Impact of pre-operative recreational marijuana use on outcomes two years after orthopaedic surgery.

PURPOSE: The purpose of this study was to investigate the relationship between recreational marijuana use and patient-reported outcomes two years after orthopaedic surgery. We hypothesized that pre-operative recreational marijuana use would be associated with less pain, better function, and better mental health measures two years after orthopaedic surgery. METHODS: Patients were retrospectively analyzed from a prospective orthopaedic registry at a single urban institution. A total of 1710 patients completed the pre-operative assessment and 1103 patients (64.5%) completed the two-year follow-up questionnaires. The cohort was then divided into two groups based on reported preoperative recreational marijuana usage, and statistical analysis was performed to determine if marijuana use was associated with two-year outcomes. Multivariable analysis was used to control for confounding variables. RESULTS: Marijuana use was reported by 47 (4.3%) patients. Significantly worse scores for two-year PROMIS Anxiety (53.2 vs. 49.2, p = 0.005), PROMIS Depression (51.1 vs. 46.5, p = 0.001), Met Expectations (63.1 vs. 74.4, p = 0.024), Surgical Satisfaction Questionnaire-8 (71.7 vs. 80.4, p = 0.005), and Numeric Satisfaction Scale (75.6 vs. 83.1, p = 0.041) were associated with marijuana use. Marijuana users also had less improvement of Numeric Pain Scores at the operative site (- 1.8 vs. - 2.7, p = 0.037) and greater decrease in Marx activity scores for lower extremities (- 12.3 vs. - 3.9, p = 0.024). Marijuana use was not an independent predictor of any outcome measure in the multivariable analysis. CONCLUSION: Marijuana use was associated with worse mental health scores, lower activity level, less pain relief, and worse satisfaction two years after orthopaedic surgery. However, after controlling for confounding variables, marijuana use was not predictive of any two-year outcome measure. STUDY DESIGN: Cross-sectional study.

A patient-centered composite endpoint weighting technique for orthopaedic trauma research.

BACKGROUND: This study aimed to address the current limitations of the use of composite endpoints in orthopaedic trauma research by quantifying the relative importance of clinical outcomes common to orthopaedic trauma patients and use those values to develop a patient-centered composite endpoint weighting technique. METHODS: A Best-Worst Scaling choice experiment was administered to 396 adult surgically-treated fracture patients. Respondents were presented with ten choice sets, each consisting of three out of ten plausible clinical outcomes. Hierarchical Bayesian modeling was used to determine the utilities associated with the outcomes. RESULTS: Death was the outcome of greatest importance (mean utility = - 8.91), followed by above knee amputation (- 7.66), below knee amputation (- 6.97), severe pain (- 5.90), deep surgical site infection (SSI) (- 5.69), bone healing complications (- 5.20), and moderate pain (- 4.59). Mild pain (- 3.30) and superficial SSI (- 3.29), on the other hand, were the outcomes of least importance to respondents. CONCLUSION: This study revealed that patients' relative importance towards clinical outcomes followed a logical gradient, with distinct and quantifiable preferences for each possible component outcome. These findings were incorporated into a novel composite endpoint weighting technique.

PROMIS Depression and Anxiety in shoulder surgery patients.

AIMS: The purpose of this study was to assess the prevalence of depression and anxiety symptoms in patients undergoing shoulder surgery using the National Institutes of Health (NIH) Patient-Reported Outcomes Measurement Information System (PROMIS) Depression and Anxiety computer adaptive tests, and to determine the factors associated with more severe symptoms. Additionally, we sought to determine whether PROMIS Depression and Anxiety were associated with functional outcomes after shoulder surgery. METHODS: This was a retrospective analysis of 293 patients from an urban population who underwent elective shoulder surgery from 2015 to 2018. Survey questionnaires included preoperative and two-year postoperative data. Bivariate analysis was used to identify associations and multivariable analysis was used to control for confounding variables. RESULTS: Mean two-year PROMIS Depression and Anxiety scores significantly improved from preoperative scores, with a greater improvement observed in PROMIS Anxiety. Worse PROMIS Depression and Anxiety scores were also significantly correlated with worse PROMIS Physical Function (PF) and American Shoulder and Elbow Surgeons scores (ASES). After controlling for confounding variables, worse PROMIS Depression was an independent predictor of worse PROMIS PF, while worse PROMIS Anxiety was an independent predictor of worse PROMIS PF and ASES scores. CONCLUSION: Mean two-year PROMIS Depression and Anxiety scores improved after elective shoulder surgery and several patient characteristics were associated with these scores. Worse functional outcomes were associated with worse PROMIS Depression and Anxiety; however, more severe two-year PROMIS Anxiety was the strongest predictor of worse functional outcomes. Cite this article: Bone Joint J 2022;104-B(4):479-485.

High-level field-evolved resistance to spinosad in Colorado potato beetle, Leptinotarsa decemlineata, in organically managed fields.

BACKGROUND: Organic pest management eschews synthetic pesticides and insecticide resistance is rarely studied in organically managed systems. Spinosad is a biologically based insecticide used widely by both organic and conventional growers. Colorado potato beetle, Leptinotarsa decemlineata, is infamous for its ability to evolve resistance to insecticides. Spinosad resistance was surveyed in conventionally managed fields in eastern New York in 2006. In response to grower reports of spinosad failure on two organic farms in 2009, resistance to spinosad was assayed in both conventionally and organically managed fields the following year, and growers were surveyed for their prior spinosad use. RESULTS: In 2006, spinosad resistance measured as median lethal dose (LD50 ) varied 9.8-fold among the eight conventional fields sampled and a laboratory susceptible strain. In 2010, the resistance ratios of LD50 values relative to a laboratory susceptible strain ranged from 17.5 to 40.6 in conventionally managed fields, and from 128.7 to 5750.3 in organically managed fields, a dramatic increase from 2006 with higher resistance ratios in organically managed fields. Organic growers reported much heavier use of spinosad in the years prior to 2010. CONCLUSION: This is the first report of high-level resistance to spinosad in Coleopterans. Selection strength due to number of years used and number of applications per season appear to have been the primary factors driving the evolution of resistance to spinosad, highlighting the need for resistance management in organic production, where fewer alternative active ingredients for resistance management are available. © 2021 Society of Chemical Industry.

Geographic Variation in Dominance of Spinosad Resistance in Colorado Potato Beetles (Coleoptera: Chrysomelidae).

Eastern New York State is frequently the site of Colorado potato beetle (Leptinotarsa decemlineata, Say) populations with the highest observed levels of insecticide resistance to a range of active ingredients. The dominance of a resistant phenotype will affect its rate of increase and the potential for management. On organic farms on Long Island, L. decemlineata evolved high levels of resistance to spinosad in a short period of time and that resistance has spread across the eastern part of the Island. Resistance has also emerged in other parts of the country as well. To clarify the level of dominance or recessiveness of spinosad resistance in different parts of the United States and how resistance differs in separate beetle populations, we sampled in 2010 beetle populations from Maine, Michigan, and Long Island. In addition, a highly resistant Long Island population was assessed in 2012. All populations were hybridized with a laboratory-susceptible strain to determine dominance. None of the populations sampled in 2010 were significantly different from additive resistance, but the Long Island population sampled in 2012 was not significantly different from fully recessive. Recessive inheritance of high-level resistance may help manage its increase.

What Is the Long-Term Impact of an Implant Stewardship Program on Orthopaedic Trauma Implant Pricing?

OBJECTIVES: To analyze the effectiveness of an implant stewardship program on implant cost containment and to estimate surgeons' responsiveness to implant price changes. DESIGN: Interrupted time series. SETTING: Level I trauma center. PATIENTS/PARTICIPANTS: Monitored usage of 5 trauma constructs by 10 surgeons over a 5-year period. INTERVENTION: Red-Yellow-Green (RYG) implant pricing comparison chart. MAIN OUTCOME MEASUREMENTS: Primary outcomes were changes in the mean price, minimum price, and the number of price changes. The secondary outcome was surgeons' responsiveness to RYG/cost changes. RESULTS: The study consisted of 2468 procedures. A mean construct price decrease of $66 per year [95% confidence interval (CI), $-170 to $-151], with distal femoral plates demonstrating the largest mean annual price decline ($486; 95% CI, $-540 to $-432). The minimum construct price decreased by $131 per year (95% CI, $-155 to $-111), with the largest reductions observed for distal femoral plates (-$436 per year; 95% CI, $-516 to $-354) and external fixators (-$122 per year; 95% CI, $-258 to $-136). The median price decrease was $407 (range: $6 to $2491) or 12.5% of the previous price. Positive changes in RYG levels increased surgeons' usage of tibial nails by 115%, femoral nails by 106%, and external fixators by 104%. Surgeons' implant selection was insensitive to RYG changes for distal femoral plates [RYG elasticity (ERYG): -0.74] and proximal tibia plates (ERYG: -0.21). CONCLUSIONS: The implant stewardship program was associated with substantial implant price reductions. Surgeons' implant selection was especially sensitive to price changes for intramedullary nails and external fixators.

Patient Satisfaction After Discharge Is Discordant With Reported Inpatient Experience.

Patient satisfaction measures are commonly used to evaluate clinical performance. However, research on the correlation between patient satisfaction scores and actual patient experience is limited. This study aimed to determine the concordance between patient satisfaction reported as an inpatient and patient satisfaction reported after discharge. The study enrolled 231 adult orthopedic patients at least 48 hours after admission to an academic hospital. Study participants rated their overall inpatient experience on a scale of 0 to 10, followed by open-ended questions on their hospital experience. Participants were then randomized to a second survey by either phone or mail at 4 to 6 weeks after discharge. Statistical and qualitative techniques were used to assess concordance in satisfaction scores and the agreement and association between patient experiences and patient satisfaction scores. The median overall patient satisfaction scores were 9.5 as inpatients (interquartile range [IQR], 8-10) and 10 at follow-up (IQR, 8-10), with a poor concordance between the inpatient and follow-up satisfaction scores (ρc=0.28). This study raises concerns regarding the validity of patient satisfaction measures to accurately quantify inpatient experience and the limitations related to its modes of administration. The authors observed poor agreement between the reported experience as an inpatient and the recollection of the inpatient experience after discharge. [Orthopedics. 2021;44(3):e427-e433.].

Conolidine: A Novel Plant Extract for Chronic Pain.

Pain, the most common symptom reported among patients in the primary care setting, is complex to manage. Opioids are among the most potent analgesics agents for managing pain. Since the mid-1990s, the number of opioid prescriptions for the management of chronic non-cancer pain (CNCP) has increased by more than 400%, and this increased availability has significantly contributed to opioid diversion, overdose, tolerance, dependence, and addiction. Despite the questionable effectiveness of opioids in managing CNCP and their high rates of side effects, the absence of available alternative medications and their clinical limitations and slower onset of action has led to an overreliance on opioids. Conolidine is an indole alkaloid derived from the bark of the tropical flowering shrub Tabernaemontana divaricate used in traditional Chinese, Ayurvedic, and Thai medicine. Conolidine could represent the beginning of a new era of chronic pain management. It is now being investigated for its effects on the atypical chemokine receptor (ACK3). In a rat model, it was found that a competitor molecule binding to ACKR3 resulted in inhibition of ACKR3's inhibitory activity, causing an overall increase in opiate receptor activity. Although the identification of conolidine as a potential novel analgesic agent provides an additional avenue to address the opioid crisis and manage CNCP, further studies are necessary to understand its mechanism of action and utility and efficacy in managing CNCP.

Quantitative Evaluation of Embolic Load in Femoral and Tibial Shaft Fractures Treated With Reamed Intramedullary Fixation.

OBJECTIVES: To compare the volume of embolic load during intramedullary fixation of femoral and tibial shaft fractures. Our hypothesis was that tibial intramedullary nails (IMNs) would be associated with less volume of intravasation of marrow than IM nailing of femur fractures. DESIGN: Prospective observational study. SETTING: Urban Level I trauma center. PATIENTS/PARTICIPANTS: Twenty-three patients consented for the study: 14 with femoral shaft fractures and 9 with tibial shaft fractures. INTERVENTION: All patients underwent continuous transesophageal echocardiography, and volume of embolic load was evaluated during 5 distinct stages: postinduction, initial guide wire, reaming (REAM), nail insertion, and postoperative. MAIN OUTCOME MEASUREMENTS: Volume of embolic load was measured based on previously described luminosity scores. The embolic load based on fracture location and procedure stage was evaluated using a mixed effects model. RESULTS: The IMN procedure increased the embolic load by 215% (-12% to 442%, P = 0.07) in femur patients relative to tibia patients after adjusting for baseline levels. Of the 5 steps measured, REAM was associated with the greatest increase in embolic load relative to the guide wire placement and controlling for fracture location (421%, 95% confidence interval: 169%-673%, P < 0.01). CONCLUSIONS: Femoral shaft IMN fixation was associated with a 215% increase in embolic load in comparison with tibial shaft IMN fixation, with the greatest quantitative load during the REAM stage; however, both procedures produce embolic load. LEVEL OF EVIDENCE: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Tourniquet use for extremity fractures has no adverse effect on number of ventilator days for patients who are treated with reamed femoral or tibial shaft nails.

INTRODUCTION: Concern exists regarding the pulmonary effects of using tourniquets for secondary extremity fractures in patients also undergoing intramedullary nail (IMN) fixation of femoral or tibial shaft fractures. Our hypothesis was that tourniquet use would be associated with increased ventilator days. METHODS: At a Level I trauma center, we conducted a retrospective review of 1966 patients with 2018 fractures (1070 femoral shaft and 948 tibial shaft) treated with IMN from December 2006 to September 2014. Medical record review and bivariate and multiple variable regression analyses were conducted, and the main outcome measurement was number of ventilator days. RESULTS: No statistically significant negative association was found between use of a tourniquet and number of ventilator days in the femoral or tibial fracture group. Use of tourniquets in the upper extremities showed a statistically significant decrease in amount of ventilator days in the femoral group (-2.2 days, p = 0.003) but no association in the tibial group (1.1 days, p = 0.36). Use of tourniquets concurrently in both upper and lower extremities of both femoral and tibial groups also had a protective effect (-6.8 days, p < 0.001 and -2.3 days, p = 0.009, respectively). Stratified and sensitivity analyses (to account for effects of mortality and missing data) showed consistently similar results. CONCLUSION: Tourniquet use for secondary extremity fractures, in patients also undergoing IMN fixation for femoral or tibial shaft fractures, was not associated with an increased number of ventilator days. A potential protective effect of tourniquet use was shown in patients with upper extremity fractures and in those with both upper and lower extremity fractures. LEVEL OF EVIDENCE: Therapeutic Level III (Retrospective cohort study).

Predictors of Symptomatic Implant Removal After Open Reduction and Internal Fixation of Tibial Plateau Fractures: A Retrospective Case-Control Study.

A retrospective case-control study was conducted at a level I trauma center to assess whether radiographic details of tibial plateau fixation can predict symptomatic implant removal. Nine hundred fifty-one tibial plateau fractures were treated with open reduction and internal fixation from 2007 to 2016. Eighty-two (9%) were treated with implant removal for localized pain over the implant. A control group was selected from the remaining patients using cumulative sampling. Records and radiographs were reviewed for predictors hypothesized to be associated with implant removal. Based on the authors' multivariable model, implant removal was associated with each additional protruding screw (adjusted odds ratio, 1.32; 95% confidence interval, 1.13-1.55; P<.001), bicondylar fractures (adjusted odds ratio, 2.13; 95% confidence interval, 1.11-4.11; P=.02), and lower body mass index (P=.05). Associations that approached significance were observed with decreased age (adjusted odds ratio, 0.82 per 10 years; 95% confidence interval, 0.66-1.01; P=.06) and closed fractures (adjusted odds ratio, 0.34; 95% confidence interval, 0.10-1.19; P=.09). The model discriminated fractures requiring implant removal with moderate accuracy (area under the curve=0.71). Each additional screw that radiographically protrudes beyond the far cortex increases the odds of symptomatic implant removal by 32%. Bicondylar fractures and lower body mass index are also associated with symptomatic implant removal. These findings might help inform patients and guide fixation techniques to reduce the likelihood of symptomatic implant removal. [Orthopedics. 2020;43(3):161-167.].

Incidence of Knee Pain Beyond 1 Year: Suprapatellar Versus Infrapatellar Approach for Intramedullary Nailing of the Tibia.

OBJECTIVE: To compare the magnitude of knee pain between the suprapatellar (SP) and infrapatellar (IP) approach for tibial nailing in patients who are more than 1 year after injury. DESIGN: Retrospective cohort study. SETTING: Academic Level I trauma center. PATIENTS/PARTICIPANTS: All tibia fracture patients 18-80 years of age treated with an intramedullary tibial nail during a 5-year period were retrospectively reviewed for inclusion. The surgical approach was determined by surgeon preference, with 3 of the 9 surgeons routinely using the SP approach. The primary outcome was knee pain during kneeling, with secondary assessments comparing knee pain during resting, walking, and the past 24 hours. INTERVENTION: Intramedullary nailing of a tibia fracture with either the SP or IP approach. MAIN OUTCOME MEASUREMENTS: Knee pain assessed with the Numeric Rating Scale between 0 and 10. A difference of >1.0 was considered to be clinically meaningful. RESULTS: The study group consisted of 262 patients (SP, n = 91; IP, n = 171) with a mean age of 41.4 years (SD = 16.6). The median follow-up was 3.8 years (range: 1.5-7.0). No difference in knee pain during kneeling was detected between the surgical approaches (IP: 3.9, SP 3.8; P = 0.90; mean difference: -0.06, 95% confidence interval, -1 to 0.9). Similarly, no differences were detected in average knee pain scores at rest (IP: 2.0, SP: 2.0; P = 1.00), walking (IP: 2.7, SP 3.0; P = 0.51), or the last 24 hours (IP: 2.6, SP 2.9; P = 0.45). CONCLUSIONS: In contrast to a study conducted by Sun et al, in which there was a statistical difference in knee pain between the SP and IP surgical approaches, we did not detect any statistical or clinical differences in knee pain between the SP and IP surgical approaches among patients with greater than 12 months of follow-up. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Does an Implant Usage Report Card Impact Orthopaedic Trauma Implant Stewardship?

OBJECTIVES: As hospitals seek to control variable expenses, orthopaedic surgeons have come under scrutiny because of relatively high implant costs. We aimed to determine whether feedback to surgeons regarding implant costs results in changes in implant selection. METHODS: This study was undertaken at a statewide trauma referral center and included 6 fellowship-trained orthopaedic trauma surgeons. A previously implemented implant stewardship program at our institution using a "red-yellow-green" (RYG) implant selection tool classifies 7 commonly used trauma implant constructs based on cost and categorizes each implant as red (used for patient-specific requirements, most expensive), yellow (midrange), and green (preferred vendor, least expensive). The constructs included were femoral intramedullary nail, tibial intramedullary nail, long and short cephalomedullary nails, distal femoral plate, proximal tibial plate, and lower-limb external fixator. Baseline implant usage from the previous year was obtained and provided to each surgeon. Each surgeon received a monthly feedback report containing individual implant utilization and overall ranking. RESULTS: The overall RYG score increased from 68.7 to 79.1 of 100 (P < 0.001). Three of the 7 implants (tibial and femoral nails and lower-limb external fixation) had significant increases in their RYG scores; implant selections for the other 4 implants were not significantly altered. A decrease of 1.8% (95% confidence interval, 0.4-3.2, P = 0.01) was noted in overall implant costs over the study period. CONCLUSION: Our intervention resulted in changes in surgeons' implant selections and cost savings. However, surgeons were unwilling to change certain implants despite their being more expensive.

Persistence and inheritance of costs of resistance to imidacloprid in Colorado potato beetle.

Reduced fitness among resistant versus susceptible individuals slows resistance evolution and makes it easier to manage. A loss of resistance costs could indicate novel adaptations or mutations contributing to resistance. We measured costs of resistance to imidacloprid in a Massachusetts resistant population compared with a Massachusetts susceptible population in 1999 in terms of fecundity, hatching success, egg development time, and sprint speed. Resistance was additive and seemed to be polygenic with high heritability. The fecundity cost appeared overdominant in 1999, and the hatch rate cost was partly recessive in 1999, but neither was significantly different from dominant or recessive. In 2004, we repeated our measures of resistance costs in Massachusetts in terms of fecundity and hatching success, and we added a new resistant population from Maine. In 2005, we compared development time of Maine resistant and the laboratory susceptible colony eggs. Significant fecundity costs of resistance were found in both population in both 1999 and 2004, and significant egg developmental time costs were found in 1999 and 2005. However, the hatching success costs of resistance were significant in 1999 and not apparent in 2004, suggesting some modification or replacement of the resistance genes in the intervening time.

Climate Change and Phenology: Empoasca fabae (Hemiptera: Cicadellidae) Migration and Severity of Impact.

Climate change can benefit individual species, but when pest species are enhanced by warmer temperatures agricultural productivity may be placed at greater risk. We analyzed the effects of temperature anomaly on arrival date and infestation severity of potato leafhopper, Empoasca fabae Harris, a classic new world long distance migrant, and a significant pest in several agricultural crops. We compiled E. fabae arrival dates and infestation severity data at different states in USA from existing literature reviews and agricultural extension records from 1951-2012, and examined the influence of temperature anomalies at each target state or overwintering range on the date of arrival and severity of infestation. Average E. fabae arrival date at different states reveal a clear trend along the south-north axis, with earliest arrival closest to the overwintering range. E. fabae arrival has advanced by 10 days over the last 62 years. E. fabae arrived earlier in warmer years in relation to each target state level temperature anomaly (3.0 days / °C increase in temperature anomaly). Increased temperature had a significant and positive effect on the severity of infestation, and arrival date had a marginal negative effect on severity. These relationships suggest that continued warming could advance the time of E. fabae colonization and increase their impact on affected crops.

The Red Queen in a potato field: integrated pest management versus chemical dependency in Colorado potato beetle control.

Originally designed to reconcile insecticide applications with biological control, the concept of integrated pest management (IPM) developed into the systems-based judicious and coordinated use of multiple control techniques aimed at reducing pest damage to economically tolerable levels. Chemical control, with scheduled treatments, was the starting point for most management systems in the 1950s. Although chemical control is philosophically compatible with IPM practices as a whole, reduction in pesticide use has been historically one of the main goals of IPM practitioners. In the absence of IPM, excessive reliance on pesticides has led to repeated control failures due to the evolution of resistance by pest populations. This creates the need for constant replacement of failed chemicals with new compounds, known as the 'insecticide treadmill'. In evolutionary biology, a similar phenomenon is known as the Red Queen principle - continuing change is needed for a population to persevere because its competitors undergo constant evolutionary adaptation. The Colorado potato beetle, Leptinotarsa decemlineata (Say), is an insect defoliator of potatoes that is notorious for its ability to develop insecticide resistance. In the present article, a review is given of four case studies from across the United States to demonstrate the importance of using IPM for sustainable management of a highly adaptable insect pest. Excessive reliance on often indiscriminate insecticide applications and inadequate use of alternative control methods, such as crop rotation, appear to expedite evolution of insecticide resistance in its populations. Resistance to IPM would involve synchronized adaptations to multiple unfavorable factors, requiring statistically unlikely genetic changes. Therefore, integrating different techniques is likely to reduce the need for constant replacement of failed chemicals with new ones.

Geographic variation in cannibalism in Colorado potato beetle (Coleoptera: Chrysomelidae) populations.

Cannibalism can have a large effect on population growth and survival in stressful environments, possibly including those created by insecticide use. In this study, we collected Colorado potato beetles from three isolated areas in the northeastern United States known for high levels of resistance to neonicotinoids. We measured resistance to imidacloprid in each of those populations, a laboratory susceptible population, and in hybrids between the three field populations and the laboratory susceptible population. We fed neonates eggs from resistant dams fed either imidacloprid-treated or untreated foliage to determine whether cannibals are exposed to toxins sequestered in eggs. We measured egg cannibalism by hatchlings within the clutch in each population and hybrids, and examined how fecundity and several variables associated with egg development varied among populations and with cannibalism, to see which traits might enhance or reduce cannibalism. Cannibalism varied significantly among populations, accounting for most of the variation in hatching success. Variability in egg development time and hatch rate in the absence of cannibalism in some populations affected rates of cannibalism. Resistance varied significantly among the field populations but was not related to cannibalism. Neonates fed eggs from dams on treated foliage showed signs of intoxication or death. Cannibalism appears to be part of a varying life history strategy in this species, with some populations laying larger and more cannibalistic clutches and the New York population laying smaller clutches with higher hatching success owing to reduced cannibalism.

Molar Refractivity and Connectivity Index Correlations for Henry's Law Virial Coefficients of Odorous Sulfur Compounds on Carbon and for Gas-Chromatographic Retention Indices.

Gas-solid chromatography was used to obtain values of the second gas-solid virial coefficient, B(2s), in the temperature range from 392 to 511 K for 10 volatile, malodorous organic sulfur compounds; ethanethiol, 1-propanethiol, methyl sulfide, 2-propanethiol, 1-methyl-1-propanethiol, 2-methyl-1-propanethiol, 2-methyl-2-propanethiol, ethyl sulfide, ethyl methyl sulfide, and tert-butyl methyl sulfide. Carbopack C (Supelco Inc.), a graphitized carbon black powder, was used as the adsorbent. Beginning with a theoretical equation for the second gas-solid virial coefficient, it was shown how a quantitative structure-retention relation (QSRR) could be developed to correlate ln B(2s) and hence chromatographic retention times with calculated molar refractivity and connectivity index values for the thiols and thioethers. It was found that both the gas-solid interaction energies and the ln B(2s) values could be correlated with calculated adsorbate molar refractivity (r(2)=0.951) and (r(2)=0.961), respectively. Connectivity index and molar refractivity together provide a r(2)=0.989 correlation of the ten ln B(2s) values at 403 K. A set of 373 organic compounds with retention indices taken from the literature was used to further test our approach. The 373 molecules were divided into 10 structural subgroups and molar refractivities and connectivity indices were calculated and used to correlate their retention index values. An overall correlation of r(2)=0.982 for the retention indices of the 373 molecules was found. Copyright 2001 Academic Press.