Water plasma, measurement

An ion-selective electrode responds to the activity of free analyte, not complexed analyte. For example, when the Pb2+ in tap water at pH 8 was measured with a sensitive ion-selective electrode, the result was [Pb2+] = 2 X 10 10 M.25 When lead in the same tap water was measured by inductively coupled plasma-mass spectrometry (Section 21-6), the result was more than 10 times greater 3 X 10-9M. The discrepancy arose because the inductively coupled plasma measures all lead and the ion-selective electrode measures free Pb2+. In tap water at pH 8, much of the lead is complexed by CO -, OH, and other anions. When the pH of tap water was adjusted to 4, Pb2+ dissociated from its complexes and the concentration indicated by the ion-selective electrode was 3 X 10-9M—equal to that measured by inductively coupled plasma. 

However, in contrast to a direct measurement, where the analyte activity in the native sample is measured, in the indirect measurement (after dilution) this possibility is lost. In the latter case, only total concentration in a sample can be back-calculated . Additionally, because water plasma in a patient sample is not measured, the indirect method of measuring blood electrolytes in hyperlipemic/hyperproteinemic samples (i.e., in the cases of low plasma water vs. plasma volume) results in a negative bias compared to direct measurement (the bias is bigger with lower water content), while for samples with a high electrolyte content (i.e., high plasma water ionic strength) the indirect measurements will result in a positive bias. 

Undoubtedly, while the direct method is more relevant, because the analyte activity in water plasma is actually measured, the reporting on blood sodium, potassium and chloride in terms of concentration in plasma is preferred by medical professionals, whatever method of measurement is used. This is justified by the fact that before ISEs had been invented, sodium, potassium and chloride were all determined by indirect methods, with flame emission spectroscopy (FES) for Na+ and K+, and coulometry for Cl. ... 

This phenomenon is explained by the fact that intravenous immunoglobulin increases the non-aqueous phase of the plasma, resulting in a relative loss of plasma water volume. Sodium is virtually restricted to serum water, so each volume of plasma measured will contain less sodium and be interpreted as hyponatremia. Using a direct ion-selective electrode avoids this problem. 

Equilibrating a gas two or more times with an aqueous sample (waters, sediment slurries, biological fluids) permits calculation of distribution coefficients and measurements of volatile organic compounds, such as hydrocarbons and halocarbons at sub-fxg/L concentrations. Classes of volatile organic compounds have different distribution coefficients, which aids in their separation and identification. The multiple gas-phase equilibration method has been used to measure the solubilities of pure hydrocarbons in waters of various salinities and of volatile hydrocarbons in oils and in water from the Cook Inlet, Gulf of Mexico, and Santa Barbara Channel It was first to detect small amounts of chloroform and other contaminants in New Orleans drinking water it measured the loss of C1-C10 hydrocarbons from oil slicks on the ocean surface and the apparent absence of dissolved hydrocarbons under the slicks in less than 8 hr. It has simultaneously measured up to 8 anesthetic gases in blood and plasma. 

Images taken from goniometer examination of a water droplet on (a) native PDMS surface, (b) PDMS surface coated with octadecyltrichlorosilane, and (c) PDMS surface treated with oxygen plasma. Measured contact angles are shown. 

Sample preparation Vortex 200 lL plasma with 800 aL cold (dry ice) MeOH for 10 s, centrifiige at 7000 g for 2 min. Dilute 2 vol of supernatant with 1 vol of water (to measure lactone form) or 1.5% phosphoric acid (to measure total amount), inject a 20 p,L aliquot. 

Wong, W.W., Cochran, W.J., Klish, W.J., Smith, E.O.B., Lee, L.S. and Klein, P.D. 1988 In vivo isotope-fractionation factors and the measurement of deuterium- and oxygen-18-dilution spaces from plasma, urine, saliva, respiratory water vapor, and carbon dioxide. American Journal of Clinical Nutrition 47 1-6. 

Fig. 2. Concentration changes of MB under UV-A (left) and fluorescent light (right) by untreated and H2+Ar plasma treated Xi02 films (blank refers to the reference line for the calibration of concentration changes due to the evaporation of water by lights during the measurements)...

The last problem of this series concerns femtosecond laser ablation from gold nanoparticles [87]. In this process, solid material transforms into a volatile phase initiated by rapid deposition of energy. This ablation is nonthermal in nature. Material ejection is induced by the enhancement of the electric field close to the curved nanoparticle surface. This ablation is achievable for laser excitation powers far below the onset of general catastrophic material deterioration, such as plasma formation or laser-induced explosive boiling. Anisotropy in the ablation pattern was observed. It coincides with a reduction of the surface barrier from water vaporization and particle melting. This effect limits any high-power manipulation of nanostructured surfaces such as surface-enhanced Raman measurements or plasmonics with femtosecond pulses. 

Trichloroethylene may occur in drinking water along with other chlorinated hydrocarbons, so effects of these chemicals in combination are of interest to public health. Hepatotoxicity, as measured by plasma enzyme activity, was increased synergistically in rats by oral administration of carbon tetrachloride combined with trichloroethylene (Borzelleca et al. 1990). In addition, synergistic effects were implicated in a 3-day study in... 

The lag-phase measurement at 234 nm of the development of conjugated dienes on copper-stimulated LDL oxidation is used to define the oxidation resistance of different LDL samples (Esterbauer et al., 1992). During the lag phase, the antioxidants in LDL (vitamin E, carotenoids, ubiquinol-10) are consumed in a distinct sequence with a-tocopherol as the first followed by 7-tocopherol, thereafter the carotenoids cryptoxanthin, lycopene and finally /3-carotene. a-Tocopherol is the most prominent antioxidant of LDL (6.4 1.8 mol/mol LDL), whereas the concentration of the others 7-tocopherol, /3-carotene, lycopene, cryptoxanthin, zea-xanthin, lutein and phytofluene is only 1/10 to 1/300 of a-tocopherol. Since the tocopherols reside in the outer layer of the LDL molecule, protecting the monolayer of phospholipids and the carotenoids are in the inner core protecting the cholesterylesters, and the progression of oxidation is likely to occur from the aqueous interface inwards, it seems reasonable to assign to a-tocopherol the rank of the front-line antioxidant. In vivo, the LDL will also interact with the plasma water-soluble antioxidants in the circulation, not in the artery wall, as mentioned above. 

Olive oil was the original model lipid for partition studies, and was used by Overton in his pioneering research [518,524], It fell out of favor since the 1960s, over concerns about standardizing olive oil from different sources. At that time, octanol replaced olive oil as the standard for partition coefficient measurements. However, from time to time, literature articles on the use of olive oil appear. For example, Poulin et al. [264] were able to demonstrate that partition coefficients based on olive oil-water better predict the in vivo adipose-tissue distribution of drugs, compared to those from octanol-water. The correlation between in vivo log Kp (adipose tissue-plasma) and log (olive oil-water) was 0.98 (r2), compared to 0.11 (r2) in the case of octanol. Adipose tissue is white fat, composed mostly of triglycerides. The improved predictive performance of olive oil may be due to its triglyceride content. 

With disruption of this barrier, molecules such as albumin freely enter the brain and ions and water follow. Because the brain lacks a well-developed lymphatic system, clearance of plasma constituents is slow, edema occurs, and intracranial pressure rises. At lower levels of exposure, subtle dysfunction of the blood-brain barrier may contribute to neurobehavioral deficits in children (Bressler and Goldstein 1991 Goldstein 1993). The particular vulnerability of the fetus and infant to the neurotoxicity of lead may be due in part to immaturity of the blood-brain barrier and to the lack of the high-affinity leadbinding protein in astroglia, which is discussed later in this section. Results of measurements of transendothelial electrical resistance across the blood-brain barrier from mice of various ages showed that lead potentiates cytokines-induced increase in ion permeability of the blood-brain barrier (Dyatlov et al. 

The accuracy of the inductively-coupled plasma procedure was assessed by analysing waters of known sulfate composition, and by comparing measured sulfate values for a wide range of samples with those obtained for the same waters by an automated spectrophotometric procedure. Good agreement is obtained between the derived sulfate measurements and the normal values for International Standard Sea Water and an EPA Quality Control Standard. 

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