Discrimination of Diptera order insects based on their saturated cuticular hydrocarbon content using a new microextraction procedure and chromatographic analysis

The nature and proportions of hydrocarbons in the cuticle of insects are characteristic of the species and age. Chemical analysis of cuticular hydrocarbons allows species discrimination, which is of great interest in the forensic field, where insects play a crucial role in estimating the minimum post-mortem interval. The objective of this work was the differentiation of Diptera order insects through their saturated cuticular hydrocarbon compositions (SCHCs). For this, specimens fixed in 70 : 30 ethanol : water, as recommended by the European Association for Forensic Entomology, were submitted to solid-liquid extraction followed by dispersive liquid-liquid microextraction, providing preconcentration factors up to 76 for the SCHCs. The final organic extract was analysed by gas chromatography coupled with flame ionization detection (GC-FID), and GC coupled with mass spectrometry was applied to confirm the identity of the SCHCs. The analysed samples contained linear alkanes with the number of carbon atoms in the C9-C15 and C18-C36 ranges with concentrations between 0.1 and 125 ng g-1. Chrysomya albiceps (in its larval stage) showed the highest number of analytes detected, with 21 compounds, while Lucilia sericata and Calliphora vicina the lowest, with only 3 alkanes. Non-supervised principal component analysis and supervised orthogonal partial least squares discriminant analysis were performed and an optimal model to differentiate specimens according to their species was obtained. In addition, statistically significant differences were observed in the concentrations of certain SCHCs within the same species depending on the stage of development or the growth pattern of the insect.

Characteristics and Therapeutic Needs of Older Patients with Oropharyngeal Dysphagia Admitted to a General Hospital

BACKGROUND

Oropharyngeal dysphagia (OD) is a prevalent geriatric syndrome causing severe nutritional and respiratory complications.

OBJECTIVE

We aimed to describe the characteristics and therapeutic needs of older patients with OD admitted to a general hospital.

DESIGN, PARTICIPANTS AND MEASUREMENTS

Prospective cohort study with patients (≥70 years) with OD consecutively admitted to a general hospital. OD was clinically assessed with the Volume-Viscosity Swallowing Test and nutritional status with the Mini Nutritional Assessment-short form. Oral health (OH) and periodontal diseases were evaluated by dentists. Functionality, frailty, sarcopenia, comorbidities, dehydration, quality of life (QoL) and mortality were also assessed.

RESULTS

We included 235 patients (87.3±5.5 years) with OD hospitalized for acute diseases (9.6±7.6 days). On admission, they had low functionality (Barthel: 51.3±25.1), frailty (Fried: 3.9±0.9; Edmonton: 10.3±2.7, 87.2-91.1% frail) and high comorbidities (Charlson: 3.7±2.0). Moreover, 85.1% presented signs of impaired safety and 84.7% efficacy of swallow. Up to 48% required fluid adaptation with a xanthan gum-based thickener (89.4% at 250 mPa·s; 10.6% at 800 mPa·s) and 93.2% a texture-modified diet (TMD) (74.4%, fork-mashable; 25.6%, pureed). A total of 98.7% had nutritional risk, 32.3% sarcopenia and 75.3% dehydration. OH was moderate (Oral Hygiene Index-simplified: 2.0±1.3) and 67.4% had periodontitis. QoL self-perception was 62.2% and 5.5% of patients died during hospitalization.

CONCLUSION

Hospitalized older OD patients have impaired safety of swallow, frailty, malnutrition, dehydration, low functional capacity and poor OH and high risk of respiratory infections. They need a multimodal intervention including fluid thickening, TMD, thickened oral nutritional supplementation and OH care to improve health status and reduce OD-associated complications.

A simple device for headspace sorptive extraction prior to gas chromatography-mass spectrometry analysis

A device for headspace sorptive extraction (HSSE) combined with gas chromatography separation and mass spectrometry detection (GC-MS) is presented. The gadget is based on a simple magnetic disk that permits the stir bar to be placed at the top of the sample vial. The complete surface of the coated stir bar is exposed to the headspace atmosphere, and the movement of the bar caused by the magnetic stirrer in the liquid sample facilitates the sorption process. The final consequence is increased sensitivity and repeatability when compared with a glass-made comercial device for the same purpose. Successful determination of ten chlorobenzenes in waters testifies the good performance of the new device.

Direct sample introduction gas chromatography and mass spectrometry for the determination of phthalate esters in cleaning products

A method using direct sample introduction (DSI) coupled to gas chromatography-mass spectrometry (GC-MS) is developed for the determination of six phthalate esters (dimethyl, diethyl, dibutyl, butylbenzyl, diethylhexyl and dioctyl phthalate) in cleaning products. The different variables involved in the DSI step, including venting time and temperature, vaporisation time and temperature, injector heating temperature and gas flow rate and pressure, were evaluated and optimised using Taguchi orthogonal arrays. The proposed method, using calibration against methanolic standards, showed good linearity in the 0.05-15 μg g(-1) range and good repeatability, with RSD values ranging from 3.5% to 5.7%. Quantification limits between 0.010 and 0.041 μg g(-1), depending on the compound, were attained, while recovery assays provided values from 83% to 115%. Twenty-seven cleaning products were analysed using the DSI-GC-MS method, being four phthalates (dimethyl, diethyl, dibutyl and diethylhexyl phthalate) found in fourteen of them at concentration levels in the 0.1-21 μg g(-1) range. Compared with the most common GC injection technique, which uses the split/splitless injector, the proposed DSI procedure provided larger peak areas and lower detection limits, as result of the greater injected volume and reduction in noise.

Determination of alkylphenols and phthalate esters in vegetables and migration studies from their packages by means of stir bar sorptive extraction coupled to gas chromatography-mass spectrometry

This paper describes a method for the determination of three alkylphenols (APs), 4-tert-octylphenol (tOP), 4-n-octylphenol (OP) and 4-nonylphenol (NP), and six phthalate esters (PEs), dimethylphthalate (DMP), diethylphthalate (DEP), di-n-butylphthalate (DBP), n-butylbenzylphthalate (BBP), di-2-ethylhexylphthalate (DEHP) and di-n-octylphthalate (DOP), in vegetables using stir bar sorptive extraction (SBSE) in combination with thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). Ultrasonic radiation was used to extract the analytes from the solid food matrix, and the extract obtained was preconcentrated by SBSE. The different parameters affecting both stages were carefully optimized. The method was applied to analyze commercial vegetables, in the form of plastic packed salads and canned greens, as well as the corresponding filling liquids of the canned food. Quantification of the samples was carried out against aqueous standards using an internal standard (anthracene). The analysis of a 2 g vegetable sample provided detection limits between 12.7 and 105.8 pg g⁻¹ for OP and DEHP, respectively. Migration studies from the plastic packages of the vegetables samples analyzed were carried out. DEP, DBP and DEHP were found to have migrated from the bags to the simulant and the same compounds were quantified in lettuce, corn salad, arugula, parsley and chard, at concentration levels in the 8-51 ng g⁻¹ range. However, OP and NP were found in only two vegetable samples and one filling liquid, but neither was detected in any package. The proposed method provided recoveries of 83-118%.

Liquid chromatography–electrothermal atomic absorption spectrometry for the separation and preconcentration of molybdenum in milk and infant formulas

Two procedures for the electrothermal atomic absorption spectrometric determination of molybdenum in milk and infant formulas using slurried samples are described. For powdered milk samples, 10% (m/v) slurries were prepared in a medium containing 25 and 75% (v/v) concentrated hydrogen peroxide and hydrofluoric acid, respectively, and introduced directly into the furnace. Palladium (200 microg mL(-1)) was used as the modifier and calibration was carried out using aqueous standards prepared in the same medium. The detection limit was 0.02 microg g(-1) for powdered milk samples suspended at 10% (m/v) (equivalent to 2 microg L(-1)). The relative standard deviation (R.S.D.) for five measurements was 1.9%, the characteristic mass being 25 pg. For liquid milk samples, a procedure was proposed based on preconcentration and removal of the matrix, using ionic exchange (Amberlite IRA 743) and elution of molybdenum with 5% (m/v) NaOH. In this case, a 30-fold improvement in the calibration slope was achieved, leading to a detection limit of 0.04 microg L(-1) for liquid samples diluted to 10%. The R.S.D. was 3.5%. Using a size-based separation procedure, it was found that molybdenum is present in its inorganic form or associated to low molecular weight substances in cow milk, while in breast milk it is associated to proteins. The reliability of the procedure was checked by comparing the results obtained with those found using a previous mineralization stage and by analyzing three certified reference materials, namely, BCR 063R (skim milk powder), NBS 1549 (non-fat milk powder) and NBS 8435 (whole milk powder).

Purge-and-trap capillary gas chromatography with atomic emission detection for volatile halogenated organic compounds determination in waters and beverages

A method for the simultaneous determination of 10 volatile halogenated organic compounds (VHOCs), including four trihalomethanes (THMs), in waters and beverages was developed. The analytes were stripped from the aqueous sample by a flow of helium, preconcentrated in a capillary trap and thermally desorbed using a purge-and-trap (PT) system. This was followed by capillary gas chromatography with microwave-induced plasma atomic emission spectrometry (GC-AED). For element-specific detection, three wavelengths were monitored, corresponding to chlorine (479 nm), bromine (478 nm) and iodine (193 nm). Each chromatographic run took 21 min, including the purge time. After careful choice of the experimental conditions, the performance of the system was evaluated. Calibration curves were obtained by plotting peak area versus concentration and the correlation coefficients for linear calibration were at least 0.9987. Detection limits, calculated for 5 ml sample volume, ranged from 0.05 microg l(-1) for chloroform to 0.5 microg l(-1) for tetrachloromethane. The method was successfully applied to the quantitative analysis of water samples of different origin and also of several beer and juice samples. The tap water samples analyzed contain variable concentrations of the four trihalomethanes, ranging from 1.0 to 66.5 microg l(-1), depending of the compound. Whereas chloroform, bromodichloromethane and bromoform were found in some of the juice samples, only chloroform was detected in the beer samples. The method is reliable and can be used for routine monitoring in water and beverages.

Stability of arsenobetaine levels in manufactured baby foods

The stability of arsenobetaine in baby foods under different experimental conditions is evaluated. Total arsenic was analyzed by electrothermal atomic absorption spectrometry, and the speciation of arsenicals was carried out by coupling liquid chromatography to hydride generation-atomic absorption spectrometry. The highest arsenic levels in the analyzed baby foods corresponded to those containing plaice (2 to 3 microg/g). The speciation data indicated that arsenobetaine, a nontoxic species, was the only arsenical present in the baby foods analyzed at levels between 0.2 and 3 microg/g. Two different procedures for extracting arsenicals from baby foods, involving a water-methanol-chloroform mixture and enzymatic hydrolysis, were tested, and similar results were obtained. Furthermore, the arsenobetaine levels remained unchanged when the baby foods were stored for different times or when the samples were freeze-dried, thus confirming the stability of arsenobetaine and the nonappearance of other arsenic species by interconversion. The reliability of the procedure was checked by analyzing a certified reference material.

Placental cadmium and lipid peroxidation in smoking women related to newborn anthropometric measurements

Smoking during pregnancy is known to be harmful for fetal growth, and cigarette smoke is the major source of cadmium exposure in the general population. Some authors suggest that cadmium accumulated in placenta may be the main cause of the decreased fetal growth shown by infants born to smoking mothers. The aim of our study was to assess any relationship between smoking during pregnancy, placental cadmium levels, placental lipid peroxidation, and anthropometric measurements of newly born babies. The mean values of placental cadmium were significantly higher in smoking mothers, who also produced offspring with reduced neonatal weight, length, head and abdominal circumferences. Lipid peroxidation correlated negatively with birth weight and abdominal circumference. Our results suggest that the cadmium accumulated in placenta is not the reason for reduced fetal growth in smoking mothers and that placental peroxidation is not enhanced by smoking, although the outcome of pregnancy seems to be negatively influenced by lipid peroxidation.

Placental lead and outcome of pregnancy

Prenatal exposure to lead produces toxic effects in the human fetus, including an increased risk of preterm delivery, low birth weight and impaired mental development. Since we believe that placental lead could be a good biomarker for fetal exposure, we assessed the relation of placental lead to intrauterine fetal growth and some adverse outcomes of pregnancy. Low concentrations of lead were found in the population studied (N, 89; mean, 113.4 ng/g dry tissue; S.D., 58.0). The cases were divided into two groups based on delivery outcome. In the group of placentas from premature rupture of membranes and preterm labor (gestational age <or=37 weeks), higher lead levels were recorded than in the placentas from term pregnancies. The proportion of abnormal pregnancy outcome in the group of placentas with lead concentrations above 120 ng/g was 40.6 versus 8.8% in placentas below this concentration. Higher placental lead levels, in general, were not related to smaller weight, head and abdominal circumference or shorter length at birth.

Determination of pesticides in waters by capillary gas chromatography with atomic emission detection

Capillary gas chromatography with atomic emission detection (GC-AED) was successfully used to separate and quantify 14 pesticides (organochlorines, organophosphorus compounds and pyrethrins) in water samples after liquid-liquid extraction with ethyl acetate. Monitoring the emission lines for elements such as chlorine, bromine and sulfur ensures nearly specific chromatograms for these elements, and markedly increases selectivity. Calibration curves were obtained by plotting peak area versus concentration and the correlation coefficients relating to linearity were at least 0.999. Each chromatographic separation takes 21 min and, since two injections are necessary, it requires approximately 1 h to analyze one sample. The method shows a precision of 4.3-8.2% (RSD), depending on the compound. The application of liquid-liquid extraction with ethyl acetate led to recoveries from spiked samples ranging from 76 to 113%. The sensitivity and linearity for the elements chlorine, sulfur, nitrogen and phosphorus were checked under the optimized conditions at their customary emission wavelength. The sensitivity and linearity for these compounds decreased in the order (atom and emission wavelength) Cl (479 nm)>S (181 nm)>P (178 nm)>N (174 nm). A study of the GC-AED system's response to chlorine concentration in eight pesticide molecules was performed and a linear relationship was found with a correlation coefficient of 0.987.

A manifold for the automatic dilution of concentrated solutions in flame atomic absorption spectrometry

A fully computer-controlled manifold is described which enables the automatic dilution and measurement of solutions which are too concentrated to be measured by direct aspiration in FAAS. The sample solution is propelled by a peristaltic pump equipped with two pump tubes of different diameters, the difference between the nebulizer uptake rate and the flow rate supplied by both tubes being compensated by solvent provided through a T-piece. The absorbance is averaged and the pump turning speed automatically increased or reduced until an absorbance value within the linear response of the spectrometer is obtained. To furnish very high dilution, the system automatically reverses the direction of the flow moved through one of the pump tubes, so that the net flow delivered by the pump is the difference between the flows propelled through the two pump tubes. In these circumstances, in addition to absorbance, the module of the Fourier transform obtained from the absorbance-time profile can be used as the analytical signal. Calibration is performed by use of a single standard solution. In this way, it is possible to determine copper in the 1-10,000 microg mL(-1) range with an RSD of 1.3-3%. Copper, zinc, calcium, and magnesium were determined in different samples to check the reliability of the procedure.

Determination of aluminium and chromium in slurried baby food samples by electrothermal atomic absorption spectrometry

Electrothermal atomic absorption spectrometry was used to determine aluminium and chromium in different types of baby foods. Samples without previous treatment were introduced into the atomizer as suspensions, which were prepared in a medium containing 0.1% (w/v) Triton X-100 (for chromium) or 10% (v/v) ethanol (for aluminium), 5% (v/v) concentrated hydrogen peroxide, and 0.5% (v/v) concentrated nitric acid. The slurries were homogenized with a potter and introduced directly into the furnace. The presence of nitric acid allowed a substantial amount of analyte to be extracted to the liquid phase. No matrix effect was observed and aqueous standard solutions were used for calibration. The detection limits were 4 and 50 pg for chromium and aluminium, respectively; characteristic masses were 3.8 pg for chromium and 18 pg for aluminium. Reliability of the procedures was checked by statistically comparing the results with those obtained with a previous microwave oven mineralization stage and by analyis of several certified reference materials. Values for the aluminium content ranged between 0.4 and 3.0 microg/g, and for chromium between 0.003 and 0.06 microg/g.

Comparison of ion-pair and amide-based column reversed-phase liquid chromatography for the separation of thiamine-related compounds

Two reversed-phase chromatographic methods for the separation of thiamine and related compounds are compared. The first procedure is based on the ion-pair technique using an octadecylsilica column, while the second uses a new amide-based stationary phase, which avoids the need to form ion-pairs, leading to narrower peaks and a simpler mobile phase. Analyses were performed by gradient elution and a photo-diode array was used for detection. Specificity was demonstrated by the retention characteristics, UV spectra and by comparing the peak purity index with commercial standards. The procedures were applied to the determination of thiamine-related compounds in pharmaceutical preparations and urine. No preliminary sample treatment was required.

Determination of copper, cobalt, nickel, and manganese in baby food slurries using electrothermal atomic absorption spectrometry

The analytical conditions for the electrothermal atomic absorption spectrometric determination of copper, manganese, nickel, and cobalt in different types of baby foods using slurried samples are presented. Suspensions were prepared in a medium containing 0.1% w/v Triton X-100, 30% v/v concentrated hydrogen peroxide, 1% v/v concentrated nitric acid, 1% w/v ammonium dihydrogenphosphate (only for copper atomization), and one drop of silicon antifoam. The slurries were homogenized by using a potter and were introduced directly into the furnace. The amount of analyte extracted to the liquid phase was investigated. The graphite furnace conditions were optimized for each element. No matrix effect was observed, and calibration could be carried out using aqueous standard solutions. The detection limits were 3.4, 2.1, 5.4, and 3.7 pg for copper, manganese, nickel, and cobalt, respectively. The reliability of the procedures was checked by statistically comparing the results obtained with those found by using a previous microwave-oven mineralization stage and by analyzing several certified reference materials.

Rapid determination of lead and cadmium in sewage sludge samples using electrothermal atomic absorption spectrometry with slurry sample introduction

Lead and cadmium concentrations in sewage sludge samples are determined by suspending the ground samples in a solution containing 10% (v/v) concentrated hydrofluoric acid, 1% (v/v) concentrated nitric acid, 0.5% (m/v) dihydrogen ammonium phosphate and 0.1% (m/v) sodium hexametaphosphate. Aliquots of 20 microL of these suspensions (4 mg/mL) are diluted to 1000 microL with the same solution and then injected into the electrothermal atomizer. The drying stage is performed by programming a 400 degrees C temperature, a ramp time of 20 s and a hold time of 15 s on the power supply of the atomizer. No ashing step is used. Platform atomization is carried out at 1600 and 1800 degrees C for Pb and Cd, respectively. Calibration is performed using aqueous standards in the 5-75 and 0.2-5 microg/L Pb and Cd ranges, respectively. Results obtained for three certified reference materials and four samples demonstrate the reliability of the procedures described.

Selenium determination in biological fluids using Zeeman background correction electrothermal atomic absorption spectrometry

Procedures for the direct determination of total selenium in urine, serum, and blood using electrothermal atomic absorption spectrometry are presented. In the selected experimental conditions, Zeeman correction is mandatory to compensate for the high background signals. The sample diluted and containing 0.1% (w/v) Triton X-100 is introduced directly into the electrothermal atomizer. A solution containing 15% (w/v) hydrogen peroxide, 0.65% (w/v) nitric acid, and 0.5% (w/v) nickel is injected separately into the atomizer. Calibration is carried out using the standard additions method. The detection limit is 30 pg selenium. If palladium, instead of nickel, is used as the chemical modifier, calibration can be carried out against aqueous standards, and the detection limit is 45 pg. In this case, three separate injections are required to prevent precipitation problems in the automatic injector. The reliability of the procedures is checked by analyzing three certified reference materials and by recovery studies. Mean recoveries are 99.7% for serum, 99.4% for urine, and 100.8% for blood samples. Relative standard deviation values are +/-4.0% for serum, +/-3.9% for urine, and +/-4.5% for blood.

Determination of phenols in wines by liquid chromatography with photodiode array and fluorescence detection

A reversed-phase LC method, optimised for the separation of trans- and cis-resveratrol, catechin, epicatechin, quercetin and rutin, is reported. Analyses were performed on a reversed-phase column by gradient elution. Detection was carried out by photodiode array, although the use of a fluorimetric detector considerably lowered the detection limits for catechin, epicatechin and both resveratrol isomers. Identification by the two different detection systems was based on retention characteristics, UV spectra and peak purity index were compared with commercial standards. The procedures were applied to the determination of the phenolic compounds in different types of wines and musts.

Determination of arsenic in biological fluids by electrothermal atomic absorption spectrometry

A procedure for the determination of the total content of arsenic in urine, serum and blood by electrothermal atomic absorption spectrometry (ETAAS) is described. Zeeman correction is used to compensate the high background signals. The samples are diluted (1 + 1 for urine and 1 + 3 for both serum and blood samples) in a medium containing 0.1% w/v Triton X-100 before being introduced directly into the furnace. A solution containing 15% w/v hydrogen peroxide, 0.65% w/v nitric acid and 0.5% w/v nickel is also introduced into the atomizer by means of a separate injection. Calibration is carried out against aqueous standards for blood and serum samples and using the standard additions method for urine samples. The detection limit is 20 pg (2 ng ml-1). The reliability of the procedure is checked by analyzing three certified reference materials and by recovery studies.

Fast determination of lead and copper in dairy products by graphite furnace atomic absorption spectrometry

A rapid and direct procedure for determining lead and copper in dairy products by electrothermal atomic absorption spectrometry (ETAAS) is described. Samples are slurried in a medium containing 50% v/v hydrogen peroxide, 1% v/v nitric acid, 0.5% w/v dihydrogen phosphate, and 20% v/v ethanol and directly injected into the furnace with no previous mineralization. Calibration is performed with aqueous standards. Limits of determination were 0.4 and 2.4 ng/mL for copper and lead, respectively. The reliability of the procedure was checked by comparison with the acid mineralization procedure and by analyzing 3 certified reference milk samples.

Determination of p-hydroxyphenylglycine by reaction with o-phthalaldehyde using a flow-injection fluorimetric procedure

In the present study, new flow injection procedures for the determination of p-hydroxyphenylglycine using either photometric or fluorimetric detection are proposed. The methods are based on the reaction of the amino acid with o-phthalaldehyde and 2-mercaptoethanol. The calibration graphs based on peak area were linear in the ranges 20-300 ng ml-1 with fluorimetric detection and 5-60 micrograms ml-1 using the photometric mode. The detection limit calculated for the fluorimetric procedure was 10 ng ml-1. The method was applied to the determination of the free p-hydroxyphenylglycine present in industrial pharmaceutical samples of a Dane salt.

Use of post-column fluorescence derivatization to develop a liquid chromatographic assay for ranitidine and its metabolites in biological fluids

Ranitidine and its main metabolites, ranitidine N-oxide and ranitidine S-oxide, were determined in plasma and urine after separation using reversed-phase liquid chromatography. The mobile phase consisted of an initial isocratic step with 7:93 (v/v) acetonitrile-7.5 mM phosphate buffer (pH 6) for 8 min, followed by a linear gradient up to a 25:75 (v/v) mixture over 1 min. Detection was carried out by a post-column fluorimetric derivatization based on the reaction of the drugs with sodium hypochlorite, giving rise to primary amines that reacted with o-phthalaldehyde and 2-mercaptoethanol to form highly fluorescent products. The calibration graphs, based on peak area, were linear in the range 0.1-4 microg/ml for all drugs. The detection limits were 30, 41 and 32 ng/ml (8.6, 12.5 and 9.1 pmol) for ranitidine S-oxide, ranitidine N-oxide and ranitidine, respectively. Chromatographic profiles obtained for plasma and urine samples showed no interference from endogenous compounds.

Extending the dynamic range of flame atomic absorption spectrometry: a comparison of procedures for the determination of several elements in milk and mineral waters using on-line dilution

Three approaches based on continuous flow methodology are assessed for the purpose of extending the dynamic range of flame atomic absorption spectrometry. The determination of several elements in infant liquid and powdered milk and water samples is used to check the performances of the manifolds. Two of the systems are fully computer-controlled and permit a calibration graph to be obtained by using a single standard solution. The results confirm that continuous flow methodology is a reliable alternative to the time-consuming common dilution procedures based on glassware. Since the systems are versatile and permit a wide range of degrees of dilution to be obtained, they can be easily adapted for the automated or semi-automated analysis of other liquid samples which are too concentrated to be aspirated directly into the atomic absorption spectrometer.

Indirect flame atomic absorption detection for the liquid chromatographic separation of alkaline metals

Alkaline metals and ammonium ion are separated by cationic exchange liquid chromatography using a 60 microg ml(-1) aqueous copper solution as the mobile phase at 1.5 ml min(-1). Detection is carried out by measuring copper with an atomic absorption spectrometer directly interfaced to the chromatograph. A simple T-piece is used to compensate the difference between the nebulizer uptake rate and the chromatographic flow-rate with air. The method is applicable to the analysis of alkaline metals and ammonium in waters. Average recovery ( n = 16) was 100.3 +/- 4.0%.

Slurry-electrothermal atomic absorption spectrometric determination of aluminium and chromium in vegetables using hydrogen peroxide as a matrix modifier

Fast heating programmes for determining aluminium and chromium in vegetables using electrothermal atomic absorption spectrometry with slurry sampling are developed using wall atomization. The build-up of carbonaceous residues inside the atomizer is avoided by adding 4% hydrogen peroxide and 1% nitric acid to the slurries instead of using an air-ashing stage. In accordance with fast-programme methodology, the conventional drying and charring steps are replaced by a modified drying stage. simplifying the heating programmes. For suspensions containing 0.1% m/V of ground vegetables, the relative standard deviation (RSD) is about +/-5% for aluminium. For chromium determination, the use of 0.5-1% m/V suspensions leads to RSDs close to +/-4%. Calibration is carried out using aqueous standards. The aluminium and chromium contents of a number of vegetable samples obtained by using the slurry approach agree with those obtained by means of a conventional procedure based on the total dissolution of the samples. The reliability of the procedures is also confirmed by analysing two certified reference materials.