A Gas Chromatographic Method for the Determination of Bicarbonate and Dissolved Gases

A gas chromatographic (GC) method for determination of p,p'-DDT in technical and formulated products was developed and it performed well in an initial small collaborative study among 4 laboratories. Samples are dissolved in chloroform, and p,p'-DDT is separated on an OV-210 column and determined by GC analysis with flame ionization detection. 2,2'-Dinitrobiphenyl is used as an internal standard. The method was subjected to an international collaborative study with 10 participating laboratories. Collaborators received matched pairs of technical DDT products and of water-dispersible powder, emulsifiable concentrate, and dustable powder formulations. Relative standard deviations for reproducibility (RSDR) for the paired samples were 1.16, 1.48, 2.08, and 1.80%, respectively. The method has been approved interim official first action by AOAC as a CIPAC-AOAC method.

An interlaboratory study was conducted to validate a gas chromatographic (GC) method for determination of 21 organochlorine pesticides, 6 pyrethroid pesticides, and 7 polychlorobiphenyl (PCB) congeners in milk, beef fat, fish, and eggs. The method was performed at low contamination levels, which represent relevant contents in food, and is an extension of the European standard (method NF-EN-1528, Parts 1-4). It enlarges the applicable scope of the reference EN method to pyrethroid pesticides and proposes the use of solid-phase extraction (SPE) as a cleanup procedure. Cryogenic extraction was made, and SPE cleanup was performed with 2 successive SPE cartridges: C18 and Florisil. After injection of the purified extract onto a GC column, residues were measured by electron capture detection. Food samples (liquid milk, beef fat, mixed fish, and mixed eggs) were prepared, tested for homogeneity, and sent to 17 laboratories in France. Test portions were spiked with 27 pesticides and 7 PCBs at levels from 26 to 45, 4 to 27, 31 to 67, and 19 to 127 ng/g into milk, eggs, fish, and fat, respectively. Based on results for spiked samples, the relative standard deviation for repeatability ranged from 1.5 to 6.8% in milk, 3 to 39% in eggs, 4.5 to 12.2% in fish, and 7 to 13% in fat. The relative standard deviation for reproducibility ranged from 33 to 50% in milk, 29 to 59% in eggs, 31 to 57% in fish, and 30 to 62% in fat. This method showed acceptable intra- and interlaboratory precision data, as corroborated by HORRAT values at low levels of pesticide and PCB contamination. The statistical evaluation of the results was performed according to the International Organization for Standardization (ISO; ISO 3534 standard) and 5725-2 Guideline.

A gas chromatographic (GC) method for determination of fenitrothion in fenitrothion technical and formulated products has been subjected to a collaborative study with 7 participating laboratories. Formulations are extracted with chloroform containing dibutyl sebacate as an internal standard and are analyzed by gas chromatography using an OV-210 column. Collaborators were furnished matched pairs of technical product and water-dispersible powder and emulsifiable concentrate formulations. Relative standard deviations for reproducibility (RSDR) for the paired samples were 0.54, 1.00, and 1.56%, respectively, for technical fenitrothion, water-dispersible powders, and emulsifiable concentrates. The method has been approved interim official first action as an alternative to the present official first action AOAC method 6.A19-6.A24, which uses a polyphenyl ether, 6 ring (PPE-6R) column packing and fluoranthene as internal standard.

The increase in carbon dioxide in the atmosphere is one of the main causes of global warming. Remote sensing technology has become an important means of monitoring the distribution of carbon dioxide gas. By remotely monitoring the temporal and spatial distributions of atmospheric carbon dioxide, people can further deepen their understanding of the global carbon process. The GOSAT (Greenhouse Gases Observing SATellite) CO2 L4B concentration data from 2010 to 2015 were validated using local station atmospheric data. The spatial and temporal distributions of the carbon dioxide concentration and its variation characteristics were analyzed. Based on the total primary productivity data and human emissions of carbon dioxide data, the influencing factors of spatial variations in carbon dioxide were analyzed. The results show that: (1) The correlation coefficient between GOSATL4B data and ground-measured data is above 0.95, which indicates that the remotely acquired data have high precision and stability. (2) The spatial distribution characteristics of carbon dioxide at different atmospheric pressure heights are quite different. The variation in the long-term series mean of carbon dioxide concentration levels at 17 vertical heights was studied. The fluctuations in concentration changes at different height levels vary, and the closer to the surface, the greater the fluctuation is. The near-surface carbon dioxide concentration (975 hPa) has the largest fluctuation. When the atmospheric pressure is low (for example, 150 or 100 hPa), the high carbon dioxide concentration region is banded and concentrated near the equator. The trends in carbon dioxide concentration over land and sea surfaces are similar, and the common pattern is that the concentration of carbon dioxide has been increasing. (3) The near-surface carbon dioxide concentration (975 hPa) has clearly different spatial characteristics. There are four high-value centers across the globe: East Asia, western Europe, the US East Coast, and Central Africa. The concentration of carbon dioxide in the Northern Hemisphere near the ground is higher than that in the Southern Hemisphere. The fluctuation in the Southern Hemisphere is relatively small, and the trend is opposite that in the Northern Hemisphere. (4) The concentration of carbon dioxide showed a significant growth trend during the study period. By studying the change characteristics of the monthly global average at the 975 hPa level (approximately 300 m above sea level) from January 2010 to October 2015, it can be seen that the global CO2 concentration has been above 400 ppm for most of the year, and it is increasing each year. (5) Compared with the Southern Hemisphere, the cyclical changes in carbon dioxide concentration in the Northern Hemisphere are obvious and large, while the trend in the Southern Hemisphere is relatively stable, and the change is small. There are opposite trends in the cyclical changes in the carbon dioxide concentration in the Northern and Southern Hemispheres. When the carbon concentration in the Northern Hemisphere resides over the annual high-value area, the Southern Hemisphere has a low-value area of carbon dioxide concentration every year. In addition, the change in carbon dioxide concentration during the year is obvious with seasonal changes. This should be related to changes in vegetation phenology and different seasons in the Northern and Southern Hemispheres. (6) Four countries in East Asia (Korea, Mongolia, Japan and China) from 2010 to 2014 were selected to analyze the relationship between GPP (gross primary production) and near-surface carbon dioxide concentration. These two factors have a significant inverse correlation. When carbon dioxide is at a minimum, the GPP is at its peak, and when carbon dioxide reaches its peak, the GPP reaches a minimum. The above relationship fully indicates that terrestrial ecosystems play an important role as carbon sink contributors in the carbon cycle. (7) The relationship between atmospheric carbon dioxide and carbon dioxide data from human activities from the Global Atmospheric Research Emissions Database was analyzed. The former is significantly and positively correlated with carbon dioxide emissions caused by human activities, indicating that human activities are an important factor in the increase in carbon dioxide.

This study describes a gas chromatographic method for the quantitative determination of residual propham and chlorpropham in potatoes. Both herbicides are extracted from the foodstuff with methylene chloride. After centrifugation and concentration, propham and chlorpropham are quantitatively determined by gas chromatography thermionic detection using a fused silica capillary column CP Sil 5CB. 2-Chloraniline is used as internal standard. Recoveries of 100 +/- 15% and 99 +/- 10% have been obtained for propham and chlorpropham in blank samples spiked at the level of 0.5, 1.0 and 5.0 mg/kg. The absolute detection limit for both compounds is 1 ng corresponding to 0.1 mg/kg. Of the 161 samples of fresh potatoes analysed using this method, 136 contained residues of these herbicides and 18 of them (11%) exceeded the maximum tolerated value of 5 mg/kg.

A simple high-throughput headspace gas chromatographic method for the determination of dissolved oxygen in aqueous samples

A full evaporation headspace gas chromatographic method for determination of monomer conversion in cellulose graft poly-methyl methacrylate

SUMMARY A gas chromatographic (gc) method for determination of anesthetic and subanesthetic concentrations of thiopental in biological fluids was developed. The method was shown to be simple, accurate, reliable, efficient, versatile, and rapid to do. The method may be preferable to the fluorimetric or other gas chromatographic methods of barbiturate analysis.

Novel headspace gas chromatographic method for determination of oxalate in oxygen delignification liquor

Development and Validation of an Automated Gas Chromatography Method for Determination of Dichloromethane in Ampicillin Sodium by Using Capillary Column Technology

Scientific evidence about the seriousness of the climate threat to agriculture is now unambiguous, but the ex- act magnitude is uncertain because of complex interactions and feedback processes in the ecosystem and the economy. Climate-related factors that would affect agricultural productivity in coming decades are: changes in temperature, precipitation, carbon dioxide (CO ), fertilization, short-term weather variability and surface water 2 run-off. Simulation of future climate in India under A2 scenario by IITM, Pune and Hadley Centre, UK, indicate that during the last quarter of present century the country will experience an increase in mean annual tempera- ture by 3-5C. Summer monsoon rainfall will increase by 20%, and extreme rainfall events would rise sharply in western and south-central parts. However, the arid western Rajasthan and the adjoining Punjab and Haryana will possibly experience notable decline in summer monsoon, and slight increase in winter rainfall, with pro- nounced variability in rainfall and fewer rainy days. Consequently, there will be higher incidence of droughts and floods in arid western India, affecting both rainy ( kharif) and winter ( rabi) season crops. Since a number of high- value crops are grown during the rabi, the negative impact on farmers economy would possibly be higher. Change in CO concentration too can show uncertainty in crop yields, but studies on the interrelationship be- 2 tween changes in rainfall, temperature and CO concentration and their effect on yield changes are quite few. 2 Adaptation and mitigation strategies to address the impact of climate change on agriculture are needed ur- gently through new research and proper interpretation of the accumulated research results from the decades of dryland research under different agro-climatic settings. Use of alternative crops or cultivars adapted to the likely changes, alteration in the planting date, and management of plant spacing and input supply might help in re- ducing the adverse impact. Use of resource-conservation technologies and a shift from sole cropping to diversi- fied farming system is highly warranted. Horticulture and agro-forestry need to be given more encouragement. Enabling policies on crop insurance, subsidies and pricing related to water and energy uses need to be strengthened at the earliest. Policies that would encourage farmers to enrich organic matter in the soil need emphasis. Also, it is necessary to develop a robust early warning system of spatio-temporal changes in weather as well as other environmental parameters. Contingency crop planning will require greater attention. Long-term strategic approaches to efficiently conserve and utilize rain water on the one hand and in-season tac- tical approaches to mitigate the adverse effects of weather aberrations on the other are also needed. Consider- ation of depletion rate of soil water is more important when the crops are grown primarily on stored soil water. Under such situations, wide rows and low plant populations are highly desirable. Water-conservation practices will become economically feasible when nutrient deficiencies are also corrected. Late onset of monsoon rains often leads to delayed planting and specific crop contingency plans have been developed for different agro-cli- matic zones to address the issue.

ABSTRACTGas chromatography (GC) is a technique used to analyze substances/molecules (as chemical species) with a system composed of chromatograph, column, and detector. This study has the objective of reviewing the use of GC in monitoring greenhouse gases (GHG; carbon dioxide: CO2; methane: CH4; nitrous oxide: N2O) emission and O2 (oxygen) uptake in soil, demonstrating results from experiments around the world and alternative use of sensors to monitor these gases in soil. Our study shows that the correct column and detector depend on analyzing gas and the advantages and disadvantages of the column and the detector. The columns, packed and capillary, have been more used and are considered better options to analyze GHG emission and O2 uptake in soil science. Thermal conductivity detector (TCD), electron capture detector (ECD) and mass selective (MS) are great choice to monitor CO2 emission; flame ionization detector (FID) equipped with methanizer allows the detection of CO2 and CH4 emission; and ECD detects the amount of N2O emitted. Moreover, both, TCD and ECD, also can be used to detect O2 uptake. GC system is complex, and to identify of GHG emission and O2 uptake is necessary the use of column (packed or capillary) and may contain multiple detectors, i.e. three (TCD, ECD, and FID) or two detectors (FID and ECD). Field and laboratory study should be run to verify the efficacy of sensors to monitor GHG emission and O2 uptake as an alternative of GC system.

Six laboratories collaboratively studied a headspace gas chromatographic method for determination of ethanol in the aqueous phase of canned salmon. Ethanol is determined by a headspace sampling technique with tert-butanol as the internal standard, using a gas chromatograph equipped with a Super Q column and a flame ionization detector. With outliers excluded, the mean recoveries from samples spiked with 25.1 and 78.4 ppm ethanol were 112 and 110%, respectively. For the 4 sample pairs quantitated, repeatability coefficients of variation ranged from 1.42 to 4.25% and reproducibility coefficients of variation from 2.55 to 8.09%, with 3 of the 4 reported values less than 5%. The method has been adopted official first action.

Effect of oxygen and carbon dioxide concentration upon the development of hematogenous metastases and transplants

Abstract. Gas exchange measurements were performed to test the hypothesis that failure of stomata to open in senescing leaves of Nicotiana glauca is caused by elevated concentrations of carbon dioxide in the intercellular spaces of leaf mesophyll tissue (ci). Senescing leaves selected for experiments were completely chlorotic and lacked positive rates of photosynthesis. When stomata in detached epidermis from senescing leaves were illuminated in CO2‐free air, they opened to similar apertures as those in detached epidermis from nonsenescing leaves. To compare the effects of changes in ci on stomatal responses of the two leaf types, leaf ‘flags’ of either nonsenescing or senescing leaves were illuminated at a photosynthetic photon flux density of 500 μmol m−2 s−1 in a gas exchange cuvette. Leaf temperatures were maintained at 23.5 ± 0.5°C, and vapour pressure differences between leaves and the air were maintained between 0.70 and 0.75kPa. Ci was adjusted by changing external concentrations of carbon dioxide in air circulating through the cuvette. Conductances and photosynthetic rates of nonsenescing leaves changed in response to changes in ci, but neither the conductances nor the photosynthetic rates of senescing leaves were affected significantly by changes in q. We conclude that guard cells of senescing leaves of Nicotiana glauca do not lose the capacity to respond to changes in carbon dioxide concentration and that increases in ci resulting from declining rates of mesophyll photosynthesis are not the sole cause of maintenance of stomatal closure during leaf senescence. The data suggest that factors external to guard cells may prevent them from responding to changes in carbon dioxide concentrations in intact senescing leaves.