via solid-phase extraction (SPE).The use of highly sensitive and specific LC/MS/MS is increasing and has simplified some of the sample preparation procedures. 

Sample preparation Intestinal efflux. Freeze intestinal efflux at -80°, lyophilize, reconstitute with 1 mL ofloxacin in MeOH 100 mM phosphoric acid 50 50, centrifuge at 3000 rpm for 10 min, inject a 20 pL aliquot. Serum. Deproteinize serum with MeOH containing ofloxacin. 

Sample preparation Add n-propyl p-aminobenzoate to plasma, deproteinize 1 mL plasma with 1 mL MeCN, inject an aliquot onto column A with mobile phase A, monitor effluent from column A with detector A, allow eluate containing verapamil to hll a 2 mL sample loop for 2 min, elute contents of sample loop onto column B with mobile phase B and at the same time allow pure mobile phase B to flow onto column B (ratio of column loop flow pure mobile phase B flow 1 9), elute contents of column B onto column C with mobile phase C, monitor effluent from column C with detector B. 

This sample preparation method (Method 1) is the result of several experiments. An attempt was also made to extract the deproteinated sample with alkali (Method 2) without previously extracting with toluene. As a comparison, an experiment was carried out in which the toluene phase was evaporated to dryness and then acetylated (Method 3). The results are given in Table 9-5. The criterion was again the recovery rate. 

Previous sample preparation steps constitute in many applications the main share of the total bioanalytical method. For laboratories with a large number of routine samples for chemical analysis, this means that a lot of time must be devoted to sample work-up procedures. This is largely the reason why much effort has been put into the development of liquid chromatographic systems that can tolerate the direct injection of physiological fluids. Any of the existing HPLC methods performing a sample enrichment and/or a deproteinization step is slower than direct... 

Dialysis can also be used as an online sample preparation technique for the deproteinization of biological samples prior to HPLC. Selecting the appropriate semipermeable membrane for the dialyzer can prevent interference from large macromolecules. Samples are introduced into the feed (or donor) chamber, and solvent is pumped through the lower acceptor (or recipient)... 

AAS is the most widely used analytical technique for the determination of lead in biological materials [57,58], The majority of AAS methods employ the electrothermal atomic absorption spectrometry (ETAAS) technique, using either Zeeman background correction or deuterium background correction for the determination of lead in biological fluids [55,59-65], Urine is less often employed as an indicator of exposure however, similar problems associated with AAS determination of lead exist for blood as well as urine (1) incomplete atomization (2) volatile lead salts (3) spectral interferences (4) buildup of carbonaceous residue reducing sensitivity and precision. These analytical problems are eliminated by optimal sample preparation, e,g., dilution, addition of matrix modifiers, deproteinization, and background correction and calibration by matrix-matched standards [66],... 

The guayule latex value is a mean of 20 latex samples prepared throughout a year from bimonthly harvests of different lines. Each value in the mean was itself a mean of foim protein determinations. All Hevea latex determinations are the mean of 4 assays s.e. Hevea latex samples were obtained from Centro Trade, Virginia Beach, Va, although the enzymatically deproteinized material is Allotex... 

DEPROTEINIZATION. A sample preparation procedure involving removal of protein, e.g., by precipitation with a reagent. 

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