Precision of flame atomic absorption measurements of arsenic, cadmium, calcium, copper, iron, magnesium, molybdenum, sodium, and zinc

Bower, Nathan W.; Ingle, J. D.

doi:10.1021/ac50012a017

Cited by 42 publications

(32 citation statements)

References 6 publications

(9 reference statements)

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“…Since more than three decades ago, there have been published many theories and methods for estimating SD with no recourse to repetition, especially in instrumental analyses. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] In spite of varied symbols and terminology in the literature, the largest part of uncertainty equations proposed can take a universal form:…”

Section: Introductionmentioning

confidence: 99%

“…Examples are LOD, 21,24,26,28 confidence intervals of linear calibration 28 and tests of significant differences. 3,4,6 Theoretical SD descriptions elaborated so far include Winefordner's theory, [18][19][20] Ingle's theory, [15][16][17] Bouman's theory 21,22 and FUMI theory (FUnction of Mutual Information). [23][24][25] Proceeding along the lines suggested by the FUMI theory, our approach is named after it.…”

Section: Introductionmentioning

confidence: 99%

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Test of Significant Differences with a priori Probability in Microarray Experiments

et al. 2003

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The advent of high-throughput array technology has now made it possible to collect data on thousands to tens of thousands of genes simultaneously. However, methods for detecting the genuine changes in the gene expression levels in cells or tissues are still evolving. [1][2][3][4][5][6][7][8][9][10][11] A straightforward method for comparing two expression levels of genes is the traditional two-sample t-test. The basic problem with the t-test in microarray experiments, however, is that the repetition is restricted within a small number in most cases, because experiments are costly or tedious to repeat. Although the importance in replication has been illustrated, 1,3,6,9 situations often arise where only single or duplicate experiments for each condition are allowed.The purpose of this paper is to put forward a method for testing the significant differences of the gene expression levels under a single pair of experiments (a control experiment and treatment experiment). In order to take into account the stochastic aspects of gene expressions, we model our algorithm on the t-test. In our approach and the t-test, the SD estimates of the gene expression levels are a criterion for the statistical judgment, but one of the key differences is how to estimate the SD for each gene.In the t-test, the SD estimates are derived from the same data set as those to be judged by the t-test, itself. This fact can be closely connected with the above-mentioned problem of replication. In our approach, the SD estimates, referred to here as a priori SD, are obtained from experimental results which are different from the target data set of the judgment.Statistics tells that the variability in the estimates of SD obeys the chi-squares distribution and is much larger than the variability in the estimates of averages, as long as the estimates are obtained by repetition. That is, the estimates of averages are more reliable. The t-test uses the SD estimates directly, but in this paper, the a prior SD is given as a function of the average of the gene expression levels. Then, we can easily expect that our approach can provide more stable judgment, but needs a sound model for the a prior SD.The idea of the a priori SD is not novel in the area of analytical chemistry. Since more than three decades ago, there have been published many theories and methods for estimating SD with no recourse to repetition, especially in instrumental analyses. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] In spite of varied symbols and terminology in the literature, the largest part of uncertainty equations proposed can take a universal form:where RSD denotes the relative standard deviation of measurements, sB denotes blank SD, A measurements (e.g., area), and I independent error. To our knowledge, Huber et al. A traditional method for comparing two expression levels of genes in microarray experiments is the two-sample t-test. Because of the difficulty in using a large number of microarrays, an alternative method is required which can provide a relia...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Test of Significant Differences with a priori Probability in Microarray Experiments

et al. 2003

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“…Btlx 1663, Los Alamos, N.M. 87544. decades, relatively good powers of detection. and minimal matrix effects provided the impetus to consider exploding-foil excitation For micro solution samples (3,4).…”

Section: Discussionmentioning

confidence: 99%

“…The different noises measured are identified below in accordance with the terminology developed by Ingle and Bower (3,4 ) . dot is the standard deviation in the signal recorded with the HC lamp and flame off and is due to amplifier-readout noise and dark current noise from the PMT.…”

Section: (3 4 )mentioning

confidence: 99%

Performance of a time multiplex multiple slit multielement flame atomic absorption spectrometer

Salin¹,

Ingle²

1978

Anal. Chem.

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The performance characteristics of a new multielement flame atomic absorption (AA) spectrometer are presented. Compared to a conventional single element AA, the absolute light level8 measured are considerably lower and additional spectral overlap problems arise. These differences do not significantly affect detection limits, sensitivities, precision, and calibration curves in most cases. Detection limits (in ppb) of 50 (Au), 8 (Cd), 40 (Co), 9 (Cu), 60 (Fe), 2 (Mg), 5 (Mn), 50 (Ni), 50 (Pb), and 20 (Zn) were obtained under favorable multielement conditions and are within a factor of two of detection limits obtained on a good quallty commercial slngle element AA operating with comparable spectral bandpass and integration time. The relative measurement precision at moderate absorbances is typically 1 % or better.The design and construction of a new multielement flame atomic absorption (AA) spectrophotometer were described along with a review of other multielement AA spectrophotometers in a recent paper ( I ) . This instrument is denoted a Time Multiplex Multiple Slit (TMMS) system. It is similar to a conventional single-element AA except that the light beams from four single element hollow cathode (HC) tubes are directed through the flame by the use of beam splitters and the exit slit is replaced by multiple exit slit array (one slit for each element). The light passing through all exit slits is directed to one photomultiplier tube (PMT). The HC lamps are pulsed on sequentially (one on a t a time) with a 12.5% duty cycle at a 12.5-Hz rate. Data acquisition is synchronized with the lamp pulsing such that the lamp signal from each element's HC lamp is directed to a separate data acquisition readout channel a t the proper time. To signal average, typically 100 ''laps'' or 10-ms duration lamp pulses are averaged for each element. The system is configured to determine simultaneously any four of the following ten elements:Cu, Mg, Pb, Mn, Au, Fe, Co, Ni, Cd, and Zn. In this paper the performance characteristics of this instrument are critically examined. EXPERIMENTALThe TMMS instrument and its general operation have been previously described ( I ) . For all flame AA ineasurements on the TMMS instrument, the burner air and CzH2 flow rates were 4.6 and 0.5 Ljmin, respectively, and the sample flow rate was 4.6 mL/min. The FMT bias voltage was adjusted to 60G800 V and R, was lo5 -10' R. Solutions were prepared from reagent grade metal salts and distilled and deionized water.The most common AA analysis lines were used in all cases except for Au and Pb. The Au 267.6 nm line provides an AA sensitivity and lamp intensity near those of the more common 242.8 nm line and avoids any possible overlaps with the Co 242.5 nm line and the Sn 242.1 nm line. The Pb 283.3 nm line was chosen as opposed to the normal 217.0 nm line because it is five times more intense and the AA sensitivity is within a factor of Present address, two of the 217.0 nm line. A Au slit was included on the mask because Au is a good internal standard element for corr...

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“…These measurements are a compilation of information from several sources, but primarily from the work of Ingle [20,21] Finally, zinc is an example of an element whose absorption wavelength is lower than 230 nm, the range where flame transmission noise dominates.…”

Section: Absorption Noise Sourcesmentioning

confidence: 99%

Comparison of Detection Limits in Atomic Spectroscopic Methods of Analysis

Epstein

1987

ACS Symposium Series

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Precision of flame atomic absorption measurements of arsenic, cadmium, calcium, copper, iron, magnesium, molybdenum, sodium, and zinc

Cited by 42 publications

References 6 publications

Test of Significant Differences with a priori Probability in Microarray Experiments

Test of Significant Differences with a priori Probability in Microarray Experiments

Performance of a time multiplex multiple slit multielement flame atomic absorption spectrometer

Comparison of Detection Limits in Atomic Spectroscopic Methods of Analysis

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