Urine sample preparation methods

The analyte binding efficiency is matrix dependent. Some matrices, such as urine and tissue extracts, can be directly loaded onto the column, other matrices such as milk may need sample processing prior to loading onto an immunoaffinity column. The simplest sample preparation method is dilution this method has been applied to serum, liver, and kidney extracts after removal of particulates. Sometimes dilution alone is not sufficient to eliminate the matrix effect and classical sample preparation techniques (solvent/solvent extraction, solid phase extraction, etc.) will be necessary prior to immunoaffinity chromatography. We found milk often needs this type of treatment. 

Berg et al. [126] have developed a method for the determination of opiates and cocaine in urine. Sample preparation was performed by adding ISTDs and 0.5 ml of... 

Figure 2 demonstrates the effects of adding octane sulfonic acid to the injection solvent for a reverse-phase separation of pyridinium and deoxypyri-dinium, components of collagen, in rat urine. These polyamine containing compounds are protonated and poorly retained under the usual acidic or neutral mobile-phase conditions. The sample preparation method is simple dilution and does not afford the removal of salts from the sample. Therefore if the analytes were inadequately retained the sensitivity, as well as the method accuracy, would suffer. As the concentration of octane sulfonic acid is increased to 50 mM (Fig. 2a), both the retention time and the peak response for the analytes improve significantly. Litde improvement is obtained at higher concentrations of octane sulfonic acid and retention is not strongly dependent on the injection volume (Fig. 2b). To protect the ion source from the fouling effects of octane sulfonic acid in the injection solvent, a timed divert valve was inserted before the ion source to shunt the excess ion pair reagents to waste during the first few minutes of each injection.

Another product of esterase cleavage is p-nitrophenol (PNP), which is generated in the human body by the degradation of parathion, parathion-methyl and parathion-ethyl. Some methods for the determination of PNP in urine are summarized in Table 9.5. PNP can, for example, be determined in the urine of occupationally exposed subjects by means of GC-ECD. Sample preparation involves acid hydrolysis, extraction with diethyl ether, derivatization with diazoethane and purification on silica gel columns. The LOD was 20 pg L with a recovery of 85-98%. This method has also been used in a study on selected pesticide residues and metabolites in urine from a survey of the US general population.In the context of another survey study, a more complicated technique to detect PNP in urine has recently been used by Hill et involving GC-MS-MS with positive chemical ionization after derivatization with l-chloro-3-iodopropane. The authors also used this method for the determination of the metabolite TCP and 10 other analytes in urine.Sample preparation involved hydrolysis with p-glucuronidase, several extraction steps using different solvents and purification by SPE (silica gel column). The LOD was 1 pg L with an inter-assay RSD... 

The determination of this important substance has for a long time been performed exclusively by chromatographic methods, as immunological tests are not available. Although HPLC/DAD can be used, GC/MS is much more sensitive. Methods with a limit of detection of 1 ng/ml have been described for the determination of chlormethiazole from serum [61]. Using the sample preparation methods described in Chapter 7, it is easily possible without derivatization to detect from urine the consumption of a chlormethiazole capsule (192 mg) even on the day after consumption. Figure 8-37 shows the chromatogram of a sample with such a low concentration. 

Only chromatographic methods are available for the determination of biperiden abuse. Using the sample preparation method described in Chapter 7, the hydroxylated metabolites (characteristic masses are given in Table 8-28) can be extracted from the urine. Whereas HPLC/DAD is only capable of detecting high-dose abuse, GC/MS can detect the consumption of therapeutic doses without derivatization. 

Ideally, the sample preparation methods must be simple, straightforward, and capable of being carried out in a routine manner. The more complex the sample preparation, the greater the chance of contamination, which ultimately affects accuracy and spike recoveries. The preferred method of sample preparation is by simple dilution with a suitable diluent such as dilute nitric acid for urine or 5-10% tetra methyl ammonium hydroxide (TMAH) for blood. However, this is not always possible with all types of biological materials. In these cases, a digestion with concentrated HNO3... 

Becanse of the differences in the matrix components of samples such as urine, blood, or serum, simple external calibration can often produce erroneous results. For that reason, it is common to use other calibration methods such as standard additions or addition calibration to achieve accurate data. These methods have been described in detail in Chapter 13, but they are required because of the matrix suppression effects caused by large variations in patients biological fluid samples. The sample preparation method used will often dictate the type of calibration curve to use, but all three... 

The methods I- 4 of sample preparation are classics. As a mle they give a high value of blank and some of them take a lot of time. Microwave sample preparation is perspective, more convenient and much more faster procedure than classical mineralization. There are some problems with the combination Cendall-Kolthoff s kinetic method and microwave sample preparation which discussed. The experimental data of different complex organic matrix are demonstrated (food products on fat, peptides, hydrocarbone matrix, urine etc). 

Several methods are available for the analysis of trichloroethylene in biological media. The method of choice depends on the nature of the sample matrix cost of analysis required precision, accuracy, and detection limit and turnaround time of the method. The main analytical method used to analyze for the presence of trichloroethylene and its metabolites, trichloroethanol and TCA, in biological samples is separation by gas chromatography (GC) combined with detection by mass spectrometry (MS) or electron capture detection (ECD). Trichloroethylene and/or its metabolites have been detected in exhaled air, blood, urine, breast milk, and tissues. Details on sample preparation, analytical method, and sensitivity and accuracy of selected methods are provided in Table 6-1. 

With the increased popularity of LC-MS, the problem of overlapping enantiomer peaks from other amino acids has largely been resolved. The mass spectrometer can act as an additional dimension of separation (based on mass to charge ratio). Thus, only amino acids having the same mass-to-charge ratio must be separated achirally (see Desai and Armstrong, 2004). This additional dimension of separation also has implications for the applications in the matrices discussed previously. With the ability of the mass spectrometer to discriminate on the basis of mass, this lessens the need for complete achiral separation. For example, an LC-MS method was recently developed to study the pharmacokinetics of theanine enantiomers in rat plasma and urine without an achiral separation before the enantiomeric separation (Desai et al., 2005). In such matrices, proteins must still be removed by appropriate sample preparation. 

A GC-MS method for determining the isotope composition of lead in blood and urine samples is based on preparation of Pb(CgH4F-p)4 using the corresponding Grignard reagent108. 

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