Role of gas dynamics in negative ion formation in an atmospheric sampling glow discharge ionization source

1993 ◽  
Vol 65 (6) ◽  
pp. 778-783 ◽  
Author(s):  
David M. Chambers ◽  
Scott A. McLuckey ◽  
Gary L. Glish
Keyword(s):  
Glow Discharge ◽  
Gas Dynamics ◽  
Negative Ion ◽  
Ionization Source ◽  
Ion Formation ◽  
Atmospheric Sampling

A novel and sensitive LC-MS/MS method for the quantitation of ceftiofur in pharmaceutical preparations and milk samples

2020 ◽  
Vol 23 ◽  
Author(s):  
Serkan Levent ◽  
Saniye Özcan ◽  
Aysun Geven ◽  
Nafiz Öncü Can
Keyword(s):  
Quantitative Estimation ◽  
Signal To Noise Ratio ◽  
Multiple Reaction Monitoring ◽  
Pharmaceutical Preparations ◽  
Calibration Method ◽  
Negative Ion ◽  
Cow Milk ◽  
Tandem Mass ◽  
Ionization Source ◽  
Liquid Chromatography Tandem Mass

Introduction:: In the present study, a sensitive and selective liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was described for the determination of ceftiofur (CEF) in cow milk and pharmaceutical preparations. CEF is an antibiotic compound, which is commonly used in the treatment of animal diseases such as respiratory system, soft tissue, and foot infections, as well as postpartum acute puerperal metritis. One of the critical features of CEF is its prescription while breastfeeding of cows; in accordance, its quantitative estimation is essential to assess its residual amounts. Methods:: In the method reported herein, after simple protein precipitation using acetonitrile, the pre-treated samples were introduced in to an LC-MS/MS instrument equipped with a Chromolith® High-Resolution RP-18 series HPLC column (100 mm × 4.6 mm from Merck KGaA, Germany). Electrospray ionization was employed as the ionization source in the triplequadrupole tandem mass spectrometer. Results:: For the calibration method using solvent-based standards; LOQ was 3.038 ng/mL, 12.15 ng/mL, and LOD was 1.215 ng/mL and 6.076 ng/mL for ESI+ and ESI- modes, respectively. On the other hand, for the method of matrix-matched standards; LOQ was 1.701 ng/mL, 10.13 ng/mL, and LOD was 0.486 ng/mL and 5.929 ng/mL for ESI+ and ESI- modes, respectively as obtained from signal to noise ratio. Conclusion:: Applicability of both positive and negative ion modes was tested, and the analyte was detected via multiple reaction monitoring. The distorting effects of the milk matrix on the MS ionization and quantitation of CEF were overcome by using matrix-matched calibration for the first time.

Temporary negative ion formation in interactions of low-energy inert gas ions (He+, Ne+) with Cs-adsorbed Cu(111) surfaces

1995 ◽  
Vol 341 (1-2) ◽  
pp. 19-28 ◽  
Author(s):  
Q.B. Lu ◽  
D.J. O'Connor ◽  
B.V. King ◽  
Y.G. Shen ◽  
R.J. MacDonald
Keyword(s):  
Low Energy ◽  
Inert Gas ◽  
Negative Ion ◽  
Ion Formation
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