Kevin J. Mulligan

Element-selective detection for chromatography by plasma emission spectrometry

Abstract High-temperature argon and helium plasmas provide stable sources for emission spectroscopy. These plasmas have proven useful as a means of selective detection for column chromatography. This review is based on a survey of the literature from 1965, when the first communication on this topic appeared. The species for which liquid and gas chromatographic effluents are monitored include metal ions and elements not traditionally determined by atomic spectrometry such as C, H, N, P. 0, S, and the halogens. Applications to a wide variety of samples are discussed.

Feasibility of the direct analysis of urine by inductively coupled argon plasma mass spectrometry for biological monitoring of exposure to metals

Urine samples have been analysed for metals using inductively coupled plasma mass spectrometry (ICP-MS). The samples were simply diluted (1 + 9) with 2% v/v nitric acid and introduced into the ICP-MS system. Data for multi-element determinations were obtained by scanning the mass range from 2 to 256 u at a rate of 0.5 scans s–1 for 4 min. Under these conditions, the detection limits are less than 1 ng ml–1 for the original urine sample with linear ranges in excess of 1 × 104. The quantitative performance of the technique applied to real samples was comparable to that obtained from established methods for antimony, mercury and cadmium. The application of this approach to certain metals is restricted by the presence of a number of interferences in the range m/z= 10–80. The system was operated for an entire working day with no evidence of deterioration in the mass spectrometer interface and with a system stability of the order of 5% relative standard deviation. Within the limits described, this method provides a useful tool for monitoring a variety of metals in urine at the levels which might be of interest in a programme of biological monitoring of human exposure.

The sequential determination of arsenic, selenium, germanium and tin as their hydrides by gas—solid chromatography with an atomic absorption detector

Abstract Arsenic, germanium, selenium and tin were sequentially determined in single samples by using hydride generation followed by gas chromatography with an atomic absorption detector. Apparent detection limits varied from 3 ppb for As to 13 ppb for Ge with linear dynamic ranges of about 1.5 orders of magnitude. Relative standard deviations, evaluated in the middle of the working range, varied from 2% to 11%. Chromatographie parameters were chosen to allow for manual lamp selection and monochromator adjustment. Data handling was done by microcomputer. The analysis time was 5 min.

Simultaneous multielement determination in microliter samples by rapid-scanning spectrometry coupled to a microwave-induced plasma

Abstract A modified electrothermal atomizer is coupled to a helium microwave-induced plasma (m.i.p.) for atomic emission spectrometry. For preliminary evaluation, this arrangement was coupled to a monochromator to quantify single elements in microliter samples. Detection limits range from 3 to 25 pg for Cd, Fe, Pb, Mn and Au and linear dynamic ranges are 2–4 orders of magnitude. The monochromator, fitted with a rapid scanning galvanometer mirror, is also used as a multielement detector. A spectral window of ca. 40 nm is rapidly scanned (10 Hz) across the exit slit and five elements from one solution are determined in rapid sequence. In the multielement mode, the detection limits are in the range 50–250 pg, as might be expected, owing to the decreased duty cycle. However, there is a significant improvement when compared to an earlier report from this laboratory. By narrowing the spectral coverage and taking data more rapidly this drawback is minimized.

Determination of polybrominated biphenyl and related compounds by gas-liquid chromatography with a plasma emission detector

Polybrominated biphenyl and related compounds were separated by gas-liquid chromatography and monitored by a microwave-induced plasma emission detector. The helium plasma was sustained at atmospheric pressure in a Beenakker cavity. By following the bromine emission at 478.55 nm, linear ranges of at least 103 with detection limits (signal to noise ratio = 3) of the order of 1 ng were achieved. These results are compared with those obtained with an electron-capture detector and the advantages of the element selectivity of the plasma system are illustrated.

Development of a rapid scanning spectrometer for gas chromatography with microwave induced plasma emission detection

Abstract A microwave induced plasma emission rapid-scanning spectrometer (up to 20 spectra per s) was explored for its potential as a chromatographic detector. Both hardware and software were developed which allow experimental control, data acquisition, and subsequent data reduction. Signal-to-noise enhancement as a function of scan number with or without data smoothing were explored. Data smoothing enhanced S/N. In addition, a spectrum produced by rapidly scanning the He MIP emission was compared with one taken in the normal manner by slowly scanning the grating. Point by point comparisons are good and as expected, considering that over the wavelength region scanned some light was imaged off the grating at the ends of the region resulting in some intensity changes. Integrated spectral chromatograms were obtained for Citex BC-26 at both chlorine and bromine lines. Data obtained over this region show results comparable to those attainable from experiments done with the monochromator monitoring a single line. With some modifications in the chromatography-plasma interface improvements from sub-microgram to nanogram in lowest levels detectable are expected.

Ion-selective behaviour of a polymeric sulphur nitride electrode for the measurement of silver(I)

Mikulski and co-workers1 reported that polymeric sulphur nitride, (SN)^, which has metallic conducting properties, can be prepared in an analytically pure form as well defined single crystals. Recently, (SN)^ has been examined with respect to its properties as an electrode material for voltammetric measurements in aqueous media with or without chemical pre-treatment.2-6. A previous study of the response of (SN)X electrodes to pH also mentioned7 that the (SN)A electrode responds to silver(I) and mercury(II) ions if present in significant concentration in the test solution. However, the potential response of the (SN)X electrode to pH did not appear to be Nemstian. In this paper we describe the pAg - potential response of the (SN)X electrode under controlled conditions and the selectivity and the potentiometric titration response of the (SN)X electrode, with or without chemical pre-treatment, to silver(I) ions. The (SN)X electrode responses are compared with those of a commercial Ag - Ag2S selective electrode.