Quantification limits

A sensitive determination of alkanesulfonates combines RP-HPLC with an on-line derivatization procedure using fluorescent ion pairs followed by an online sandwich-type phase separation with chloroform as the solvent. The ion pairs are detected by fluorescence. With l-cyano-[2-(2-trimethylammonio)-ethyl]benz(/)isoindole as a fluorescent cationic dye a quantification limit for anionic surfactants including alkanesulfonates of less than 1 pg/L per compound for a 2.5-L water sample is established [30,31]. 

Quantification Limit of determination Instrument for detection and quantification... 

Best practices in establishing detection and quantification limits for pesticide residues in foods... 

The definitions of method detection and quantification limits should be reliable and applicable to a variety of extraction procedures and analytical methods. The issue is of particular importance to the US Environmental Protection Agency (EPA) and also pesticide regulatory and health agencies around the world in risk assessment. The critical question central to risk assessment is assessing the risk posed to a human being from the consumption of foods treated with pesticides, when the amount of the residue present in the food product is reported nondetect (ND) or no detectable residues . 

There are several factors involved in defining the limitations of an analytical method. Selecting the right method for defining these limitations can be as important as the actual definitions. Factors that must be taken into consideration in defining detection and quantification limits are ... 

Another factor of interest in defining fhe instrumental limitations is the instrumental quantification limit (IQL), which may be defined as the smallest amount of an analyte that can be reliably quantified by the instrument. 

Extending this principal to equation (10), the instrumental quantification limit (IQL, Cq) may be calculated using the equation... 

Comparison of methods for calculating detection and quantification limits for analytical methods used for food... 

Several methods have been discussed for the determination of method limitations when evaluating procedures for the determination of pesticides in food. A brief comparison of the methods discussed for the determination of the detection and quantification limits of methods used for the analysis of food products can be found in Table 2. 

NMR spectroscopy is most effective in qualitative analysis when the samples examinated are substantially pure compounds and has been used to confirm the theoretically predicted low-energy conformations of the Af-acylated hindered amine light stabiliser Tinuvin 440 [210]. Trace amounts of PDMS (quantification limit 0.1 ppm) in plastic additives, dyes and pigments were determined by 111 NMR after Soxhlet extraction [211]. ll NMR was also used for the detection of octadecanol, an impurity in Irganox PS 802 (3,3 -dioctadecyl thiodipropionate). NMR has identified the nature of a supposedly UV stabiliser of empirical formula C17H18N3CIO [44] (Scheme 5.2). 

CV) ranged from 17 to 39%. The %CV was highest near the quantification limit of the assay. The results from the first- and second-generation assays were highly correlated (r = 0.96), allowing meaningful comparisons of virus concentrations in specimens tested with either assay. 

The quantification limit is relevant to concentration domain. Reporting LQs should always be completed by the conditions of precision. 

The uncertainty of the results between the detection limit and the limit of quantification decreases continuously up to the precision set in advance by the precision factor k. In reaching and exceeding the quantification limit, analytical results can be reported as usual see Sect. 8.1. 

In this regard several sophisticated chromatographic methods, with a quantification limit down to about 0.2 ng/g, have been developed and published for the determination of zearalenone. The methods were mainly based on high-performance liquid chromatography (HPLC) with fluorescence detection (Krska 1998 Visconti and Pascale 1998 Schuhmacher et al. 1998 Tanaka et al. 2000), but HPLC with mass spectrometry detection was also used (Shirai et al. 2000 Josephs et al. 2001). 

Another RP-HPLC technique has been applied for the determination of synthetic food dyes in soft drinks with a minimal clean-up. Separation of dyes was obtained in an ODS column (150 x 4 mm i.d. particle size 5 pm). Solvents A and B were methanol and 40 mM aqueous ammonium acetate (pH = 5), respectively. Gradient conditions were 0-3 min, 10 per cent A 3-5 min, to 25 per cent A 5-8 min, 25 per cent A 8-18 min, to 75 per cent A 18-20 min, 75 per cent A. The flow rate was 1 ml/min and dyes were detected at 414 nm. The separation of synthetic dyes achieved by the method is shown in Fig. 3.35. The concentrations of dyes found in commercial samples are compiled in Table 3.21. The quantification limit depended markedly on the type of dye, being the highest for E-104 (4.0 mg/1) and the lowest for E-102 and E-110 (1.0 mg/1). The detection limit ranged from 0.3 mg/1 (E-102 and E-110) to 1.0 mg/ml (E-104 and E-124). It was suggested that the method can be applied for the screening of food colourants in quality control laboratories [113]. 

Abstract A preconcentration method using Amberlite XAD-16 column for the enrichment of aluminum was proposed. The optimization process was carried out using fractional factorial design. The factors involved were pH, resin amount, reagent/metal mole ratio, elution volume and samphng flow rate. The absorbance was used as analytical response. Using the optimised experimental conditions, the proposed procedure allowed determination of aluminum with a detection limit (3o/s) of 6.1 ig L and a quantification limit (lOa/s) of 20.2 pg L, and a precision which was calculated as relative standard deviation (RSD) of 2.4% for aluminum concentration of 30 pg L . The preconcentration factor of 100 was obtained. These results demonstrated that this procedure could be applied for separation and preconcentration of aluminum in the presence of several matrix. 

Food So far only a handful of studies have investigated the presence of OPFRs in food samples. In a market basket study performed by the US FDA [87], most of the OPFRs (EHDPP, TCEP, TC/PP, TnBP, TPP, TCP) were found only at the ng/g level. More than 91% of the results were below the quantification limit in most t3q>es of samples. Higher detection frequencies were observed for TPP in margarine and caramels (mean 45 ng/g). 

In urine, OPFR metabolites have been detected, but the median concentrations of the diaryl and dialkyl phosphates remained mostly below the quantification limit. Ranges of concentrations of dialkyl and diaryl phosphates are shown in Table 4. In the study of Schindler et al. [302, 303], the detection frequency was highest for BCEP (50%), followed by DPP (30%), BCPP (12%), and DBP (3%). Di-w-cresyl and di-/7-cresyl phosphate were not found in any sample, probably due to lower exposure in the indoor environment. Reemtsma et al. [304] found also monoaryl and alkyl phosphates in human urine, of which the monobutyl phosphate was the... 

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