DETECTION LIMITS. Provided below is a list of maximum acceptable reporting limits and units for various constituents in aqueous and sediment matrices. Contractor may not deviate from maximum acceptable reporting limits without approval of County. Contractor must provide laboratory and electronic data report (EDR) results in the units specified in the following table. Contractor must provide reasonable explanation for alternate proposed reporting limits. Aqueous Samples Reporting Limit AND Units Na, Mg, K, Ca 1.0 mg/L SO4, Cl, HCO3, CO3 1.0 mg/L SO4 in Rainwater 0.5 mg/L F 0.1 mg/L B 0.1 mg/L Nitrite + Nitrate as NO3 0.4 mg/L NH3 as N 0.1 mg/L TKN 0.2 mg/L Total Phosphorus as PO4 0.06 mg/L Orthophosphate as P 0.02 mg/L SiO2 0.5 mg/L Total Non-filterable Residue 5.0 mg/L Volatile Non-filterable Residue 5.0 mg/L Total Filterable Residue 5.0 mg/L Ag, Cd, Cr, Cu, Ni, Pb, Sb in freshwater 0.5 ug/L As, Se, in freshwater 0.4 ug/L Tl,in freshwater 0.2 ug/L Hg in freshwater 0.01 ug/L Zn in freshwater 2 ug/L Fe, Mn in freshwater 5 ug/L Ag, As, Be, Cd, Cr, Cu, Fe, Ni, Pb, Se, Sb, Tl, Zn, in seawater 0.05 ug/L Hg in seawater 0.5 ng/L Oil & Grease 5 mg/L MBAS 0.1 mg/L Organochlorine Pesticides (except Toxaphene) 2 ng/L Toxaphene 20 ng/L PCB Congeners 2 ng/L PCB Arochlors 20 ng/L Organophosphate Pesticides 5 ng/L Carbaryl in freshwater 2 ug/L Pyrethroid Pesticides in freshwater 2 ng/L Fipronil Insecticides 5 ng/L Sediment Samples (dry/ wt) Organochlorine Pesticides (except Toxaphene) 2 ug/kg Toxaphene 20 ug/kg PCB Congeners 2 ug/kg PCBs (arochlors) 20 ug/kg Pyrethroid Pesticides 5 ug/kg Fipronil Insecticides 5 ug/kg PAHs 2 ug/kg Cadmium 0.05 mg/kg Copper 0.05 mg/kg Chromium (total) 0.05 mg/kg Lead 0.05 mg/kg Mercury 0.05 mg/kg Nickel 0.05 mg/kg Selenium 0.05 mg/kg Silver 0.05 mg/kg Zinc 0.05 mg/kg
DETECTION LIMITS. As described by Xxxx (2005), the instrument response to particle-free air (a “dynamic zero” test) was routinely measured by placing a Teflon filter mounted in a Teflon filter housing in the sample line immediately upstream of the denuder. Dynamic zero testing was performed during the bimonthly (twice a month) maintenance with at least three 10-minute cycles run with the Teflon filter installed. Standard deviations for the study-mean dynamic zero tests were in the range 0.2-0.3 μg/m3 for the three instruments deployed over the period February 2002 through July 2005, corresponding to an MDL of 0.6-0.9 μg/m3. For semicontinuous instruments, dynamic zero tests have been used both to estimate method detection limits (from the standard deviation of the replicated measurements) and estimate an offset to be applied to the data. For the R&P 8400N, however, the interpretation of dynamic zero tests is not clear. Xxxxxxxx et al. (2004) conducted dynamic zero tests with a HEPA filter at the inlet of an 8400N. They postulate that nitric acid and ammonia were likely adsorbed by the HEPA filter and the observed response resulted from these precursor gases desorbing from the denuder into the ammonia- and nitric acid-free sample stream (presumably to form ammonium nitrate). Thus, in terms of the ambient PM2.5 data, the dynamic zero response might provide insights into a positive bias from sharp decreases in ambient concentrations of the precursor gases which would promote denuder off gassing. This scenario assumes that ammonium nitrate formation from denuder off gassing is both thermodynamically and kinetically favorable. While this is a plausible interpretation of dynamic zero testing, more work is needed to determine whether this is correct. In the interim, the estimated MDL of 0.6-0.9 μg/m3 should be used with caution. For example, this may be an upper bound since the dynamic zero response exhibited seasonal behavior (Xxxx, 2005) and the standard deviations used to estimate the MDL include such variation Precision. Six weeks of collocated data was collected in January-February 2005 to quantify the collocated precision in the measurements (Figure 4-2). The units showed excellent agreement, and the scatter provides insights into the collocated precision of the 8400N measurements at hourly resolution. Xxxxxx’x regression was performed on the data using on the data using record-specific uncertainties of the form σi = a + b×Ci, with a = 0.30 μg/m3 and b = 0.05; Ci is the hour...
DETECTION LIMITS. Dynamic zero measurements were periodically performed by placing a HEPA filter on the inlet. The MDL, defined as three times the standard deviation of these zero air measurements, was 4.5μg/m3.
DETECTION LIMITS. Effective MDL values, estimated as three times the standard deviation of 29 field blanks, are 0.18 (nitrate), 0.94 (sulfate) , and 0.01 μg/m3 (ammonium). The MDL for sulfate is significantly influenced by one value and its removal reduced the sulfate MDL from 0.94 to 0.20 μg/m3, which is consistent with the MDL for nitrate. This revised MDL was used in subsequent data analysis. Ambient concentration values were not blank-corrected.
DETECTION LIMITS. Field blanks were periodically collected by briefly placing a filter in the sampling train in the absence of flow. EC and OC blank corrections were derived for each calendar year and applied to the respective ambient data. For the period 7/1/01 – 6/30/03 there were 76 field blanks with concentrations 0.14 ± 0.10 μg/m3 for TC, 0.10 ± 0.06 μg/m3 for OC, and 0.04 ± 0.05 μg/m3 for EC (assuming the setpoint flow rate of 12 LPM for 24 hours). Using three times the standard deviation as the MDL yields detection limits of 0.30 μg/m3 for TC, 0.18 μg/m3 for OC, and 0.15 μg/m3 for EC.
DETECTION LIMITS. Provided below is a list of maximum acceptable reporting limits and units for various constituents in aqueous and sediment matrices. Contractor may not deviate from maximum acceptable reporting limits without approval of County. Contractor must provide laboratory and electronic data report (EDR) results in the units specified in the following table. Contractor must provide reasonable explanation for alternate proposed reporting limits.
DETECTION LIMITS. Table 3-1 summarizes the field blanks data collected during the measurement program. In each case, the filter was deployed identical to an ambient sample (including pre- and post-sampling flow checks and the standard field latency between setup and takedown). Mean field blank masses were statistically indistinguishable from zero (95% CL) and thus no field blank correction was applied to the gravimetric mass data. The last column of Table 3-1 lists MDL concentration values based on three times the standard deviation of the field blank data and operation at the setpoint flowrate.
DETECTION LIMITS. Table 4-5 summarizes the DRI-reported MDL values and laboratory blank instrument detection limits (IDL) observed in this study. Sodium and magnesium concentration data are reported as qualitative only.
DETECTION LIMITS. Xx (2005) presents the method used to estimate detection limits for the PILS- IC sulfate and nitrate data. Table 4-2 reports the reliable range of results for both sulfate and nitrate as defined by the lower limit of detection (LLD) and by the lower and upper limit of quantification (LLQ, ULQ). The lower limit of detection was estimated from the lowest calibration standard concentration with an IC detector response (analyte peak) signal-to-noise ratio greater than three. The baseline noise of a chromatogram is affected by the hardware and operating conditions of the IC (column type, eluant composition and concentration, solution (including water) quality, degree of internal IC temperature fluctuation, whether or not the eluant is degassed, and whether or not a suppressor is used). The lower limit of quantification (LLQ) was the lowest concentration within the linear range, just as the upper limit of quantification (ULQ) was determined by the highest concentration within the linear range. For sulfate, the LLD did not correspond to the LLQ because although chromatogram peaks were clearly distinguishable from the baseline at the lowest concentration standard, concentrations below Level 2 did were nonlinear (i.e., the Milli-Q and Level 1 standards were typically above the regression line generated from the calibration data). Xxxxxx et al. (2003) documented that past field studies have also witnessed detectable sulfate and nitrate peaks during blank runs, possibly attributable to DI water (sulfate) and background NOx entering through ineffective denuders (nitrate). Table 4-2. Detection limits (reliable ranges) for sulfate and nitrate by PILS-IC. Sulfate (μg/m3) Nitrate (μg/m3) LLD LLQ ULQ LLD/LLQ ULQ Sample loops 0.03 0.33 33 0.02 22 Concentrator pre-columns 0.05 0.53 53 0.04 35 Reported values are not true method detection and quantifiable limits, but rather are operational definitions based on the calibrations standards corresponding to an IC conductivity signal-to-noise ratio greater than three (LLD) and the calibration standards denoting the linear range (or at the extreme values of the calibration standard concentration range if linear to that concentration).
DETECTION LIMITS. Practical quantitation limits are shown in Appendix A1. In all cases, except where noted, these detection limits are at or below applicable Health Risk Limits (or Health Based Values or Maximum Contaminant Levels).
