The rewards of fundamental atomic spectrometry research.

Atomic spectrometry research is the life-blood of the atomic spectrometry instrument industry. The instrument designer can be expected to innovate in the execution of instrumentation and should be expected to be the expert in optical, electronic and software engineering. Fundamentally new technology has required too long a period of gestation to be compatible with commercial time scales and budgets. But in the past decade, the pressure from stockholders for increased return on investments has put increasingly strong pressure on management to reduce expenses and focus increasingly on projects that guarantee a fast payback. This pressure falls particularly heavily on the larger companies; the same companies that a decade or more ago were the ones that brought the more far-reaching and expensive new concepts to market. Fundamental research in atomic spectrometry has been accomplished in the past several decades mostly in the academic environment and in research institutions that are Federally funded. All of the Federally funded research institutions have been forced to alter their missions to more tangible and immediate goals, and many have also seen severe financial reductions.

Rapid and reliable method for the determination of aluminium in bone by electrothermal atomic absorption spectrometry.

A reliable method for the determination of aluminium in bone by electrothermal atomic absorption spectrometry (ETAAS) is described. Bone samples were digested in concentrated HNO3 using a closed-vessel microwave digestion system. Accurate and precise results were obtained by calibration against aqueous Al standards prepared in solutions containing 1% v/v HNO3 and 1.0 g l-1 Ca, as Ca(NO3)2, as modifier. No modifier was needed for the bone digestate. A method detection limit (3 sigma) of 0.023 microgram g-1 for bone was obtained. The between-day precision for bone digestate was about 7% at a mean concentration of 10 micrograms l-1. The method was validated against the NIST standard reference materials SRM 1486 Bone Meal and SRM 1577b Bovine Liver. To help confirm the concept of the Al in bone method, essentially the same method, with some minor modifications, was used for the determination of Al in serum and dialysis fluid. The method performance was monitored by participation in two international interlaboratory comparison programmes for serum and dialysis fluid Al available from Canada (CHUL, Québec) and the UK (Robens Institute). The performance over a 10 month period was excellent for both serum and dialysis fluid proficiency test samples distributed by these programmes.

Transferability of blood lead determinations by furnace atomic absorption spectrophotometry and continuum background correction.

We have examined and proved feasible the transfer of a method for blood lead determination, developed and optimized for a Zeeman-corrected instrument, to a continuum-corrected furnace atomic absorption spectrophotometer. Numerous reference materials analyzed with the continuum-corrected instrument gave results within 10 micrograms/L (0.05 mumol/L) at low values and varied by < 6% at values > 200 micrograms/L (0.97 mumol/L). Forty-four routine human blood specimens were analyzed by the same method with both continuum- and Zeeman-corrected instrumentation, and gave results that agreed within about the same limits as found with reference materials. The day-to-day precision was about 1/5 the accuracy results. The detection limit was approximately 5 micrograms/L (0.025 mumol/L).

Quality-assurance procedures for graphite-furnace atomic-absorption spectrometry.

A procedure is described for quality-control in graphite-furnace atomic-absorption spectrometry. It uses an NBS standard reference material to avoid errors in standard preparation, and very simple instrumental conditions, with no matrix modifier or pyrolysis step. The characteristic mass and the Zeeman ratio are calculated for Ag, Cu, and Cr, and deviations from the expected values for these quantities are correlated with potential instrumental malfunctions.

Direct-calibration method for determination of aluminum in serum is comparable with the protein-precipitation technique.

We compared results by two methods for serum Al determination: matrix modification with direct calibration in a stabilized-temperature platform furnace (Clin Chem 28, 2139, 1982) and a technique involving extraction with nitric acid before atomic absorption spectrometry (Clin Chem 30, 1216, 1984). The two methods gave similar results with use of either a deuterium or a Zeeman system of background correction, but gave different slopes for standard additions (mA X s per microgram/L), depending on the Al content of the serum, an effect not seen with aqueous solutions. These differences do not affect the accuracy of the Al determination up to 150 micrograms/L.

Direct determination of cadmium in urine with use of a stabilized temperature platform furnace and Zeeman background correction.

In this determination of Cd in urine, simple aqueous standards were used to which NaCl and the matrix modifier were added. The urine was diluted fivefold with water. The mean analytical recovery of added Cd for urine samples was 101%, with individual variations of less than 4%. We used the stabilized temperature platform furnace, Zeeman background correction, pyrolytically coated graphite tubes, and (NH4)2HPO4 plus HNO3 as a matrix modifier. The sensitivity of the method provided a characteristic amount of 0.35 pg of Cd per 0.0044 A X s, obtained with integrated absorbance readings. The absolute Cd detection limit in urine was 0.15 pg, corresponding to 0.04 microgram/L of urine. Lower relative detection limits for Cd in urine can be attained if the analytical situation demands it.

Determination of phenylalanine in serum using reversed-phase liquid chromatography and fluorescence detection.

A liquid chromatography procedure is reported for determining phenylalanine in small volumes of serum. A 10-microliter volume of serum was deproteinized with ethanol and an aliquot was derivatized with dansyl chloride reagent. The dansylated phenylalanine and the norleucine internal standard were separated using reversed-phase chromatography and measured with a fluorescence detector. Linearity was excellent over the range 50-800 mg/l. Within-run precision was better than 4%. Total analysis time including chromatography was approximately 40 min. As little as 300 pg of dansylated phenylalanine was detected.

Estrogen determination using liquid chromatography with precolumn fluorescence labeling.

A liquid chromatography procedure is described for the determination of some estrogens using fluorescence detection. The estrogens are labeled by precolumn derivatization with 5-dimethylaminonaphthalene-1-sulfonylchloride (dansyl chloride) and chromatographed on a reversed-phase, C-18 column with a mobile phase consisting of methanol, water, and acetic acid. The eluted analytes are measured with a fluorescence detector using excitation and emission wavelengths of 350 and 540 nm, respectively. The chief advantage of this new procedure is its sensitivity, requiring smaller amounts of sample to detect and quantitate estrogens in biological materials. We could detect less than 400 pg of estriol. With our procedure, this corresponded to about 25 ng in the final reaction mixture, before derivatization. The use of smaller sample volumes could improve this limit. Linearity for dansylated estriol, estrone, and estradiol was excellent over the estrogen range below 100 micrograms in the sample. This corresponds to approximately 1.7 micrograms on the column. Within-run precision was better than 5% for the full extraction and derivatization procedure for estriol from pregnancy urine samples. Chromatography is complete within 10 min for dansylated estriol, estrone, and estradiol.

Determination of polyamines by liquid chromatography and precolumn labelling for fluorescence detection.

Procedures are described for the separation and detection of picomole quantities of putrescine, spermidine, and spermine by liquid chromatography. The polyamines are labelled by precolumn derivatization with dansyl chloride followed by reversed-phase chromatography with a methanol and water mobile phase. The derivatized polyamines are measured with a fluorescence detector using an excitation wavelength of 340 nm and emission wavelength of 515 nm. The polyamines are eluted within 12 min and 0.5 ng of each could be detected. Some preliminary data on urine samples is presented.

A fluorescence detector for high-pressure liquid chromatography.

We describe a fluorescence spectrophotometer adapted with a micro quartz flow cell to record the output of modern liquid chromatographs. The optical system is double beam in that the light source variations are cancelled out by a second photomultiplier, thus enhancing the sensitivity of the technique. The emission spectra may be scanned by stopping the flow in the chromatographic column and scanning the fluorescence detector. Many specific applications have been studied: polycyclic aromatic hydrocarbons, several vitamins, porphyrins, methyl anthranilate, etc. These are studied in natural samples and it is shown that the specificity of the fluorescence detector frequently obviates the need for sample preparation. The sensivitity available with the fluorescence detector for fluorescing compounds is often much greater than is available with variable-wavelength ultraviolet spectrophotometers. We report picogram-level detectability in real samples for many of the compounds that we have studied.