Sample Preparation Issues

Sample preparation plays the key role in producing a reliable MALDI mass spectrum of a polymer [17-24]. In sample preparation, depending on the nature of 

---

In most cases, the sample titer curves followed the predicted titer standard curve based upon known concentration ratios. Observed variations in linearity were traced back to inconsistencies in labeling rather than cross-reactivity or sample preparation issues such as pipetting or mixing errors. Overall, antigen arrays performed better than antibody arrays. While the exact reasons for the... 

Sample preparation procedures commonly used in the field of drug residues analysis are briefly described below. Since some of these overlap and cannot be strictly separated, the intent of the authors is to attempt to outline the complexity of die sample preparation issue rather than to give a comprehensive listing of the relevant literature. 

Detailed discussion of titratable acidity and pH, gives a good overview of the theory and some applications of each analysis. Also addresses sample preparation issues. 

Sr). Over the past 30 years, lead and strontium isotope ratios have been measured with thermal ionization mass spectrometry (TIMS). Elemental salts are deposited on a filament heated to produce ionized particles, which are then sent into a mass spectrometer where they are detected by multiple Faraday cups arrayed such that ions of several masses are collected simultaneously. TIMS is capable of high precision isotope discrimination, but the instruments tend to be large and expensive, and extensive sample preparation is required prior to sample introduction. Newer ICP-MS-based technologies like multi-collector ICP-MS (especially laser ablation) circumvent some of the sample preparation issues while exploiting the precision of simultaneous mass discrimination, but they are still limited by the number and configuration of ion collectors. 

Sample preparation issues inherent with on-line extraction techniques that deal with the addition of triethylamine to the mobile phase and the calculation of extraction recovery are likely to be addressed for future applications however, this method appears to... 

In this section, some of the general sample preparation issues that influence protein analysis by MALDI-MS experiments are described. 

Electrochemical methods are in general free from the difficulties associated with the current industry testing methods and present an opportunity for a relatively quick, simple, and inexpensive approach, free of temperature limitations and sample preparation issues. Electrochemistry has been previously employed to inspect lubricant condition over the life of engine oils [6, 7]. For example, electrochemical impedance spectroscopy (EIS) has been used for characterization of both engine oils [8] and nonaqueous colloidal dispersions [9]. 

Traditional analytical methods to analyze amphetamines include gas chromatography-mass spectrometry where derivatization is often required to fecilitate analysis. Besides sample preparation issues, it has been demonstrated that injection port chemistry in the GC can lead to misleading results with some members of the amphetamine class. To circumvent these issues, liquid chromatography-mass spectrometry (LC-MS/ MS) offers the promise of a simpler sample preparation procedure and fewer analytical concerns. This chapter describes an LC-MS/MS technique for the analysis of 14 ATSs in blood, serum/plasma, and urine. The method is quantitative and has reporting limits in the low ng/mL range. Electrospray ionization is used in the positive ion mode. Two transitions for each compound are monitored along with ion ratios. 

In Section 2 the general features of the electronic structure of supported metal nanoparticles are reviewed from both experimental and theoretical point of view. Section 3 gives an introduction to sample preparation. In Section 4 the size-dependent electronic properties of silver nanoparticles are presented as an illustrative example, while in Section 5 correlation is sought between the electronic structure and the catalytic properties of gold nanoparticles, with special emphasis on substrate-related issues. 

Chassaigne H, and Lobinski R (1998) Characterization of horse kidney metallothionein isoforms by electrospray MS and reversed-phase HPLC-electrospray MS. Analyst 123 2125- 2130. Chemosphere (1999) Special issue - Sources of error in methylmercury determination during sample preparation, derivatisation and detection. Chemosphere 39 1037-1224. 

The development of a robust analytical method is a complex issue. The residue analyst has available a vast array of techniques to assist in this task, but there are a number of basic rules that should be followed to produce a reliable method. The intention of this article is to provide the analyst with ideas from which a method can be constructed by considering each major component of the analytical method (sample preparation, extraction, sample cleanup, and the determinative step), and to suggest modern techniques that can be used to develop an effective and efficient overall approach. The latter portion emphasizes mass spectrometry (MS) since the current trend for pesticide residue methods is leading to MS becoming the method of choice for simultaneous quantitation and confirmation. This article also serves to update previous publications on similar topics by the authors. ... 

Special issue on Sample Preparation for Chromatographic Analysis, Anal. Chim. Acta 236 (1) (1990). 

This chapter describes the key clinical data preparation issues and the different classes of clinical data found in clinical trials. Each class of data brings with it a different set of challenges and special handling issues. Sample case report form (CRF) pages are provided with each type of data to aid you in visualizing what the data look like. The key data preparation issues presented are concepts that apply universally across the various classes of clinical trial data. 

Experimental considerations Sample preparation and data evaluation are similar to membrane osmometry. Since there is no lower cut-off as in membrane osmometry, the method is very sensitive to low molar mass impurities like residual solvent and monomers. As a consequence, the method is more suitable for oligomers and short polymers with molar masses up to (M)n 50kg/mol. Today, vapour pressure osmometry faces strong competition from mass spectrometry techniques such as matrix-assisted laser desorption ionisation mass spectrometry (MALDI-MS) [20,21]. Nevertheless, vapour pressure osmometry still has advantages in cases where fragmentation issues or molar mass-dependent desorption and ionization probabilities come into play. 

Infrared spectroscopy/microscopy certainly is the primary method of choice when organic substances have to be identified. Sample preparation usually is simple for identification purposes, but will be an issue for imaging experiments, and spatial resolution may then well be only in the range of a few micrometers, depending on the used experimental approach (transmission, ATR). 

---