Detection and Quantitation Limit

The method was validated in accordance to the guidelines of the international conference on harmonization (ICH). Data with respect to accuracy, within- and between run precision, recovery, detection and quantitation limits were reported and found to be within the accepted international criteria. Neither endogeneous substances nor the commonly used dmgs were found to interfere with the retention times of the analytes. Standard solutions of the dmg and quality control preparations at high and low level concentrations were demonstrated to be stable at room temperature and/or -20°C for long and short periods of time. 

Valproic acid has been determined in human serum using capillary electrophoresis and indirect laser induced fluorescence detection [26], The extract is injected at 75 mbar for 0.05 min onto a capillary column (74.4 cm x 50 pm i.d., effective length 56.2 cm). The optimized buffer 2.5 mM borate/phosphate of pH 8.4 with 6 pL fluorescein to generate the background signal. Separation was carried out at 30 kV and indirect fluorescence detection was achieved at 488/529 nm. A linear calibration was found in the range 4.5 144 pg/mL (0 = 0.9947) and detection and quantitation limits were 0.9 and 3.0 pg/mL. Polonski et al. [27] described a capillary isotache-phoresis method for sodium valproate in blood. The sample was injected into a column of an EKI 02 instrument for separation. The instrument incorporated a conductimetric detector. The mobile phase was 0.01 M histidine containing 0.1% methylhydroxycellulose at pH 5.5. The detection limit was 2 pg/mL. 

Fig. 3.38.The IUPAC names of Sudan azo dyes are as follows Sudan 1 = 1— [(2,4-dimethylphenyl)azo]-2-naphtalenol Sudan II = l-(phenylazo)-2-naphtol Sudan III = l-(4-phenylazophenylazo)-2-naphtol Sudan IV = o-tolyazo-o-tolyazo-beta-naphtol and Disperse Orange 13 = 4-[4-(phenylazo)-l-naphtylazo]-phenol. Azo dyes were separated in an ODS column (250 x 2.1 mm i.d. particle size 5 /xm) at 35°C. The isocratic mobile phase consisted of 0.1 per cent formic acid in methanol-0.1 per cent formic acid in water (97 3, v/v). The flow rate was 200 /xl/min. MS conditions were nebulizing and desolvation gas were nitrogen at the flow rates of 50 and 5551/h, respectively electrospray voltage, 3.0 kV cone voltage 25 V source temperature, 110°C desolvation temperature, 110°C. Azo dyes were extracted from the samples by homogenizing 1 g of sample with 10 ml of acetone, then the suspension was centrifuged and an aliquot of 3 ml of supernatant was mixed with 1 ml of deionized water, filtered and used for analysis. LC-ESI-MS/Ms SRM traces of standards and spiked samples are listed in Fig. 3.39. It was found that the detection and quantitation limits depended on both the chemical structure of the dye and the character of the accompanying matrix. LOD and LOQ values in chilli tomato sauce...

MIGRATION TIME OF THE DYES UNDER OPTIMIZED CONDITIONS, DETECTION AND QUANTITATION LIMITS, AND ACHIEVED RECOVERIES AFTER PRECONCENTRATION OF THE SPIKED RIVER WATER ANALYSED... 

Two approaches are generally used to develop methods with lower detection and quantitation limits for target compounds. One approach involves the use of sample cleanup methods such as size exclusion chromatography (SEC) for the... 

M. Alcala, J. Leon, J. Ropero, M. Blanco and R.J. Romanach, Analysis of low content drug tablets by transmission near infrared spectroscopy selection of calibration ranges according to multivariate detection and quantitation limits of PLS models, J. Pharm. Sci, 97(12), 5318-5327 (2007). 

The DPP technique working at pH 4.5 for peak I was selected, which exhibited adequate repeatability, reproducibility, and selectivity. The recovery was 99.97 1.5% and the detection and quantitation limits were 5.13 x 10 7 and 1.11 x 10 6 M, respectively. The method was applied successfully to the individual assay of capsules to verify the content uniformity of zaleplon. 

Existing definitions of various detection and quantitation limits can be confusing to a non-laboratory person. Despite misleading similarities of these definitions, there is a logic and order to the basic concepts that they express. Various detection limits that we commonly refer to in our daily work (the IDLs, MDLs, and PQLs) are discussed in this chapter in the increasing order of magnitude of their numeric values. Some of these detection limits are determined experimentally and depend on the matrix and the method of preparation and analysis, while others may be arbitrary values selected by the laboratory or the data user. The relationship between these three levels of detection is approximately 1 5 10. 

Practical Tips Detection and quantitation limits (continued)... 

Perform prevalidation linearity study By analyzing sufficient data points to determine the linear range, sample preparation concentrations and related compound detection and quantitation limits can be estimated. Consideration must be given to the capability of the HPLC instrumentation that will eventually run the method. 

EDTA was determined in human plasma and urine by capillary electrophoresis/MS [85]. Using a BC stable labile isotope, the detection and quantitation limits were found to be 7.3 and 14.6 ng/mL, respectively. The running buffer was pH 3.5 ammonium formate/formic acid buffer, at an inlet pressure 50 mb and a separation potential of -30 KV. The same authors [86] utilized this technique for the determination of EDTA as the nickel chelate in environmental water. 

The computer not only corrects for background radiation, sample quenching and instrument efficiency, it calculates the statistics for LSC counting as presented by Currie (1). The data outputs are, therefore, more meaningful, because detection and quantitation limits are known. 

From the Requirements Specifications, the nser can derive the instrnment type and its minimal Functional Specifications. For example, if an instrument is schednled to rnn overnight, the number of samples should be specified so that the system can inject antomatically. The UV/visible detector s baseline noise specification can be determined from the specified detection and quantitation limit of an HPLC analysis. The required data evaluation will determine the demands on the evaluation software. 

Fig. 9 Calculation of the detection and quantitation limits from the 95% prediction interval of the regression line. LC peak areas were obtained for six analyte concentrations between 0.05 pg/ml and 1 pg/ml with six repeated injections each. The regression line is shown with the 95% prediction intervals (dotted lines) in the lower concentration range. The probability distributions of the blank (B, first curve from left), of the analyte concentration corresponding to the detection limit (DL, second curve from left) and the quantitation limit (QL, third curve from left) are indicated. The limits of the 95% prediction interval represent the 95% limits of the probability distribution of the corresponding concentration, i.e., the interval around the concentration where (future) experimental results can be expected in 19 out of 20 cases. All experimental results within the probability distribution of the blank (gray shaded area) cannot be distinguished from the blank. This amounts to 50% of all values in the case of the detection limit and 5% for the quantitation limit.

In the literature, there is some discussion regarding how detection limits are defined, calculated, and interpreted. It is therefore important to state clearly how the detection and quantitation limits should be calculated in the validation protocol. Both the USP and the ICH guidelines similarly define the LOD and LOQ in ways that are widely accepted in the industry. In the most straightforward case, any compound detected with a response at about 3 times the noise response level is construed to be at its LOD. For the LOQ, the value is... 

For validating analytical methods for testing stability samples, the following elements need to be considered accuracy, precision, linearity, range, specificity, robustness, and detection and quantitation limits. Each of these terms is defined and discussed below. 

Detection and quantitation limits (DL and QL) - are these sufficiently low to allow adequate detection or quantitation of the analyte For an analysis with a defined impurity limit, the QL should be, at maximum, half the limit value. 

Drotaverine hydrochloride and mefenamic acid The second-order derivative spectra were used for simultaneous determination of drotaverine (DRO) and mefenamic acid (MEF). Calibration graphs were constructed over the concentration range of 4-24 pg/mL-i for DRO and MEF. Detection and quantitation limit were 0.4348 and 1.3176 pg/mL-i for DRO and 0.6141and 1.8611 pg/mL-i for MEF. The method was applied for determination of both ingredients in combined dosage forms. 32... 

SBSE presents a series of advantages over the rest of extraction techniques is solvent-free (environmental friendly) could be completely automated don t requires pre-treatment of samples (reduces analytical errors) and presents greater sensitivity than SPME, reaching lower detection and quantitation limits. However, it presents two clear disadvantages compared with the other extraction techniques PDMS is the only phase commercially available to date, limiting the extraction of polar substances and a specific thermal desorption unit is required for optimize the process (Castro et al., 2008). The increase of the extraction yields for the recovery of polar compoimds could be carry out by in-site derivatization. Recently, other phases under development were referred, namely those based on the sol-gel technology, restricted access materials and molecular imprinted polymers (Prieto et al., 2010). 

The flame ionization detector is the most commonly used for GC. It is considered an economical detector. The gas used for the detector is hydrogen and air. Signal out put of the flame detector is very sensitivity, Ipg/s, however the sensitivity also depends upon the sample preparation and the GC instrument. For example for benzene with the headspace GC-FID of one model is 0.02 ppm and 0.06 ppm for detection and quantitation limits, respectively which is more sensitive than the other model of the same manufacturer (Agilent technology, 2007). In quantitative analysis of a known compound by a GC, a MS detector can be used but usually avoided for routine analysis due to the running cost. 

A related term is the limit of quantitation (LOQ) which should be above the LOD. For example, the ACS guidelines on environmental analysis [9] specify that the LOD should be three times the S/N and the LOQ ten times the S/N. The definitions of the USP are similar and also state that the LOQ should be no less than two times the LOD [10]. Other agencies may have other guidelines, but all are concerned with Ae same need to specify detection and quantitation limits, and the relationship between them. Iliey are not the same. 

Rapid UPLC method for the determination of retinol and a-, y-, and 5-tocopherols in foods was accomplished by Shim and his coworkers [100]. The method was validated in terms of precision, accuracy, and linearity. The separation was performed on a reversed-phase Cjg column with 2 4m particle size, 2 mm i.d., and 75 mm length, followed by fluorescence detection. The recovery of retinol was more than 84.5% in all cases, while the detection and quantitation limits of the UPLC analysis were 0.015 and 0.045 mg/kg, respectively. The precision values were less than... 

As discussed in Section 4.4.8 and Appendix 4.1, the El source is an archetypal example of a mass flow dependent detector for chromatography, as a result of the high level of pumping applied to the source that removes the analyte almost as soon as it enters. Further, the characteristics that led to the high level of spectral reproducibility, mentioned above, also lead to excellent quantitative precision with a wide linear dynamic range and low detection and quantitation limits. The main drawback of the El source is its limitation to thermally stable and volatile analytes also, in a significant number of... 

---