Green HPLC methods

SOURCE J. Vial and A. Jardy, Experimental Comparison of Different Approaches to Estimate LOD and LOQ (fan HPLC Method Anal. Chem. 1999, 71, 2672 and J. M. Green, A Practical Guide to Analytical Method Validation, Anal. Chem. 1996, 68, 305A. 

Inulin is measured colorimetrically, either by acid hydrolysis to generate a green product, or by a series of enzymatic reactions based on inulinase with subsequent reduction of NADH. HPLC methods are used for the remaining exogenous GFR tracers. PAH and TEA are measured colorimetrically (Newman and Price 1999). 

StiU it has been possible to determine spectroscopic data for some samples. Figure 2.32 shows the absorption spectra of the higher fullerenes C76, C78, and Cg4 as obtained from fullerene soot by HPLC methods. Solutions of the single substances appear yellow-green (C76), brown (C2V-C78), golden-yellow (D3-C78), and... 

Retinol and retinyl esters can be identified on TLC plates by their yellow-green fluorescence under long-wave (366-nm) UV light most other retinoids are not fluorescent under UV and must be identified by nonspecific techniques such as iodine vapor or charring with sulfuric acid (Furr et al., 1992). Bargagna et al. (1991) developed TLC, HPTLC, and HPLC methods for identification of retinoic acids, retinol, and retinyl acetate in topical facial creams and solutions. 

As a practical example and reference, we now describe in detail the HPLC method for separation and quantification of carotenoid pigments in foods of different origin green vegetables, ripe fruits, processed vegetables, and animal products. 

A French Standard, which corresponds to ISO 10095 issued in 1992, specifies a method for determination of caffeine in green or roasted coffee or in coffee extracts (decaffeinated or not).33 Caffeine is extracted with water at 90°C in the presence of MgO. The extract is filtered, then cleaned-up on a mini-column packed with a silica phenyl group derivative, and analyzed by HPLC on a C18 column with a methanol/water (30 70) mobile phase and a UV detector operating at 254 to 280 nm. 

A method for determining the caffeine content of regular and decaffinated green and roasted coffee beans and of regular and decaffeinated coffee extract powders, using HPLC, is specified in a British Standard Instruction.34 Caffeine is extracted from the sample with water at 90°C in the presence of magnesium oxide. The mixture is filtered and an aliquot purified on a silica microcolumn modified with phenyl groups. The caffeine content is then determined by HPLC with UV detection.35... 

Another isocratic elution method was applied for the determination of flavonols in green and black tea leaves and green tea infusions by RP-HPLC. The chemical structures of the flavonols studied are shown in Fig. 2.66. Infusions of teas were prepared by mixing lg of tea leaves with 100 ml of boiling water for 5min, then they have filtered and used for HPLC analysis. The infusion step was repeated three times. Flavonoids were hydrolysed by mixing lg of tea leaves with 40 ml of 60 per cent aqueous ethanol and 5 ml of 6 M HC1. The suspension was heated at 95°C for 2 h, then filtered and the volume was adjusted to 50 ml with 60 per cent aqueous ethanol. Separation was performed in an ODS column (150 X 4.6mm i.d.) operated at 30°C. The isocratic mobile phase consisted of 30 per cent aqueous ACN in 0.025 M KH2P04, and the pH was adjusted to 2.5 with 6 M HC1. The... 

Thus, RP-HPLC-MS has been employed for the analysis of sulphonated dyes and intermediates. Dyes included in the investigation were Acid yellow 36, Acid blue 40, Acid violet 7, Direct yellow 28, Direct blue 106, Acid yellow 23, Direct green 28, Direct red 79, Direct blue 78 and some metal complex dyes such as Acid orange 142, Acid red 357, Acid Violet 90, Acid yellow 194 and Acid brown 355. RP-HPLC was realized in an ODS column (150 X 3 mm i.d. particle size 7 /.an). The composition of the mobile phase varied according to the chemical structure of the analytes to be separated. For the majority of cases the mobile phase consisted of methanol-5 mM aqueous ammonium acetate (10 90, v/v). Subsituted anthraquinones were separated in similar mobile phases containing 40 per cent methanol. The flow rate was 1 ml/min for UV and 0.6 ml/min for MS detection, respectively. The chemical structure of dye intermediates investigated in this study and their retention times are compiled in Table 3.28. It was found that the method is suitable for the separation of decomposition products and intermediates of dyes but the separation of the original dye molecules was not adequate in this RP-HPLC system [162],... 

Ferreira. Development of an HPLC/ CA090 diode-array detector method for simultaneous determination of seven hydroxyl-cinnamic acids in green coffee. J LiqChromRelTechnol 1997 20(13) CA091... 

A recent interlaboratory comparison of HPLC and fluorometric methods reported good agreement between laboratories for vitamin C in green beans (42). 

An HPLC separation method with diode array detector and mass spectrometric (MS) detection equipped with atmospheric pressure ionization (API) was developed to determine flavone, flavonol, and flavanone in various vegetables, including green bean, broccoli, brussels sprouts, celery, kale, leek, onion, parsley, pepper (green, yellow, and red), and tomato (118). The flavonoids were analyzed as aglycones after acid hydrolysis. The extraction and acid hydrolysis conditions are based on previous work by Hertog et al. (119). Quercetin is the overall major flavonol, followed by kaempferol. The flavones, apigenin and luteolin, were found only in limited foods,... 

High-performance gel filtration chromatography was used to separate trigonelline, chloro-genic acid (CGA), and CF in green coffee by De Maria et al. (281). The method has the advantage, with respect to RP-HPLC, of an aqueous eluent. 

There are a large number of other published procedures for the separation of a number of sweeteners and preservatives at one time these are all based on reverse-phase HPLC. Perhaps one of the most startling is the method published by Williams (1986). This uses a small particle size (3 xm) C8 column and allows the separation of a range of colours, sweeteners and preservatives in less than 5 min. The materials separated were amaranth, quinoline yellow, quinine sulphate, sunset yellow, caffeine, aspartame, saccharin, vanillin, sorbic acid, benzoic acid and green S. 

The development of green Foodomics runs parallel to the improvement and design of techniques able to assess the environmental impact of the different protocols/processes/operations involved. At present several techniques can be found in the literature to test, for instance, the impact of analytical chemistry methods (such as the Greeness profile, the HPLC-EAT, or the Analytical Eco-Scale) and the environmental impacts associated with a product or process, over its entire life cycle (such as Life Cycle Assessment). Nevertheless, techniques able to provide a more holistic view of the different aspects... 

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