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Table 3

Effects of Adulterants on Intercept® Enzyme Immunoassays

Table 3

Effects of Adulterants on Intercept® Enzyme Immunoassays

Substance

EIA Result at 10 min. (adulterant only)

EIA Result at 10 min. (adulterant + secobarbital)

Sugar

No effect

No effect

Toothpaste

No effect

No effect

Cranberry Juice

No effect

No effect

TUMS® '

No effect

No effect

Orange Juice

No effect

False negative

Cola

No effect

No effect

Cough Syrup

No effect

False negative

Antiseptic

No effect

No effect

Water

No effect

No effect

shown in Table 3. The exact mechanism for some adulterants affecting the EIA assays is not known; but most likely this is an effect of pH. It should be noted that particular attention should be given to waiting 5-10 min prior to collection, which will remedy these effects.

5. Intercept Oral-Fluid Sample GC-MS Confirmation Method

In the algorithm used for Intercept, a presumptive positive specimen requires a GC-MS-MS analysis to assure true positivity. However, the levels to be determined require improved procedures compared with those commonly used for urine testing. Although numerous instruments are available that are capable of performing Intercept confirmations, the general steps and target ions would be the same. Therefore, this section presents a sample procedure used for the most difficult analyte, THC (8), followed by critical factors used to identify other typical DOA targets. Ultimately, each laboratory will validate its equipment and adopted procedures.

Quantitative analysis of THC in oral-fluid specimens can be performed by GC MS MS on a Finnegan TSQ 7000 Triple Stage Quadrupole (ThermoQuest, San Jose, CA) equipped with a 5% phenyl methyl silicone capillary column (15-m x 0.25-mm i.d.). The capillary inlet system can be operated in the split-less mode. Instrumental conditions were as follows: injection port, 275°C; GC temperature program, 100°C for 0.5 min, ramp 45°C/min to 235°C, hold 1.5 min, ramp 45°C/min to 310°C, and hold 1.5 min; transfer line, 250°C; source, 200°C; manifold, 90°C. A total of 200 ^L of each oral-fluid specimen was used in the extraction procedure. Initially, internal standard (D3-THC) at a concentration of 0.5 ng/mL was added to each specimen, calibrator, and control sample. Each sample was treated with 2 mL of 0.2 M NaOH and 3 mL of hexane: ethyl acetate (9: 1 v/v). The tubes were rocked for 30 min and then cen-trifuged. The upper organic layer was removed, acidified with 3 mL of 0.1 M HCl, and rocked an additional 15 min. Following centrifugation, the upper organic layer was removed and evaporated to dryness at 40°C. The residue was derivatized with 30 |L of bis(trimethylsilyl)-trifluoroacetamide (BSTFA) (1% trimethylchlorosilane [TMCS]) and 30 |L of ethyl acetate at 70°C for 30 min. A calibration standard of THC was prepared for each batch at 0.5 ng/mL concentration in artificial saliva (certified blank matrix). The following parent ions were selected for each compound to form product ions: THC, m/z 386 and D3-THC, m/z 389. The following product ions were selected for quantita-tion: THC, m/z 371 and D3-THC, m/z 374. For a specimen to be considered positive for THC, both the parent and product ions had to be present and within 2% of the retention time of the calibrator. In addition, the area of each ion had to be greater than the corresponding area of the ion in the calibration standard. The assay exhibited a between-run precision for THC in oral-fluid specimens of 4.3% at 0.25 ng/mL and 9.5% at 1 ng/mL. The assay limit of quantitation (LOQ)/LOD for THC was 0.2 ng/mL for a 0.2-mL extracted specimen.

Other compounds can be similarly analyzed. For reference, Table 4 lists the target analytes and their target ions that may be detected in oral fluids, and Table 5 shows typical LOQ/LOD values of various drugs of abuse obtained by GC-MS-MS using Intercept diluent. The target analytes, in some cases, are similar to those in urinalysis, but in other cases, such as with THC and cocaine (benzoylecgonine [BE]), they identify the compounds specific to oral fluids. Laboratories working with Intercept samples should validate their own instruments and methods.

Confirmation of presumptively positive specimens is perhaps the single most important procedure for any testing laboratory. The confirmation result will be the focus of any contested tests in a court of law. The defensibility of the procedure will require detailed attention to all aspects of the analysis. Therefore, the above information serves to provide some insight to potential approaches and expected results for confirmation of Intercept samples.

6. Analysis of Intercept Testing Results

The Intercept device has been reviewed by the US Food and Drug Administration (FDA) for all of the assays discussed in this chapter. The Intercept system for oral-fluid analysis has been further tested in a large number of studies. The largest study to date includes an overall analysis of 77,000 specimens

Table 4

Ions Monitored for Internal Standard and Analytes

Table 4

Ions Monitored for Internal Standard and Analytes

Analyte

Description

Quant Ions

THC d-3

Internal Std

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