Automated acoustic matrix deposition for MALDI sample preparation

Novel high-throughput sample preparation strategies for MALDI imaging mass spectrometry (IMS) and profiling are presented. An acoustic reagent multispotter was developed to provide improved reproducibility for depositing matrix onto a sample surface, for example, such as a tissue section. The unique design of the acoustic droplet ejector and its optimization for depositing matrix solution are discussed. Since it does not contain a capillary or nozzle for fluid ejection, issues with clogging of these orifices are avoided. Automated matrix deposition provides better control of conditions affecting protein extraction and matrix crystallization with the ability to deposit matrix accurately onto small surface features. For tissue sections, matrix spots of 180-200 microm in diameter were obtained and a procedure is described for generating coordinate files readable by a mass spectrometer to permit automated profile acquisition. Mass spectral quality and reproducibility was found to be better than that obtained with manual pipet spotting. The instrument can also deposit matrix spots in a dense array pattern so that, after analysis in a mass spectrometer, two-dimensional ion images may be constructed. Example ion images from a mouse brain are presented.     

Automated small tilt-angle measurement using Lau interferometry

A technique for a tilt-angle measurement of reflecting objects based on the Lau interferometry coupled with the moire readout has been proposed. A white-light incoherent source illuminates a set of two gratings, resulting in the generation of the Fresnel image due to the Lau effect. The Fresnel image is projected onto a reflecting object. The image reflected from the object is superimposed onto an identical grating, which results in the formation of a moiré fringe pattern. The inclination angle of moiré fringes is a function of tilt angle of the object. Theory and experimental arrangement of the proposed technique is presented and results of the investigation are reported.     

Automated target preparation for microarray-based gene expression analysis

DNA microarrays have rapidly evolved toward a platform for massively paralleled gene expression analysis. Despite its widespread use, the technology has been criticized to be vulnerable to technical variability. Addressing this issue, recent comparative, interplatform, and interlaboratory studies have revealed that, given defined procedures for "wet lab" experiments and data processing, a satisfactory reproducibility and little experimental variability can be achieved. In view of these advances in standardization, the requirement for uniform sample preparation becomes evident, especially if a microarray platform is used as a facility, i.e., by different users working in the laboratory. While one option to reduce technical variability is to dedicate one laboratory technician to all microarray studies, we have decided to automate the entire RNA sample preparation implementing a liquid handling system coupled to a thermocycler and a microtiter plate reader. Indeed, automated RNA sample preparation prior to chip analysis enables (1) the reduction of experimentally caused result variability, (2) the separation of (important) biological variability from (undesired) experimental variation, and (3) interstudy comparison of gene expression results. Our robotic platform can process up to 24 samples in parallel, using an automated sample preparation method that produces high-quality biotin-labeled cRNA ready to be hybridized on Affymetrix GeneChips. The results show that the technical interexperiment variation is less pronounced than with manually prepared samples. Moreover, experiments using the same starting material showed that the automated process yields a good reproducibility between samples.     

Automated microdroplet platform for sample manipulation and polymerase chain reaction

We present a fully automated system performing continuous sampling, reagent mixing, and polymerase chain reaction (PCR) in microdroplets transported in immiscible oil. Sample preparation and analysis are totally automated, using an original injection method from a modified 96-well plate layered with three superimposed liquid layers and in-capillary laser-induced fluorescence endpoint detection. The process is continuous, allowing sample droplets to be carried uninterruptedly into the reaction zone while new drops are aspirated from the sample plate. Reproducible amplification, negligible cross-contamination, and detection of low sample concentrations were demonstrated on numerous consecutive sample drops. The system, which opens the route to strong reagents and labor savings in high-throughput applications, was validated on the clinically relevant quantification of progesterone receptor gene expression in human breast cancer cell lines.     

Microwave-assisted sample combustion: a technique for sample preparation in trace element determination

A novel digestion procedure based on sample combustion ignited by microwave radiation is proposed for organic samples. Certified samples of bovine liver, pig kidney, and skim milk were used as examples to demonstrate the performance of the proposed procedure. Cadmium and copper were determined in these samples by electrothermal atomic absorption spectrometry. Samples (between 50 and 250 mg) were wrapped with paper and placed on a homemade quartz holder that was positioned inside to quartz vessels used in a commercial microwave oven. Ammonium nitrate solution was added to the paper, and vessels were pressurized with oxygen to 15 bar. The rotor containing four vessels was placed inside the oven, and microwave radiation was applied for 20 s at 1400 W. Combustion was complete in few seconds, and an additional reflux step, which was optional, was applied. The agreement to the certified values was between 96 and 105% for both analytes. Only with the combustion step, the residual carbon (RC) was below 1.3%. The RC decreased to less than 0.4% when an additional reflux step with concentrated nitric acid was applied.     

浅析气体分析仪样品的制取

在现代空分设备中,气体分析仪起到显示工况参数、指导操作等作用。但如果分析的样品不能满足及时、有效、有代表性的要求,就不能使分析仪发挥应有的作用。论述将气体分析仪所分析的样品快速、准确、有代表性地传送至仪器进行分析的经验及注意事项。     

制备聚丙烯腈初生纤维干燥样品研究

通过干喷湿纺纺丝工艺制得聚丙烯腈(PAN)初生纤维,采用不同的干燥方法获得PAN初生纤维干燥样品,考察对比自然晾干、鼓风干燥和冷冻干燥3种方法分别对样品物理特征、表面形貌和内部结构的影响。3种干燥方法均会使初生纤维样品发生收缩,样品截面积和长度均减小,但是变化程度不同。并且3种干燥方法对PAN初生纤维表面形貌、结晶特征、二甲基亚砜(DMSO)残留量以及孔结构产生不同的影响。结果表明冷冻干燥对PAN初生纤维的影响最小,可以有效的保留PAN初生纤维的原始结构,可用于制备聚丙烯腈初生纤维干燥样品。     

Analysis of silicate materials using the microwave-assisted sample preparation

A technique of microwave-assisted preparation of natural and commercial silicate materials for subsequent spectrophotometric determination of the major rock-forming components (silicon, aluminum, iron, titanium, and phosphorus) is described. The total duration of analysis is several times less than for a standard technique. In particular, the time taken for the digestion is shortened to 1 h for ten samples undergoing digestion simultaneously; the time of complexation of aluminum with aluminon and of phosphorus with molybdenum heteropoly acid is reduced from a few hours to 12 min.     

A MALDI sample preparation method suitable for insoluble polymers

Polyamides are insoluble or poorly soluble in common organic solvents, which makes normal sample preparation for matrix-assisted laser desorption/ionization (MALDI) mass spectrometry very difficult. An new analytical protocol for MALDI analysis of polyamides or other insoluble samples is described. It consists of pressing a pellet from a solid mixture of the polymer and a matrix, both in the form of finely ground powder. This sample preparation is compared with the common dried droplet sample preparation method and found to perform much better, both in terms of robustness against variation of experimental parameters and high-mass capability.     

Automated system for measurement of vibration characteristics of small units

An automated system for measurement of vibration characteristics using laser and holographic interferometry is described. Russia. Translated from Izmeritel’naya Tekhnika, No. 12, pp. 41–44, December, 1999.     

Reverse ulta-microtomy: a new method of TEM sample preparation

 Two variations of a new method of TEM metal sample preparation are proposed, hereby labeled RUM1 and RUM2, for ”reverse ultra-microtomy” 1 and 2, respectively. With these techniques, the TEM samples are formed from bulk specimens by successively slicing off layers, with an ultra-microtome, until the remnant is partially thinned to electron transparency. This requires the sample to be embedded with excellent adhesion in a mounting material whose mechanical properties resemble that of the sample. While these methods are by far slower than ordinary microtomy wherein the individual slices are used as samples, preparation times are comparable to those for creating TEM samples by standard techniques. Furthermore, the methods (i) can be used where electropolishing fails, (ii) can be favorably applied to finely layered materials and composites, (iii) permit studies of near-surface structure gradients, and (iv) permit the simultaneous observation of an original surface and the underlying material. The methods have been successfully demonstrated through comparisons between samples created through RUM1 and 2 and standard TEM samples. Artifacts caused by the new method of reverse microtoming are shown to be very much reduced compared to direct microtoming. Received: 26 September 1997 / Accepted: 1 October 1997     

Study of interaction between croscarmellose and escitalopram during sample preparation

During routine analysis of an escitalopram tablet formulation, it was seen that there was a systematic deviation between content uniformity (CU - one tablet analysis) and assay analysis (ten pooled tablets). In the presence of the excipients from the tablet, it was found that the extraction of the active pharmaceutical ingredient (API) was incomplete. It was shown that the commonly used tablet disintegrant croscarmellose sodium (crosslinked carboxy-methyl cellulose) had a significant interaction with escitalopram. This was later found to be the explanation for the lower extraction during assay testing. Under normal conditions, the extraction took place in acidic medium which caused protonation of the amine and thereby the interaction of charged species in solution. The interaction of API was studied further with pure croscarmellose and the entire tablet matrix. A range of conditions was considered, including altering extraction volumes, organic solvents, pH of the extraction solvent, and addition of competitive binder in various concentrations. It was seen that arginine was the most effective cationic competitive binder of those tested and that adding it at a suitable concentration level could significantly improve the analytical methods. In the present case, an improvement in recovery was from 98.5% to almost 100% was achieved.     

多农药残留的茶叶自制质控品的研究

目的:研究多农药残留的茶叶质控品自制方法。方法:采用定量喷施法自制了20种茶叶中常检农药残留质控品。结果:该方法的制成的农药残留质控品的回收率在定量喷施量的68.4%~92.5%,RSD均小于10%(n=6),该质控品2个月内的定值结果无显著性差异。结论:该方法操作简便,可用于茶叶中常检农药残留量的测定时的质控品。     

基于Bayes小子样二项分布单元可靠性评定的仿真方法

对于小子样二项分布单元可靠度下限评定，经典方法有很大局限性，文中介绍了Bayes方法。并在其基础上提出基于Bayes方法的Monte Carlo仿真方法，示例证明，该方法有很好的应用前途。     

Automated radioanalytical system incorporating microwave-assisted sample preparation, chemical separation, and online radiometric detection for the monitoring of total 99Tc in nuclear waste processing streams

An automated fluidic instrument is described that rapidly determines the total (99)Tc content of aged nuclear waste samples, where the matrix is chemically and radiologically complex and the existing speciation of the (99)Tc is variable. The monitor links microwave-assisted sample preparation with an automated anion exchange column separation and detection using a flow-through solid scintillator detector. The sample preparation steps acidify the sample, decompose organics, and convert all Tc species to the pertechnetate anion. The column-based anion exchange procedure separates the pertechnetate from the complex sample matrix, so that radiometric detection can provide accurate measurement of (99)Tc. We developed a preprogrammed spike addition procedure to automatically determine matrix-matched calibration. The overall measurement efficiency that is determined simultaneously provides a self-diagnostic parameter for the radiochemical separation and overall instrument function. Continuous, automated operation was demonstrated over the course of 54 h, which resulted in the analysis of 215 samples plus 54 hly spike-addition samples, with consistent overall measurement efficiency for the operation of the monitor. A sample can be processed and measured automatically in just 12.5 min with a detection limit of 23.5 Bq/mL of (99)Tc in low activity waste (0.495 mL sample volume), with better than 10% RSD precision at concentrations above the quantification limit. This rapid automated analysis method was developed to support nuclear waste processing operations planned for the Hanford nuclear site.