ESIS reference materials

An adequate route for preliminary product identification, in cases when reference sample is not available, could involve HPLC combined with DAD or MS. The goal of paper I was to investigate and compare the use of HPLC-DAD and electrospray ionization (ESI) MS to provide rapid and preliminary identification of the product without any reference material available at an initial stage of a synthesis. 

Lube, T, Danzer, R., Kiibler, J., Dusza, J.. Erauw, J.-P., Klemm, H., and Sglavo, V.M. (2002) Strength and fracture toughness of the ESIS silicon nitride reference material, in Fracture Beyond 2000... 

T. Lube, R. Danzer "An ESIS Testing Program for a Silicon Nitride Reference Material , in A. Neimitz, I.V. Rokach, D. Kocanda, K. Golos (Eds ), Fracture Beyond 2000 - Proc. of ECF 14, Vol. II, EMAS Publications, Sheffield, 2002, 401-408... 

FIGURE 18.3 Extracted ion current profiles of the water-soluble vitamins detected in a green kiwi extract (see reference [138] for the details). The LC—SRM (standard reference material) chromatogram was acquired by a high-flow ESI source (TurboIonSpray source). Each analyte was identified on the basis of the retention time, the two selected SRM transitions and their relative abundance. Only the most intense SRM ion current is reported in the figure. 

Gradient RP-HPLC separation with 0.1% formic acid and methanol as mobile phase components (0.25 mL/min) combined either with ESI-time-of-flight [23] MS detection or with chemiluminescence nitrogen detection (CLND) was used to identify and, respectively, quantify illicit drugs in seized material without primary reference standards [24], The method exploits the accurate mass measurement provided by TOE MS, enabling the unequivocal identification of molecular formula of the unknown analyte, and the CNLD equimolar response to nitrogen. 

Calibrants are required to calibrate the mass scale of any mass spectrometer, and it is important to find reference compounds that are compatible with a particular ion source. Calibrants commonly used in electron ionization (El) and chemical ionization (Cl), such as perfluorocarbons, are not applicable in the ESI mode. The right calibrants for LC-ESI-MS should (1) not give memory effects (2) not cause source contamination through the introduction of nonvolatile material (3) be applicable in both positive- and negative-ion mode. The main calibrants used or still in use to calibrate ESI-MS can be divided into the following categories polymers, perfluoroalkyl triazines, proteins, alkali metal salt clusters, polyethers, water clusters, and acetate salts. 

In con (ras( to all other applications referred to in this article, that make use of 3.0-5 pm particles, Kintz et al. chose an ACQUITY C18 column (Waters) of 50 mm length and 2.1 mm I.D. packed with 1.7 pm particles. They analysed scopolamine from hair samples by LC-ESI-MS/MS with a flow of 0.3 ml/min [56], The retention time of scopolamine was as short as 1.13 min and the LOQ was excellent at 0.2 pg/ mg hair. This LOQ was 25-times lower than that obtained with conventional 3.5 pm material as reported before by the same research group (Table 8) [57],... 

As a result of the catalyst and process conditions used in their manufacture, the particular copolymers of current major interest are atactic, and contain typically up to about 50 mol% ( 80 wt%) styrene. These materials have been described as pseudo-random , since successive head-to-tail styrene chain insertions have been shown to be absent, even at high levels of styrene incorporation [1,2]. The term ethylene-styrene interpolymer (ESI) is used here to describe the specific ethylene-styrene copolymers produced via INSITE Technology. For convenience, all subsequent comonomer contents are expressed in weight percentages, unless otherwise stated. For example, the code ES70 refers to an interpolymer having 70 wt.% comonomer styrene incorporation. 

ESI is often referred to as a soft ionization techniqne in that little fragmentation of intaet moleeular ions is produced. Despite the numerous benefits of ESI MS, it suffers from a shorteoming in that it is snsceptible to ion suppression effeets from high concentrations of bnffer, salt, and other endogenous material in matrix solntions. 

Reference Pavan, A. and Williams, J. G., Development of a Standard for Determining K,< and G,c for Plastics at High Loading Rates the ESIS Protocol for 1 m/s Testing, Limitations of Test Methods for Plastics, ASTM STP1369, J. S. Peraro, Ed., American Society for Testing and Materials, West Conshohocken, PA, 2000. 

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