Urine analysis sample times

Typically, a PK study is composed of three phases, namely the in-life phase, bioanalysis, and data analysis. The in-life phase includes administering the compound to animals or humans and collecting samples from an appropriate matrix of interest such as blood or urine at predetermined time intervals for bioanalysis. The bioanalytical phase involves analysis of a drug and/or its metabohte(s) concentration in blood, plasma, serum, or urine. This analysis typically involves sample extraction and detection of analytes via LC-MS/MS. The third phase is data analysis using noncompartmental or compartmental PK computational methods. 

In the case of picloram and the phenoxy compounds, analysis of samples from total urine excreted each 24 h enabled us to determine the amount of absorbed dose. It has been shown (Matsumura, 1970 Gehring, 1973 and Sauerhoff, 1977) that both 2,4-0 and 2,4,5-T are excreted In the urine almost quantitatively within 5 days of being orally Ingested therefore, measuring the total amount of these compounds excreted In the urine over this time gives a good measurement of absorbed dose. 

Urine is also a good specimen for detecting ethanol because it is easy to obtain and handle. However, the ethanol concentration represents an average value between the last voided time and sampling time. Although ethanol is stable in urine, it is preferable to transfer urine to a container containing sodium fluoride at a final concentration of 1—2% and store at 4°C prior to analysis. 

Essential features of an automated method are the specificity, ie, the assay should be free from interference by other semm or urine constituents, and the sensitivity, ie, the detector response for typical sample concentration of the species measured should be large enough compared to the noise level to ensure assay precision. Also important are the speed, ie, the reaction should occur within a convenient time interval (for fast analysis rates), and adequate range, the result for most samples should fall within the allowable range of the assay. 

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. 

In most studies, phytoestrogen intake has been estimated by direct methods that evaluate food intake either by recall (food-frequency questionnaires -FFQs) or by record (food diary), and subsequently by composition databases based on information of this kind. Food-frequency questionnaires are widely administered to subjects involved in epidemiological studies. Their validity and reproducibility is considered sufficient when statistically correlated to data obtained from dietary records (a properly-completed and comprehensive food diary) and from analysis of blood and urine samples (Kirk et ah, 1999 Huang et al, 2000 Yamamoto et al, 2001 Verkasalo et al, 2001). FFQs can be repeated several times a year and may be administered to large populations. Such an approach provides an easy and low-cost method of assessing the... 

There are a number of other elements appearing from time to time in the laboratory. From these, chromium and nickel are most common. Both appear in enhanced concentrations in workers exposed to welding fumes, in galvanization processes, and in processing of ores. Prolonged exposure to Cr and/or Ni causes cancer and affects the kidney. Preferred methods of determination of Ni and Cr in urine are GF-AAS. Because of the risk of contamination of the very low concentrations in urine, extreme precautions in sample handling and analysis must be carried out. 

The progress made in interfacingHPLC instruments with mass spectrometry has been a significant development for laboratory analyses in the pharmaceutical industry. The low concentrations of test drugs in extracts of blood, plasmas, serums, and urine are no problem for this highly sensitive HPLC detector. In addition, the analysis is extremely fast. Lots of samples with very low concentrations of the test drugs can thus be analyzed in a very short time. At the MDS Pharma Services facility in Lincoln, Nebraska, for example, a very busy pharmaceutical laboratory houses over 20 LC-MS units, and they are all in heavy use daily. 

For high reproducibility of migration times and peak areas the sample matrix should be identical for all samples analyzed together. While this is challenging for forensic applications where analytes in whole blood or urine are determined, this requirement can be fulfilled easily in pharmaceutical analysis. After sample preparation of the drug product, the sample matrix is similar in most cases. The composition of blood or urine depends on its source. Thus, the changing sample matrix has more impact on the quality of the CE analysis. 

---