Direct Gas Analysis Research Articles

Balke-Ware Vo2peak Prediction Equations Are Inaccurate For Cancer Survivors

INTRO: Cancer and its treatments may cause cardiotoxicities such as cardiomyopathy, EKG abnormalities, lower left ejection fractions, reduced cardiac output, and decreased blood perfusion in tissues. Physical abatements related to cancer and its treatments can be reduced with an individualized exercise prescription. Proper cardiovascular testing is crucial for an exercise prescription and can result in improved VO2Peak (VO2P) as a measure of cardiovascular health and overall quality of life. Currently, a cancer-specific protocol (CANCER) is the only validated treadmill protocol for cancer survivors. Despite this, the Balke-Ware (BW) protocol is often used in clinical settings but it has only been validated for apparently healthy individuals. It is unknown if the BW is appropriate for cancer survivors. PURPOSE: To determine if (1) measured VO2P from BW and CANCER protocols differ and (2) if predictive VO2P equations for the BW are accurate for testing cardiovascular fitness in cancer survivors. METHODS: Thirty-four subjects participated in the study. Subjects completed the CANCER and BW protocols one week apart in randomized order. Measured VO2P was obtained from gas analysis using a research grade metabolic cart. Predicted VO2P was calculated using BW prediction equations from the completed BW gas analysis test. A paired samples t-test was used to test for significance (p < 0.05) for both comparisons. RESULTS: All subjects completed the CANCER protocol, but one subject could not complete the BW. No significant differences were found in VO2P values (mL·kg-1 ·min-1) between CANCER (28.1 ± 0.65) and BW (26.3 ± 0.76) (p = 0.192). Significant differences were found between predicted and actual VO2P from the BW protocol (19.7 ± 1.33 vs. 26.3 ± 0.76, respectively) (p < 0.001). CONCLUSION: Data indicates if direct gas analysis is available, BW appropriately determines VO2P in cancer survivors. However, if direct gas analysis is unavailable, BW predictive VO2P equations significantly underestimate VO2P in cancer survivors. The CANCER protocol provides accurate VO2P values with or without a metabolic cart. Therefore, in a clinical setting where using direct gas analysis may not be practical, the CANCER protocol remains the current gold standard for assessing cardiovascular fitness in cancer survivors.

High accuracy in-situ direct gas analysis of Li-ion batteries

Cycling of lithium-ion batteries containing Ni-rich NMC cathodes at high voltage involves intense gas generation. From a safety standpoint, it is critical to understand how different gas species respond to changes in upper cut-off voltages. In this manuscript, we introduce a novel experimental set up for real-time analysis of gas generation in prismatic pouch cells. In a typical experiment, a lithium-ion pouch cell is directly connected to a quadruple mass spectrometer using a glass capillary. Pressure difference helps move the generated gases to the mass spectrometer column for full analysis. The gaseous species are probed during both formation cycle and aging cycles in Li-ion pouch cells comprising NMC811 cathodes and graphite anodes. The gases are generated upon the creation of the solid electrolyte interphase on graphite during the first formation charge. Ethylene (C2H4) is the major gas generated during formation cycle due to the decomposition of ethylene carbonate. H2, CH4, C2H6, O2, CO and CO2 are also monitored during formation cycle. For the aging cycles, three upper cut-off voltages 4.2, 4.4 and 4.6 V are selected to investigate the impact of upper cut-off voltages on gas generation. Higher upper cut-off voltages do not significantly affect the amount of O2 measured, as a part of the generated oxygen could have reacted with electrolytes. On the other hand, the generation of CO2 is found to be very sensitive to upper cut-off voltage. During similar aging cycles, 6167 nmol gNMC−1 of CO2 is generated in 4.6 V cycle, versus 1650 nmol gNMC−1 in 4.4 V cycle, versus 91 nmol gNMC−1 in 4.2 V cycle.

Animal science meets agricultural practice: Preliminary results of an innovative technical approach for exhaled breath analysis in cattle under field conditions

In human and veterinary medicine, the search for exhaled volatiles as potential markers for disease detection has gained increasing attention because exhaled breath analysis bears the advantages of being continuous, non-invasive and reveals instantly available results. The aim of this study was to introduce a technical set-up for breath analysis in bovines. The technical set-up allows (i) CO2-controlled sampling and preconcentration of alveolar gas and (ii) direct breath gas analysis via proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) in parallel. While alveolar gas sampling enables the analysis by gas chromatography-mass spectrometry for unequivocal substance identification, PTR-ToF-MS ensures real-time identification of confounding signals within one measurement. Applicability of the system to conscious cattle and reliability of the signals obtained under field conditions were tested at eight dairy farms. This first testing phase in veterinary practice confirmed that the set-up was well tolerated by each of the cows and that reliable measured values (i.e., raw data) were gained at different respiratory rates. Inspiration could be clearly distinguished from expiration, thus providing the basis for excluding ambient air contamination. Consecutive measurements under standardised conditions in two bovines aged 5–6 months revealed effects of time of day, food intake and handling that need to be evaluated in-depth in future studies with larger groups of animals. As result of these proof-of-concept trials, the introduced technical set-up can be recommended for future studies evaluating exhaled markers in cattle. Breath gas analysis offers a new research area in veterinary medicine and is one step forward towards refining large animal studies, even under field conditions.

Cardiorespiratory fitness in adolescents with obesity: a 6-month follow-up study

The aim of this study was to investigate whether the effects of a multidisciplinary intervention on cardiorespiratory fitness are maintained after 6-month follow-up in adolescents with obesity. One-hundred and seven adolescents with obesity were intentionally allocated in two groups: experimental or control. Adolescents in experimental group underwent a multidisciplinary intervention (supervised aerobic exercise, psychological, nutritional, and clinical counseling). Cardiorespiratory fitness (direct gas analysis), body composition (dual-energy-DXA), anthropometry and blood lipids were measured before intervention (baseline), at the end of the 24-week intervention (post-intervention) and six months after the end of the intervention (follow-up). Cardiorespiratory fitness reduced in control group with no changes in experimental group, and these differences were maintained in the follow-up assessment (control group: 24.2±4.4 ml.kg-1.min-1 to 22.6±4.9 ml.kg-1.min-1; follow-up: 22.6±4.9 ml.kg-1.min-1 vs. experimental group: 28.0±4.0 ml.kg-1.min-1 to 29.7±4.0 ml.kg-1.min-1; follow-up: 28.9±5.7 ml.kg-1.min-1). Reductions in z-score body mass index (BMI) and increases HDL-C after multidisciplinary intervention were maintained after a 6-month follow-up. In conclusion, the benefits of a multidisciplinary intervention on cardiorespiratory fitness, BMI and blood lipids are maintained after a 6-month follow-up. These findings indicate that multidisciplinary interventions produce long-term health consequences. Reinforcing the importance of lifestyle changes as a therapeutic approach for the treatment of obesity in adolescents.

Non-proximate mass spectrometry using a heated 1-m long PTFE tube and an air-tight APCI ion source

Direct and rapid trace-level gas analysis is highly needed in various fields such as safety and security, quality control, food analysis, and forensic medicine. In many cases, the real samples are bulky and are not accessible to the space-limited ion source of the mass spectrometer. In order to circumvent this problem, we developed an airtight atmospheric-pressure chemical ionization (APCI) ion source equipped with a flexible 1-m-long, 2-mm-i.d. PTFE sniffing tube. The ambient air bearing sample gas was sucked into the heated PTFE tube (130 °C) and was transported to the air-tight ion source without using any extra pumping system or a Venturi device. Analytes were ionized by an ac corona discharge located at 1.5 mm from the inlet of the mass spectrometer. By using the airtight ion source, all the ionized gas in the ion source was introduced into the vacuum of the mass spectrometer via only the evacuation of the mass spectrometer (1.6 l min−1). Sub-pg limits of detection were obtained for carbaryl and trinitrotoluene. Owing to its flexibility and high sensitivity, the sniffing tube coupled with a mass spectrometer can be used as the stethoscope for the high-sensitive gas analysis. The experimental results obtained for drugs, hydrogen peroxide and small alkanes were discussed by DFT calculations.

Multidisciplinary intervention in obese adolescents: predictors of dropout.

Objective To identify biological and psychosocial factors associated with dropout in a multidisciplinary behavioral intervention in obese adolescents.Methods A total of 183 adolescents (15.4±1.6 years), pubertal (Tanner stage 3 or 4) and obese (34.7±4.0kg/m2), were enrolled in a 12-week behavioral intervention, which included clinical consultations (monthly), nutritional and psychological counseling (once a week), and supervised aerobic training (three times/week). The studied variables were weight, height, body mass index, body composition (skinfold), cardiorespiratory fitness (direct gas analysis), blood lipids and self-reported symptoms of eating disorders (bulimia, anorexia and binge eating), anxiety, depression, body image dissatisfaction and quality of life. Statistical analysis included binary logistic regression and independent t-tests.Results Of the adolescents, 73.7% adhered to the program. The greatest chance for dropout was observed among adolescents older than 15 years (odds ratio of 0.40; 95%CI: 0.15-0.98), with more anorexia symptoms (odds ratio of 0.35; 95%CI: 0.14-0.86) and hypercholesterolemia (odds ratio of 0.40; 95%CI: 0.16-0.91) at baseline.Conclusion Older adolescents, with more symptoms of eating disorders and total cholesterol have less chance to adhere to multidisciplinary treatments.

Development and validation of an automated step ergometer.

Laboratory ergometers have high costs, becoming inaccessible for most of the population, hence, it is imperative to develop affordable devices making evaluations like cardiorespiratory fitness feasible and easier. The objective of this study was to develop and validate an Automated Step Ergometer (ASE), adjusted according to the height of the subject, for predicting VO2max through a progressive test. The development process was comprised by three steps, the theoretical part, the prototype assembly and further validation. The ASE consists in an elevating platform that makes the step at a higher or lower level as required for testing. The ASE validation was obtained by comparing the values of predicted VO2max (equation) and direct gas analysis on the prototype and on a, treadmill. For the validation process 167 subjects with average age of 31.24 ± 14.38 years, of both genders and different degrees of cardiorespiratory fitness, were randomized and divided by gender and training condition, into untrained (n=106), active (n=24) and trained (n=37) subjects. Each participant performed a progressive test on which the ASE started at the same height (20 cm) for all. Then, according to the subject’s height, it varied to a maximum of 45 cm. Time in each stage and rhythm was chosen in accordance with training condition from lowest to highest (60–180 s; 116–160 bpm, respectively). Data was compared with the student’s t test and ANOVA; correlations were tested with Pearson’s r. The value of α was set at 0.05. No differences were found between the predicted VO2max and the direct gas analysis VO2max, nor between the ASE and treadmill VO2max (p= 0.365) with high correlation between ergometers (r= 0.974). The values for repeatability, reproducibility, and reliability of male and female groups measures were, respectively, 4.08 and 5.02; 0.50 and 1.11; 4.11 and 5.15. The values of internal consistency (Cronbach’s alpha) among measures were all >0.90. It was verified that the ASE prototype was appropriate for a step test, provided valid measures of VO2max and could therefore, be used as an ergometer to measure cardiorespiratory fitness.

A systematic review and meta-analysis of submaximal exercise-based equations to predict maximal oxygen uptake in young people.

Many equations to predict maximal oxygen uptake (VO2max) from submaximal exercise tests have been proposed for young people, but the composition and accuracy of these equations vary greatly. The purpose of this systematic review was to analyze all submaximal exercise-based equations to predict VO2max measured via direct gas analysis for use with young people. Five databases were systematically searched in February 2013. Studies were included if they used a submaximal, exercise-based method to predict VO2max; the actual VO2max was gas analyzed; participants were younger than 18 years; and equations included at least one submaximal exercise-based variable. A meta-analysis and narrative synthesis were conducted. Sixteen studies were included. The mean equation validity statistic was strong, r = .786 (95% CI 0.747-0.819). Subgroup meta-analysis suggests exercise mode may contribute to the overall model, with running- and walking-based predictive equations reporting the highest mean r values (running r = .880; walking r = .821) and cycling the weakest (r = .743). Selection of the most appropriate equation should be guided by factors such as purpose, logistic limitations, appropriateness of the validation sample, the level of study bias, and the degree of accuracy. Suggestions regarding the most accurate equation for each exercise mode are provided.

Relation between leukocyte count, adiposity, and cardiorespiratory fitness in pubertal adolescents.

Objective To compare the total and differential leukocyte count in obese and normal-weight adolescents, and to verify their possible relations with cardiorespiratory fitness and adiposity indicators.Methods A cross-sectional study conducted with 139 adolescents (107 obese and 32 normal weight) aged between 13 and 18 years. Cardiorespiratory fitness was determined by direct gas analysis during an incremental treadmill test. Total leukocytes and subsets were estimated by flow cytometry. Body composition was assessed by dual-energy X-ray absorptiometry. The t-test for independent samples was used for comparison between groups. The relation between leukocytes, cardiorespiratory fitness and adiposity indicators was verified by Pearson’s correlation and multiple linear regression (adjusted for age and body mass index) tests.Results Obese adolescents had higher leukocyte (8.12±2.36u/L x 103; p=0.001), neutrophil (4.33±1.86u/L x 103; p=0.002), and monocyte (0.70±0.22u/L x 103; p=0.002) counts compared to the levels of normal weight subjects. After the necessary adjustments, cardiorespiratory fitness had a negative association with leukocytes, neutrophils, and monocytes in boys.Conclusion Obese adolescents had higher total and differential leucocyte count when compared to normal weight individuals. We also observed a weak positive association between adiposity and total leukocyte, monocyte, and neutrophil counts, and in boys, a negative association between cardiorespiratory fitness and total count of leukocytes, monocytes, and neutrophils.

Calibration strategy for semi-quantitative direct gas analysis using inductively coupled plasma mass spectrometry

A process is described by which an ICP-MS equipped with an Octopole Reaction System (ORS) is calibrated using liquid phase standards to facilitate direct analysis of gas phase samples. The instrument response to liquid phase standards is analyzed to produce empirical factors relating ion generation and transmission efficiencies to standard operating parameters. Empirical factors generated for liquid phase samples are then used to produce semi-quantitative analysis of both mixed liquid/gas samples and pure gas samples. The method developed is similar to the semi-quantitative analysis algorithms in the commercial software, which have here been expanded to include gas phase elements such as Xe and Kr. Equations for prediction of relative ionization efficiencies and isotopic transmission are developed for several combinations of plasma operating conditions, which allows adjustment of limited parameters between liquid and gas injection modes. In particular, the plasma temperature and electron density are calculated from comparison of experimental results to the predictions of the Saha equation. Comparisons between operating configurations are made to determine the robustness of the analysis to plasma conditions and instrument operating parameters. Using the methods described in this research, the elemental concentrations in a liquid standard containing 45 analytes and treated as an unknown sample were quantified accurately to ± 50% for most elements using 133Cs as a single internal reference. The method is used to predict liquid phase mercury within 12% of the actual concentration and gas phase mercury within 28% of the actual concentration. The results verify that the calibration method facilitates accurate semi-quantitative, gas phase analysis of metal species with sufficient sensitivity to quantify metal concentrations lower than 1 ppb for many metallic analytes.

Are We There Yet? Pediatric Screening for Inflammatory Biomarkers and Low Cardiorespiratory Fitness to Identify Youth at Increased Risk of Cardiovascular Disease

Are We There Yet? Pediatric Screening for Inflammatory Biomarkers and Low Cardiorespiratory Fitness to Identify Youth at Increased Risk of Cardiovascular Disease

Effects of different exercise intensities on energy expenditure and hunger sensation in young adults

The aim of this study was to investigate the acute and short-term effects of different aerobic exercise intensities on postexercise energy expenditure, respiratory exchange ratio (RER),and hunger sensation in young adults. Twenty healthy, physically active (>6 months) young men of normal weight (22.41±1.76 kg/m²) participated in this study. All subjects were randomly submitted to four experimental conditions: control (no exercise); LIE, low-intensity exercise (40% of VO2peak); MIE, exercise of moderate intensity (60% of VO2peak), and HIE, high-intensity exercise (80% of VO2peak). The magnitude of (EPOC - excess post-exercise oxygen consumption),and RER were measured by direct gas analysis. A visual analogue scale was used to rate hunger sensation at baseline, immediately after the experimental session, and after 30, 60, 90 and 120 minutes of passive recovery. The results showed a positive correlation between the magnitude of EPOC and exercise intensity (r=0.74, p<0.01), with the duration and magnitude depending on exercise intensity. For all experimental conditions, the hunger sensation was greater in the LIE group (p<0.01). The hunger scores increased over the 120 minutes of passive recovery in all exercise and control sessions. The results suggest that the magnitude of EPOC is higher after HIE,promoting higher postexercise energy expenditure and a concomitant increase in fat utilization (lower RER) and transient suppression of hunger sensation in young adults.

Multicomponent quantification with a novel method applied to gradient gas sensor microarray signal patterns

Abstract Industrial monitoring can be performed efficiently by an electronic nose (EN) not only in case of direct gas analysis but also if liquids have to be analysed for volatile components. The control of a binary biocide mixture contained in oil–water emulsions is presented as an example for a multicomponent quantification. A carrier gas was bubbled through the lubricant emulsion at elevated temperature to enhance the evaporation of the two biocide components to be determined by a gradient gas sensor microarray. A linear discriminant analysis trained with well-defined model mixtures showed a reasonable multicomponent quantification with a special two-dimensional interpolation.

Assessment of Trentingrana cheese ageing by proton transfer reaction-mass spectrometry and chemometrics

Proton transfer reaction-mass spectrometry (PTR-MS) data have been analysed by chemometric techniques to monitor cheese ageing by means of on-line direct head-space gas analysis. Twenty cheese loaves of Trentingrana, a trademarked cheese produced in northern Italy, of different origin and ripening degree, were sampled over the whole Trentingrana production area. An increase of the spectral intensity with ripening has been observed for most of the PTR-MS peaks and a univariate analysis identified 16 mass peaks that were significantly different for ripened and young cheeses, respectively. Moreover, the usefulness of different discriminant analyses and class modelling techniques have been investigated. Discriminant Partial Least Squares analysis, while indicating average behaviour and possible outliers, was not able to correctly classify all samples. Soft class modelling performed better and allowed a 100% correct classification. Partial least square calibration predicted the ageing time of each loaf with reasonable accuracy with a maximum cross-validation error of 3.5 months.

Validity of a V·O2maxPrediction Equation of the 2-km Walk Test in Female Seniors

Walking is a useful exercise mode for most adults due to its general ease, acceptability, and safety. Therefore, many field tests based on performance in walking have been developed to predict V.O (2 max). Even if these tests are much easier to perform than laboratory tests, field tests have to be valid. The objective of the paper was to explore the accuracy and bias of a V.O (2 max) prediction equation of the 2-km Walk Test, in an active female senior group (n=18, mean age: 66.1+/-4.4). V.O (2 max) (l . min (-1)) was measured during cycle ergometry by direct gas analysis from a maximal test (step: 30 W, time: 2 min 30). V.O (2 max) related to body mass was then calculated (ml . min (-1) . kg (-1)). Subjects completed also the 2-km Walk Test (UKK Institute). V.O (2 max) (ml . min (-1) . kg (-1)) was then predicted from age, sex, body mass index, heart rate, and walking time measured during the 2-km Walk Test. Predicted V.O (2 max) and measured V.O (2 max) were highly correlated (r=0.63, p<0.01). Predicted V.O (2 max) (20.5+/-6.1 ml . min (-1) . kg (-1)) was not significantly different from measured V.O (2 max) (18.7+/-3.4 ml . min (-1) . kg (-1)). Prediction equation bias with its 95 % limits of agreement was - 1.8+/-4.8 ml . min (-1) . kg (-1) with a coefficient of variation of 24.2 %. In an active female senior population, the 2-km Walk Test offers a fairly accurate V.O (2 max) prediction. The training and learning effects can be neglected because when the test was repeated no significant bias was observed between the two trials.

Inclusion Of Anthropometric Data Improves YMCA Prediction Of Vo2peak

A very popular submaximal protocol for estimation of VO2peak is the YMCA bike test. Steady state heart rate (HR) is measured at multiple submaximal workloads and extrapolated to the subject's estimated maximal HR (220-age). The VO2 corresponding to the estimated maximal HR is accepted as the estimated VO2 peak. The accuracy of VO2 peak estimation from the YMCA protocol has not been thoroughly investigated. Purpose The purpose of this study was to investigate and attempt to improve the accuracy of the YMCA protocol. Considering the availability of anthropometric data, BMI and body fat percentage (estimated through skinfolds) were utilized (through regression analysis) in and attempt to improve the accuracy. Methods Thirty females (20.8±1.4 years, 63.3±8.5kg, 23.9±4.1% fat) participated in the study. The standard YMCA protocol was completed (with simultaneous measurement of metabolic data) and then continued (resistance increased 50Watts/min) to volitional exhaustion. ANOVA with repeated measures was used to compare: a) VO2 peak estimated from the standard YMCA protocol (YVO2); b) VO2 peak estimated using the Houston non-exercise VO2 prediction equation (HVO2); and c) VO2peak measured by direct gas analysis (MVO2). Regression analysis on twenty-five of the subjects was used to develop two VO2 peak prediction equations (utilizing YVO2 and each of the anthropometric variables - BMI or Fat %). The equations were then cross-validated using the remaining subjects. Results All differences between MVO2 (36.98 ml/ kg/min±5.1), YVO2 (34.8 ml/kg/min±6.3), and HVO2 (38.97 ml/kg/min±3.4) were significant (p ≤ 0.05). VO2 values predicted with the BMI (35.9 ml/kg/min±3.3) and body fat (36.5 ml/kg/min±2.8) regression equations were not significantly different from MVO2 (37.9 ml/kg/min±3.4) in the subjects used for cross-validation. Conclusion The current results demonstrate that by simply adding BMI or estimated percent fat to the popular YMCA formula, a more accurate estimation of aerobic capacity can be obtained in college-aged females.

FTIR emission spectroscopymethods and procedures for real time quantitative gas analysisin industrial environments

Diagnostic tools for real time and direct gas analysis have beendeveloped. The simultaneous measurements of gas and particletemperatures (280-330 °C) and gas concentrations (CO,CO2, HCl, H2O) are demonstrated in a hotparticle-laden flue gas with a fibre-optic probe connected to a Fourier transform infrared spectrometer. The gas temperature isfound from the thermal radiation at the 2350 cm-1 CO2fundamental band, whereas the gas concentrations aredetermined by comparing the measured transmittance spectra witha spectroscopic database and validation measurements using theHotgas facility at Risø. Measurement uncertainties arediscussed. The measured local gas temperatures and concentrations are in good agreement with measurements made withconventional equipment.

Polycyclic Aromatic Hydrocarbon Formation in Opposed Flow Diffusion Flames of Ethane

The effect of fuel-side carbon density on the levels of polycyclic aromatic hydrocarbon (PAH) formation in atmospheric pressure, opposed flow, ethane diffusion flames has been studied using heated micro-probe sampling and gas chromatography/mass spectrometry (GC/MS). Mole fraction profiles of about 30 major and minor species, as well as trace aromatic and substituted aromatic hydrocarbons and PAHs (up to C 14H 10, e.g., cyclopenta[cd]pyrene), were quantified by direct gas analysis of samples withdrawn from within the flame without any pre-concentration. Results indicate that fuel-side carbon density and changes in flame temperature markedly influence the levels of benzene and PAH formed within opposed flow diffusion flames. Significant O 2 penetration was also noted on the fuel-rich side of the flame at a lower fuel dilutions, suggesting PAH formation may be also associated with O 2-catalyzed reactions.

Determination of carbon dioxide evolution rate using on-line gas analysis during dynamic biodegradation experiments

Respirometry is a precious tool for determining the activity of microbial populations. The measurement of oxygen uptake rate is commonly used but cannot be applied in anoxic or anaerobic conditions or for insoluble substrate. Carbon dioxide production can be measured accurately by gas balance techniques, especially with an on-line infrared analyzer. Unfortunately, in dynamic systems, and hence in the case of short-term batch experiments, chemical and physical transfer limitations for carbon dioxide can be sufficient to make the observed carbon dioxide evolution rate (OCER) deduced from direct gas analysis very different from the biological carbon dioxide evolution rate (CER).To take these transfer phenomena into account and calculate the real CER, a mathematical model based on mass balance equations is proposed. In this work, the chemical equilibrium involving carbon dioxide and the measured pH evolution of the liquid medium are considered. The mass transfer from the liquid to the gas phase is described, and the response time of the analysis system is evaluated.Global mass transfer coefficients (K(L)a) for carbon dioxide and oxygen are determined and compared to one another, improving the choice of hydrodynamic hypotheses. The equations presented are found to give good predictions of the disturbance of gaseous responses during pH changes.Finally, the mathematical model developed associated with a laboratory-scale reactor, is used successfully to determine the CER in nonstationary conditions, during batch experiments performed with microorganisms coming from an activated sludge system.

The use of ICP to determine delivery rates of transportable metal contaminants from metal organic liquid sources

Direct gas analysis was performed on metal organic (MO) liquid source bubblers em-ployed for MOCVD growth of vanadium doped and undoped GaAs and AlGaAs thin films. Using either direct or standard addition methods, the lower limit of quantitation (LLQ) for transportable Si was 5 × 10s−11 moles/min with precision better than 10% (25 cc/min H2 carrier). The other transportable contaminants sought during a typical anal-ysis were P, S, Cd, Cu, Zn, Fe, Cr, Ni, Mo, Mn, Sn, Pb, Ca, Mg, and Ge. None of these were detected with a LLQ estimated to be less than 10s−10 moles/min.