Internal standard instruments, flame

The intensity of sodium emission in a flame at 589.0 run is compared with that of standards. If an internal standard instrument is available, the ratio of sodium to lithium emission is measured. 

Finally, the flame photometric methods for determination of sodium and potassium have been adapted to the device. In this case, after the addition of lithium as internal standard, the electrolytes are dialyzed into the recipient stream, which is then pumped into an atomizer-burner of more or less conventional design. A colorimeter has been designed to allow for simultaneous recording of sodium and potassium, utilizing a two-channel recorder as optional equipment. This arrangement would tend to conserve sample. Without the dual recorder, the recorder supplied as part of the basic instrument is used, and the specimens are sampled once for sodium and once for potassium. 

The first commercially available flame photometer was introduced in the 1940s by the Perkin-Elmer Corporation. In 1948, Beckmann Instruments, Inc., introduced a flame attachment that could be used with their popular model D.U. spectrophotometer. By the late 1950s, instruments had been developed that used lithium as an internal standard to maximize precision. Autodilution features and microprocessor-controlled operations became widely used options in the 1970s. The most recent significant development was the introduction of cesium as the internal standard, by Instrumentation Laboratory, Inc. (Figs. 1-3). This development makes concurrent lithium determinations more practical. 

Fig. 1 Flame photometer using cesium as the internal standard. (Courtesy of Instrumentation Laboratory, Inc.)...

To omit unconventional instrumentation that was not suitable for routine analysis, as proposed by De Graeve et al.88, Bellia et al.81 developed a quite simple method to determine papaverine in blood samples, using conventional flame ionization or a nitrogen-phosphorus detector. The internal standard, strychnine, was added to the sample prior to extraction, which was carried out with toluene after basification, back extraction with acetic acid and extraction of the liberated base with diethyl ether. The gas chromatography was done on a packed column with 2 % 0V-101 at 275°C. To minimize the adsorption effects, the column was silanized by in situ injection and by injection of a concentrated solution of papaverine and the internal standard prior to routine analysis. Precision and accuracy of the method is shown in Table 14.13. 

Ute intensities of flame emission lines can be influenced by a variety of instrumental factors, including flame temperature, flow rate of solution, and nebulizer efficiency. We can compensate for variations in these factors by using the inteihal standard method. Here, we add the same amount of internal standard to mixtures containing known amounts of the analyte and to the samples of unknown analyte con-... 

USEPA Methods 610 and 8100 describe standard methods using a 1.8 m X 2 mm i.d. glass column packed with 3% OV-17 on Chromosorb W-AW-DCMS or a 30-m fused-silica capillary GC with flame ionization detection (GC-FID). When used to analyze the EPAig the closely eluting pairs, PHN/ANC, B[a]A/CHR, B[b]F/B[k]F, and IND/ D[ah]A are not completely resolved. Internal standards are added to correct for variability in instrument performance and injection volume. 

Sodium and potassium in serum are determined in the clinical laboratory by atomic-emission spectroscopy, using an instrument designed specifically for this purpose [5]. Two filter monochromators isolate the sodium and potassium emission lines. A lithium internal standard is used, and the ratios of the Na/Li and K/Li signals are read out on two separate meters. The internal standard compensates for minor fluctuations in flame temperature, aspiration rate, and so forth. A cool flame, such as air-propane, is used to minimize ionization. Typically, the serum sample and standards are diluted 1 200 with a 100 ppm Li solution and aspirated directly. The instrument can be adjusted to read directly in meq/1 for sodium and potassium by adjusting the gain while aspirating appropriate standards. 

Internal Standards. When internal standardization is used, the ratio of the signals of the analyte line and an internal standard line is measured. This technique is well known in emission spectrometry, where the internal standard is either the major element in the matrix or an added element of known concentration. In AAS, this technique may be employed when a double-channel (or multi-channel) instrument is in use and simultaneous measurements at two wavelengths are possible. This technique eliminates small variations in nebulizer and flame performance. Such variations are not corrected by double beam spectrometers. 

The requirement that the analytes be quantitated using an internal standard mode of instrument calibration is due to the fact that mass spectrometers are intrinsically unstable that is, their response factor varies with time when compared to other GC detectors such as the flame ionization detector (FID). The internal standard technique of instrument calibration is... 

Fig. 1. GLC of fecal bile acids from germfree, gno-tobiotic, and conventional rats. The first peak in each chromatogram is the internal standard 5a-cholestane. Instrument, Hewlett-Packard 402 gas chromatograph. Column, 2-m glass Utube packed with 1% SE-30 on 80-120 mesh Gas Chrom Q. Isothermal 220°C. Nitrogen carrier gas 75 ml/min. Flame ionization detector. Bile acids were analyzed as the trimethylsilyl ethers of the bile acid methyl esters. From Kellogg et al. (44). Reprinted with permission of the Journal of Lipid Research.

See also Atomic Absorption Spectrometry Principles and Instrumentation Interferences and Background Correction Flame. Atomic Emission Spectrometry Inductively Coupled Plasma. Quality Assurance Internal Standards. 

Several instrument manufacturers supply flame photometers designed specifically for the determination of sodium, potassium, lithium, and sometimes calcium in blood serum, urine, and other biological fluids. Single-channel and multichannel (two to four channels) instruments are available for these determinations. In the multichannel instruments, each channel can be used to determine a separate element without an internal standard, or one of the channels can be reserved for an internal standard such as lithium. The ratios of the signals from the other channels to the signal of the lithium channel are then taken to compensate for flame noise and noise from fluctuations in reagent flow rate. Flame photometers such as these have been coupled with flow injection systems to automate the sample-introduction process (see Section 33B-3). Typical precisions for flow-injection-analysis-based flame photometric determinations of lithium, sodium, and potassium in serum are on the order of a few percent or less. Automated flow injection procedures require l/KIO the amount of sample and 1/10 the time of batch procedures. -... 

It should be noted that the costs of calibration standards, reference materials, chemicals, solutions, and acids are also something you have to plan for, but will not be used in this evaluation as they are not considered instrument-running costs. However, they are also required to carry out a complete assessment of each of the four techniques. For example, in ICP-MS, multielement standards are generally less expensive than purchasing the same number of single-element standards. In flame AA, it is fairly common to use iouization buffers to minimize the effects of easily ionizable elements. In ETA, matrix modifiers are widely used to change the volatility of analyte or matrix elements. Whereas in ICP-OES and ICP-MS, internal standards are used in the majority of analyses, especially if the sample matrices are different from the calibration standards. 

Sodium and Potassium. For the electrolytes, sodium and potassium the flame pho meter is the instrument of choice (29). This instrument permits readily the dilution of the serum 200 fold, for analysis, using an internal lithium standard. Most instruments require 1 ml for analysis. It is therefore practicable to measure out 3pi and dilute it to 1 ml. This is best done with a sampler-diluter of high precision. The tip of the diluter needs to be a drawn out polyethylene tip, or the 5 pi will not be measured with any degree of accuracy. 

ISO 13506 2008. Protective clothing against heat and flame - test method for complete garments - prediction of bum injury using an instrumented manikin. Geneva International Organization for Standardization 2008. 

Following ASTM International FI930 Standard Test Method for Evaluation of Flame Resistant Clothing for Protection Against Fire Simulations Using an Instrumented Manikin... 

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