Bradley T. Jones

Determination of Cadmium in Biological Samples

Abstract Even though normal exposure levels to Cd may be small, the human body is inefficient at excreting the heavy metal, so it slowly accumulates over the period of a lifetime. Eventually, the Cd level in the body may become toxic and give rise to harmful effects. Cadmium exposure could therefore be linked to diseases associated with aging such as osteoporosis, prostate cancer, and pancreatic cancer. These potential links have driven the development of a myriad of analytical techniques for the determination of Cd in biological samples. Natural biological Cd concentrations are typically low, so preconcentration steps and sensitive instruments are frequently a necessity. In addition, the complex matrices of biological specimens such as blood, urine, serum, and tissue often require a form of matrix modification or separation. This review provides an overview of these methods with 200 references from the literature published between 1995 and 2005. The analytical methods for the determination of Cd in biological samples include: spectrophotometry, atomic emission spectrometry, atomic absorption spectrometry, atomic fluorescence spectrometry, inductively coupled plasma mass spectrometry, and electrochemistry. In addition, Cd speciation techniques, using high‐performance liquid chromatography and capillary electrophoresis, are briefly discussed. Amanda C. Davis and Peng Wu contributed equally to this work.

Field instrumentation in atomic spectroscopy

The techniques of field analytical chemistry (FAC) have the potential to reduce both analysis time and cost by providing analytical data on site while eliminating the need for sample collection and transport. These methods could be of considerable interest in the fields of environmental monitoring and industrial process control. Much of FAC is accomplished through the use of portable analytical instruments. The emphasis of this review was on field-portable atomic spectrometry, with particular focus upon two techniques: laser-induced breakdown spectroscopy (LIBS) and tungsten coil atomic absorption spectrometry (W Coil AAS). LIBS and W Coil AAS have been described in detail, with special attention to instrumentation, analytical performance, applications and examples of portable devices. The two techniques were compared and found to be complimentary. Competing technology, not necessarily based upon atomic spectrometry, was also briefly discussed in order to provide a glimpse of the overall picture of FAC techniques used for the determination of metals. These rival techniques include X-ray fluorescence spectrometry (XRF), immunoassay, capillary electrophoresis (CE), and electrochemical sensors.

Recent Advances in Portable X‐Ray Fluorescence Spectrometry

Abstract X‐ray fluorescence (XRF) spectrometry is a nondestructive, rapid, simultaneous multi‐element analytical methodology for solid or liquid samples. Its applications are broad and XRF spectra cover most elements, with a dynamic range from 100% down to the µg/g level. X-ray fluorescence is a well‐established laboratory‐based method, but it is also one of the few atomic spectrometric techniques that can be used for field portable instrumentation. In this manuscript, the recent advances in portable XRF spectrometry are reviewed with 80 references. The principles and instrumentation are briefly discussed, and many applications of the technique are described, including the analysis of soils, sediments, waters, liquid wastes, air, dust, archaeological artifacts, works of art, paint, metals, alloys, minerals, and forensic samples. Portable XRF is especially suitable for fast screening applications when the specific analytes of interest are unknown. The technique does not have accuracy and limit of detection (LOD) values comparable to those of conventional laboratory‐based atomic spectrometric techniques, such as inductively coupled plasma atomic emission spectrometry, inductively coupled plasma mass spectrometry, or electrothermal atomization atomic absorption spectrometry, but it finds its niche in its portability.

Portable, Battery-Powered, Tungsten Coil Atomic Absorption Spectrometer for Lead Determinations

A compact, inexpensive atomic absorption spectrometer has been designed, constructed, and evaluated for the determination of lead at the μg/L level. The new device is made feasible by the combination of a reliable tungsten coil atomizer, a miniature spectrometer/charge-coupled device combination mounted on a PC card, and a near-line background-correction method. The finished spectrometer can be powered by a normal 12-V car battery, controlled with a laptop computer, and transported in any automobile. The overall dimensions of the original prototype system are 19 in. × 8 in. × 3 in. (excluding the computer), and it has no moving parts. The total estimated cost of the system including the computer is less than

Rapid photothermal intracellular drug delivery using multiwalled carbon nanotubes.

6000. The limit of detection for Pb is 20 pg (20-μL sample volume), the linear dynamic range is two orders of magnitude, and the precision for the technique is 5% RSD at concentrations ten times greater than the detection limit. The accuracy of the technique was determined with the use of NIST SRM #1579a “Powdered Lead-Based Paint” containing 11.995 wt % Pb and NIST SRM 955a “Lead in Blood” containing 54.43 μg/dL Pb. The accuracy for the paint sample was 95.1% (11.41 wt % found) with the use of the calibration curve method (aqueous standards) and 97.2% (11.66 wt % found) with the method of standard additions. The accuracy for the blood sample was 93.5% (50.9 μg/dL found) with the calibration curve method and 96.6% (56.3 μg/dL found) with the method of standard additions. The limiting source of noise for the instrument is detector noise, so that the performance of the device can be improved by increasing the optical throughput of the system.

Tungsten devices in analytical atomic spectrometry

Carbon nanotubes are unique materials that absorb infrared (IR) radiation, especially between 700 and 1100 nm, where body tissues are most transparent. Absorbed IR promotes molecular oscillation leading to efficient heating of the surrounding environment. A method to enhance drug localization for peritoneal malignancies is perfusion of warm (40-42 degrees C) chemotherapeutic agents in the abdomen. However, all tissues in the peritoneal cavity are subjected to enhanced drug delivery due to increased cell membrane permeability at hyperthermic temperatures. Here we show that rapid heating (within ten seconds) of colorectal cancer cells to 42 degrees C, using infrared stimulation of nanotubes as a heat source, in the presence of the drugs oxaliplatin or mitomycin C, is as effective as two hours of radiative heating at 42 degrees C for the treatment of peritoneal dissemination of colorectal cancer. We demonstrate increased cell membrane permeability due to hyperthermia from multiwalled carbon nanotubes in close proximity to cell membranes and that the amount of drug internalized by colorectal cancer cells heated quickly using carbon nanotubes equals levels achieved during routine application of hyperthermia at 42 degrees C. This approach has the potential to be used as a rapid bench to bedside clinical therapeutic agent with significant impact for localizing chemotherapy agents during the surgical management of peritoneal dissemination of colorectal cancer.

Direct determination of cadmium in urine by tungsten-coil inductively coupled plasma atomic emission spectrometry using palladium as a permanent modifier

Abstract Tungsten devices have been employed in analytical atomic spectrometry for approximately 30 years. Most of these atomizers can be electrically heated up to 3000 °C at very high heating rates, with a simple power supply. Usually, a tungsten device is employed in one of two modes: as an electrothermal atomizer with which the sample vapor is probed directly, or as an electrothermal vaporizer, which produces a sample aerosol that is then carried to a separate atomizer for analysis. Tungsten devices may take various physical shapes: tubes, cups, boats, ribbons, wires, filaments, coils and loops. Most of these orientations have been applied to many analytical techniques, such as atomic absorption spectrometry, atomic emission spectrometry, atomic fluorescence spectrometry, laser excited atomic fluorescence spectrometry, metastable transfer emission spectroscopy, inductively coupled plasma optical emission spectrometry, inductively coupled plasma mass spectrometry and microwave plasma atomic spectrometry. The analytical figures of merit and the practical applications reported for these techniques are reviewed. Atomization mechanisms reported for tungsten atomizers are also briefly summarized. In addition, less common applications of tungsten devices are discussed, including analyte preconcentration by adsorption or electrodeposition and electrothermal separation of analytes prior to analysis. Tungsten atomization devices continue to provide simple, versatile alternatives for analytical atomic spectrometry.

Simultaneous determination of Cu, Cd and Pb in drinking-water using W-Coil AAS.

Cadmium is determined in urine samples collected from patients with age-related diseases. The urine is simply diluted 1:1 with water and placed on a tungsten coil electrothermal vaporizer treated with 200mug of a permanent Pd modifier. A straightforward vaporization program is used to deliver the Cd vapor to an inductively coupled plasma atomic emission spectrometer. A high resolution spectrometer and a charge coupled device detector provide spectra across a 4.8nm window encompassing two separate Cd emission lines: 226.5 and 228.8nm. The limit of detection is 0.2mug/L at each wavelength, and the linear dynamic range spans three orders of magnitude. The accuracy as measured with a urine standard reference material is 94%. The Pd modifier continues to be effective even after 150 vaporization cycles. Direct analysis of urine with the Pd modifier using simple aqueous calibration solutions provides results that are comparable to those observed after a much more complex method: chelation, extraction, and internal standardization without the modifier. The mean concentrations found by the two techniques differ by only 9%. The permanent Pd modifier allows direct analysis of limited sample volumes with decreased risks of contamination.

DETERMINATION OF CADMIUM WITH A PORTABLE, BATTERY-POWERED TUNGSTEN COIL ATOMIC ABSORPTION SPECTROMETER

An inexpensive, multi-element, W-coil atomic absorption spectrometer has been developed. Atomization occurs on W-coils extracted from commercially available slide projector bulbs. The system has minimal power requirements, 120 ACV and 15 A. A small, computer controlled CCD spectrometer is used as the detector. A multi-element Cu, Cd and Pb hollow cathode lamp is used as the source. 20 mul volumes are deposited on the coil and atomized at 6.7 A or approximately 2200 degrees C. Cu, Cd and Pb were simultaneously determined in tap water, drinking water and a quality control sample. The instrument detection limits are 0.8, 0.2 and 3.0 mug/l for Cu, Cd and Pb, respectively.

Low-Cost, Modular Electrothermal Vaporization System for Inductively Coupled Plasma Atomic Emission Spectrometry

A portable atomic absorption spectrometer is described that is powered by a 12 V car battery. The atomization device is a tungsten coil extracted from a common projector lamp bulb. The coil is housed in a glass cell, and the atomization environment is purged with 10% H2 in Ar (available as a standard commercial welding gas) to prevent oxidation. The detection system is a miniature charge-coupled device (CCD) spectrometer mounted on a PC board. The device is controlled by a laptop computer. Background correction measurements are performed by the near-line method. Aqueous standard solutions provide a Cd detection limit of 3 μg/L (60 pg) for a 20 μL sample volume. Accuracies for the determination of Cd in urine, soil, and stream water are typically better than 90%, with relative standard deviations in the 10% range.