Cadmium: toxicology and analysis. A review

A video compression system comprises a pre-processing section (102), and encoder (106), and post-processing section (114). The pre-processing section (102) employs a median decimation filter (122) which combines median filtering and decimation process. The pre-processing section (102) also employs adaptive temporal filtering and content adaptive noise reduction filtering to provide images with proper smoothness and sharpness to match the encoder characteristics. The encoder (106) employs a two pass look-ahead allocation rate buffer control scheme where the numbers of bits allocated and subsequently generated for each block may differ. In the first pass, the means square error for each block is estimated to determine the number of bits assigned to each block in a frame. In the second pass, the degree of compression is controlled as a function of the total number of bits generated for all the preceding blocks and the sum of the bits allocated to such preceding blocks.

Digital video compression system utilizing vector adaptive transform

3 Slurry Sample Introduction 3.1 Preparation and Mixing of Slurries 3.1.1 Use of stabilizing agents 3.1.2 Magnetic stirring and vortex mixing 3.1.3 Ultrasonic agitation 3.1.4 Gas mixing of slurry 3.1.5 Pre-digestion of slurry 3.1.6 Electric dispersion in a condensed medium 3.2 Influence of Particle Size 3.3 Influence of Slurry Concentration 3.4 Chemical Modification 3.5 Calibration 3.6 Applications of Slurry Sample Introduction

Solid sampling in electrothermal atomic absorption spectrometry using commercial atomizers. A review

Recent advances in absolute analysis by graphite furnace atomicabsorption spectrometry

Ultrasonic slurry graphite furnace atomic absorption spectrometry is a useful technique for automated direct analysis of solids. The effectiveness of ultrasonic agitation for mixing samples is demonstrated. This analytical approach is evaluated to identify sources of imprecision. Strategies for optimizing slurry preparations are discussed, focusing on particle size, density, analyte partitioning, and sampling limitations. Finally, a teflon bead method is presented for grinding biological and botanical samples. An optimized general approach for ultrasonic slurry sampling is presented.

Advances in ultrasonic slurry graphite furnace atomic absorption spectrometry

A graphite cup inserted into a graphite tube was investigated for the direct analysis of solid samples using graphite furnace AAS. Arsenic, cadmium, chromium, copper, lead and manganese were determined in reference materials. Atomisation from the cup delays sample volatilisation untilthe tube has stabilised in temperature so that the same effect is obtained as with a L'vov platform. Background attenuation and non-spectral interferences are substantially reduced under these near-thermal equilibrium conditions, so that all determinations can be carried out against acid reference solutions. The reproducibility of the results is typically around 10%. The values obtained are not always within the recommended or certified range; the accuracy is more than acceptable, however, for a semi-quantitative determination or for screening purposes.

Solid sampling in graphite furnace atomic-absorption spectrometry using the cup-in-tube technique

A device for atomizing a sample for so-called flameless atomic absorption spectroscopic measurements of the type in which an electrically conducting hollow tube, into which the sample is introduced as by a central port in the side of the tube, is heated by the passage of current from electrodes contacting the ends of the tube. A protective inert gas is caused to surround the interior and exterior of the tube to exclude air to avoid oxidation of the sample tube which may be graphite. The improvement comprises introducing the protective gas into both ends of the sample tube so that it leaves the interior through the central port from which it may be sucked outside of a surrounding housing. The exterior walls of the sample tube may be provided with protective gas either by means of an auxiliary gas flow or by leading the gas from the bore around the outside of the tube before withdrawing it through the surrounding housing. By introducing the gas flow generally from the cooler ends to the hotter medial portion of the tube, decomposition products or samples are not condensed on cooler parts, from which they could later be vaporized and contaminate the atomized sample elements during subsequent analyses.

Device for atomizing a sample for flameless atomic absorption measurements

Microanalysis using mechanized solid sampling with graphite-furnace atomic-absorption gives accurate results in the determination of trace elements in different NBS Standard Reference Materials. Analytical conditions are optimized by use of the method of standard additions, and all capabilities of a microcomputer controlled graphite furnace, such as matrix modification by oxygen ashing, temperature ramping and maximum power heating for atomization are used. Direct calibration against acid standards is possible.

Improvements in graphite-furnace atomic-absoption microanalysis with solid sampling

An automatic sampling apparatus particularly adapted for flameless atomic absorption spectrometers has a turntable carrying a ring of sample containers. The turntable is rotatably mounted on a base plate which in turn is mounted for limited pivotal movement on a support. A rinse station for a sample probe is provided on the base plate adjacent the periphery of the turntable. A sample probe in the form of an elongated tube angled at one end to form a pipette-like tip is mounted for swinging movement about a transverse axis and concomitant rotation about its longitudinal axis so that, at both limits of movement about the transverse axis, the probe tip is directed generally downwardly. At one limit of probe displacement, and with the base plate at one limit of pivotal movement, the probe tip is immersed in, and discharges, rinse liquid at the rinse station; by pivotal movement of the base plate, one of the sample containers positionally replaces the rinse station and the probe tip enters the container to aspirate sample liquid therefrom. The turntable is indexed each time the base plate is pivoted from one limit of its movement to the other and back so that the rinse station is replaced sequentially by each of the sample containers. When the probe is swung to the other limit of its displacement, the tip deposits sample liquid in a sample cell, e.g., the sample port of a heated graphite atomizer. The flow of rinse liquid, and aspiration and deposit of sample liquid, is effected by means of a plurality of pumps and conduits connected in a series flow communication between a source of rinse liquid and the end of the probe tube remote from the tip. The pumps are actuated in timed relation to the movement of the probe, turntable and base plate and include an air pump which introduces a slug of air to separate the sample from the rinse liquid which normally occupies the entire fluid flow system (i.e., pumps and conduits) except for the tip end of the probe.

Sampling procedure and device for flameless atomic absorption spectroscopy

An automatic sampling apparatus for withdrawing samples from a continuously flowing liquid for analysis by a flameless atomic absorption spectrometer includes a sample vessel which, at predetermined times, receives pumped samples of the liquid to be tested, a neutral dilutant liquid, or a calibrated liquid for recalibrating the spectrometer system. A probe having a pipette-like tip is mechanically actuated to dip into the sample vessel and an intake and dispensing pump connected to the probe draws a small sample into the probe tip whereupon the probe mechanism lifts and rotates the probe and inserts the tip into the graphite atomizer tube of the atomic absorption spectrometer. The probe mechanism then returns the probe where it is first flushed with a flushing liquid pumped through the probe and is then returned to the sample vessel to draw the next test sample.

Rolf Tamm

Papers

Solid sampling in graphite furnace atomic-absorption spectrometry using the cup-in-tube technique

Device for atomizing a sample for flameless atomic absorption measurements

Improvements in graphite-furnace atomic-absoption microanalysis with solid sampling

Sampling procedure and device for flameless atomic absorption spectroscopy

Automatic liquid flow sampling apparatus