Vegetation samples

Moret et al. [280] applied precolumn derivatization with Dns-Cl and OPA to the same sample (vegetables) extracts and compared the results. Figure 19.6 reports HPLC traces obtained for a spinach sample (Kromasil C18 column, 250x4.6mm i.d., 5[tm particle size). 

Plant oils and animal fat samples (vegetable oils, tallow, lard, fish oils) do not need to be extracted before methylation. A small amount of these samples (10 to 20 mg) can be subjected to the methylation procedures directly. 

According to IUPAC, the LoD is defined as three times the standard deviation of the mean of the blank determinations added to the mean of the blank measures [12]. The LoD obtained for the PFA procedure (Table 1.3) is 8.2 pgkg-1 Pb. This value is low enough to quantify lead in the vast majority of foodstuffs. This method was successfully applied for various food samples, vegetable and animal tissues. No interferences from other elements have been observed. Matrix effects were seen with some samples, but were eliminated simply by diluting the samples. 

Microbiological Sampling. Vegetative Cells. Cellular samples were obtained at various times after inoculation by sampling a known aliquot of the culture medium. These samples were centrifuged (Sorvall Superspeed RC 2-B, 7000 rpm) at 6°C for 10 min. The supemate was... 

Lentil club sandwiches, noodle salads and tempeh Reubens grace the menu at Slice Of Life Cafe (742 South St., b 716-271-8010). Although locals scoff that the place serves rabbit food, its creative yet inexpensive fare draws a good crowd. The India House Cafe (1009 S. Clinton Ave., b 716-271-0242) is a smaller, allvegetarian version of the India House restaurant next door. Sample vegetable curries and the like in a casual, uniquely Indian atmosphere. The store attached to the cafe sells Indian spices wholesale to the public. 

Microwave-assisted desorption coupled to in situ headspace solid-phase microextraction (HS-SPME) was first proposed as a possible alternative pretreatment of samples collected from workplace monitoring. Therefore, pretreatment that takes a short time and uses little or no organic solvents has led to the recent development of a new extraction technique. Solid-phase micro-extraction (SPME) coupled with GC analysis has been used successfully to analyze pollutants in environmental matrices. MHS has been developed to achieve one-step, in situ headspace sampling of semivolatile organic compounds in aqueous samples, vegetables, and soil [7, 55-58]. 

Activation analysis can be applied to most types of material, including food products, urine, feces, air pollution particulates, river water, marine samples, vegetation, soils, sediments, ores, plastics, petroleum products, pharmaceuticals, coal, metals, alloys, semiconductor materials, clays, ceramics, and glasses. Variations in the analytical procedures for multielemental analysis are dictated by the matrix and so are detection Hmits. Table 2 compares the detection limits for an air particulate sample on filter paper and those for a deep-sea sediment to the detection limits in the ideal situation. Petroleum products, pharmaceuticals, plastics, carbon products, and air filters are not activated to produce y-rays, so the spectrum is free of any interferences from the matrix. This means that detection limits are low and over 60 elements can be determined simultaneously. Soils, sediments, clays, and glasses have elements such as sodium and scandium in their matrices that can produce backgroimd activities that result in poorer detection limits for most elements. 

Animal fats and vegetable oils are triacylglycerols, or triesters, formed from the reaction of glycerol (1,2, 3-propanetriol) with three long-chain fatty acids. One of the methods used to characterize a fat or an oil is a determination of its saponification number. When treated with boiling aqueous KOH, an ester is saponified into the parent alcohol and fatty acids (as carboxylate ions). The saponification number is the number of milligrams of KOH required to saponify 1.000 g of the fat or oil. In a typical analysis, a 2.085-g sample of butter is added to 25.00 ml of 0.5131 M KOH. After saponification is complete, the excess KOH is back titrated with 10.26 ml of0.5000 M HCl. What is the saponification number for this sample of butter ... 

Numerous high pressure Hquid chromatographic techniques have been reported for specific sample forms vegetable oHs (55,56), animal feeds (57,58), seta (59,60), plasma (61,62), foods (63,64), and tissues (63). Some of the methods requite a saponification step to remove fats, to release tocopherols from ceHs, and/or to free tocopherols from their esters. AH requite an extraction step to remove the tocopherols from the sample matrix. The methods include both normal and reverse-phase hplc with either uv absorbance or fluorescence detection. AppHcation of supercritical fluid (qv) chromatography has been reported for analysis of tocopherols in marine oHs (65). 

Sample pre-treatment. Novel procedures of electrochemical sample treatment have been proposed to decrease the signal interference with native cholinesterase inhibitors present in fruits and vegetables. Polyphenolic compounds were removed by electrolysis with soluble A1 anode followed by the oxidation of thionic pesticides with electrogenerated chlorine. The procedure proposed makes it possible to decrease the background current and the matrix effect by 80-90%. Thus, the detection limits of about 5 ppb of Pai athion-Methyl and Chloropyrifos-Methyl were obtained in spiked grape juice without any additional sepai ation or pre-concentration stages. 

The problem was, then, to determine the correct time of drying at a specified temperature by calibration against some reference method. As indicated above, it was also necessary to establish reproducible methods of sampling and grinding of the vegetable, and of maintaining in the oven a uniform temperature and a low pressure of water vapor, and to consider other experimental factors (18). 

It is of interest now to compare the moisture values obtained by the lyophilization procedure with those by the redrying procedure. Comparison in Table III for four vegetables shows that the results of the two independent methods agree within 0.1 or 0.2%. In view of this good agreement it seems fairly reasonable to assume that the measurements represent a very close approximation to the actual water present in the samples. 

At that time few micro-organisms capable of using methanol as sole source of carbon methylotrophs and energy (methylotrophs) had been isolated, and so steps were taken to isolate such organisms from samples of soil, water and vegetation. 

Previously no stress or applied stress lasting 16 hours with sample coated with vegetable oil prior to testing for the short-term stress-strain behavior shown. 

The sample preparation was very simple the sample was centrifuged to remove plant cell residues and 10 pi of the clear juice was placed on the column. This type of separation is common with fruits, vegetables and juices and samples can be obtained by preliminary homogenizing the total tissues and then centrifuging. If it is suspected that the residue still contains significant quantities of the substances of interest, then it can be washed with water or if necessary with solvents and the washings combined with the separated supernatant liquor. The results obtained are shown in figure 15. 

Vegetation sampling plot (Siccama) CONTOUR INTERVAL 100 FEET... 

This sensitivity to vegetation also appears in the data from our study of modem plants and animals. More than a thousand samples spanning a wide range of species of both plants and animals were selected from a five-county area in northeastern Wisconsin. While herbivores have significantly lower... 

A large study of fruits and vegetables available in Canada examined 5,784 Canadian samples and 16,198 imported (including from the United States) samples (Neidert and Saschenbrecker 1996). Of the... 

As a result of its use as an insecticide on fruit trees, vegetables, and other crops, endosulfan is released directly to the atmosphere during application. The compound is applied principally by air-blast equipment or boom sprayers (WHO 1984). No information was found in the available literature regarding atmospheric releases from manufacturing or formulation operations, or occurrence of the compound in air samples collected at NPL sites. 

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