Blood measurement

Dioctyl sebacate (DOS) with relative permittivity e of 3.9 and 2-nitrophenyl octyl ether (NPOE) with e = 23.9 are the traditionally used sensor membrane plasticizers. The choice of a plasticizer always depends on a sensor application. Thus, NPOE appears to be more beneficial for divalent ions due to its higher polarity, but for some cases its lipophilicity is insufficient. Furthermore, measurements with NPOE-plasticized sensors in undiluted blood are complicated by precipitation of charged species (mainly proteins) on the sensor surface, which leads to significant potential drifts. Although calcium selectivity against sodium and potassium for NPOE-based membranes is better by two orders of magnitude compared to DOS membranes, the latter are recommended for blood measurements as their lower polarity prevents protein deposition [92],... 

Adult females given a single intravenous injection of 0.6 mg/kg BW blood measured 1 h to 42 days postinjection As a percentage of the total dose administered, PCB 77 concentrations in blood fell from 4.4% at 1 h to 0.14% at 42 days. About 60% of the total dose was excreted in feces, and 10% in urine 18... 

With arsine exposure, there may be potential severe hemolysis (the breakdown of red blood cells and the release of hemoglobin). Ensure adequate oxygenation by arterial blood measurement or pulse oxygenation monitoring. Use diuretics to maintain urinary flow. 

Blood measurements of HCFC-141b were made prior to exposure, after each exercise period (55, 145, and 225 min into exposure), and 24 h postexposure (Utell et al. 1997). Mean peak circulating concentrations occurred after 225 min (approximately 4 h) of exposure and were 0.90, 1.65, and 2.98 fig/g of blood, respectively, at the three nominal concentrations. The relationship between exposure concentration and blood level appeared linear and reached a plateau at the 250-ppm concentration by 145 min. For all exposure concentrations, the blood concentrations at 55 min were within 80% of the concentrations at 225 min. For volunteers that underwent neurobehavioral testing, circulating HCFC-141b concentrations after 6 h at 500 and 1,000 ppm were 1.56 and 3.33 ug/g, respectively. These values were similar to those at 4 h. 

Figure 3.2 This line graph demonstrates the amounts of morphine and codeine in the blood, measured by high performance liquid chromatr raphy.

Adult females given a single intravenous injection of 0.6 mg/kg BW blood measured 1 h to 42 days postinjection... 

For simultaneous blood measurement of the four metabolites (lactate, pyruvate, ACAC and ), blood that has been deproteinised with perchloric acid is used as a sample. Spectrophotometric enzymatic methods according to reactions given in Fig. 1.4.3 were developed for automated analysers to minimise sample volume and improve precision [1,10,11,17]. 

A calibration curve is recorded for each plate (Fig. 4.1.10). 4-MU standards at absolute concentrations of 0.25 pmol (5 pi), 0.5 pmol (10 pi), 1.0 pmol (20 pi), 2.5 pmol (50 pi) and 5.0 pmol (100 pi) are measured in duplicates. The volume for each well is adjusted with demineralized water to the volume used in the assay. Before measurement, 200 pi stop solution are added and the plate is shaken for 5 min on a plate shaker. Fluorescence is read with an excitation wavelength of 355 nm and an emission wavelength of 460 nm. For leukocyte and dried blood measurements blanks that contain substrate and buffer solution without leukocyte homogenate or dried blood spots are prepared. After incubation and addition of the stop solution, the plate is read immediately for all assays based on leukocytes, while one dried blood spot from an arbitrary sample is added to each blank in case of dried blood assays. Hence, hemoglobin is eluted from blood spots for 30 min and these spots are removed again before measurement. It is crucial to match the age of these specimens to the age of the patient samples. If large variations (several weeks) are evident concerning the age of the samples on the same plate then a separate blank for each patient sample has to be prepared. 

The most intriguing container for biofluids is, of course, the body itself. While in vivo measurements of urine hold no appeal because it is regularly and painlessly excreted, blood measurements are obviously attractive. There have been three main approaches for transcutaneous Raman spectroscopy of blood, all sketched in Fig. 16.4. 

The reference electrode (system) and its stability in clinical analyzers is a crucial problem because all typical ISSs (and GSSs) use this electrode. Currently silver chloride electrodes are used. They work in two systems an open liquid junction or a constraint liquid junction with concentrated KC1 (>2M) or sodium formate (4M) as the equitransferent hypertonic electrolyte bridge. The latter better serves whole blood measurements. 

The calibration is done with one or more blood glucose measurements using blood glucose strips. The blood measurement will then set the glucose sensitivity... 

Eisele S, Ammon H, Kindervater R, Grobe A, Gopel W. Optimized biosensor for whole blood measurements using a new cellulose based membrane. Biosensors Bioelectronics 1994, 9, 119-124. 

Glucose sensors are mainly used to determine blood glucose in clinical chemistry and diabetes home monitoring. The detection limit is around 1 pM and increases by additional diffusion barriers for undiluted whole-blood measurement and in-vivo application. Typical response times are below one min. Screen-printed electrodes are often made for single use. Entrapment of GOD in polyurethane and amperometric indication of hydrogen peroxide may result in a massively stabilized glucose sensor which may be reused more than 1000 times. 

Several tests can show if you have been exposed to benzene. Some of these tests may be available at your doctor s office. All of these tests are limited in what they can tell you. The test for measuring benzene in your breath must be done shortly after exposure. This test is not very helpful for detecting very low levels of benzene in your body. Benzene can be measured in your blood. However, since benzene disappears rapidly from the blood, measurements may be accurate only for recent exposures. In the body, benzene is converted to products called metabolites. Certain metabolites of benzene, such as phenol, muconic acid, and S-phenyl-N-acetyl cysteine (PhAC) can be measured in the urine. The amount of phenol in urine has been used to check for benzene exposure in workers. The test is useful only when you are exposed to benzene in air at levels of 10 ppm or greater. However, this test must also be done shortly after exposure, and it is not a reliable indicator of how much benzene you have been exposed to, since phenol is present in the urine from other sources (diet, environment). Measurement of muconic acid or PhAC in the urine is a more sensitive and reliable indicator of benzene exposure. The measurement of benzene in blood or of metabolites in urine cannot be used for making predictions about whether you will experience any harmful health effects. Measurement of all parts of the blood and measurement of bone marrow are used to find benzene exposure and its health effects. 

Laurell G, Andersson A, Engstrbm B, Ehrson H (1994) Cisplatin in perilymph and blood measured with microdialysis. Case report. CMA/Mikrodialysis AB, Stockholm. 

When the workers were investigated at the university in Stockholm and the level of acrylamide in their blood measured, the results were very surprising. As is normal in such a study, a group of control subjects, volunteers who had not been exposed to the sealant or any other source of acrylamide, was investigated at the same time as the workers. The... 

Plasma and urinary levels of pantothenic acid have been measured in dietary surveys as well as in controlled studies of the vitamin deficiency. One fairly recent study with human subjects involved the feeding of a pantothenic acid-free diet for 9 weeks. The urinary pantothenic acid levels (4-6 mg/day) in vitamin-sufficient subjects were roughly half that of the intake (10 mg/day). With consumption of the vitamin-free diet, urinary pantothenic acid levels gradually declined to about 0.8 mg/day over the 9-week period (Fry et ai., 1976). Both urinary and blood serum levels of pantothenate have been used to assess dietary status. Values from urinary measurements seem to be somewhat better correlated with intake of this vitamin, than blood measurements data (Berg, 1997). 

Connor K, Harris M, Edwards M, Budinsky R, Clark G, Chu A, Finley B, Rowlands J. The influence of diet on AH receptor activity in human blood measured with a cell-based bioassay Evidence for naturally occurring AH receptor ligand activity in vivo. 2006 in press. 

Whole blood measurement of serotonin is popular because time-consuming isolation of platelets is not... 

There are no convenient or reliable functional tests of pantothenic acid status, thus assessment is made by direct measurement of whole blood or urine pantothenic acid concentrations. Urine measurements are perhaps the easiest to conduct and interpret, and concentrations are closely related to dietary intake, Whole blood measurements are preferred to plasma, which contains only free pantothenic acid and is insensitive to changes in pantothenic acid intake. Concentrations of pantothenic acid in aU of the above fluids can be measured by microbiological assay, most commonly using Lactobacillus plantarum. Whole blood must first be treated with an enzyme preparation to release pantothenic acid fi om CoA. Other techniques that have been used to measure pantothenic acid in human samples include radioimmunoassay and gas chromatography, Other techniques that have been developed include gas chromatography-mass spectrometry and a stable isotope dilution assay. CoA and AGP can be measured by enzymatic methods. ... 

Third, assays need to describe methods used for obtaining minimal detection limits (e.g., mean plus 3 SD of 20 replicates of a zero calibrator) and total imprecision, describing at what concentration a 10% CV is attained. Preanalytical factors that should be described include the effects of storage time and temperature, glass versus plastic tubes and gel separator tubes, and the influence of anticoagulants and whole blood measurements. As more assay systems are devised for POCT, the same rigors applied to the central laboratory methodologies need to be adhered to by the POCT systems. 

Fig. 10. a Correlation of glucose measurement in whole blood, measured by micro-thermometric biosensor and by the Reflolux-S blood glucose analyser, b Correlation of glucose measurement in whole blood measured by micro-thermometric biosensor and by the Ektachem blood glucose analyzer... 

Application of the miniaturized biosensors for metabolite estimation in whole blood is another important concept for future development. The improvement in sensitivity, linear range and response time was achieved by miniaturization of the sensors and has been proven in the case of whole-blood glucose, urea and lactate. A useful feature of miniaturization is that the smaller the flow channel, the smaller are the dispersion and dilution effects, favouring whole blood measurement with minimum error. In the case of clinical estimations, the results of the measurement on miniaturized thermal biosensor are more reliable. 

A highly useful measure of dose, but one that is not always readily obtainable, is the concentration of the chemical in the body. The most readily measured body fluid that provides a useful indication of dose is the blood. Measurements of urine and expired air levels are easily obtainable, but these media contain excretion products whose concentrations are not always easily related to the dose the body s tissues actually received. The concentrations of a chemical or its metabolites actually in target tissues can also be used as the dose measure while this is the most meaningful measure, it is also the most difficult to obtain. 

Without question, sodium and potassium have been the analytes receiving the most attention in conjunction with the development of new analyzers. Almost all instruments on the market utilize the potassium-selective membrane system based on the antibiotic valinomycin in a PVC membrane matrix. For blood measurements, such a membrane is quite adequate. However, in undiluted urine samples, a negative error in the measurement of potassium has been reported (KIO). Apparently, this interference comes from a negatively charged lipophilic component of the urine which can partition into the PVC membrane, reducing the membrane potential (i.e., the membrane is not permselective). Fortunately, this problem can be overcome by incorporating the valinomycin in a silicone rubber-based membrane matrix (A4) into which the unknown anionic component apparently has a less favorable partition coefficient. 

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