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Haiping Qi

Publications and source records attributed to Haiping Qi.

41 records · Page 3Linked to original sources
USGS2006

Determination of the δ 15 N of total nitrogen in solids; RSIL lab code 2893

The purpose of the Reston Stable Isotope Laboratory (RSIL) lab code 2893 is to determine the δ( 15 N/ 14 N), abbreviated as δ 15 N , of total nitrogen in solid samples. A Carlo Erba NC 2500 elemental analyzer (EA) is used to convert total nitrogen in a solid sample into N 2 gas. The EA is connected to a continuous flow isotope-ratio mass spectrometer (CF-IRMS), which determines relative difference in the isotope-amount ratios of stable nitrogen isotopes ( 15 N/ 14 N)of the product N 2 gas. The combustion is quantitative; no isotopic fractionation is involved. Samples are placed in a tin capsule and loaded into the Costech Zero Blank Autosampler of the EA. Under computer control, samples are dropped into a heated reaction tube that contains an oxidant, where the combustion takes place in a helium atmosphere containing an excess of oxygen gas. Combustion products are transported by a helium carrier through a reduction tube to remove excess oxygen and convert all nitrous oxides into N 2 and through a drying tube to remove water. The gas-phase products, mainly CO 2 and N 2 , are separated by a gas chromatograph. The gas is then introduced into the isotope-ratio mass spectrometer (IRMS) through a Finnigan MAT (now Thermo Scientific) ConFlo II interface, which also is used to inject N 2 reference gas and helium for sample dilution. The IRMS is a Thermo Scientific Delta V Plus CF-IRMS. It has a universal triple collector, two wide cups with a narrow cup in the middle, capable of measuring mass/charge ( m/z ) 28, 29, 30, simultaneously. The ion beams from N 2 are as follows: m/z 28 = N 2 = 14 N 14 N; m/z 29 = N 2 = 14 N 15 N primarily; m/z 30 = NO = 14 N 16 O primarily, which is a sign of contamination or incomplete reduction.

Techniques and Methods↗
USGS2006

Determination of the δ 15 N and δ 13 C of total nitrogen and carbon in solids; RSIL lab code 1832

The purpose of the Reston Stable Isotope Laboratory (RSIL) lab code 1832 is to determine the δ( 15 N/ 14 N), abbreviated as δ 15 N, and the δ( 13 C/ 12 C), abbreviated as δ 13 C, of total nitrogen and carbon in a solid sample. A Carlo Erba NC 2500 elemental analyzer (EA) is used to convert total nitrogen and carbon in a solid sample into N 2 and CO 2 gas. The EA is connected to a continuous flow isotope-ratio mass spectrometer (CF-IRMS), which determines the relative difference in stable nitrogen isotope-amount ratio ( 15 N/ 14 N) of the product N 2 gas and the relative difference in stable carbon isotope-amount ratio ( 13 C/ 12 C) of the product CO 2 gas. The combustion is quantitative; no isotopic fractionation is involved. Samples are placed in tin capsules and loaded into a Costech Zero Blank Autosampler on the EA. Under computer control, samples then are dropped into a heated reaction tube that contains an oxidant, where combustion takes place in a helium atmosphere containing an excess of oxygen gas. Combustion products are transported by a helium carrier through a reduction furnace to remove excess oxygen and to convert all nitrous oxides into N 2 and through a drying tube to remove water. The gas-phase products, mainly CO 2 and N 2 , are separated by a gas chromatograph. The gas is then introduced into the IRMS through a Finnigan MAT (now Thermo Scientific) ConFlo II interface. The Finnigan MAT ConFlo II interface is used for introducing not only sample into the IRMS but also N 2 and CO 2 reference gases and helium for sample dilution. The flash combustion is quantitative; no isotopic fractionation is involved. The IRMS is a Thermo Scientific Delta V CF-IRMS. It has a universal triple collector, two wide cups with a narrow cup in the middle; it is capable of measuring mass/charge ( m/z ) 28, 29, 30 or with a magnet current change 44, 45, 46, simultaneously. The ion beams from these m/z values are as follows: m/z 28 = N 2 = 14 N/ 14 N; m/z 29 = N 2 = 14 N/ 15 N primarily; m/z 30 = NO = 14 N/ 16 O primarily, which is a sign of contamination or incomplete reduction; m/z 44 = CO 2 = 12 C 16 O 16 O; m/z 45 = CO 2 = 13 C 16 O 16 O primarily; and m/z 46 = CO 2 = 12 C 16 O 18 O primarily.

Techniques and Methods↗
USGS2006

Determination of the δ 34 S of low-concentration sulfate in water; RSIL lab code 1949

The purpose of the Reston Stable Isotope Laboratory (RSIL) lab code 1949 is to determine the δ( 34 S/ 32 S), abbreviated as δ 34 S, of dissolved sulfate having a concentration less than 20 milligrams per liter. Dissolved sulfate is collected on an anion-exchange resin in the field, eluted in the laboratory with 3 M KCl, and precipitated with BaCl 2 at pH 3 to 4 as BaSO 4 . The precipitated BaSO 4 is filtered and dried before introduction into an elemental analyzer (EA) Carlo Erba NC 2500. The EA is used to convert sulfur in a BaSO 4 solid sample into SO 2 gas, and the EA is connected to a continuous flow isotope-ratio mass spectrometer (CF-IRMS), which determines differences in the isotope-amount ratios of stable sulfur isotopes ( 34 S/ 32 S) of the product SO 2 gas. The combustion is quantitative; no isotopic fractionation is involved. Samples are placed in a tin capsule and loaded into the Costech Zero Blank Autosampler of the EA. Under computer control, samples are dropped into a heated reaction tube that combines the oxidation and reduction reactions. The combustion takes place in a helium atmosphere containing an excess of oxygen gas at the oxidation zone at the top of the reaction tube. Combustion products are transported by a helium carrier through the reduction zone at the bottom of the reaction tube to remove excess oxygen and through a separate drying tube to remove any water. The gas-phase products, mainly CO 2 , N 2 , and SO 2 , are separated by a gas chromatograph. The gas is then introduced into the isotope-ratio mass spectrometer (IRMS) through a Finnigan MAT (now Thermo Scientific) ConFlo II interface, which is also used to inject SO 2 reference gas and helium for sample dilution. The IRMS is a Thermo Scientific Delta V Plus CF-IRMS. It has a universal triple collector with two wide cups and a narrow cup in the middle. It is capable of measuring mass/charge ( m/z ) 64 and 66 simultaneously. The ion beams from SO 2 are as follows: m/z 64 = SO 2 = 32 S 16 O 16 O; m/z 66 = SO 2 = 34 S 16 O 16 O primarily.

Techniques and Methods↗
USGS2003

Two new organic reference materials for δ13C and δ15N measurements and a new value for the δ13C of NBS 22 oil

Analytical grade L-glutamic acid is chemically stable and has a C/N mole ratio of 5, which is close to that of many of natural biological materials, such as blood and animal tissue. Two L-glutamic acid reference materials with substantially different 13 C and 15 N abundances have been prepared for use as organic reference materials for C and N isotopic measurements. USGS40 is analytical grade L-glutamic acid and has a δ 13 C value of −26.24‰ relative to VPDB and a δ 15 N value of −4.52‰ relative to N 2 in air. USGS41 was prepared by dissolving analytical grade L-glutamic acid with L-glutamic acid enriched in 13 C and 15 N. USGS41 has a δ 13 C value of +37.76‰ and a δ 15 N value of +47.57‰. The δ 13 C and δ 15 N values of both materials were measured against the international reference materials NBS 19 calcium carbonate ( δ 13 C = +1.95‰), L-SVEC lithium carbonate ( δ 13 C = −46.48‰), IAEA-N-1 ammonium sulfate ( δ 15 N = 0.43‰), and USGS32 potassium nitrate ( δ 15 N = 180‰) by on-line combustion continuous-flow and off-line dual-inlet isotope-ratio mass spectrometry. Both USGS40 and USGS41 are isotopically homogeneous; reproducibility of δ 13 C is better than 0.13‰, and that of δ 15 N is better than 0.13‰ in 100-μg amounts. These two isotopic reference materials can be used for (i) calibrating local laboratory reference materials, and (ii) quantifying drift with time, mass-dependent fractionations, and isotope-ratio-scale contraction in the isotopic analysis of various biological materials. Isotopic results presented in this paper yield a δ 13 C value for NBS 22 oil of −29.91‰, in contrast to the commonly accepted value of −29.78‰ for which off-line blank corrections probably have not been quantified satisfactorily.

Rapid Communications in Mass Spectrometry↗