Determination of tri-n-butyltin and di-n-butyltin in fish as hydride derivatives by reaction gas chromatography

Organotin speciation in environmental matrices by automated on-line hydride generation-programmed temperature vaporization-capillary gas chromatography–mass spectrometry detection

In the present contribution, a new automated on-line hydride generation methodology was developed for dibutyltin and tributyltin speciation at the trace level, using a programmable temperature-vaporizing inlet followed by capillary gas chromatography coupled to mass spectrometry in the selected ion-monitoring mode acquisition (PTV-GC/MS(SIM)). The methodology involves a sequence defined by two running methods, the first one configured for hydride generation with sodium tetrahydroborate as derivatising agent and the second configured for speciation purposes, using a conventional autosampler and data acquisition controlled by the instrument's software. From the method-development experiments, it had been established that injector configuration has a great effect on the speciation of the actual methodology, particularly, the initial inlet temperature (-20 degrees C; He: 150 ml/min), injection volume (2 microl) and solvent characteristics using the solvent venting mode. Under optimized conditions, a remarkable instrumental performance including very good precision (RSD < 4%), excellent linear dynamic range (up to 50 microg/ml) and limits of detection of 0.12 microg/ml and 9 ng/ml, were obtained for dibutyltin and tributyltin, respectively. The feasibility of the present methodology was validated through assays upon in-house spiked water (2 ng/ml) and a certified reference sediment matrix (Community Bureau of Reference, CRM 462, Nr. 330 dibutyltin: 68+/-12 ng/g; tributyltin: 54+/-15 ng/g on dry mass basis), using liquid-liquid extraction (LLE) and solid-phase extraction (SPE) sample enrichment and multiple injections (2 x 5 microl) for sensitivity enhancement. The methodology evidenced high reproducibility, is easy to work-up, sensitive and showed to be a suitable alternative to replace the currently dedicated analytical systems for organotin speciation in environmental matrices at the trace level.

Quantitative analysis of acrolein in heated vegetable oils by liquid chromatography with pulsed electrochemical detection

A sensitive and selective analytical method for the determination of acrolein in heated vegetable oils by liquid chromatographic separation with pulsed electrochemical detection is described. An optimized triple-step pulsed waveform, based on the formation/inhibition of PtOH species on the electrode surface, a consequence of the absence/presence of adsorbing analytes, is described for the sensitive detection of acrolein in acidic medium. Under these optimized experimental conditions the proposed analytical method allowed detection limits of 0.15 microM without pre- or postcolumn derivatization or tedious cleanup procedures. The proposed analytical method was successfully employed for the sensitive determination of acrolein in fresh and heated vegetable oils with good mean recoveries, selectivity, and analytical reproducibility.

Analytical procedures for the determination of organotin compounds in sediment and biota: a critical review

Analytical procedures reported over the last 10 years for the determination of organotin compounds in sediment and biota have been critically reviewed in terms of sample handling, sensitivity, analytical cost, environmental acceptance, accuracy and precision. Critical steps in the analytical procedures are identified. Finally, research needs in extraction and determination are suggested.

Speciation of organotin compounds by capillary electrophoresis using indirect ultraviolet absorbance detection

Capillary electrophoresis (CE) with indirect photometric detection was investigated for the separation of organotin species. Compounds such as dimethyltin (DMT), dibutyltin (DBT), and tributyltin (TBT) are important pollutants in the aqueous environment and techniques are needed to analyze directly aqueous environmental samples quickly and economically. By adjusting the mobile phase to pH 2.65 by HCl, tributyltin, dibutyltin and dimethyltin in aqueous solutions were separated by capillary electrophoresis using indirect ultraviolet (UV) absorbance detection. Pyridine was used as the UV absorption additive at 254 nm and separation was achieved in 6 min. Peak tailing obtained at higher pH suggests strong interaction between the dimethyltin cation and the negatively charged capillary wall. Cetyltrimethylammonium bromide (CTAB) was added to the mobile phase to improve the peak shapes when the pH of the mobile phase was greater than 3.5. Separations of organotin species in mobile phases with or without CTAB were compared. The change of electrophoretic mobility in mobile phases with different pH values indicates that DMT and DBT start to undergo hydrolysis at a pH 3.0. It was also found that the choice of the buffer anions is critical in the separation of the tin compounds as complexes appear to form with DMT and DBT in the presence of oxalate and citrate.

Comparison of flame ionization and inductively coupled plasma mass spectrometry for the detection of organometallics separated by capillary supercritical fluid chromatography

Organotin compounds are separated by capillary supercritical fluid chromatography (SFC) and a comparison of the detection by flame ionization (FID) and inductively coupled plasma mass spectrometry (ICP-MS) is presented. Resolution, detection limits, linear dynamic range and reproducibility are the parameters compared between SFC-FID and SFC-ICP-MS, for the detection of tri- and tetraorganotin compounds. The resolution obtained in the SFC-FID system is not always observed in SFC-ICP-MS. Degradation in resolution is due to fluctuations in transfer line temperature. Baseline resolution for the organotins considered is achieved in both systems by using a longer column. Detection limits (DLs) are calculated as 3 sigma/S, where sigma is the standard deviation of the blank signal and S is the slope of the calibration curve. Detection limits of 10.3, 12.5, 12.0 and 9.0 pg are obtained for tetrabutyltin, tributyltin chloride, triphenyltin chloride and tetraphenyltin, respectively, using SFC-FID. An improvement in detection limits of one order of magnitude is achieved by SFC-ICP-MS for the same organotins (0.26, 0.80, 0.57 and 0.20 pg, respectively). The relative standard deviations using SFC-FID for five 50-nl injections, containing 0.5 ng Sn, ranged from 3.2 to 6.4%. Using SFC-ICP-MS, five replicate injections of 0.05 ng Sn give R.S.D.s from 1.3 to 3.4%.