John A. Groves

Mineral Oil Metal Working Fluids (MWFs)— development of Practical Criteria for Mist Sampling

Not all mineral oil metalworking fluids (MWFs) in common use form stable airborne mists which can be sampled quantitatively onto a filter. This much has been known for some time but no simple method of identifying oils too volatile for customary filter sampling has been developed. Past work was reviewed and experiments were done to select simple criteria which would enable such oils to be identified. The sampling efficiency for a range of commercial mineral oil MWF were assessed by drawing clean air through spiked filters at 2 l. min(-1) for periods up to 6 h before analysis. The physical properties of MWF are governed by their composition and kinematic viscosity was found to be the most practical and easily available index of the potential for sample loss from the filter. Oils with viscosities greater that 18 cSt (at 40 degrees C) lost less than 5% of their weight, whereas those with viscosities less than 18 cSt gave losses up to 71%. The losses from the MWF were mostly aliphatic hydrocarbons (C(10)-C(18)), but additives such as alkyl benzenes, esters, phenols and terpene odorants were also lost. The main recommendation to arise from the work is that filter sampling can be performed on mineral oils with viscosities of 18 cSt (at 40 degrees C) or more with little evaporative losses from the filter. However, sampling oils with viscosities less than 18 cSt will produce results which may significantly underestimate the true value. Over a quarter of UK mineral oil MWFs are formulated from mineral oils with viscosities less than 18 cSt (at 40 degrees C). The problem of exposure under-estimation and inappropriate exposure sampling could be widespread. Further work is being done on measurement of mixed phase mineral oil mist exposure.

Use of eigenvalues for determining the number of components in window factor analysis of spectroscopic and chromatographic data

Abstract Three methods for determining eigenvalues, namely (1) mean-centred sequential scores, (2) mean-centred sequential loadings and (3) uncentred data, are described, and compared on simulations and real data of two-way data matrices. The sequential direction may be time (high-performance liquid chromatography (HPLC)) or wavelength (infrared spectroscopy (IR)), with the non-sequential direction wavelength (HPLC) or sample number (IR). It is shown that method 1 is very dependent on peak shapes. Method 2 works well except when there is low variability in the non-sequential direction. Method 3 performs poorly in the presence of heteroscedastic noise. It is concluded that standard statistical approaches for eigenanalysis must be used with caution in chemometric methods for window factor analysis (WFA).

Chemical pollutants in X-ray film processing departments

A survey of X-ray film processing departments revealed the main airborne contaminants to be sulphur dioxide and acetic acid at concentrations of about 0.1 ppm. Glutaraldehyde was not detected either in the ambient air or in the exhaust duct from an automatic film processor. Laboratory studies confirmed sulphur dioxide and acetic acid as the main headspace constituents above working strength processing solutions but glutaraldehyde and butyraldehyde were also detected.

THE MEASUREMENT OF AIRBORNE GLUTARALDEHYDE BY HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY

Abstract A published method for measuring personal exposure to glutaraldehyde has been evaluated. A change to the composition of the eluent used in the high-performance liquid chromatography analysis is suggested along with a more robust calibration procedure. Test atmospheres of glutaraldehyde were used to show that sampling efficiency is unaffected by humidity changes in the range 20–70% using sampling flow rates of up to 500 ml min −1 . Samples can be stored at room temperature for up to 4 weeks after collection. The method has a detection limit of about 3 ppb for a 21. sample equivalent to about 1/65th of the current occupational exposure limit for glutaraldehyde.

RESOLUTION OF INFRARED SPECTRA OF MIXTURES OF POTENTIAL ORGANIC WORKPLACE POLLUTANTS BY FACTOR ANALYSIS

Abstract A new approach for factor analysis of MIR spectra is proposed and applied to 15 mixtures of three potential workplace pollutants. PCA is performed on small regions of the overall experimental data matrix consisting of ω spectral frequencies and 15 spectra. The window is moved across the spectral data set, and the number of significant components in each window is computed. Regions where only one component absorbs (‘composition one’) are then identified. Correlations between the abstract concentration profiles for these points are used to sort the composition one regions into three groups. Each group represents a single component. Elimination of one of these groups permits new orthogonal spectra to be computed consisting of two components. The process is further repeated to yield one pure spectrum. Choosing and eliminating different groups allows the other pure spectra to be revealed. For correct choice of window size, the recovery of the pure spectra is good. It is shown that combination of orthogonal loadings spectra is mathematically equivalent to rotation as used in evolutionary factor analysis in HPLC.

AN INVESTIGATION OF THE COMPOSITION OF THE VAPOUR EVOLVED FROM AQUEOUS GLUTARALDEHYDE SOLUTIONS

Abstract The composition of the vapour evolved from aqueous glutaraldehyde solutions has been studied using gas chromatography, Fourier transform infra-red spectrometry and high-performance liquid chromatography. This included a study of commercial sterilizing products at concentrations of about 2% glutaraldehyde, both with and without added activator. The main component evolved is monomeric glutaraldehyde with smaller amounts of methanol and butyraldehyde. An investigation of the atmosphere above an activated sterilizing solution suggests that concentrations of up to 2 ppm glutaraldehyde can be formed.

The Development of an Improved Method for the Determination of Coal Tar Pitch Volatiles(CTPV) in Air

Test samples were collected at a range of sites using the MDHS 68 sampler, a 7-hole sampler, and a cyclone respirable-dust sampler. Glass fibre, Zefluor, Fluoropore and silver (0.8 and 5 microns) filters were compared for weighing error, handling characteristics, and amount collected. The effects of a carbon back-up, of extraction solvent, and of analytical method were studied. The current HSE method for the sampling and analysis of coal tar pitch volatiles, MDHS 68 has been reviewed. It is recommended that the MDHS 68 sampler be replaced by a 7-hole head containing a silver or PTFE filter (approximately 1 micron pore size), with a graphitized carbon back-up if efficient collection of 2 to 4-ring PAHs is required. Cyclohexane is recommended as the extraction solvent. Methods of analysis which quantify the fume as a whole (MDHS 68, u.v., ELSD) were shown to give a response which varied according to the type of CTPV generating process. Therefore analysis of specific PAHs of occupational interest, by GC-MS or HPLC is recommended.

Workplace Exposure to Rosin-based Solder Flux Fume During Hand Soldering

The patterns and extent of exposure to rosin based solder flux fume have been investigated in two surveys and a number of individual site visits carried out by the UK Health and Safety Executive (HSE). Determination of solder fume was by measurement of airborne resin acid particulate. Both static and personal sampling was carried out over time periods ranging from 15 minutes to several hours. Resin acid concentrations were found to vary from less than 1 microgram m-3 to 2289 micrograms m-3. The effects of various types of local exhaust ventilation on resin acid concentrations have been observed. On-tool tip extraction systems were generally found to be the best control measure available; however good design, positioning and system maintenance is essential for efficient capture of the fume. The resin acid concentrations detected at these twenty-six sites suggest that the proposed British long and short term occupational exposure limits are realistically attainable targets, particularly where good working practices and/or effective fume control measures are in place.

Resolution of mid-infrared spectra by factor analysis using spherical projections: influence of noise, spectral similarity, wavelength resolution and mixture composition on success of the method

A new method for the resolution and recovery of mid-infrared spectra by factor analysis is described. The key to the method is to determine a few ‘composition-one’ points in a set of mixture spectra, where one component uniquely absorbs. The method involves filtering the data using Savitzky–Golay filters, performing principal components analysis, elimination of composition-zero (noise) points, normalization of scores (projection onto the surface of a hypersphere), determining the best N composition-one points for each compound, and finally factor rotation/recovery of spectra. The method is evaluated using two criteria of success namely, the number of true composition-one points recovered and the correlation between true and recovered spectra. The influence of spectral similarity, spectral resolution, component concentration, noise levels, and cut-off threshold is investigated on two separate simulated datasets. Finally, the method is shown to work on a real dataset.

Analysis of Chrysoidine dyes using high-performance thin-layer chromatography and a proposed method for the measurement of Chrysoidine Y and R in air samples

A method for the analysis of chrysoidine dyes using high-performance thin-layer chromatography is described. The composition of chrysoidine dyes manufactured in the UK is examined and proposals are made for a sampling and analysis scheme to measure the concentrations of the dyes in air. A modification of the technique for screening of the dyes to determine whether o-toluidine was used in their manufacture is also described.