Speciation of inorganic and organotin compounds in biological samples by liquid chromatography with inductively coupled plasma mass spectrometric detection

This paper describes the effect of inorganic tin chloride on the separation of trimethyl-, tributyl- and triphenyltin-chlorides by reversed-phase ion-pair high-performance liquid chromatography with detection by inductively coupled plasma mass spectrometry. The detection limits are 1.6 pg, 1.5 pg and 2.3 pg as tin for trimethyltin, tributyltin and triphenyltin, respectively. The relative standard deviation for ten injections of 20 ng of the tin compounds was less than 5%. Inorganic tin was held strongly on the columns used, to a greater extent on the silica column compared to the polymer column. Extraction and determination of tributyltin and triphenyltin as chlorides in fish tissue (certified reference material) and tuna fish (grocery store) were performed. The recovery study from fish tissue showed an efficiency of over 90% for both tributyltin and triphenyltin and over 60% recovery for spiked tuna.

Alternate methods of sample introduction for plasma mass spectrometry

The most common method of sample introduction for plasma mass spectrometry is solution nebulization, which suffers from a number of short-comings; therefore, a great deal of effort has been placed on the investigation of other sample introduction methods. The common solution nebulization method and its disadvantages are discussed and, in some detail, several alternative methods of sample introduction are reviewed. The methods include electrothermal vaporization, hydride generation, liquid chromatography, gas chromatography, and supercritical fluid chromatography. Advantages and disadvantages of each of these methods will be discussed along with examples from work performed in our laboratory.

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%.

Elimination of the chloride interference on the determination of arsenic using hydride generation inductively coupled plasma mass spectrometry

In the determination of arsenic, attention has recently focused on the speciation of As(III) and As(V). Reversed-phase HPLC can be used to efficiently separate these two arsenic species. When inductively coupled plasma mass spectrometry is used for arsenic detection, an isobaric interference at m/z 75 is caused by the presence of chloride in the sample. These experiments describe the use of hydride generation in conjunction with a polypropylene-membrane gas-liquid separator to completely eliminate the transport of chloride to the plasma. A detection limit of 0.46 ppb for As(III) was achieved with this system. The chromatographic resolution of the system was not compromised by the addition of the gas-liquid separator. A determination of the arsenic content of a NIST urine sample was performed to demonstrate the effectiveness of the chloride elimination.

Arsenic speciation by ion chromatography with inductively coupled plasma mass spectrometric detection

Four As compounds were successfully separated and detected by single-column ion chromatography with inductively coupled plasma (ICP) mass spectrometric detection. The mass spectral interferent ArCl+ was reduced by chromatographically resolving chloride from the negatively charged arsenic species. Determination of four As species was investigated in urine, club soda and wine. Detection limits of 0.16 ng of As(III), 0.26 ng of As(v), 0.073 ng of dimethylarsinic acid (DMA) and 0.18 ng of methylarsonic acid (MMA) in wine were obtained. Sensitivity was further improved by using an He-Ar mixed gas ICP as the ionization source. However, the intensity of the ArCl+ interference was also increased using this plasma. Detection limits of 0.063 ng of As(III), 0.037 ng of As(v), 0.032 ng of DMA and 0.080 ng of MMA in club soda were achieved using the He-Ar plasma source. Similar limits of detection were found in urine and wine.

Investigation of matrix-induced interferences in mixed-gas helium-argon inductively coupled plasma mass spectrometry

The effects of various matrix constituents, Cd, Co, Pb, and synthetic ocean water, on analyte ion signal were investigated in He-Ar plasma source mass spectrometry. Analyte ion signal suppressions and enhancements were observed in the presence of varying concomitants. The method used for optimizing analyte ion lens signal determined whether suppression or enhancement was encountered. Tuning on a nitric acid standard solution results in a suppressed signal, whereas tuning on the analyte in the presence of the matrix results in signal enhancement, relative to that obtained with no concomitant present. The heavier mass lead concomitant had the greatest effect on the ion signal. Additionally, lighter analyte elements were affected to a greater extent than heavier analytes in the presence of high concomitant concentrations.

Evaluation of inductively coupled plasma mass spectrometry as an elemental detector for supercritical fluid chromatography

Supercritical fluid chromatography coupled with inductively coupled plasma mass spectrometry shows high potential for the determination at ultratrace levels of organometallic compounds of environmental interest. In this study the determination of organotin compounds at ultratrace levels is demonstrated. In this work a supercritical fluid chromatography/inductively coupled plasma mass spectrometry (SFC/ICPMS) interface was developed. Separation of tetraalkyltin compounds shows detection levels in the subpicogram range (0.034 pg for tetrabutyltin; 0.047 pg for tetraphenyltin). The linear ranges are over 3 orders magnitude (1-1000 pg). The reproducibility of sample injections are better than 5% RSD.

Lead speciation by HPLC-ICP-AES and HPLC-ICP-MS

Speciation of inorganic lead (Pb2+) and several trialkyllead species (trimethyllead chloride [TML], triethyllead chloride [TEL], and triphenyllead chloride [TPhL]) is investigated using high-performance liquid chromatography (HPLC) with detection by both inductively coupled plasma emission spectroscopy (ICP-AES), and inductively coupled plasma mass spectrometry (ICP-MS). Reversed-phase, ion-pairing, and ion-exchange HPLC modes are studied. Optimal chromatographic conditions for ICP-AES detection include a reversed-phase separation utilizing a step gradient from 10 to 70% methanol. However, the gradient has been found to destabilize the plasma when using ICP-MS detection. An isocratic separation with a 30% methanol mobile phase has been found to be the best compromise between plasma stability and chromatographic resolution. Detection limits using ICP-MS detection are 3 orders of magnitude improved over ICP-AES detection.

Helium microwave-induced plasma mass spectrometric detection for reversed-phase high-performance liquid chromatography

Reversed-phase high-performance liquid chromatography (HPLC) is directly coupled to helium microwave-induced plasma mass spectrometry (He MIP-MS) for the element-selective detection of halogenated organic compounds. Absolute detection limits are approximately 50 pg Br for brominated compounds, 1 pg I for iodinated compounds, and 10 ng Cl for chlorinated compounds. The linear dynamic range for Br- and I-containing compounds is 3-4 orders of magnitude. However, the linear range for chlorinated species is severely limited by high background at m/z = 35. The relative standard deviation for repetitive injections is less than 10%. The helium microwave-induced plasma is operated at moderate powers (300-350 W) and with a total helium consumption of 6-8 L/min. The effect of organic solvents on the background mass spectrum is investigated.

Application of a rapid scanning plasma emission detector and gas chromatography for multi-element quantification of halogenated hydrocarbons

A microwave induced plasma emission detector is used as an element-selective detector for gas chromatography. The spectrometer, which is fitted with a rapid scanning galvanometer mirror, is used to scan a pre-selected spectral window to provide information in the multi-element mode. This information is used to determine the per mole response of some elements as a function of molecular structure. Despite the low microwave powers employed, the response per mole appears to be independent of the molecular structure. Detection limits and linear dynamic ranges are determined by narrowing the spectral coverage to increase the sensitivity. Calibration curves are linear over several orders of magnitude and detection limits are at the pg/sec levels.