High-speed Liquid Chromatography Research Articles

Результати оцінки безпечності для споживачів добавки дієтичної «Тайро Ультра», створеної для підтримки нормальної функції щитоподібної залози

In recent years, Ukraine has seen an increase in consumer interest in dietary supplements made on the basis of traditional Ayurvedic recipes and containing natural organic-mineral complexes. Monitoring their safety for consumer’s health is an urgent task of modern preventive medicine. Aim. Generalization of the results of a comprehensive sanitary and hygienic assessment of the safety for consumers the dietary supplement «Tyro Ultra», created to support the normal function of the thyroid gland. Materials and Мethods. Residual concentrations of pesticides were estimated by the methods of ultra-high-performance highspeed mass spectrometric liquid chromatography with electron spray ionization (Waters, USA) and gas chromatography; the content of heavy metals – by the atomic emission method (Shimadsu ICPE - 9820); content of radionuclides – by spectrometry; investigated microbiological indicators. Results. It has been established that the dietary supplement «Tyro Ultra» meets the requirements of Ukrainian legislation; its chemical and microbiological composition does not pose a threat to the health of consumers, provided that the method and dosage of the dietary supplement are in accordance with the manufacturer's recommendations. According to the review of scientific sources, the components of the «Tyro Ultra» formulation have the potential to normalize metabolism, optimize the chemical composition of the diet, and create optimal dietary conditions to support the normal functioning of the thyroid gland. Conclusions. Assessing the safety of traditional Ayurvedic formulations is an important and at the same time difficult task due to their multi-component composition. Further studies of products made on the basis of traditional recipes will contribute to the expansion of our imagination about means that have the potential of targeted influence on the level of adaptation capabilities of the human body in conditions of negative impact on the environment. Keywords: dietary supplements, sanitary and hygienic assessment, thyroid gland.

A Low Arginine/Ornithine Ratio is Associated with Long-Term Cardiovascular Mortality.

The long-term prognostic value of the bioavailability of L-arginine, an important source of nitric oxide for the maintenance of vascular endothelial function, has not been investigated fully. We therefore investigated the relationship between amino acid profile and long-term prognosis in patients with a history of standby coronary angiography. We measured the serum concentrations of L-arginine, L-citrulline, and L-ornithine by high-speed liquid chromatography. We examined the relationship between the L-arginine/L-ornithine ratio and the incidence of all-cause death, cardiovascular death, and major adverse cardiovascular events (MACEs) in 262 patients (202 men and 60 women, age 65±13 years) who underwent coronary angiography over a period of ≤ 10 years. During the observation period of 5.5±3.2 years, 31 (12%) patients died, including 20 (8%) of cardiovascular death, while 32 (12%) had MACEs. Cox regression analysis revealed that L-arginine/L-ornithine ratio was associated with an increased risk for all-cause death (unadjusted hazard ratio, 95% confidence interval) (0.940, 0.888-0.995) and cardiovascular death (0.895, 0.821-0.965) (p＜0.05 for all). In a mod el adjusted for age, sex, hypertension, hyperlipidemia, diabetes, current smoking, renal function, and log10-transformed brain natriuretic peptide level, cardiovascular death (0.911, 0.839-0.990, p=0.028) retained an association with a low L-arginine/ L-ornithine ratio. When the patients were grouped according to an L-arginine/L-ornithine ratio of 1.16, the lower L-arginine/L-ornithine ratio group had significantly higher incidence of all-cause death, cardiovascular death, and MACEs. A low L-arginine/L-ornithine ratio may be associated with increased 10-year cardiac mortality.

Перспективні напрямки розробки засобів, що здатні підвищувати адаптаційні можливості організму людини в умовах негативного впливу середовища життєдіяльності

Abstract. The ever-increasing anthropogenic chemical load throughout the world prompts the search for sources of biologically active substances (BAS) capable of increasing the adaptive capabilities of a person exposed to the harmful effects of the environment. Aim. Scientific substantiation of the optimal composition of recipes and features of the production technology of products with immunomodulating and adaptogenic effects (dietary supplements, detoxification products for external use, including cosmetic preventive products for hand skin disinfection), based on technologically processed vegetable waste used in the production of pharmaceutical products Proteflazidum®". Material and Methods. The chemical composition of the ethanol extract of the plant raw material "Proteflazidum®" and the waste of its production - meal was studied. The mass fraction of flavonoid compounds aglycones of tricin, apigenin, luteolin, amino acids, sugars, carboxylic acids, natural polymers (pectin substances, chlorophylls and hemicellulose), ethanol (%, vol) was determined. The methods of ultra-high-performance high-speed liquid chromatography with diode-matrix detection (UPLCPDA, Waters, USA) were used; method of ultra-high-performance mass spectrometric high-speed liquid chromatography with electron spray ionization (UPLC-MC/MC, Waters, USA). A study of the dietary supplements "Immunoflazid Light" (syrup) and "Immunoflazid Pro" (capsules), manufactured in accordance with TU U 10.8-25589583-001:2020, was conducted according to safety indicators: the content of heavy metals, pesticides and radionuclides for compliance with the requirements of GN 4.4.8.073 -2001 "Temporary hygienic standards for the content of chemical and biological contaminants in biologically active supplements", approved by the resolution of the chief state sanitary doctor of Ukraine dated 04.20.2001. No. 131 and GN 6.6.1.1-130-2006 "Permissible levels of the content of radionuclides 137Cs, 90Sr in food and drinking water", approved by the order of the Ministry of Health of Ukraine dated 05.03.2006 under No. 256. A spectrometer was used to determine the content of lead, cadmium, and mercury atomic emission "SHIMADSU ICPE - 9820"; for the determination of radionuclides, the spectrometer "SEG-001", "AKP-S" and the spectrometer "SEB-01-70" were used. Methods of measuring pesticides according to DSTU EN 12393-1:2003, DSTU EN 12393-2:2003, DSTU EN 12393-3:2003 and GOST 30349-96. Results. The waste of vegetable raw materials, which is formed as a result of the production of the "Proteflazidum®", is a valuable source of BAS, which allows you to consider them as raw materials for creating recipes of products with an adaptogenic effect - dietary supplements and raw materials for the production of products for external use, including cosmetic prophylactic and means for hand skin disinfection. According to safety indicators, the new products belong to low-hazard substances when applied to the skin (hazard class 4), do not show skin-irritating, skin-resorptive and sensitizing properties, alcohol-free products do not irritate the mucous membrane of the eyes. Conclusions. Proteflazidum® production waste is a valuable raw material for the creation of a wide range of products with an adaptogenic effect (dietary supplements, raw materials for the production of products for external use, including cosmetic prophylactics and products for hand skin disinfection). Key Words: Proteflazidum®, Herba Deschampsia Сaespitosa L., Herba Calamagrostis Epigeios L., bioflavonoids, pectin substances.

Determination of Firocoxib and Its Related Substances in Bulk Drug Substance Batches of Firocoxib by a High-Speed Reversed-Phase HPLC Method With a Short Fused-Core Biphenyl Column.

Firocoxib is a nonsteroidal anti-inflammatory drug. It provides control of postoperative pain and inflammation associated with soft tissue and orthopedic surgery in dogs, and control of pain and inflammation associated with osteoarthritis in horses. A high-speed stability-indicating reversed-phase high-performance liquid chromatography method was developed to determine firocoxib and its related substances in bulk batches of firocoxib drug substance. Firocoxib was dissolved in neat acetonitrile (ACN) and analyzed on a short HALO (fused-core) biphenyl column (30 × 4.6mm i.d., 2.7-μm particle size) at flow rate of 2.5mL/min. Column temperature was maintained at 50°C. Mobile phase A is composed of 0.1% of H3PO4 in water and mobile phase B is composed of ACN. Analytes were detected with UV detection at 240nm and quantitated against an external reference standard. Firocoxib and its related compounds were adequately separated within 4min by a gradient elution. The method was validated for specificity, linearity, accuracy, precision and robustness according to method validation guidelines described in The International Conference on Harmonization. The validation data demonstrated that this method is sensitive, accurate, robust, specific and stability-indicating.

Characterization of Tyrosinase Inhibitors in Dryopteris crassirhizoma Rhizome Using a Combination of High-Speed Counter-Current Chromatography, Affinity-Based Ultrafiltration, and Liquid Chromatography-Tandem Mass Spectrometry.

Dryopteris crassirhizoma rhizome (DCR) inhibits melanin production in B16F10 melanoma cells and tyrosinase activity. The melanin content and tyrosinase activity of DCR-treated zebrafish embryos were determined to evaluate the in vivo inhibitory effect of DCR on melanogenesis. Moreover, an off-line hyphenated method combining the high-speed counter-current chromatography, affinity-based ultrafiltration, and liquid chromatography–tandem mass spectrometry was used to identify and characterize the DCR compounds with tyrosinase inhibitory activity. Our results indicated that DCR significantly decreased the melanin content and tyrosinase activity in zebrafish embryos in a dose-dependent manner; moreover, 22 compounds in DCR presented tyrosinase inhibitory activity. In silico molecular docking prediction data indicated that the 22 compounds in DCR can form stable conformations in the active site pocket of tyrosinase.

Isolation and purification of soyasapogenol A and B starting from soy hypocotyls: High-speed counter‐current chromatography versus preparative high‐performance liquid chromatography

Soyasapogenols derived from soyasaponins, which abundantly occur in soy hypocotyls, are of great importance as bioactive compounds due to their physiological activities. However, there is a lack of a high-efficiency and scalable preparation and isolation procedure. This work extends research on applying and comparing high-speed countercurrent chromatography (HSCCC) and preparative high-performance liquid chromatography (prep-HPLC) either singly and/or combinedly in preparative isolation of soyasapogenol A and B. The comparison reveals that the yield of 0.24 and 0.21% of soyasapogenol A and B with the purity of 98.09 and 98.90%, respectively, were obtained from the starting material of soy hypocotyls in two-steps HSCCC separation procedure. In contrast, prep-HPLC allowed isolation and purification of these two target compounds with significantly lower productivity and higher solvent consumption. An optimal two-phase solvent system of n-hexane–ethyl acetate–methanol–water (3:6:4:2, v/v/v/v) was selected to separate soyasapogenols in HSCCC procedure. The present investigation indicates that two-steps HSCCC can potentially provide a fast, high yielding, and more environmentally friendly tool for the preparative separation and purification of soyasapogenol A and B starting from the materials of soy hypocotyls.

Three new C21 steroidal glycosides isolated from Metaplexis japonica and their potential inhibitory effects on tyrosine protein kinases

Three new steroidal glycosides, metapregnoside A–C (II–IV), together with one known compound, byzantionoside B (I), were isolated from the fresh whole herb of Metaplexis japonica by using high-speed countercurrent chromatography and semi-preparative liquid chromatography. Their structures and relative configurations were elucidated by spectroscopic methods including 1D NMR, 2D NMR and HR-ESI-MS. The potential targets of compound I–IV were identified by virtual screening. And the potential inhibitory effects of these compounds on tyrosine protein kinases were compared by molecular docking. Byzantionoside B (I) was the first isolated compound from Metaplexis genus. The docking score of metapregnoside C (IV) was the highest. And the sugar chain residues at position C-20 in the pregn-4-en-3-one derivatives is the main factor affecting their docking scores on tyrosine protein kinases Fes/Fps.

Measurement of urinary kininogen (KNG) fragments as a noninvasive tool for early diagnosis of pancreatic cancer (PaCa).

209 Background: There is a clear need to identify a non-invasive biomarker for early diagnosis of PaCa, in order to improve the overall survival of PaCa patients. Secretion of large amounts of proteases is a hallmark of PaCa, which results in an abundance of protease-induced cleavage products being excreted in the urine. This has led to speculation that measurement of PaCa-specific fragments in the urine might be useful as a tool for discrimination between PaCa patients and healthy controls. Herein, we introduce urinary KNG fragments as a promising biomarker for early diagnosis of PaCa. Methods: Urine samples were collected from PaCa patients and healthy volunteers, with the written informed consent, from January 2014 to July 2016. Urinary protein tryptic fragments derived from protein C-termini were measured using isobaric tags (iTRAQ) for their relative quantitation, and the diagnostic ability of the urinary levels of these fragments was evaluated by receiver operating characteristic (ROC) curve analysis. The fragments which showed an area-under-the-curve (AUC) of over 0.8 were selected as candidate fragments for further validation by the multiple-reaction-monitoring technique (MRM) combined with high-speed liquid chromatography. The urinary level of each candidate fragment was quantified by MRM, and the diagnostic capability of each for discriminating PaCa patients from healthy controls was evaluated by ROC curve analysis. Results: Urine samples of 39 PaCa patients (7 resectable, 32 unresectable) and 42 healthy controls were examined by iTRAQ to find 12,783 fragments. ROC curve analysis was carried out to select two candidate fragments (fragments A, B), both of which turned out to be KNG cleavage products. The urinary levels of the two fragments were measured in 23 resectable PaCa, 118 unresectable PaCa patients, and 42 healthy volunteers using high-speed-LC-/MRM. The AUCs of serum CA19-9 and urinary levels of fragments A and B for discriminating patients of PaCa from healthy controls were 0.89, 0.81 and 0.70, respectively. Conclusions: Urinary KNG fragments showed favorable diagnostic capability and were considered as promising, noninvasively measurable biomarkers of PaCa.

Evaluation of Pressure Stable Chip-to-Tube Fittings Enabling High-Speed Chip-HPLC with Mass Spectrometric Detection.

Appropriate chip-to-tube interfacing is an enabling technology for high-pressure and high-speed liquid chromatography on chip. For this purpose, various approaches, to connect pressure resistant glass chips with HPLC pumps working at pressures of up to 500 bar, were examined. Three side-port and one top-port connection approach were evaluated with regard to pressure stability and extra column band broadening. A clamp-based top-port approach enabled chip-HPLC-MS analysis of herbicides at the highest pressure and speed.

Separation and purification of six compounds from the flowers of Cerasus yedoensis (Matsum.) by high-speed countercurrent chromatography in stepwise elution mode

ABSTRACTSix compounds from the flower of Cerasus yedoensis (Matsum.) were successfully isolated by high-speed countercurrent chromatography (HSCCC) and preparative high performance liquid chromatography using stepwise elution with a pair of two-phase solvent systems composed of ethyl acetate–n-butanol–formic acid–water at volume ratio of 4:1.5:0.15:5 and ethyl acetate–ethanol–formic acid–water at volume ratio of 4:1:0.15:5 for the first time. This separation process produced (a) 141 mg of 1-O-caffeoyl-β-D-glucopyranoside, (b) 28 mg of p-coumaric acid glucoside, (c) 13 mg of chlorogenic acid, (d) 21 mg of quercetin-3-O-β-D-glucopyranoside, (e) 19 mg of kaempferol 3-O-β-D-glucopyranoside, and (f) 25 mg of caffeic acid from 400 mg of crude sample with the purities of 96.51, 98.82, 94.96, 99.01, 82.51, and 82.45%, respectively. MS, 1H NMR, and 13C NMR analyses were used for the chemical structure identification.

Purification of Ferulic Acid, Senkyunolide I and Senkyunolide H from the Volatile Oil of <i>Rhizoma chuanxiong</i> Using High-Speed Countercurrent Chromatography and Preparative Liquid Chromatography

A high-speed countercurrent chromatography and preparative liquid chromatography method was successfully applied to the separation and purification of ferulic acid, senkyunolide I and senkyunolide H from the volatile oil of the traditional Chinese medicinal plant Rhizoma Chuanxiong. For the first time, using a two-phase solvent system composed of N-butanol–acetic acid–water (4:1:5, v/v) and a flow rate of 2 mL·min-1, a mixture of SEI and SEH was rapidly obtained by high-speed countercurrent chromatography (HSCCC). The mixture was separated by pre-HPLC with a methanol–water (50:50) mobile phase and flow rate of 5 mL·min-1. The purities of the separated components as determined by high-performance liquid chromatography were 93%, and the combination of ESI-MS and NMR analyses confirmed the chemical structures of the three compounds.

Separation of complex sugar mixtures on a hydrolytically stable bidentate urea-type stationary phase for hydrophilic interaction near ultra high performance liquid chromatography

A stationary phase bearing both bridged bis-ureido and free amino groups (USP-HILIC-NH2 -2.5SP) for high-speed hydrophilic interaction liquid chromatography separations was prepared using a one-pot two-step procedure starting from 2.5 μm totally porous silica particles. Highly polar compounds, such as polyols, hydroxybenzoic acids, and sugars, were successfully analyzed in shorter times and with higher peak efficiency, when compared to results obtained with a bidentate urea-type column packed with 5 μm particles. Increased sugarophilicity and better peak shape were attested for the USP-HILIC-NH2 -2.5SP column (100 × 3.2 mm id) when compared with two commercially available UHPLC columns, namely an acquity BEH amide packed with totally porous 1.7 μm microparticles and a HILIC Kinetex column packed with core-shell 2.6 μm particles. Finally, the new column was employed in the separation of complex mixture of sugars (mono-, di-, and oligosaccharides) and in the analysis of beer samples. The resulting chromatograms showed good selectivity and overall resolution, while the catalyzing effect of the free amino moieties resulted in excellent peak shapes and in the absence of split peaks due to sugar anomerization phenomena.

Degradation characteristics of 2,4-dichlorophenoxyacetic acid in electro-biological system

The reductive degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) was studied in an electro-biological system, a biological system and an electric catalytic system, respectively. Electrochemical characteristics were monitored by cyclic voltammetry and the intermediate products of 2,4-D degradation were determined by high speed liquid chromatography (HPLC). The results showed that all 2,4-D degradations in the three systems conformed to the kinetics characteristics of one-order reaction, and the degradation kinetics constants were 28.74×10−2h−1, 19.73×10−2h−1 and 3.54×10−2h−1, respectively. The kinetics constant in the electro-biological system was higher than the sum in the other two systems by 19%. The electrochemical assistance provided the electrons and accelerated the electron transfer rate in the microbial degradation of 2,4-D. The degradation resulted from the microbial reduction strengthened by the electrochemical assistance. The electron transfer existed between the electrode, cytochrome, NAD and the pollutants. A long-range electron transfer process could be achieved on the multi-phase interfaces between the electrode, bacteria and the pollutants.

Effect of high-pressure polymerization on mechanical properties of PMMA denture base resin

The aim of this study was to assess the effect of high-pressure polymerization on mechanical properties of denture base resin. A heat-curing denture base resin and an experimental PMMA were polymerized under 500MPa of pressure by means of an isostatic pressurization machine at 70°C for 24h to make rectangular specimens whose dimensions were 30mm×2mm×2mm. Each specimen was deflected on a three-point flexural test until either fracture occurred or the sample was loaded up to 8mm in deflection. The molecular weight of the PMMA without filler was analyzed using the high-speed liquid chromatography system. Increased ductility without fracture was shown in the specimens subjected to high pressure, while most of the control specimens (ambient pressure) fractured. The mean toughness of the PMMA specimens polymerized under the high pressure was significantly higher than the same material polymerized under ambient pressure (p<0.01). The high pressure groups of the denture resin and the PMMA revealed a significantly lower mean 0.2% yield stress, flexural strength, and elastic modulus than control groups (p<0.01). There were certain amounts of higher molecular weight polymers in the high pressure specimens than were present in the controls. The increased toughness shown in the PMMA polymerized under the high pressure was presumably attributed to the higher molecular weight produced by the pressure. The result suggests a potential application of the high-pressure polymerization to the development of PMMA-based denture resin with improved fracture resistance.

Dissolution Tests of Loxoprofen Sodium Hydrate Tablets Using Ultra High-speed Liquid Chromatography

Ultra high-speed liquid chromatography (ultra high-speed LC) has become an increasingly popular method in analytical research fields. This novel analytical system provides fast and efficient chromatographic separation over a wide range of flow rate and pressure. In this study, we applied an ultra high-speed LC system to the analysis of active ingredients, such as loxoprofen sodium hydrate and some additives in the drug formulation. As part of the ultra high-speed LC system utilized in this study was a LaChrom Ultra system (Hitachi, Tokyo, Japan) equipped with a L-2455U diode array detector and a LaChrom Ultra C18 (particle size, 2 μm) column ; as a result, short time stability tests of drugs were accomplished efficiently. Loxoprofen sodium hydrate is one of the most popular non-steroidal anti-inflammatory drugs (NSAIDs) used in Japan. The use of generic products has been strongly encouraged in order to reduce healthcare costs. The active ingredients, strengths, dosage forms and regimen of generic products are the same as those of the innovator's products. However, there are many generic products of loxoprofen sodium hydrate. The most important factor in selection is information concerning the quality of the product. For oral drug products, dissolution tests should be performed, since they provide important information concerning the bioequivalence of generic products. After dissolution tests of brand-name drugs and generic products, their elution behaviors were evaluated by high-speed analysis. We achieved a fast analysis of loxoprofen within 1.0 min, and compared the elution behavior between, the brand-name drug and generic products.

Separation of Aromatic Nitro Compounds by One-dimensional Dual Band Thin-Layer Chromatography and High Speed Liquid Chromatography

Separation of Aromatic Nitro Compounds by One-dimensional Dual Band Thin-Layer Chromatography and High Speed Liquid Chromatography

Determination of parabens in cosmetic products by solid‐phase microextraction of poly(ethylene glycol) diacrylate thin film on fibers and ultra high‐speed liquid chromatography with diode array detector

The fabrication of a solid-phase microextraction (SPME) fiber through UV-induced polymerization of poly(ethylene glycol) diacrylate (PEG-DA) for determination of parabens in cosmetic products is presented in this work. The PEG-DA polymer coating was covalently attached to the fiber by introducing a surface modification with 3-(trichlorosilyl)propyl methacrylate (TPM). The PEG-DA polymer thin film coated on the fiber was homogeneous and wrinkled, which led to an increase of the surface area and high extraction efficiency. The extraction performances of the prepared SPME fibers were assessed by preconcentration of parabens including methylparaben, ethylparaben, propylparaben and benzylparaben from cosmetic products. The analysis was performed on an ultra high-speed liquid chromatography with diode array detector. The prepared SPME fibers exhibited good repeatability (for one fiber) and reproducibility (fiber-to-fiber) with RSDs of 5.4 and 6.9%, respectively. The optimized SPME method supported a wide linear range of 0.50-160 μg/mL and the detection limits for parabens were in the range of 0.12-0.15 μg/mL (S/N=3). The developed method was successfully applied for determination of parabens in cosmetic products with different natures.

The quantitative determination of fluocinolone acetonide and acetonide acetate in formulated products by high pressure liquid chromatography.

Abstract A chromatographic procedure for the determination of fluocinolone acetonide and acetate is described. The method employs high speed liquid chromatography through a Permaphase ODS column with an aqueous methanol eluant phase. The application of the method to the determination of fluocinolone acetonide and acetate in cream, and ointment formulations, is described.

Reaction monitoring of tocopherols with active nitrogen oxides by ultra high-speed liquid chromatography

Ultra high-speed liquid chromatography (LC) has become increasingly popular in analytical research fields. This analytical system provides fast and efficient chromatographic separation over a wide range of flow rate and pressure. In this study, we applied an ultra high-speed LC system to monitor the reaction of α-, γ-, and δ-tocopherols with active nitrogen species. By using an ultra high-speed LC system equipped with a photo-diode array detector, short time analysis and detection of a wide range of reaction products were accomplished efficiently. The analysis time of tocopherol and its major oxidation products were greatly shortened compared to conventional HPLC methods (more than 10 times). The ultra reversed-phase LC was demonstrated to be as a powerful tool for monitoring rapid oxidation reactions of tocopherols with active nitrogen species.

Analysis for Organic Acid by Postcolumn Ultra High-Speed Liquid Chromatography

An ultra high-speed liquid chromatograph (UHLC) offers a reduction in the analysis time compared with conventional HPLC by using a column with finer particles and an apparatus resistant to high pressure. Although postcolumn methods are excellent techniques for the analysis of samples containing contaminants, such as foodstuffs, the postcolumn method has not been applied to UHLC because of problems associated with diffusion of the target peak and the reactivity. A postcolumn method using UHLC has not been reported due to some problems such as diffusion of the sample in a reaction part. We successfully applied a postcolumn method using UHLC through optimization of the instrumental system and the analytical conditions with Ascentis Express RP-Amide and LaChromUltra C18-AQ columns. This afforded the high-speed analysis of 10 organic acids ; tartaric acid, formic acid, malic acid, lactic acid, acetic acid, pyroglutamic acid, citric acid, succinic acid, propionic acid and fumaric acid ; within 4 min with good separation and reproducibility. Their limits of detection (S/N = 3) were between 9 to 29 mg/L. The results of measurements of food samples by the postcolumn method using UHLC were similar to those obtained by the postcolumn method using HPLC. Therefore, it can be said that effective measurements are possible using the postcolumn method by UHLC, and that this system is particularly useful for materials that contain large amounts of contaminants, such as foodstuffs.