Contaminants, HPLC analysis

Scotter, M.J., Castle, C., Roberts, D., Method development and HPLC analysis of retail foods and beverages for copper chlorophyll (E141[i]) and chlorophyllin (E14[ii]) food colouring materials. Food Additives and Contaminants, 22,1163, 2005. 

The submitters used HPLC analysis to determine the enantiomeric purity (Daicel Co. CHIRALCEL OB column 99.5/0.5 hexane/2-propanol mixture, 1.0 mL/min flow rate detection at 254-nmS-isomer tp, 19.2 min, R-isomer tp 24.6 min)). Under these conditions, however, the propiophenone contaminant Is coincident with the S-enantiomer thus affording unreliable enantiomeric analysis. 

With respect to sample preparation, it is necessary to develop effective and fast procedures involving only a few steps in order to avoid contamination, reduce analysis time and to improve the quality of analytical work. Microsampling and the use of smaller sample sizes is required and also the further development of analytical techniques. In particular, there is a need for the development of online and/or hyphenated techniques in ICP-MS. Microsampling combined with the separation of small amounts of analytes will be relevant for several chromatographic techniques (such as the development of micro- and nano-HPLC). There is a demand for further development of the combination of LA-ICP-MS as an element analytical technique with a biomolecular mass spectrometric technique such as MALDI- or ESI-MS for molecular identification and quantification of protein phosphorylation as well as of metal concentrations, this also enables the study of post-translational modifications of proteins, e.g. phosphorylation. 

Figure 12.11—Comparison of UV andfluorescence detection after chromatographic separation. Aflatoxins, which are carcinogenic contaminants present in certain batches of grain cereals, are controlled by HPLC analysis. It can be seen that the peak intensities in UV detection vary with concentration whereas fluorescence detection is much more sensitive to aflatoxin G2 and B2. (Reproduced by permission of SUPELCO.)...

When Fab-B(SH) has been eluted, connect a second, larger Sephadex G25 column (2 6-cm diameter, bed height 20 cm) to the chart recorder. After the 30 min-mcubation, load the Fab-A(SH)/o-PDM/DMF mixture onto this second G25 column, and elute at a flow rate of approx 200 mL/h. Collect the Fab-A(mal) protein peak (elutes after 8-10 min), taking a 45-pL sample for HPLC analysis Stop collecting when the chart recorder pen has returned half way to baseline to avoid contamination with o-PDM/DMF, which elutes as a large second peak... 

The analysis of the purified monophosphoryl lipid A by reverse-phase HPLC revealed the degree of purity of the fractions TLC-1, -3, -5, and -7 (23). TLC-1 and -3 each gave one major peak (85%), and these peaks had identical elution times. TLC-5 showed one major (72%) and one minor (18%) peak. TLC-7 resolved into one major (48%) and two minor (21 and 16%) peaks. One of the minor peaks in TLC-7 (16%) was the overlapping contaminant of the minor components in TLC-5. Representative results of the HPLC analysis of C-labeled TLC-3 and -5 are shown in Figure 2. 

Employee Exposure Monitoring. Industrial hygiene assessment of surface concentrations associated with a potent compound handled solely in liquid form within a chemical laboratory hood was conducted to assess the potential for downstream contamination potential. Handling operations assessed included dilutions of sample solutions and HPLC analysis. Wipe samples were collected from the following surfaces within and outside of the laboratory ... 

As was the case in air-pollution research, in water pollution work the largest concern is the monitoring of the environment to determine if contamination is occurring and to follow the subsequent reduction of the level of problematic substances. As was mentioned earlier, PAHs are of environmental concern and, as such, are being monitored in air and water. Figure 2-14 shows the HPLC analysis of a National Bureau of Standards (NBS) sample of... 

Figure 4.4 The HPLC analysis of a reaction mixture containing AMP and alkaline phosphatase. Separations were carried out on a reversed-phase column with a mobile phase of potassium phosphate (pH 5.5) and 10% methanol. The column was eluted isocratically, and the detection was at 254 nm. Two sets of tracings were obtained, according to the following schedules. For the original reaction mixture (A) immediately after the addition of enzyme, (B) after 10 minutes, and (C) after 15 minutes. For the reaction mixture to which had been added EHNA (5 /xAf), an inhibitor of adenosine deaminase, the suspected contaminant (D ) after 2 minutes, ( ) after 10 minutes, and (F) after 40 minutes. (From Rossomando et al., 1981.)...

Preliminary extraction of 5-HIAA may be used as an initial purification step before HPLC analysis. Organic solvents, anion-exchange resins, and other solid phase extraction procedures have aU been used. For many systems, direct injection of urine onto the analytical column is a common practice,and samples are often merely diluted with a buffer to protect the HPLC system from contamination. Methods that analyze 5-HIAA without prior sample cleanup rely on the selectivity of the HPLC separation combined with fluorescence or electrochemical detection to provide the requisite specificity. 

It is obvious that the cleaner the sample, the longer the column life. On the other hand extensive clean-up procedures are time consuming. A compromise can be the use of precolumns to protect the analytical column against contamination caused by impurities present in the sample. Precolumns can be prepared from less expensive material than the analytical columns, i.e. pellicular packings or large diameter particles, which can be easily dry-packed. However, microparticulate stationary phases have also been used. As HPLC analysis of alkaloids often deals with the determination of low concentrations of alkaloids in a complex matrix, some factors concerning the sample preparation which influence the detection limit are worth consideration. 

The first contaminant identified in L-tryptophan implicated in EMS was EBT. Based upon HPLC analysis, preparations of such L-tryptophan revealed a distinct peak, initially called peak E1A1° or peak 97,1213 that is a dimeric form of L-tryptophan.513 Thus, early on, the presence of EBT became associated with EMS.2 6 Ito et al.14 studied EBT, purified by using HPLC, for its behavior in an acid environment. EBT is unstable in such an environment and decomposes to form L-tryptophan and compounds that were named peak X/X ... 

Extracts from environmental samples are seldom sufficiently free of contaminants that they can be analyzed directly, since the high-resolution columns used for GC or FIPLC analysis must not be overloaded with compounds other than the analyte. Pretreatment of the sample before GC, GC-MS, or HPLC analysis is therefore often a critical step in the analysis of extracts from complex matrices, and this is particularly important when the concentrations of... 

Two specific peaks, located respectively at 254 and 288 nm, are always present on UV spectra profiles. The first one is characteristic of the presence of the 16 USEPA PAHs (Chapter 3). Thus, for a quantitative application, the absorbance value at this wavelength measurement is proposed as a PAH index for a simple estimation of global PAH concentration in contaminated soil. A validation of this approach is given by HPLC analysis of the 16 USEPA PAHs (Fig. 25). 

HPLC is a method for the analysis and characterization of steroid receptors based on characteristics such as molecular weight. Qualitative relationships and multiple forms of the receptor can be maintained by the rapid gel-exclusion system, and contaminants can be readily identified (P2). Advantages of using HPLC include rapid analysis time, minimal receptor modification, improved resolution, and high reproducibility. Unfortunately the HPLC assay is tedious, requiring saturation analysis for each sample and quantitative validity has not been established for this procedure. Other disadvantages associated with HPLC methods include the requirement for expensive equipment and sophisticated technical skills. Therefore, HPLC analysis of receptor proteins is currently used only in research studies. 

The submitter indicates that HPLC analysis of the product shows the purity to be 99.7% (with 0.1% of ergosterol). The HPLC conditions for this unchecked analysis are as follows column Chromegasphere SI-60 (3 i, 15-cm x 5-mm) (purchased from ES Industries) mobile phase 5% EtOAc in heptane (2 mL/min) detection 275 nm. The retention times of 1 and 4 are 19.54 and 16.27 min, respectively. The checkers observed signals due to a trace olefinic contaminant in the H NMR of the product at 8 6.47 and 5.95. 

Comparison of Soxhlet, ultrasonic, SFE, and PLE for high and low PAH contaminated soils showed that the best results were achieved using PLE with acetone - toluene 1 1 but PLE or ultrasonic extraction with just acetone was adequate when performing subsequent HPLC analysis. Another comparisons of sample preparation of sewage sludge showed no real differences in the recoveries of PAHs by Soxhlet, SFE, USE, PLE, or MAE when each method was optimized. ... 

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