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PubMed1988

Automated sequential trace enrichment of dialysates and robotics. A technique for the preparation of biological samples prior to high-performance liquid chromatography.

The development of the sample preparation process, the automated sequential trace enrichment of dialysates, in association with a cartesian robotic sampler is described. The system has been applied to the total automation of the preparation of biological samples and high-performance liquid chromatographic analysis. Concepts of the technique are reported together with an examination of its application to free and total analyte estimation. Examples of chromatographic separations obtained from the preparation of a variety of different analytes and sample materials are given.

Amino Acids↗

PubMed2006

Application of hydrocyanic acid vapor generation via focused microwave radiation to the preparation of industrial effluent samples prior to free and total cyanide determinations by spectrophotometric flow injection analysis.

A sample preparation procedure for the quantitative determination of free and total cyanides in industrial effluents has been developed that involves hydrocyanic acid vapor generation via focused microwave radiation. Hydrocyanic acid vapor was generated from free cyanides using only 5 min of irradiation time (90 W power) and a purge time of 5 min. The HCN generated was absorbed into an accepting NaOH solution using very simple glassware apparatus that was appropriate for the microwave oven cavity. After that, the cyanide concentration was determined within 90 s using a well-known spectrophotometric flow injection analysis system. Total cyanide analysis required 15 min irradiation time (90 W power), as well as chemical conditions such as the presence of EDTA-acetate buffer solution or ascorbic acid, depending on the effluent to be analyzed (petroleum refinery or electroplating effluents, respectively). The detection limit was 0.018 mg CN l(-1) (quantification limit of 0.05 mg CN l(-1)), and the measured RSD was better than 8% for ten independent analyses of effluent samples (1.4 mg l(-1) cyanide). The accuracy of the procedure was assessed via analyte spiking (with free and complex cyanides) and by performing an independent sample analysis based on the standard methodology recommended by the APHA for comparison. The sample preparation procedure takes only 10 min for free and 20 min for total cyanide, making this procedure much faster than traditional methodologies (conventional heating and distillation), which are time-consuming (they require at least 1 h). Samples from oil (sour and stripping tower bottom waters) and electroplating effluents were analyzed successfully.

Journal Article↗

PubMed1992

Preparation of muscle samples for comparative electron microscopy.

The interpretation of muscle structure by scanning electron microscopy (SEM) has not been consistent among various studies. Consequently, the literature is confusing with respect to the identity of T-tubules, transverse ridges, Z-disks, and intermyofibrillar connections. The objective of this research was to evaluate the effects of different methods of sample preparation and imaging on ultrastructural details of previously identified transverse structures and intermyofibrillar connections and to verify or disprove the commonality of these structures under different viewing conditions. Scanning electron microscopy coupled with a cold stage, SEM at room temperature, and transmission electron microscopy (TEM) of thin sections were most appropriate for exposing detail of inter- and intracellular structures and for measuring sarcomere length and spacing of intermyofibrillar connections. Scanning electron microscopy of samples mounted on a cold stage, fractured, and sublimed provided excellent images of meat and muscle ultrastructure and may be used in correlative microscopy. Sarcomere length and spacing between intermyofibrillar connections were similar among most specimen preparation techniques and were affected similarly by heat treatments. Results indicate that the regularly spaced transverse structures viewed by conventional SEM and the intermyofibrillar connections viewed by low-temperature SEM are Z-disks.

Animals↗

PubMed2004

Applied study on magnetic nanometer beads in preparation of genechip samples.

A protocol for enrichment and adsorption of karyocyte from whole blood by using magnetic nanometer beads as solid-phase absorbents was presented. The PCR amplification could be accomplished by using the nanobeads with karyocyte as template directly and the PCR products were applied on an oligonucleotide array to do gene typing. The HLA-A PCR amplification system and a small HLA-A oligonucleotide microarray were applied as the platform and an experiment protocol of separating karyocyte from whole blood using the magnetic nanometer beads (Fe2O3) were set up. The experimental conditions were also discussed. It showed that pH level of PBS eluent, Taq enzyme quantity and fragment length of products could influent the amplification results, and the magnetic nano-beads could succeed in sample preparation in microarray to provide a promising way in automatic detection and lab-on-a-chip.

Adsorption↗

PubMed1997

Preparation of PCR samples from food by a rapid and simple centrifugation technique evaluated by detection of Escherichia coli O157:H7.

A sample treatment method based on buoyant density centrifugation which separates bacteria from food, concentrates bacteria and removes PCR inhibitors is described. The method involves a one minute centrifugation of food homogenate layered over a gradient medium (Percoll or BacXtractorTM) in Eppendorf tubes, followed by a single wash step. The small scale of this treatment makes it possible to process many samples in a short time. To evaluate the method beef and minced beef samples, spiked with strains of Escherichia coli O157:H7, were treated and then analysed by PCR aimed at verocytotoxin- (VT1 and VT2) and eae-genes. The detection limits in 1:10 (w/v) beef and minced beef homogenates were 125-250 cfu ml-1 (1250-2500 cfu g-1) and 1000 cfu ml-1 (1 x 10(4) cfu g-1), respectively. The enrichment of spiked samples in buffered peptone water at 37 degrees C for 6 hours before buoyant density centrifugation and PCR, allowed 0.5 cfu g-1 beef and 5 cfu g-1 minced beef to be detected. This combination of enrichment and buoyant density centrifugation was also used for analysis of 43 beef samples from a consignment in which E. coli O157:H7 had been detected, and detected VT-genes in all 43 samples. E. coli O157:H7 was also separated and detected in spiked samples of milk, lettuce, shrimps, and blue cheese at arbitrary concentrations of 3000 cfu ml-1. The present sample preparation method has the potential to be applicable to many other combinations of bacteria and food, and in connection with other detection methods than PCR as well.

Centrifugation, Density Gradient↗

PubMed2003

Mixing apparatus for preparing NMR samples under pressure.

The size limit for protein NMR spectroscopy in solution arises in large part from line broadening caused by slow molecular tumbling. One way to alleviate this problem is to increase the effective tumbling rate by reducing the viscosity of the solvent. Because proteins generally require an aqueous environment to remain folded, one approach has been to encapsulate hydrated proteins in reverse micelles formed by a detergent and to dissolve the encapsulated protein in a low-viscosity fluid. The high volatility of suitable low-viscosity fluids requires that the samples be prepared and maintained under pressure. We describe a novel apparatus used for the preparation of such samples. The apparatus includes a chamber for mixing the detergent with the low-viscosity solvent, a second chamber for mixing this with hydrated protein, and a 5-mm (o.d.) zirconium oxide NMR sample tube with shut-off valves designed to contain pressures on the order of 10 bar, sufficient for liquid propane. Liquids are moved from one location to another by introducing minor pressure differentials between two pressurization vessels. We discuss the operation of this apparatus and illustrate this with data on a 30-kDa protein complex (chymotrypsin:turkey ovomucoid third domain) encapsulated in reverse micelles of the detergent, sodium bis (2-ethylhexyl) sulfosuccinate, aerosol-ot (AOT), dissolved in liquid propane.

Animals↗

PubMed2004

Preliminary investigation of electrodynamic charged droplet processing to couple capillary liquid chromatography with matrix-assisted laser desorption/ionization mass spectrometry.

Charged droplet processing methodology, that utilizes electrodynamic levitation technology to control the trajectories of picoliter volume charged droplets and deliver them to a target plate at atmospheric pressure, has been developed. Termed wall-less sample preparation (WaSP), this methodology offers several features that could prove beneficial to the preparation of sample spots from separation column effluents for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) analysis. These features include solute pre-concentration factors of 10(1) to 10(3) due to volatile solvent evaporation prior to droplet deposition onto the target plate, high spatial accuracy of the deposition position of each processed droplet (+/-5 microm), and the ability to prepare sample spots as small as 20 microm in diameter from a single droplet. Here a new mode of operation of this methodology is described and used as an offline post-column pre-concentrating interface between capillary liquid chromatography (capLC) and a target plate for offline MALDI-MS. Using a fraction from the capLC separation of peptides produced by the proteolytic digestion of the protein cytidine 5'-triphosphate:phosphocholine cytidylyltransferase, MALDI sample spots were prepared using the dried-droplet method, direct piezoelectric droplet dispensing, and the processing of piezo-dispensed droplets by WaSP. The sample spot morphology was investigated using light microscopy, and peptide ion abundances produced by MALDI were measured using time-of-flight (TOF) MS. The advantages of developing an online capLC/WaSP interface with MALDI-MS in the future are discussed along with some of the challenges that may be encountered in such an endeavor.

Choline-Phosphate Cytidylyltransferase↗

PubMed1976

Contaminants in illicit amphetamine preparations.

Samples from illicit preparations of amphetamine and methamphetamine were investigated by combined gas chromatography-mass spectrometry (GC/MS) to detect and identify contaminants, excipients, and by-products from manufacture. In addition, these samples were subjected to energy-dispersive X-ray (EDX), and it was determined that the preparations of these compounds were made in the present of zinc, probably as a reductant. In addition to identifying polycondensation products from these preparations, the illicit origin of amphetamine-type drugs can generally be determined by the detection of contaminants and by-products present in submitted samples. Thus, a multidisciplinary analytical approach yields data of potential value for comparative examinations and possibly for legal purposes.

Amphetamines↗

PubMed1983

Actin-myosin interactions visualized by the quick-freeze, deep-etch replica technique.

A new method of preparing biological samples for electron microscopy has been used to re-examine the structure of actin filaments, actin filaments decorated by myosin subfragment-1 (S1), and insect flight muscles. Samples were quick-frozen by contact with a block of copper cooled to approximately 4 K; then were freeze-fractured, deep-etched, rotary-replicated with platinum, and viewed in a transmission electron microscope. By this approach, actin filaments display prominent transverse bands whose repeat (approximately 5.5 nm) and pitch (approximately 15 to 20 degrees) fit with the expected left-handed "genetic" helix. Freeze-etched actin filaments do not, however, display the usual two-start helix as prominently as is seen after negative staining, and they also appear substantially thicker than after negative staining (9 to 10 nm versus 8 nm). The latter two-start helix appears very clearly after S1 decoration. Nevertheless, freeze-etched acto-S1 does not display the "arrowheads" that are seen after negative staining. Instead it displays the outer envelope of the helically deployed S1, and as would be expected from current models derived from optical reconstruction of negatively stained samples, this surface view looks only slightly polarized. Finally, the quick-freeze, deep-etch approach provides particularly distinct images of the crossbridges in insect flight muscles. These are plentiful and regularly arranged in rigor muscles, but rare in muscles relaxed with ATP before freezing. In rigor muscles fixed with aldehydes, these crossbridges assume a broad distribution of inclination, ranging from 45 degrees to 90 degrees with a mean of approximately 80 degrees, which is less tilt than has been seen before in thin-sectioned muscles. However, when aldehyde fixation is followed by exposure to tannic acid with or without uranyl acetate block-staining, crossbridges assume a more acute angle with respect to the fiber axis, centering around 45 degrees. This is associated with a commensurate reduction in interfilament spacing within the muscle fibers, such that tilted crossbridges are not any longer than untilted ones (both measuring approximately 15 nm). At the opposite extreme, crossbridges often become stretched in unfixed muscles, owing to an unnatural increase in interfilament spacing that occurs during sample preparation; in such regions, crossbridges display narrow "stalks", which invariably emerge from the thick filaments at close to 90 degrees. We conclude that crossbridge shape and orientation is strongly affected by different methods of sample preparation, and this will make it difficult to visualize natural crossbridge movements by electron microscopy.

Actins↗

PubMedDate not supplied

Proteomic analysis of lipid microdomains from lipopolysaccharide-activated human endothelial cells.

The endothelium plays a critical role in orchestrating the inflammatory response seen during sepsis. Many of the inflammatory effects of Gram-negative sepsis are elicited by lipopolysaccharide (LPS), a glycolipid component of bacterial cell walls. Lipid-rich microdomains have been shown to concentrate components of the LPS signaling system. However, much remains to be learned about which proteins are constituents of lipid microdomains, and how these are regulated following cell activation. Progress in this area would be accelerated by employing global proteomic analyses, but the hydrophobicity of membrane proteins presents an analytical barrier to the effective application of such approaches. Herein, we describe a method to isolate detergent-resistant membranes from endothelial cells, and prepare these samples for proteomic analysis in a way that is compatible with subsequent separations and mass spectrometric (MS) analysis. In the application of these sample preparation and MS analyses, 358 proteins from the lipid-rich microdomains of LPS-activated endothelial cell membranes have been identified of which half are classified as membrane proteins by Gene Ontology. We also demonstrate that the sample preparation method used for solubilization and trypsin digestion of lipid-rich microdomains renders the membrane spanning sequences of transmembrane proteins accessible for endoproteolytic hydrolysis. This analysis sets the analytical foundation for an in-depth probing of LPS signaling in endothelial cells.

Cells, Cultured↗

PubMed1992

Preparation of samples for high-performance liquid chromatography of inositol phosphates.

A simple method is described for the removal of extraneous material from tissue extracts prior to anion-exchange high-performance liquid chromatography of inositol phosphates. Samples are prepared by extraction with trichloroacetic acid or perchloric acid followed by removal of the excess acid. The extracts are then passed through small Dowex-50 cation-exchange columns and eluted with water. Dowex-50 pretreatment removes most of the ultraviolet absorbing material and cations from the samples but does not alter the content of inositol phosphates. This treatment results in improved reliability of chromatography, especially with respect to weakly retained molecules such as adenosine 5'-phosphate and the isomers of inositol monophosphate. In addition, sample pretreatment improves the useful lifetime of the analytical anion-exchange columns.

Animals↗

PubMed2000

Higher throughput bioanalysis by automation of a protein precipitation assay using a 96-well format with detection by LC-MS/MS.

Generic methodology for the automated preparation and analysis of drug levels in plasma samples within a drug discovery environment was achieved through the redesign of a protein precipitation assay to a microtiter (96-well) plate format and the application of robotic liquid handling for performance of all transfer and pipetting steps. Validation studies revealed that the application of robotics to sample preparation, in general, maintained the analytical accuracy and precision compared with preparing samples manually. The use of rapid gradient LC-MS/MS for analysis coupled with flow diversion of the solvent front allowed the introduction of protein-precipitated samples into the mass spectrometer without the necessity for source cleaning. The problem inherent in automatically pipetting plasma, caused by fibrinogen clots, was overcome by storing samples at -80 degrees C and thus precluding clot formation. The resulting methodology allowed sample preparation for a 96-well plate designed to accommodate 54 unknowns, duplicate 12-point calibration curves, and 6 sets of quality controls at three levels in approximately 2 h. This approach allowed an increase in throughput of sample preparation and analysis to >400 samples per day per LC-MS/MS instrument with minimal manual intervention. Overall, substantial time savings were realized, demonstrating that automation is an increasingly essential tool in a drug discovery bioanalytical environment.

Automation↗

PubMed1991

Improved amplification of cytomegalovirus DNA from urine after purification of DNA with glass beads.

Cytomegalovirus can be detected in a variety of specimens including leukocytes, urine, saliva, feces, and various tissues by polymerase chain reaction (PCR) amplification of viral DNA. Although methods for amplification are fairly standard, sample preparation is not well characterized, especially for tissue. Typically, preparation of samples for PCR amplification ranges from simple boiling to phenol/chloroform extraction and quantification before testing. Several reports have described inhibition of the PCR in some samples types. Here we show that reliable detection of cytomegalovirus DNA in urine is obtained only after some degree of DNA purification, presumably because of PCR inhibition by a yet unidentified component present in a few of the urine samples tested. Glass, in the form of fine beads, was used to adsorb DNA such that protein and other substances could be selectively eluted before the recovery of DNA for PCR amplification. Urine samples prepared by this method did not show inhibition, and results correlated well with those by tissue culture for detection of cytomegalovirus.

Acquired Immunodeficiency Syndrome↗

PubMed1998

Isotope ratio determination in boron analysis.

Traditionally, boron (B) isotope ratios have been determined using thermal ionization mass spectrometry (TIMS) and, to some extent, secondary ion mass spectrometry (SIMS). Both TIMS and SIMS use a high-resolution mass analyzer, but differ in analyte ionization methods. TIMS uses electrons from a hot filament, whereas SIMS employs an energetic primary ion beam of Ga+, Cs+, or O- for analyte ionization. TIMS can be used in negative or positive ion modes with high sensitivity and precision of B isotope ratio determination. However, isobaric interferences may be a problem, if the sample is not well purified and/or memory of the previous sample is not removed. Time-consuming sample preparation, analyte (B) purification, and sample determination processes limit the applications of TIMS for routine analyses. SIMS can determine B and its isotope ratio in intact solid samples without destroying them, but has poorer resolution and sensitivity than TIMS, and is difficult to standardize for biological samples. Development of plasma-source mass spectrometry (MS) enabled the determination of B concentration and isotope ratio without requiring sample purification. Commonly used plasma-source MS uses an Ar inductively coupled plasma (ICP) as an ionization device interfaced to a low-resolution quadrupole mass analyzer. The quadrupole ICP-MS is less precise than TIMS and SIMS, but is a popular method for B isotope ratio determination because of its speed and convenience. B determination by ICP-MS suffers no spectroscopic interferences. However, sample matrices, memory effects, and some instrument parameters may affect the accuracy and precision of B isotope ratio determination if adequate precautions are not taken. New generations of plasma-source MS instruments using high-resolution mass analyzers provide better sensitivity and precision than the currently used quadrupole ICP-MS. Because of the convenience and high sample throughput, the high-resolution ICP-MS is expected to be the method of choice for B isotope ratio determination. The current state of instrumental capabilities is adequate for B isotope determination. However, precision and accuracy are primarily limited by sample preparation, introduction, and analytical methodology, including 1. Analyte loss and isotope fractionation during sample preparation. 2. The precision of B isotope determination in small samples, especially those containing low concentrations. 3. Difficult matrices. 4. Memory effects. Sample preparation by alkali fusion allows rapid and complete decomposition of hard-to-digest samples, but high-salt environments of the fused materials require extensive sample purification for B ratio determination. The alternative wet-ashing sample decomposition with HF also results in B loss and isotopic fractionation owing to the high volatility of BF3. Open-vessel dry- or wet-ashing methods usually do not work well for animal samples, and are also prone to B loss and contamination. Closed-vessel microwave digestion overcomes these problems, but the digests of biological materials have high C contents, which cause spectral interference on 11B and affect 11B/10B ratios. Exchange separation/preconcentration of B using exchange (cation or anion exchange, B-specific resin, e.g., Amberlite IRA-743) tend to cause B isotope fractionation, and C eluting from these resin columns may interfere with B isotope ratio determination. Memory effects of B that occur during sample determination may cause serious errors in B isotope ratio determination, especially when samples varying in B concentrations and/or isotope composition are analyzed together. Although the utilization of high-resolution plasma-source MS will undoubtedly improve analytical precision, it is the sample preparation, sample introduction, and analytical methodology that represent the primary limitation to accurate and precise B isotope ratio determination.

Boron↗

PubMed2000

Rapid bioanalytical determination of dextromethorphan in canine plasma by dilute-and-shoot preparation combined with one minute per sample LC-MS/MS analysis to optimize formulations for drug delivery.

The determination of dextromethorphan in canine plasma is used to demonstrate the high throughput bioanalytical approach of automated dilute-and-shoot (DAS) sample preparation followed by a 1 min isocratic liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. Dilute-and-shoot preparation is commonly used for the determination of drugs in several biological matrices such as urine and saliva, but is not typically used with plasma samples because the amount of protein present in plasma can lead to a variety of problems including column failure. As a result, plasma sample preparation usually removes protein by precipitation, extraction or filtration; however, the dilute-and-shoot approach solubilizes proteins throughout the chromatographic portion of the assay. The attributes of this approach are compared with a previously validated liquid/liquid extraction procedure for determination of dextromethorphan in plasma. Accuracy and precision of both methods are similar. The lower limit of quantitation (LLOQ) of the dilute-and-shoot approach is much higher at 2 ng/ml versus 5 pg/ml with the liquid/liquid extraction; however, the sample throughput of the preparation portion of the dilute-and-shoot approach is more than 50-fold greater. The ruggedness of the dilute-and-shoot method was thoroughly investigated because of the problems traditionally associated with the direct injection of diluted plasma onto an LC-MS/MS instrument. With the optimal conditions, greater than 1,000 injections of diluted plasma have been successfully performed on a single column in less than 19 h making this technique an excellent approach for the rapid preparation and high throughput of plasma samples containing drug levels in the ng/ml range or higher. Application of this methodology to measure the levels of dextromethorphan in canine plasma to evaluate drug delivery from various formulations is also presented.

Animals↗

PubMedDate not supplied

A precollaborative study of weight determination methods for quick frozen shrimp.

A precollaborative study compared the accuracy and precision of official AOAC methods with other selected methods for determining net weight of IQF-glazed shrimp and block-glazed shrimp, assessed the ruggedness of the methods with respect to changes in the levels of the factors under study, and selected candidate methods for use in a collaborative study. Methods tested for determining deglazed (frozen) net weight of IQF-glazed shrimp were (1) AOAC Method 963.18 and (2) the Water Bath Dip Method. Methods tested for determining thawed net weight of IQF-glazed shrimp were (1) AOAC Method 967.13, (2) Modified AOAC Method(mnb) 967.13, (3) Modified AOAC Method(pb) 967.13, (4) the Codex Method, (5) the Air Thaw Method, and (6) Modified AOAC Method 963.18. The same methods except Modified AOAC Method 963.18 were tested for determining thawed net weight of block-glazed shrimp. A total of 864 0.45 kg (1 lb), 0.90 kg (2 lb), and 1.35 kg (3 lb) IQF-glazed shrimp test samples and 234 2.25 kg (5 lb) block-glazed shrimp test samples were collected. During sample preparation, test samples were subjected to either water with or without sodium tripolyphosphate (STP). During deglazing (IQF-glazed shrimp only) and/or thawing, test samples were allocated in a factorial design to assess the effects of STP presence (no STP and STP), sieve mesh sizes (2.83 and 2.38 mm; 0.11 and 0.09 in.), and sieve diameters (20 and 30 cm; 8 and 12 in.). During weighing, test samples were further allocated to a sequence of weighing procedures designed to assess the effects of using sieve weights (dry and wet) in combination with paper towel use (no and yes) and tared pan weights when calculating determined net weights. On the basis of the results of this precollaborative study, Modified AOAC Method(pb) 967.13 and the Air Thaw Method seem to be the best methods to determine net weight of IQF-glazed and block-glazed shrimp. Therefore, to validate method choices in the collaborative study, the authors recommend analysis of IQF-glazed shrimp and block-glazed shrimp test samples, each prepared with or without STP, by Modified AOAC Method(pb) 967.13 and the Air Thaw Method. To fulfill AOAC requirements, IQF-glazed shrimp and block-glazed shrimp test samples, each prepared with or without STP, must be analyzed by official methods: AOAC Method 963.18 (IQF-glazed shrimp only) and AOAC Method 967.13. During testing, sieve mesh size will be either 2.83 or 2.38 mm (0.11 or 0.09 in.), sieve diameter will be limited to 30 cm (12 in.), and weighing procedure will be limited to tared pan.

Animals↗

PubMed1991

A technique for the preparation of cross-sectional TEM samples of ZnSe/GaAs heterostructures which eliminates process-induced defects.

Cross-sectional transmission electron microscopy (TEM) sample preparation of ZnSe/GaAs epitaxial films is investigated. Conventional argon ion milling is shown to produce a high density (approximately 5-8 x 10(11)/cm2) of small (diameter approximately 60-80 A) extended defects (stacking faults, microtwins, double positioning twins, etc.). In addition, transmission electron diffraction results indicate a thin ZnO layer can also occasionally form upon ion milling or electron-beam irradiation although the exact conditions for ZnO formation are not well understood. Conventional TEM (amplitude contrast) and high-resolution TEM (phase contrast) imaging in combination with transmission electron diffraction studies were performed to determine the optimum method of removing the ion milling related damage and ZnO layers during sample preparation. HF/HCl, NaOH/H2O, H2SO4/H2O2/H2O and Br2/CH3OH etching mixtures as well as low voltage argon or iodine ion milling were studied. A low energy (2 keV) iodine or argon ion milling step was shown to remove the ZnO layer and reduced the density of the extended defects associated with Ar+ ion milling, but was unsuccessful in removing all of the defects. Auger electron spectroscopy results indicate residual iodine was either left on the surface or implanted beneath the surface during iodine ion milling. Etching the XTEM samples in HF/HCl was shown to be effective in removing the ZnO layer but had little or no effect on the ion milling induced defects. Etching the samples in a 0.5% Br2/CH3OH solution resulted in complete elimination of the ion milling induced extended defects including the residual defects associated with iodine ion milling. In addition the Br2/CH3OH etch produced the best surface morphology. Thus a brief (1-2 seconds) Br2/CH3OH etch after conventional preparation (argon ion milling) of cross-sectional ZnSe/GaAs TEM samples appears to be an inexpensive and superior alternative to iodine ion milling.

Arsenic↗

PubMed1997

Preparation of cross-sectional TEM samples for low-angle ion milling.

The ideal ion-milled transmission electron microscope (TEM) sample would contain large, thin areas in selected regions, minimal top and bottom surface amorphization, and minimal preferential etching of adjacent materials. This desire has led to studies of these effects and improvements in designs and techniques for ion mills. Minimizing the incident angle of the ion beam to the surface of the sample has been found to be one of the most effective techniques for fulfilling these requirements. A new generation of ion mills has recently been designed to allow low-angle ion milling for the production of very high quality cross-sectional TEM samples. To take advantage of the low-angle ion milling capabilities and high-powered ion sources in these mills, new sample preparation techniques are required. In this paper, a simple technique of mounting material in a specialized titanium grid for cross-sectional TEM sample preparation is presented. This technique is designed to take full advantage of the powerful capabilities of these new low-angle ion mills.

Microscopy, Electron↗