Laser-enhanced ionization as a selective detector for the liquid chromatographic determination of alkyltins in sediment

Abstract

6, 11), led to variable recoveries and low values for most elements (Table IV). Hydrofluoric acid has been used for the dissolution of geologic samples (6). There has also been a report of HF use with some biological samples, particularly when silicon analyses are needed (3). However, when HF was added to our system, unacceptable amounts of particulate matter remained after digestion of the fecal samples; there were poor recoveries of most elements except for phosphorous and zinc. Digestions seemed to be more complete with nitric acid-hydrogen peroxide or nitric-perchloric acid combinations. However, some elements, including iron and copper, were poorly recovered when these combinations were used.We have successfully used our method to digest a wide range of diet, food, and fecal samples with differing fat contents. Traditional open flask digestion procedures (9) generally require up to 20 mL of a 1:5 perchloric-nitric mixture and 8-13 h to digest a 0.5-g sample of either freeze-dried feces or diet in an open 50-mL Erlynmeyer flask on a hot plate.Compared with this open-flask, hot-plate procedure, the microwave procedure offers considerable advantages in speed and safety. Blank values are lower because less acid is required and the sample is not exposed to a hood environment for long periods of time. The closed system maintains sample integrity well and thus permits the determination of more volatile elements. In a preliminary study, we obtained 97-105% recoveries of added boron by using the closed microwave digestion method, whereas boron recoveries were nil when conventional nitric-perchloric digestion techniques (9) were used. Thus, the microwave digestion method is relatively safe, simple, and rapid with good precision and accuracy. This procedure seems to be particularly suited for providing digested samples for elemental determinations by ICP-ES.

Laser-excited atomic fluorescence in a flame as a high-sensitivity detector for organomanganese and organotin compounds following separation by high-performance liquid chromatography

“…The theoretical basis for the high sensitivity and selectivity of LEAFS has been reviewed by Falk (7), Omenetto (8), and Alkemade (9). Recently, lasers have been employed as part of a detection system in the HPLC-laser-enhanced ionization (HPLC-LEI) detection of organotin compounds in a flame atom cell (10). In the work presented here, we report the use of high-performance liquid chromatography-ultraviolet (HPLC-UV), HPLCcontinuum source excited flame atomic fluorescence spectrometry (HPLC-AFC), and HPLC-flame laser-excited atomic fluorescence spectrometry (HPLC-flame LEAFS) instrumentation for the separation and quantitation of toxic organomanganese species.…”

“…Several HPLC interfaces have been reported for the determination of tributyl-and other alkyltin compounds. The following systems have been used for alkyltin determinations: HPLC-flame AAS with a detection limit of 10-20 ng of Sn (20); HPLC-DCP, for which no detection limit data have been reported ( 21); HPLC-GFAAS with a detection limit of 0.5 ng of Sn (22); HPLC-flame LEI with a detection limit of 60 pg of Sn (10); and HPLC hydride generation with a detection limit of 8-14 pg of Sn (20). Jewett and Brinckman (23) and Ebdon et al (24) reported that a strong cation-exchange HPLC column, used in conjunction with an ammonium acetate buffered eluent, provided satisfactory sepEiration of a wide variety of alkyltin species.…”

“…Secondly, dilution of a small-volume (20-pL) analyte injection, due to dispersion on the column and analyte expansion in a large dead volume flame burner chamber, also degrades the detection limit. Epler et al (10) observed a much larger, 100-fold, degradation in the LOD for HPLC-flame LEI of organotin species compared to direct flame LEI of inorganic tin. The workers attributed the degradation in the detection limit to the limited sample volume injected on the column and to chromatographic dispersion in the separation process.…”

“…Variations in the efficiency of flame atomization for individual organomanganese compounds may account for the observed sensitivity and detection limit differences. Epler et al (10) observed "Control rat urine samples, 1.0 mL, were spiked with 1-10 mg of Mn of each species, and the sample was processed as outlined in the text. 6 Data in parentheses refer to the relative standard deviations of the recoveries, expressed as a percentage, based on five replicate samples.…”

Spatially Resolved Temperature Determination of an Air/Acetylene Flame Using the Two-Step Laser-Enhanced Ionization Technique

“…21 The LEI technique can also be interfaced to ¯ow injection to reduce matrix interference effects 22,23 and serve as a chromatographic detector. 24,25 As reported previously, by measuring ion mobility and diffusion coef® cients of a thermometric species, one may determine the ¯ame temperature on the basis of the Einstein relation. 20 The advantage of the LEI method lies in its capabilities of achieving high spatial resolution and avoiding optical interference from scattered radiation and ¯ame background radiation.…”