Parts per billion by mass

A biochemist studying breakdown of the insecticide DDT finds that it decomposes by a first-order reaction with a half-life of 12 yr. How long does it take DDT in a soil sample to decompose from 275 ppbm to 10. ppbm (parts per billion by mass) ... 

As an illustration of the concept of mean lifetime, consider all sulfur-containing compounds in the troposphere. If the average mixing ratio of these compounds is 1 part per billion by mass (ppbm) and a steady state is assumed to exist, then with the mass of the troposphere about 4 x 1021 g, the total mass of sulfur-containing compounds in the troposphere is Q = 4 x 1012 g. If natural and anthropogenic sources of sulfur contribute to give a total P of about 200 x 1012gyr, the mean lifetime of sulfur compounds in the troposphere is estimated to be... 

A concentration of 10-100 parts per billion (by mass) of Ag is an effective disinfectant in swimming pools. However, if the concentration exceeds this range, the Ag can cause adverse health effects. One way to maintain an appropriate concentration of Ag is to add a slightly soluble salt to the pool. Using K p values from Appendix D, calculate the equilibrium concentration of Ag in parts per billion that would exist in equilibrium with (a) AgCl, (b) AgBr, (c) Agl. 

The EPA limit for lead in the water supply is 15 parts per billion by mass. Calculate the number of lead ions present in 1.00 kg of water that is at the EPA limit for lead. 

MS = mass spectroscopy PID = photoionization detector ppbv = parts per billion by volume... 

The differences in sorptive behavior of Th, Pu, U, and Np are evident by examining Table II. Plutonium and thorium isotopes at tracer concentrations (parts per billion, element mass/clay mass) were equilibrated for 24 hours with the < 2-pm fraction (clay) of a silt loam soil. The pH of the equilibration solutions was 6.5 and the aqueous phase contained Ca at a concentration of 5 mM. Both tetravalent actinides failed to remain 1n solution. Whether this is a direct function of sorption mechanisms or simply related to the solubility of the ions in solution is not distinguished by the results. Uranyl ion was not removed to the same extent as the tetravalent species. Neptunium(V) sorbed very poorly. It should be noted that while Np(V) is a mono-charged cation, Np02+ does not sorb like Na+. 

Nickel carbonyl, Ni(CO)4, is one of the most toxic substances known. The present maximum allowable concentration in laboratory air during an 8-hr workday is 1 ppb (parts per billion) by volume, which means that there is one mole of Ni(CO)4 for every lO moles of gas. Assume 24 °C and 1.00 atm pressure. What mass of Ni(CO)4 is allowable in a laboratory room that is 12 ft X 20 ft X 9 ft ... 

Cucumber fruits were studied by using the same analytical approach as they contain only five key volatiles and their concentration in cucumber tissue seems to be less variable than in tomato (see, for example. Ref. 12). Table 4 shows the El and API correlations for the five compounds each one could be attributed to a single ion mass on the API, and calibration with authentic standards allowed conversion of the ion signal into concentration units (parts per billion by volume). The amount of the Cg volatiles present in the macerated tissue was estimated by microwaving a sample of cucumber to inactivate the enzyme system that produces Cg and Cg volatile compounds. Inactivation was confirmed by APIMS analysis of the headspace above the treated samples. Microwaved samples were macerated after spiking them with known amounts of the Cg volatiles, then measuring volatile compound release in the blender apparatus. The values obtained from the spiked standards were then compared with the release traces from cucumber samples and the amounts of nonenal and nona-2,4-dienal estimated as 5 and 8mg/kg fresh tissue, respectively. These values compare well with the... 

This model estimate is supported by a comparison of radiocarbon monoxide ( CO) in low-latitude clean Southern Hemispheric air with that over the northern Indian Ocean, as measured from samples taken from the RW Brown. The clean air samples south of the ITCZ contained on average 55 parts per billion by volume (ppbv) of CO and 6.2 molecules of CO/cm whereas north of the ITCZ, this was 155 ppbv and 9.7 molecules/cm [26]. The CO difference between these air masses must be of biogenic origin, i.e., mainly biomass burning, because fossil fuels are radiocarbon-depleted. Previous analysis has shown that biomass burning adds 0.038 molecules of " CO/cm per ppbv of CO [26]. If we assume further that... 

G.24 The concentration of toxic chemicals in the environment is often measured in parts per million (ppm) or even parts per billion (ppb). A solution in which the concentration of the solute is. 1 ppb by mass has. 3 g of the solute for every billion grams (1000 t) of the solution. The World Health Organization has set the acceptable standard for lead in drinking water at... 

Chian et al. [69] point out that the Bellar and Iichtenberg [65] procedure of gas stripping followed by adsorption onto a suitable medium and subsequent thermal desorption onto a gas chromatograph-mass spectrometer is not very successful for trace determinations of volatile polar organic compounds such as the low molecular weight alcohols, ketones, and aldehydes. To achieve their required sensitivity of parts per billion, Chian et al. [69] carried out a simple distillation of several hundred ml of sample to produce a few ml of distillate. This achieved a concentration factor of between 10 and 100. The headspace gas injection-gas chromatographic method was then applied to the concentrate obtained by distillation. 

Lopez-Avila et al. [159] have described a method for the determination of low parts per billion concentrations of Dicamba and 2,4-D in soil. Stable-labelled isotopes are spiked into samples before extraction and the ratio of unlabelled compound and stable-labelled isotope was used to quantitate the unlabelled compound. Analysis is by high-resolution gas chromatography-mass spectrometry. Ten standard soil samples containing Dicamba and 2,4-D at known concentrations were analysed. Compound concentrations ranged from 100 to lOOOOug per kg for soil samples. Average recoveries were over 84% and method precision, given as relative standard deviation, was better than 19%. 

The masses of isotopes can be measured with accuracies better than parts per billion (ppb), e.g., m40Ar = 39.9623831235 0.000000005 u. Unfortunately, determinations of abundance ratios are less accurate, causing errors of several parts per million (ppm) in relative atomic mass. The real limiting factor, however, comes from the variation of isotopic abundances from natural samples, e.g., in case of lead which is the final product of radioactive decay of uranium, the atomic weight varies by 500 ppm depending on the Pb/U ratios in the lead ore. [8]... 

Figure 3 is the resulting advice for an example of a good QA/QC match with the user s needs. In this example, a high level of confidence was established, the methodology was both verified and validated, two samples were to be taken and analyzed by gas chromatography-mass spectrometry (GC-MS) at levels below 10 parts-per-billion (ppb). These conditions might be typical of analyses for 2,3,7,8-Tetrachloro- -dioxin (TCDD) in polluted water. 

This kind of measurement is sometimes called a mass-mass percent solution because one mass is divided by another. Very dilute concentrations (as in the concentration of a contaminant in drinking water) are sometimes expressed as a special mass percent called parts per million (ppm) or parts per billion (ppb). In these metrics, the mass of the solute is divided by the total mass of the solution, and the resulting fraction is multiplied by 10 (ppm) or by 10 (ppb). 

Parts per billion, ppb, the mass ratio multiplied by 109, may also be used.)... 

The single most unique characteristic of the SIMS technique is its sensitivity. It can be as good as one part per billion (ppb). For example, if silicon is sputtered at a rate of 10 A/sec over an area of 100-pm x 100-/zm, then 10"u cm3/sec of material is removed. Given the density of silicon, this reduces to approximately 5 x 1011 atoms/sec. If 1% of these atoms are ionized (by charge transfer with the surface) and 10% of those ionized are collected in the mass spectrometer, then the measured ion intensity will be 5 x 10s ions/sec. If we assume we can distinguish 5 ions/sec, then a detection sensitivity of 1 part in 108 is achievable. This sensitivity is many orders of magnitude better than other techniques. 

Elemental iron, the major element in Earth s core, is the fourth most abundant element in Earth s crust (about 5.0% by mass overall, 0.5%-5% in soils, and approximately 2.5 parts per billion in seawater.) In the crust, iron is found mainly as the oxide minerals hematite, Fe203, and magnetite, Fe304. Other common mineral forms are siderite, FeC03, and various forms of FeO(OH). Iron is an essential element in almost all living organisms. In the human body, its concentration ranges between 3 and 380 parts per million (ppm) in bone, 380-450 ppm in blood, and 20-1,400 ppm in tissue. 

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