The Reference Standard

Based on known ocpcrimontal AG values, and Q, were estimated. The system phenol-HMPA in CCI4. was chosen as the reference standard the H-boud free energy factors C, and Q were set at -2.50 (phenol) and 4,00 (HMPA) respectively. 

The actual value of the enthalpy of hydrogenation of 1,3-butadiene is —243 k,l rnol Both are hydrogenated to the same product, u-biitaiie hence the enthalpy diagram (Fig. 7-4) shows that bnta-1,3-diene is 11 kJ rnol. lower in enthalpy than it ought" to be on the basis of the reference standard, bnt-l-ene. 

Using cyclohexene as the reference standard, calculate the resonance energies of cyclohexa-1,3-diene = —224 kJ moU ), cyclohexa-1,4-diene =... 

Spectroscopically determined values of P vai y, but they aie usually around —2.4 eV. In the section on resonance stabilization, we saw that thermodynamic measurements of the total resonance stabilization of butadiene yield 11 and 29 kJ mol according to the reference standard chosen. Calculate the delocalization energy of buta-1,3-diene in units of p. Determine two values for the size of the energy unit p from the thermochemical estimates given. Do these agree well or poorly with the spectroscopic values ... 

Entry into Confined Spaces. In 1993 OSHA adopted a confined space entry rule (93) requiring employers to evaluate the workplace to (/) determine if it contains any confined spaces, (2) mark or identify such confined spaces, and (2) develop and implement a permit program for entry into such spaces. The program must include a permit system which specifies the steps to be taken to identify, evaluate, control, and monitor possible electrical, mechanical, and chemical ha2ards select and use equipment institute stand-by attendance and estabflsh communications. The reference standard (93) should be studied for details. 

Rhinitis is characterized by nasal stuffiness with partial or full obstmction, and itching of the nose, eyes, palate, or pharynx, sneezing, and rhinorrhoea. If left untreated it can lead to more serious respiratory diseases such as sinusitis or asthma. Although several types of dmgs are available for treatment, nasal spray topical corticosteroids are widely regarded as the reference standard in rhinitis therapy (250). 

In which documents do you define the reference standards, codes of practice, quality plans, and procedures to be complied with during production ... 

Establish the normal, maximum, and minimum gas flow for the system where the unit will operate. This is usually in standard cubic feet per minute, per hour or per day. Note the catalog units carefully, and also that the reference standard temperature is usually 60°F for gas or vapor flow. 

It is crucial in quantitative GC to obtain a good separation of the components of interest. Although this is not critical when a mass spectrometer is used as the detector (because ions for identification can be mass selected), it is nevertheless good practice. If the GC effluent is split between the mass spectrometer and FID detector, either detector can be used for quantitation. Because the response for any individual compound will differ, it is necessary to obtain relative response factors for those compounds for which quantitation is needed. Care should be taken to prevent contamination of the sample with the reference standards. This is a major source of error in trace quantitative analysis. To prevent such contamination, a method blank should be run, following all steps in the method of preparation of a sample except the addition of the sample. To ensure that there is no contamination or carryover in the GC column or the ion source, the method blank should be run prior to each sample. 

The top and the bottom x-ray detector each contain a multiplier phototube coated with phosphor. This tube compares the intensity of the x-ray beam entering the detector with that of the light from the reference standard, a discharge lamp. The reference beam is part of a circuit that maintains the x-ray source at constant intensity. The deviation wedge comes to rest when the intensities of the transmitted x-ray beams stand in a predetermined ratio. At this point, the unbalance in the servo system has been compensated, and the position of the deviation wedge consequently indicates the thickness of the strip. In 1955, this application was made fully automatic that is, the unbalance (or error signal) just mentioned was used to readjust tandem cold reduction mills of the United States Steel Corporation. Automatic control proved significantly more effective than manual control. 

A 12.60% NC was used as the reference standard for all samples of this material TNT and HMX were compared against pure samples of each other, respectively... 

In Table 2, results are given comparing the three above FNAA techniques for total nitrogen and corresponding HMX content of three synthetic Octol samples containing 70, 60 and 80% HMX respectively. Chemical analysis by extraction is also included as another basis for comparison. An 80/20 Octol (80% HMX) was used as the reference standard for the activation assays... 

The performance of AOS vs. the other surfactants was tested with three foam boosters, namely, amide oxide (AO), lauryl myristic monoethanol amide (LMMEA), and coco diethanolamide (coco DEA) at 90 10 anionic/booster ratio. Blends were evaluated at 0.025% active, 41 °C, and 140 ppm vegetable shortening oil. The results in Fig. 21 show that AOS blends outperform the reference standard whereas the other blends were of equal or less performance. The AOS/LMMEA blend gave superior performance. It was further shown that the addition of a small amount of AES (10% on total actives) further enhanced the performance of the AOS system (see Fig. 22). AOS when formulated with AES and amide therefore has outstanding dishwashing performance and is an attractive candidate for use in formulating light-duty liquids. 

The external standard method requires that the standard is chromatographed separately from the sample and thus, the chromatographic conditions must be maintained extremely constant. The great advantage of the external standard method is that the reference standard (or standards) can be identical to the solute (or solutes) of interest in the sample. Thus, a synthetic mixture can be made up in which the concentration of the components is closely similar to those of the sample. 

A series of novel l-substituted-4-phenyl-l,2,3-triazolo(4,3-a)quinazolin-5(4H)-ones 1 were synthesized by the cyclization of 2-hydrazino-3-phenyl-quinazolin-4(3H) 2 with various one carbon donors. The starting material 2-hydrazino-3-phenylquinazolin-4(3H)-one 2, was synthesized from aniline 7 by a novel innovative route. When tested for their in vivo Hi-antihistaminic activity on conscious guinea pigs all the test compounds protected the animals from histamine-induced bronchospasm significantly, whereas the compound l-methyl-4-phenyl-l,2,3-triazolo(4,3-a)quinazolin-5(4H)-one lb (percentage protection 70.7%) was found to be equipotent with the reference standard chlorpheniramine maleate (percentage protection 71%). These compounds show negligible sedation (5%) when compared to the reference standard (26%). Hence they could serve as prototype molecules for future development [1,4,5]. 

As sedation is one of the major side effects associated with antihistamines, the test compounds were also evaluated for their sedative potentials. This was determined by measuring the reduction in locomotor activity using an ac-tophotometer [6,7]. The test compounds and the reference standards (chlorpheniramine maleate and cetirizine) were administrated orally at a dose of 5 mg/kg in 1% CMC. 

FIGURE 10.12 TLC of photolyzed solutions of folic acid along with the reference standards. The photolyzed solutions of folic acid at pH 5.0 (1), 6.0 (2), 7.0 (3) and (4) folic acid (5) pterin-6-carboxylic acid (6) and p-aminobenzoyl-L-glutamic acid (7) were applied to silica gel GF254 precoated plates using ethanol/ammnonia (13.5 mol/l)/l-propanol (60 20 20, v/v) as a solvent. (Reprinted with permission from Akhtar, M.J., Khan, M.A., and Ahmad, I.J., Pharm. Biomed. Anal., 31, 579-588, 2003. Copyright (2003) Elsevier.)... 

Also, a chromatographic profile or fingerprint of trace unknowns can be established and monitored, so that if product performance unexpectedly changes, there will be a starting point for troubleshooting. The effects of experimental variables on sample recoveries should be measured directly by controlled variation of an experimental factor, using the reference standard, or suitable external standards, or spiked addition of an external standard to the reference standard. A detailed example of the use of internal and external standards is presented in Chapter 4. 

The reference standards are used to quantitate the standards that are employed in the kits to generate the standard curves. The kit standards are recombinant single-stranded DNA molecules that are added to either negative serum or plasma at known concentrations. Because the standard curve is not constructed with reference standards, Chiron initially chose to use the term equivalent to describe the units of nucleic acid quantitation in clinical samples. An equivalent was defined as the amount of nucleic acid in a clinical sample that gave a signal equal to one molecule of the reference standard nucleic acid. The term copy rather than equivalent is used to describe the units of nucleic acid quantitation in the HIV-1 bDNA assay. The terms are now used interchangeably. 

The test material for this study was Lorsban 4E Insecticide in 2.5-gallon plastic jugs, as well as Lorsban 50W in 5-pound bags. The reference standards were chlorpyrifos (0,0-diethyl-0-[3,5,6-trichloro-2-pyridinyl] phosphorothio-ate), CAS No. 002921-88-2 and 3,5,6-TCP (3,5,6-tiichloro-2-pyridinyl). 

The chlorpyrifos reference standard was used in conjunction with the analysis of coverall dosimeter sections (arms, legs, torso), air tubes, Gelman filters, head patches, and handwashes, while the 3,5,6-TCP was used as the reference standard during urine analysis. 

Compare the refractive index of the substance to be examined with the refractive index of the reference standard of valproic acid, which has a known refractive index of 1.422-1.425 [10,11],... 

Two different and possibly complementary approaches have been explored. One utilizes a panel of quantifiable internal reference standards (QIRS), which are common proteins present widely in tissues in relatively consistent amounts.11,22 In this instance because the reference proteins are intrinsic to the tissue they are necessarily subjected to identical fixation and processing, and incur no additional handling or cost, other than synchronous performance of a second IHC assay (stain), such that the intensity of reaction for the QIRS and the test analyte can be compared by IA, allowing calculation of the amount of test analyte (protein) present on a formulaic standard curve basis. The other approach seeks to identify external reference materials and to introduce these into each step of tissue preparation for cases where IHC studies are anticipated in this instance the logistical issues of production, distribution, and inclusion of the reference standard into all phases of tissue processing also must be considered, along with attendant costs. 

The ultraviolet chemical assay for erythromycin remains largely unchanged from that described by Kuzel et al.9 in 1954. This procedure is essentially as follows. The reference standard, alkali reagent, and buffer solutions are prepared prior to the assay. 

The reference standard solution is prepared by dissolving about 35 mg. accurately weighed erythromycin standard in 100 ml. methanol in a 250 ml. volumetric flask. This is diluted with phosphate buffer pH 7.0 to 250 ml., mixed, and allowed to cool to room temperature, then again diluted to the mark and mixed well. 

Determined by GPC with polymethyl methacrylate (PMMA) as the reference standard. "Molecular weight distributions. 

K is equilibrium constant. If we consider the reference standard state to be gaseous, K = K because the activity and fugacity coefficients are unity in very dilute solution and ideal gas, respectively. Then ( g)0 and (ks)o will be the same. 

When preparing standard solutions, be sure to dry the reference standard properly, preferably on the day of use. Care should be taken to ensure that the drug powder is completely dissolved. In the case of prednisone reference standard, the powder becomes very hard upon drying, making it slower to dissolve. Dissolving the powder first in a small amount of alcohol helps to overcome this problem. 

It is not surprising that the data produced as total petroleum hydrocarbons (EPA 418.1) suffer from several shortcomings as an index of potential ground-water contamination or health risk. In fact, it does not actually measure the total petroleum hydrocarbons in the sample but rather, measures a specific range of hydrocarbon compounds. This is caused by limitations of the extraction process (solvents used and the concentration steps) and the reference standards used for instrumental analysis. The method specifically states that it does not accurately measure the lighter fractions of gasoline [benzene-toluene-ethylbenzene-xylenes fraction (BTEX)], which should include the benzene-toluene-ethylbenzene-xylenes fraction. Further, the method was originally a method for water samples that has been modified for solids, and it is subject to bias. 

An example of cIEF e-gram showing antibody peak integration is shown in Figure 23. The p7 values of the two main peaks (main peak 1 and 2) were recorded. As an identity assay, a reference standard is always included in the same run sequence. The cIEF profile of the sample is compared with the profile of the reference standard. The criterion for an identity test is usually that the sample be comparable to reference standard, as measured by a comparison of the p7 values of the sample and the reference standard, with no new peaks visible. 

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