Parts per thousand

Marecek and colleagues developed a new electrochemical method for the rapid quantitative analysis of the antibiotic monensin in the fermentation vats used during its production. The standard method for the analysis, which is based on a test for microbiological activity, is both difficult and time-consuming. As part of the study, samples taken at different times from a fermentation production vat were analyzed for the concentration of monensin using both the electrochemical and microbiological procedures. The results, in parts per thousand (ppt), are reported in the following table. 

Ketkar and co-workers developed a new analytical method for measuring trace levels of atmospheric gases.The analysis of a sample containing 40.0 parts per thousand (ppt) 2-chloroethylsulfide yielded the following results... 

This focusing action gives an ion beam, in which the m/z values can be measured so accurately that the resolution of a magnetic/electric-sector instrument (separation of ions of different m/z values) is measured as a few parts per million, compared to the more modest few parts per thousand in, say, a quadmpole or ion-trap instrument. 

Eig. 4. The bulk oxygen isotopic composition of different meteorite classes where (—) is the terrestial fractionation line. The 5 notation refers to the normalized difference between or ratios to those in standard mean ocean water (SMOW) in relative units of parts per thousand. The... 

Table 2. Occurrence of the Provitamins D in Selected Plants and Animals, Parts per Thousand of Total Sterol...

Figure 1 The solubility of the prineipal atmospherie gases in seawater, as a funetion of temperature. Units are millilitres of gas eontained in a litre of seawater of salinity 35 psu, assuming an overlying atmosphere purely of eaeh gas. Note that salinity is defined in terms of a eonduetivity ratio of seawater to a standard KCl solution and so is dimensionless. The term praetieal salinity unit , or psu, is often used to define salinity values, however. It is numerieally praetieally identieal to the old style unit of parts per thousand by weight...

Kettering and Midgley were the first to identify it as a prime antiknock agent, though the compound had been known since 1852. They estimated that only a veiy small amount of TEL—a few parts per thousand— would result in a 25 percent increase in horsepower as well as fuel efficiency. 

Chlorinity When a sample of sea water is titrated with silver nitrate, bromides and iodides, as well as chlorides are precipitated. In calculating the chlorinity (Cl), the entire halogen content is taken as chloride, and chlorinity is defined as the weight in grams of silver required for precipitation of total halogen content per kilogram of sea water, multiplied by 0-328 533. (Chlorinity is always expressed as parts per thousand, using the symbol %o.)... 

Table 2.14 gives the composition of sea water of 19 parts per thousand chlorinity. 

Table 2.14 Major constituents of sea water (parts per thousand)...

Variations of salinity In the major oceans the salinity of sea water does not vary widely, lying in general between 33 and 37 parts per thousand, a figure of 35 parts per thousand, equivalent to 19-4 parts per thousand chlorinity is commonly taken as the average for open-sea water. 

Local conditions may modify this profoundly in special areas. In the Arctic and Antarctic, and where there is dilution by large rivers, the salinity may be considerably less, and it may vary greatly according to season. Salinity is well below normal in the Baltic, and may fall nearly to zero at the head of the Gulf of Bothnia. In enclosed seas like the Mediterranean, Black Sea and Red Sea, on the other hand, where there is rapid evaporation, salinity may reach 40 parts per thousand. The total salt content of the inland Dead Sea is 260 g/kg compared to 37 g/kg for the Atlantic Ocean. 

An anti-oxygen such as catechol or hydroquinone is used to prevent polymerization. Hydroquinone should be added in the ratio of one part per thousand unless the phenylethylene is to be used immediately.1... 

Since the difference between Wv and Wa does not usually exceed 1 to 2 parts per thousand, we may write ... 

The relative error is the absolute error divided by the true value it is usually expressed in terms of percentage or in parts per thousand. The true or absolute value of a quantity cannot be established experimentally, so that the observed result must be compared with the most probable value. With pure substances the quantity will ultimately depend upon the relative atomic mass of the constituent elements. Determinations of the relative atomic mass have been made with the utmost care, and the accuracy obtained usually far exceeds that attained in ordinary quantitative analysis the analyst must accordingly accept their reliability. With natural or industrial products, we must accept provisionally the results obtained by analysts of repute using carefully tested methods. If several analysts determine the same constituent in the same sample by different methods, the most probable value, which is usually the average, can be deduced from their results. In both cases, the establishment of the most probable value involves the application of statistical methods and the concept of precision. 

Small variations in isotopic composition are usually described by comparing the ratio of isotopes in the sample material to the ratio of isotopes in a reference material. The standard measure of isotopic composition is X defined in parts per thousand (per mil or %o) by... 

The density of seawater is controlled by its salt content or salinity and its temperature. Salinity is historically defined as the total salt content of seawater and the units were given as grams of salt per kilogram of seawater or parts per thousand (%o). Salinity was expressed on a mass of seawater basis because mass, rather than volume, is conserved as temperature and... 

The effectiveness of a number of crude oil dispersants, measured using a variety of evaluation procedures, indicates that temperature effects result from changing viscosity, dispersants are most effective at a salinity of approximately 40 ppt (parts per thousand), and concentration of dispersant is critical to effectiveness. The mixing time has little effect on performance, and a calibration procedure for laboratory dispersant effectiveness must include contact with water in a manner analogous to the extraction procedure otherwise, effectiveness may be inflated [587]. Compensation for the coloration produced by the dispersant alone is important only for some dispersants. 

The much lower amount of formic acid formation during methanol oxidation compared with formaldehyde oxidation agrees with expectations if we assume that formic acid is predominantly formed by further oxidation of (free) molecular formaldehyde produced in a first step of methanol oxidation. Under the present reaction conditions, only a very small fraction, about 1 part per thousand, of the total reactant passing through the cell reacts to give formaldehyde, formic acid, or CO2. The rest... 

The modem HPLC system is a very powerful analytical tool that can provide very accurate and precise analytical results. The sample injection volume tends to be a minor source of variation, although fixed-loop detectors must be flushed with many times their volume in sample to attain high precision. Assuming adequate peak resolution, fluorimetric, electrochemical, and UV detectors make it possible to detect impurities to parts per billion and to quantitate impurities to parts per thousand or, in favorable cases, to parts per million. The major sources of error in quantitation are sample collection and preparation. Detector response and details of the choice of chromatographic method may also be sources of error. 

A second source of error may be in the detector. Detector linearity is an idealization useful over a certain concentration range. While UV detectors are usually linear from a few milliabsorbance units (MAU) to 1 or 2 absorbance units (AU), permitting quantitation in the parts per thousand level, many detectors are linear over only one or two decades of operation. One approach in extending the effective linear range of a detector is high-low injection.58 In this approach, an accurate dilution of a stock sample solution is prepared. The area of the major peak is estimated with the dilution, and the area of the minor peak is estimated with the concentrated stock. This method, of course, relies on linear recovery from the column. Another detector-related source of error that is a particular source of frustration in communicating... 

The saltiness of the ocean is defined in terms of salinity. In theory, this term is meant to represent the total number of grams of dissolved inorganic ions present in a kilogram of seawater. In practice, salinity is determined by measuring the conductivity of a sample and by calibration through empirical relationships to the International Association of Physical Sciences of the Ocean (IAPSO) Standard Sea Water. With this approach, salinity can be measured with a precision of at least 0.001 parts per thousand. This is fortunate, considering that 75% of all of the water in the ocean falls neatly between a salinity of 34 and 35. Obviously, these high-precision measurements are required to observe the small salinity variations in the ocean. 

In bacterial cells, marker compounds are present at the part per hundred to part per thousand level. In environmental samples, which represent a complex mixture of components, such markers are often present at the part per ten thousand to part per hundred thousand level. In certain clinical samples, in some instances, these markers may be present as low as parts per... 

Isotope ratios are reported using the delta (8) notation in parts per thousand or per mil (%o) 8 X = (Rsample — Rstandard) x 1000/R... 

Methods for pretreatment of samples for 13C analysis had been described in Chen et al. (2002a). After pretreatment, soil samples and plant debris were sent to the State Key Laboratory of Loess and Quaternary Geology, Chinese Academy of Sciences (CAS), for 13C analyses. The 13C analyses were conducted using a Finnigan MAT-251 mass spectrometer manufactured by Finnigan-Mat Company, with a precision of 0.2%o. Results are reported as 513C, in parts per thousand of the 13C/12C ratio from that of the International Pee Dee belemnite (PDB) standard, where ... 

Procedures for pretreatment of soil samples and synthesis of sample benzene for 14C analysis had been described in Chen et al. (2002b). Sample benzene was often left for 3-4 weeks to allow any radon with half-life of 3.82 days that may be present to decay. 14C activity of the CgFL was then determined using a 1220-QUANTULUS ultralow-level liquid scintillation spectrometer manufactured by WALLAC Company, Sweden. The 14C analyses were conducted at the Guangzhou Institute of Geochemistry, CAS. Results are reported as A14C, in parts per thousand of the 14C/12C ratio from that of the standard (oxalic acid decay corrected to 1950) (Stuiver and Po-lach 1977), and corrected for bomb 14C (Chen et al. 2002b), where ... 

The most abundant isotope of carbon has a mass of 12 atomic mass units, 12C. A less abundant stable isotope is 13C. And much less abundant is the radioactive isotope t4C, also called radiocarbon. It is convenient to express the abundances of these rare isotopes in terms of ratios of the number of atoms of the rare isotope in a sample to the number of atoms of the abundant isotope. We call this ratio r, generally a very small number. To arrive at numbers of convenient magnitude, it is conventional to express the ratio in terms of the departure of r from the ratio in a standard, which I call. v, and to express this departure in parts per thousand of s. Thus the standard delta notation is... 

For measurement of the oaks we used, per force, a mass spectrometer of somewhat low accuracy, and achieved the accuracy to demonstrate that trees are thermometers by making many measurements on each sample. On the tree sequences which we measured later, we used high precision spectrometers with accuracies of 0.1 parts per thousand (ppt) for 180/160 and 13C/12C, and 2 ppt for D/H. The measurements are expressed in terms of 8D and 6 g. 

The difference between the true result and the measured value. It is conveniently expressed as an absolute error, defined as the actual difference between the true result and the experimental value in the same units. Alternatively, the relative error may be computed, i.e. the error expressed as a percentage of the measured value or in parts per thousand. ... 

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